Scott Main | 50e990c | 2012-06-21 17:14:39 -0700 | [diff] [blame] | 1 | page.title=Bluetooth |
Joe Fernandez | 33baa5a | 2013-11-14 11:41:19 -0800 | [diff] [blame] | 2 | page.tags=wireless,bluetoothadapter,bluetoothdevice |
Scott Main | 50e990c | 2012-06-21 17:14:39 -0700 | [diff] [blame] | 3 | @jd:body |
| 4 | |
kmccormick | f14ff1c | 2013-06-06 11:14:57 -0700 | [diff] [blame] | 5 | <div id="qv-wrapper"> |
| 6 | <div id="qv"> |
Scott Main | 50e990c | 2012-06-21 17:14:39 -0700 | [diff] [blame] | 7 | |
kmccormick | f14ff1c | 2013-06-06 11:14:57 -0700 | [diff] [blame] | 8 | <h2>In this document</h2> |
Scott Main | 50e990c | 2012-06-21 17:14:39 -0700 | [diff] [blame] | 9 | <ol> |
kmccormick | f14ff1c | 2013-06-06 11:14:57 -0700 | [diff] [blame] | 10 | <li><a href="#TheBasics">The Basics</a></li> |
| 11 | <li><a href="#Permissions">Bluetooth Permissions</a></li> |
Scott Main | 50e990c | 2012-06-21 17:14:39 -0700 | [diff] [blame] | 12 | <li><a href="#SettingUp">Setting Up Bluetooth</a></li> |
| 13 | <li><a href="#FindingDevices">Finding Devices</a> |
| 14 | <ol> |
| 15 | <li><a href="#QueryingPairedDevices">Querying paired devices</a></li> |
| 16 | <li><a href="#DiscoveringDevices">Discovering devices</a></li> |
| 17 | </ol></li> |
| 18 | <li><a href="#ConnectingDevices">Connecting Devices</a> |
| 19 | <ol> |
| 20 | <li><a href="#ConnectingAsAServer">Connecting as a server</a></li> |
| 21 | <li><a href="#ConnectingAsAClient">Connecting as a client</a></li> |
| 22 | </ol></li> |
| 23 | <li><a href="#ManagingAConnection">Managing a Connection</a></li> |
| 24 | <li><a href="#Profiles">Working with Profiles</a> |
| 25 | <ol> |
| 26 | <li><a href="#AT-Commands">Vendor-specific AT commands</a> |
| 27 | <li><a href="#HDP">Health Device Profile</a> |
| 28 | </ol></li> |
| 29 | </ol> |
| 30 | |
| 31 | <h2>Key classes</h2> |
| 32 | <ol> |
| 33 | <li>{@link android.bluetooth.BluetoothAdapter}</li> |
| 34 | <li>{@link android.bluetooth.BluetoothDevice}</li> |
| 35 | <li>{@link android.bluetooth.BluetoothSocket}</li> |
| 36 | <li>{@link android.bluetooth.BluetoothServerSocket}</li> |
| 37 | </ol> |
| 38 | |
| 39 | <h2>Related samples</h2> |
| 40 | <ol> |
| 41 | <li><a href="{@docRoot}resources/samples/BluetoothChat/index.html">Bluetooth Chat</a></li> |
| 42 | <li><a href="{@docRoot}resources/samples/BluetoothHDP/index.html">Bluetooth HDP (Health Device Profile)</a></li> |
| 43 | </ol> |
| 44 | |
| 45 | </div> |
| 46 | </div> |
| 47 | |
| 48 | |
| 49 | <p>The Android platform includes support for the Bluetooth network stack, |
| 50 | which allows a device to wirelessly exchange data with other Bluetooth devices. |
| 51 | The application framework provides access to the Bluetooth functionality through |
| 52 | the Android Bluetooth APIs. These APIs let applications wirelessly |
| 53 | connect to other Bluetooth devices, enabling point-to-point and multipoint |
| 54 | wireless features.</p> |
| 55 | |
| 56 | <p>Using the Bluetooth APIs, an Android application can perform the |
| 57 | following:</p> |
| 58 | <ul> |
| 59 | <li>Scan for other Bluetooth devices</li> |
| 60 | <li>Query the local Bluetooth adapter for paired Bluetooth devices</li> |
| 61 | <li>Establish RFCOMM channels</li> |
| 62 | <li>Connect to other devices through service discovery</li> |
| 63 | <li>Transfer data to and from other devices</li> |
| 64 | <li>Manage multiple connections</li> |
| 65 | </ul> |
| 66 | |
kmccormick | f14ff1c | 2013-06-06 11:14:57 -0700 | [diff] [blame] | 67 | <p>This document describes how to use <em>Classic Bluetooth</em>. Classic |
| 68 | Bluetooth is the right choice for more battery-intensive operations such as streaming |
| 69 | and communicating between Android devices. For Bluetooth devices with low power requirements, |
| 70 | Android 4.3 (API Level 18) introduces API support for Bluetooth Low Energy. To learn more, |
| 71 | see <a href="{@docRoot}guide/topics/connectivity/bluetooth-le.html">Bluetooth Low Energy</a>.</p> |
Scott Main | 50e990c | 2012-06-21 17:14:39 -0700 | [diff] [blame] | 72 | |
| 73 | <h2 id="TheBasics">The Basics</h2> |
| 74 | |
| 75 | <p>This document describes how to use the Android Bluetooth APIs to accomplish |
| 76 | the four major tasks necessary to communicate using Bluetooth: setting up |
| 77 | Bluetooth, finding devices that are either paired or available in the local |
| 78 | area, connecting devices, and transferring data between devices.</p> |
| 79 | |
| 80 | <p>All of the Bluetooth APIs are available in the {@link android.bluetooth} |
| 81 | package. Here's a summary of the classes and interfaces you will need to create Bluetooth |
| 82 | connections:</p> |
| 83 | |
| 84 | <dl> |
| 85 | <dt>{@link android.bluetooth.BluetoothAdapter}</dt> |
| 86 | <dd>Represents the local Bluetooth adapter (Bluetooth radio). The |
| 87 | {@link android.bluetooth.BluetoothAdapter} is the entry-point for all Bluetooth |
| 88 | interaction. Using this, |
| 89 | you can discover other Bluetooth devices, query a list of bonded (paired) |
| 90 | devices, instantiate a {@link android.bluetooth.BluetoothDevice} using a known |
| 91 | MAC address, and create a {@link android.bluetooth.BluetoothServerSocket} to |
| 92 | listen for communications |
| 93 | from other devices.</dd> |
| 94 | |
| 95 | <dt>{@link android.bluetooth.BluetoothDevice}</dt> |
| 96 | <dd>Represents a remote Bluetooth device. Use this to request a connection |
| 97 | with a remote device through a {@link android.bluetooth.BluetoothSocket} or |
| 98 | query information about the |
| 99 | device such as its name, address, class, and bonding state.</dd> |
| 100 | |
| 101 | <dt>{@link android.bluetooth.BluetoothSocket}</dt> |
| 102 | <dd>Represents the interface for a Bluetooth socket (similar to a TCP |
| 103 | {@link java.net.Socket}). This is the connection point that allows |
| 104 | an application to exchange data with another Bluetooth device via InputStream |
| 105 | and OutputStream.</dd> |
| 106 | |
| 107 | <dt>{@link android.bluetooth.BluetoothServerSocket}</dt> |
| 108 | <dd>Represents an open server socket that listens for incoming requests |
| 109 | (similar to a TCP {@link java.net.ServerSocket}). In order to connect two |
| 110 | Android devices, one device must open a server socket with this class. When a |
| 111 | remote Bluetooth device makes a connection request to the this device, the |
| 112 | {@link android.bluetooth.BluetoothServerSocket} will return a connected {@link |
| 113 | android.bluetooth.BluetoothSocket} when the |
| 114 | connection is accepted.</dd> |
| 115 | |
| 116 | <dt>{@link android.bluetooth.BluetoothClass}</dt> |
| 117 | <dd>Describes the general characteristics and capabilities of a Bluetooth |
| 118 | device. This is a read-only set of properties that define the device's major and |
| 119 | minor device classes and its services. However, this does not reliably describe |
| 120 | all Bluetooth profiles and services supported by the device, but is useful as a |
| 121 | hint to the device type.</dd> |
| 122 | |
| 123 | <dt>{@link android.bluetooth.BluetoothProfile}</dt> <dd>An interface that |
| 124 | represents a Bluetooth profile. A <em>Bluetooth profile</em> is a wireless |
| 125 | interface specification for Bluetooth-based communication between devices. An |
| 126 | example is the Hands-Free profile. For more discussion of profiles, see <a |
| 127 | href="#Profiles">Working with Profiles</a></dd> |
| 128 | |
| 129 | <dt>{@link android.bluetooth.BluetoothHeadset}</dt> <dd>Provides support for |
| 130 | Bluetooth headsets to be used with mobile phones. This includes both Bluetooth |
| 131 | Headset and Hands-Free (v1.5) profiles.</dd> |
| 132 | |
| 133 | <dt>{@link android.bluetooth.BluetoothA2dp}</dt> <dd> Defines how high quality |
| 134 | audio can be streamed from one device to another over a Bluetooth connection. |
| 135 | "A2DP" stands for Advanced Audio Distribution Profile.</dd> |
| 136 | |
| 137 | <dt>{@link android.bluetooth.BluetoothHealth}</dt> |
| 138 | <dd> Represents a Health Device Profile proxy that controls the Bluetooth service.</dd> |
| 139 | |
| 140 | <dt>{@link android.bluetooth.BluetoothHealthCallback}</dt> |
| 141 | |
| 142 | <dd>An abstract class that you use to implement {@link |
| 143 | android.bluetooth.BluetoothHealth} callbacks. You must extend this class and |
| 144 | implement the callback methods to receive updates about changes in the |
| 145 | application’s registration state and Bluetooth channel state.</dd> |
| 146 | |
| 147 | <dt>{@link android.bluetooth.BluetoothHealthAppConfiguration}</dt> |
| 148 | |
| 149 | <dd>Represents an application configuration that the Bluetooth Health third-party |
| 150 | application registers to communicate with a remote Bluetooth health |
| 151 | device.</dd> |
| 152 | |
| 153 | <dt>{@link android.bluetooth.BluetoothProfile.ServiceListener}</dt> |
| 154 | |
| 155 | <dd>An interface that notifies {@link android.bluetooth.BluetoothProfile} IPC |
| 156 | clients when they have been connected to or disconnected from the service (that |
| 157 | is, the internal service that runs a particular profile). </dd> |
| 158 | |
| 159 | </dl> |
| 160 | |
| 161 | |
| 162 | |
| 163 | |
| 164 | <h2 id="Permissions">Bluetooth Permissions</h2> |
| 165 | |
kmccormick | f14ff1c | 2013-06-06 11:14:57 -0700 | [diff] [blame] | 166 | <p>In order to use Bluetooth features in your application, you must declare |
| 167 | the Bluetooth permission {@link android.Manifest.permission#BLUETOOTH}. |
| 168 | You need this permission to perform any Bluetooth communication, |
| 169 | such as requesting a connection, accepting a connection, and transferring data.</p> |
| 170 | |
| 171 | <p>If you want your app to initiate device discovery or manipulate Bluetooth |
| 172 | settings, you must also declare the {@link android.Manifest.permission#BLUETOOTH_ADMIN} |
| 173 | permission. Most applications need this permission solely for the |
Scott Main | 50e990c | 2012-06-21 17:14:39 -0700 | [diff] [blame] | 174 | ability to discover local Bluetooth devices. The other abilities granted by this |
| 175 | permission should not be used, unless the application is a "power manager" that |
| 176 | will modify Bluetooth settings upon user request. <strong>Note:</strong> If you |
kmccormick | f14ff1c | 2013-06-06 11:14:57 -0700 | [diff] [blame] | 177 | use {@link android.Manifest.permission#BLUETOOTH_ADMIN} permission, then you must |
Scott Main | 50e990c | 2012-06-21 17:14:39 -0700 | [diff] [blame] | 178 | also have the {@link android.Manifest.permission#BLUETOOTH} permission.</p> |
| 179 | |
| 180 | <p>Declare the Bluetooth permission(s) in your application manifest file. For |
| 181 | example:</p> |
| 182 | |
| 183 | <pre> |
| 184 | <manifest ... > |
| 185 | <uses-permission android:name="android.permission.BLUETOOTH" /> |
| 186 | ... |
| 187 | </manifest> |
| 188 | </pre> |
| 189 | |
| 190 | <p>See the <a |
| 191 | href="{@docRoot}guide/topics/manifest/uses-permission-element.html"><uses-permission></a> |
| 192 | reference for more information about declaring application permissions.</p> |
| 193 | |
| 194 | |
| 195 | <h2 id="SettingUp">Setting Up Bluetooth</h2> |
| 196 | |
| 197 | <div class="figure" style="width:200px"> |
| 198 | <img src="{@docRoot}images/bt_enable_request.png" /> |
| 199 | <strong>Figure 1:</strong> The enabling Bluetooth dialog. |
| 200 | </div> |
| 201 | |
| 202 | <p>Before your application can communicate over Bluetooth, you need to verify |
| 203 | that Bluetooth is supported on the device, and if so, ensure that it is enabled.</p> |
| 204 | |
| 205 | <p>If Bluetooth is not supported, then you should gracefully disable any |
| 206 | Bluetooth features. If Bluetooth is supported, but disabled, then you can request that the |
| 207 | user enable Bluetooth without leaving your application. This setup is |
| 208 | accomplished in two steps, using the {@link android.bluetooth.BluetoothAdapter}.</p> |
| 209 | |
| 210 | |
| 211 | <ol> |
| 212 | <li>Get the {@link android.bluetooth.BluetoothAdapter} |
| 213 | <p>The {@link android.bluetooth.BluetoothAdapter} is required for any and all Bluetooth |
| 214 | activity. To get the {@link android.bluetooth.BluetoothAdapter}, call the static {@link |
| 215 | android.bluetooth.BluetoothAdapter#getDefaultAdapter()} method. This returns a |
| 216 | {@link android.bluetooth.BluetoothAdapter} that represents the device's own |
| 217 | Bluetooth adapter (the Bluetooth radio). There's one Bluetooth adapter for the |
| 218 | entire system, and your application can interact with it using this object. If |
| 219 | {@link android.bluetooth.BluetoothAdapter#getDefaultAdapter()} returns null, |
| 220 | then the device does not support Bluetooth and your story ends here. For example:</p> |
| 221 | <pre> |
| 222 | BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter(); |
| 223 | if (mBluetoothAdapter == null) { |
| 224 | // Device does not support Bluetooth |
| 225 | } |
| 226 | </pre> |
| 227 | </li> |
| 228 | |
| 229 | <li>Enable Bluetooth |
| 230 | <p>Next, you need to ensure that Bluetooth is enabled. Call {@link |
| 231 | android.bluetooth.BluetoothAdapter#isEnabled()} to check whether Bluetooth is |
| 232 | currently enable. If this method returns false, then Bluetooth is disabled. To |
| 233 | request that Bluetooth be enabled, call {@link |
| 234 | android.app.Activity#startActivityForResult(Intent,int) startActivityForResult()} |
| 235 | with the {@link android.bluetooth.BluetoothAdapter#ACTION_REQUEST_ENABLE} action Intent. |
| 236 | This will issue a request to enable Bluetooth through the system settings (without |
| 237 | stopping your application). For example:</p> |
| 238 | <pre> |
| 239 | if (!mBluetoothAdapter.isEnabled()) { |
| 240 | Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE); |
| 241 | startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT); |
| 242 | } |
| 243 | </pre> |
| 244 | |
| 245 | <p>A dialog will appear requesting user permission to enable Bluetooth, as shown |
| 246 | in Figure 1. If the user responds "Yes," the system will begin to enable Bluetooth |
| 247 | and focus will return to your application once the process completes (or fails).</p> |
| 248 | |
| 249 | <p>The {@code REQUEST_ENABLE_BT} constant passed to {@link |
| 250 | android.app.Activity#startActivityForResult(Intent,int) startActivityForResult()} is a locally |
| 251 | defined integer (which must be greater than 0), that the system passes back to you in your |
| 252 | {@link |
| 253 | android.app.Activity#onActivityResult(int,int,Intent) onActivityResult()} implementation as the |
| 254 | <code>requestCode</code> parameter.</p> |
| 255 | |
| 256 | <p>If enabling Bluetooth succeeds, your activity receives the {@link |
| 257 | android.app.Activity#RESULT_OK} result code in the {@link |
| 258 | android.app.Activity#onActivityResult(int,int,Intent) onActivityResult()} |
| 259 | callback. If Bluetooth was not enabled |
| 260 | due to an error (or the user responded "No") then the result code is {@link |
| 261 | android.app.Activity#RESULT_CANCELED}.</p> |
| 262 | </li> |
| 263 | </ol> |
| 264 | |
| 265 | <p>Optionally, your application can also listen for the |
| 266 | {@link android.bluetooth.BluetoothAdapter#ACTION_STATE_CHANGED} broadcast Intent, which |
| 267 | the system will broadcast whenever the Bluetooth state has changed. This broadcast contains |
| 268 | the extra fields {@link android.bluetooth.BluetoothAdapter#EXTRA_STATE} and {@link |
| 269 | android.bluetooth.BluetoothAdapter#EXTRA_PREVIOUS_STATE}, containing the new and old |
| 270 | Bluetooth states, respectively. Possible values for these extra fields are |
| 271 | {@link android.bluetooth.BluetoothAdapter#STATE_TURNING_ON}, {@link |
| 272 | android.bluetooth.BluetoothAdapter#STATE_ON}, {@link |
| 273 | android.bluetooth.BluetoothAdapter#STATE_TURNING_OFF}, and {@link |
| 274 | android.bluetooth.BluetoothAdapter#STATE_OFF}. Listening for this |
| 275 | broadcast can be useful to detect changes made to the Bluetooth state while your |
| 276 | app is running.</p> |
| 277 | |
| 278 | <p class="note"><strong>Tip:</strong> Enabling discoverability will automatically |
| 279 | enable Bluetooth. If you plan to consistently enable device discoverability before |
| 280 | performing Bluetooth activity, you can skip |
| 281 | step 2 above. Read about <a href="#EnablingDiscoverability">enabling discoverability</a>, |
| 282 | below.</p> |
| 283 | |
| 284 | |
| 285 | <h2 id="FindingDevices">Finding Devices</h2> |
| 286 | |
| 287 | <p>Using the {@link android.bluetooth.BluetoothAdapter}, you can find remote Bluetooth |
| 288 | devices either through device discovery or by querying the list of paired (bonded) |
| 289 | devices.</p> |
| 290 | |
| 291 | <p>Device discovery is a scanning procedure that searches the local area for |
| 292 | Bluetooth enabled devices and then requesting some information about each one |
| 293 | (this is sometimes referred to as "discovering," "inquiring" or "scanning"). |
| 294 | However, a Bluetooth device within the local area will respond to a discovery |
| 295 | request only if it is currently enabled to be discoverable. If a device is |
| 296 | discoverable, it will respond to the discovery request by sharing some |
| 297 | information, such as the device name, class, and its unique MAC address. Using |
| 298 | this information, the device performing discovery can then choose to initiate a |
| 299 | connection to the discovered device.</p> |
| 300 | |
| 301 | <p>Once a connection is made with a remote device for the first time, a pairing |
| 302 | request is automatically presented to the user. When a device is |
| 303 | paired, the basic information about that device (such as the device name, class, |
| 304 | and MAC address) is saved and can be read using the Bluetooth APIs. Using the |
| 305 | known MAC address for a remote device, a connection can be initiated with it at |
| 306 | any time without performing discovery (assuming the device is within range).</p> |
| 307 | |
| 308 | <p>Remember there is a difference between being paired and being connected. To |
| 309 | be paired means that two devices are aware of each other's existence, have a |
| 310 | shared link-key that can be used for authentication, and are capable of |
| 311 | establishing an encrypted connection with each other. To be connected means that |
| 312 | the devices currently share an RFCOMM channel and are able to transmit data with |
| 313 | each other. The current Android Bluetooth API's require devices to be paired |
| 314 | before an RFCOMM connection can be established. (Pairing is automatically performed |
| 315 | when you initiate an encrypted connection with the Bluetooth APIs.)</p> |
| 316 | |
| 317 | <p>The following sections describe how to find devices that have been paired, or |
| 318 | discover new devices using device discovery.</p> |
| 319 | |
| 320 | <p class="note"><strong>Note:</strong> Android-powered devices are not |
| 321 | discoverable by default. A user can make |
| 322 | the device discoverable for a limited time through the system settings, or an |
| 323 | application can request that the user enable discoverability without leaving the |
| 324 | application. How to <a href="#EnablingDiscoverability">enable discoverability</a> |
| 325 | is discussed below.</p> |
| 326 | |
| 327 | |
| 328 | <h3 id="QueryingPairedDevices">Querying paired devices</h3> |
| 329 | |
| 330 | <p>Before performing device discovery, its worth querying the set |
| 331 | of paired devices to see if the desired device is already known. To do so, |
| 332 | call {@link android.bluetooth.BluetoothAdapter#getBondedDevices()}. This |
| 333 | will return a Set of {@link android.bluetooth.BluetoothDevice}s representing |
| 334 | paired devices. For example, you can query all paired devices and then |
| 335 | show the name of each device to the user, using an ArrayAdapter:</p> |
| 336 | <pre> |
| 337 | Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices(); |
| 338 | // If there are paired devices |
| 339 | if (pairedDevices.size() > 0) { |
| 340 | // Loop through paired devices |
| 341 | for (BluetoothDevice device : pairedDevices) { |
| 342 | // Add the name and address to an array adapter to show in a ListView |
| 343 | mArrayAdapter.add(device.getName() + "\n" + device.getAddress()); |
| 344 | } |
| 345 | } |
| 346 | </pre> |
| 347 | |
| 348 | <p>All that's needed from the {@link android.bluetooth.BluetoothDevice} object |
| 349 | in order to initiate a connection is the MAC address. In this example, it's saved |
| 350 | as a part of an ArrayAdapter that's shown to the user. The MAC address can later |
| 351 | be extracted in order to initiate the connection. You can learn more about creating |
| 352 | a connection in the section about <a href="#ConnectingDevices">Connecting Devices</a>.</p> |
| 353 | |
| 354 | |
| 355 | <h3 id="DiscoveringDevices">Discovering devices</h3> |
| 356 | |
| 357 | <p>To start discovering devices, simply call {@link |
| 358 | android.bluetooth.BluetoothAdapter#startDiscovery()}. The |
| 359 | process is asynchronous and the method will immediately return with a boolean |
| 360 | indicating whether discovery has successfully started. The discovery process |
| 361 | usually involves an inquiry scan of about 12 seconds, followed by a page scan of |
| 362 | each found device to retrieve its Bluetooth name.</p> |
| 363 | |
| 364 | <p>Your application must register a BroadcastReceiver for the |
| 365 | {@link android.bluetooth.BluetoothDevice#ACTION_FOUND} Intent in |
| 366 | order to receive information about each |
| 367 | device discovered. For each device, the system will broadcast the |
| 368 | {@link android.bluetooth.BluetoothDevice#ACTION_FOUND} Intent. This |
| 369 | Intent carries the extra fields |
| 370 | {@link android.bluetooth.BluetoothDevice#EXTRA_DEVICE} and |
| 371 | {@link android.bluetooth.BluetoothDevice#EXTRA_CLASS}, containing a |
| 372 | {@link android.bluetooth.BluetoothDevice} and a {@link |
| 373 | android.bluetooth.BluetoothClass}, respectively. For example, here's how you can |
| 374 | register to handle the broadcast when devices are discovered:</p> |
| 375 | <pre> |
| 376 | // Create a BroadcastReceiver for ACTION_FOUND |
| 377 | private final BroadcastReceiver mReceiver = new BroadcastReceiver() { |
| 378 | public void onReceive(Context context, Intent intent) { |
| 379 | String action = intent.getAction(); |
| 380 | // When discovery finds a device |
| 381 | if (BluetoothDevice.ACTION_FOUND.equals(action)) { |
| 382 | // Get the BluetoothDevice object from the Intent |
| 383 | BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE); |
| 384 | // Add the name and address to an array adapter to show in a ListView |
| 385 | mArrayAdapter.add(device.getName() + "\n" + device.getAddress()); |
| 386 | } |
| 387 | } |
| 388 | }; |
| 389 | // Register the BroadcastReceiver |
| 390 | IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND); |
| 391 | registerReceiver(mReceiver, filter); // Don't forget to unregister during onDestroy |
| 392 | </pre> |
| 393 | |
| 394 | <p>All that's needed from the {@link android.bluetooth.BluetoothDevice} object |
| 395 | in order to initiate a |
| 396 | connection is the MAC address. In this example, it's saved as a part of an |
| 397 | ArrayAdapter that's shown to the user. The MAC address can later be extracted in |
| 398 | order to initiate the connection. You can learn more about creating a connection |
| 399 | in the section about <a href="#ConnectingDevices">Connecting Devices</a>.</p> |
| 400 | |
| 401 | <p class="caution"><strong>Caution:</strong> Performing device discovery is |
| 402 | a heavy procedure for the Bluetooth |
| 403 | adapter and will consume a lot of its resources. Once you have found a device to |
| 404 | connect, be certain that you always stop discovery with |
| 405 | {@link android.bluetooth.BluetoothAdapter#cancelDiscovery()} before |
| 406 | attempting a connection. Also, if you |
| 407 | already hold a connection with a device, then performing discovery can |
| 408 | significantly reduce the bandwidth available for the connection, so you should |
| 409 | not perform discovery while connected.</p> |
| 410 | |
| 411 | <h4 id="EnablingDiscoverability">Enabling discoverability</h4> |
| 412 | |
| 413 | <p>If you would like to make the local device discoverable to other devices, |
| 414 | call {@link android.app.Activity#startActivityForResult(Intent,int)} with the |
| 415 | {@link android.bluetooth.BluetoothAdapter#ACTION_REQUEST_DISCOVERABLE} action |
| 416 | Intent. This will issue a request to enable discoverable mode through the system |
| 417 | settings (without stopping your application). By default, the device will become |
| 418 | discoverable for 120 seconds. You can define a different duration by adding the |
| 419 | {@link android.bluetooth.BluetoothAdapter#EXTRA_DISCOVERABLE_DURATION} Intent |
| 420 | extra. The maximum duration an app can set is 3600 seconds, and a value of 0 |
| 421 | means the device is always discoverable. Any value below 0 or above 3600 is |
| 422 | automatically set to 120 secs). For example, this snippet sets the duration to |
| 423 | 300:</p> |
| 424 | |
| 425 | <pre>Intent discoverableIntent = new |
| 426 | Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE); |
| 427 | discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300); |
| 428 | startActivity(discoverableIntent); |
| 429 | </pre> |
| 430 | |
| 431 | <div class="figure" style="width:200px"> |
| 432 | <img src="{@docRoot}images/bt_enable_discoverable.png" /> |
| 433 | <strong>Figure 2:</strong> The enabling discoverability dialog. |
| 434 | </div> |
| 435 | |
| 436 | <p>A dialog will be displayed, requesting user permission to make the device |
| 437 | discoverable, as shown in Figure 2. If the user responds "Yes," then the device |
| 438 | will become discoverable for the specified amount of time. Your activity will |
| 439 | then receive a call to the {@link android.app.Activity#onActivityResult(int,int,Intent) |
| 440 | onActivityResult())} callback, with the result code equal to the duration that the device |
| 441 | is discoverable. If the user responded "No" or if an error occurred, the result code will |
| 442 | be {@link android.app.Activity#RESULT_CANCELED}.</p> |
| 443 | |
| 444 | <p class="note"><strong>Note:</strong> If Bluetooth has not been enabled on the device, |
| 445 | then enabling device discoverability will automatically enable Bluetooth.</p> |
| 446 | |
| 447 | <p>The device will silently remain in discoverable mode for the allotted time. |
| 448 | If you would like to be notified when the discoverable mode has changed, you can |
| 449 | register a BroadcastReceiver for the {@link |
| 450 | android.bluetooth.BluetoothAdapter#ACTION_SCAN_MODE_CHANGED} |
| 451 | Intent. This will contain the extra fields {@link |
| 452 | android.bluetooth.BluetoothAdapter#EXTRA_SCAN_MODE} and |
| 453 | {@link android.bluetooth.BluetoothAdapter#EXTRA_PREVIOUS_SCAN_MODE}, which tell you the |
| 454 | new and old scan mode, respectively. Possible values for each are |
| 455 | {@link android.bluetooth.BluetoothAdapter#SCAN_MODE_CONNECTABLE_DISCOVERABLE}, |
| 456 | {@link android.bluetooth.BluetoothAdapter#SCAN_MODE_CONNECTABLE}, or {@link |
| 457 | android.bluetooth.BluetoothAdapter#SCAN_MODE_NONE}, |
| 458 | which indicate that the device is either in discoverable mode, not in |
| 459 | discoverable mode but still able to receive connections, or not in discoverable |
| 460 | mode and unable to receive connections, respectively.</p> |
| 461 | |
| 462 | <p>You do not need to enable device discoverability if you will be initiating |
| 463 | the connection to a remote device. Enabling discoverability is only necessary when |
| 464 | you want your application to host a server socket that will accept incoming |
| 465 | connections, because the remote devices must be able to discover the device |
| 466 | before it can initiate the connection.</p> |
| 467 | |
| 468 | |
| 469 | |
| 470 | <h2 id="ConnectingDevices">Connecting Devices</h2> |
| 471 | |
| 472 | <p>In order to create a connection between your application on two devices, you |
| 473 | must implement both the server-side and client-side mechanisms, because one |
| 474 | device must open a server socket and the other one must initiate the connection |
| 475 | (using the server device's MAC address to initiate a connection). The server and |
| 476 | client are considered connected to each other when they each have a connected |
| 477 | {@link android.bluetooth.BluetoothSocket} on the same RFCOMM channel. At this |
| 478 | point, each device can obtain input and output streams and data transfer can |
| 479 | begin, which is discussed in the section about <a |
| 480 | href="#ManagingAConnection">Managing a Connection</a>. This section describes how |
| 481 | to initiate the connection between two devices.</p> |
| 482 | |
| 483 | <p>The server device and the client device each obtain the required {@link |
| 484 | android.bluetooth.BluetoothSocket} in different ways. The server will receive it |
| 485 | when an incoming connection is accepted. The client will receive it when it |
| 486 | opens an RFCOMM channel to the server.</p> |
| 487 | |
| 488 | <div class="figure" style="width:200px"> |
| 489 | <img src="{@docRoot}images/bt_pairing_request.png" /> |
| 490 | <strong>Figure 3:</strong> The Bluetooth pairing dialog. |
| 491 | </div> |
| 492 | |
| 493 | <p>One implementation technique is to automatically prepare each device as a |
| 494 | server, so that each one has a server socket open and listening for connections. |
| 495 | Then either device can initiate a connection with the other and become the |
| 496 | client. Alternatively, one device can explicitly "host" the connection and open |
| 497 | a server socket on demand and the other device can simply initiate the |
| 498 | connection.</p> |
| 499 | |
| 500 | <p class="note"><strong>Note:</strong> If the two devices have not been previously paired, |
| 501 | then the Android framework will automatically show a pairing request notification or |
| 502 | dialog to the user during the connection procedure, as shown in Figure 3. So |
| 503 | when attempting to connect devices, |
| 504 | your application does not need to be concerned about whether or not the devices are |
| 505 | paired. Your RFCOMM connection attempt will block until the user has successfully paired, |
| 506 | or will fail if the user rejects pairing, or if pairing fails or times out. </p> |
| 507 | |
| 508 | |
| 509 | <h3 id="ConnectingAsAServer">Connecting as a server</h3> |
| 510 | |
| 511 | <p>When you want to connect two devices, one must act as a server by holding an |
| 512 | open {@link android.bluetooth.BluetoothServerSocket}. The purpose of the server |
| 513 | socket is to listen for incoming connection requests and when one is accepted, |
| 514 | provide a connected {@link android.bluetooth.BluetoothSocket}. When the {@link |
| 515 | android.bluetooth.BluetoothSocket} is acquired from the {@link |
| 516 | android.bluetooth.BluetoothServerSocket}, |
| 517 | the {@link android.bluetooth.BluetoothServerSocket} can (and should) be |
| 518 | discarded, unless you want to accept more connections.</p> |
| 519 | |
| 520 | <div class="sidebox-wrapper"> |
| 521 | <div class="sidebox"> |
| 522 | <h2>About UUID</h2> |
| 523 | |
| 524 | <p>A Universally Unique Identifier (UUID) is a standardized 128-bit format for a string |
| 525 | ID used to uniquely identify information. The point of a UUID is that it's big |
| 526 | enough that you can select any random and it won't clash. In this case, it's |
| 527 | used to uniquely identify your application's Bluetooth service. To get a UUID to |
| 528 | use with your application, you can use one of the many random UUID generators on |
| 529 | the web, then initialize a {@link java.util.UUID} with {@link |
| 530 | java.util.UUID#fromString(String)}.</p> |
| 531 | </div> |
| 532 | </div> |
| 533 | |
| 534 | <p>Here's the basic procedure to set up a server socket and accept a |
| 535 | connection:</p> |
| 536 | |
| 537 | <ol> |
| 538 | <li>Get a {@link android.bluetooth.BluetoothServerSocket} by calling the |
| 539 | {@link |
| 540 | android.bluetooth.BluetoothAdapter#listenUsingRfcommWithServiceRecord(String, |
| 541 | UUID)}. |
| 542 | <p>The string is an identifiable name of your service, which the system will |
| 543 | automatically write to a new Service Discovery Protocol (SDP) database entry on |
| 544 | the device (the name is arbitrary and can simply be your application name). The |
| 545 | UUID is also included in the SDP entry and will be the basis for the connection |
| 546 | agreement with the client device. That is, when the client attempts to connect |
| 547 | with this device, it will carry a UUID that uniquely identifies the service with |
| 548 | which it wants to connect. These UUIDs must match in order for the connection to |
| 549 | be accepted (in the next step).</p> |
| 550 | </li> |
| 551 | |
| 552 | <li>Start listening for connection requests by calling |
| 553 | {@link android.bluetooth.BluetoothServerSocket#accept()}. |
| 554 | <p>This is a blocking call. It will return when either a connection has been |
| 555 | accepted or an exception has occurred. A connection is accepted only when a |
| 556 | remote device has sent a connection request with a UUID matching the one |
| 557 | registered with this listening server socket. When successful, {@link |
| 558 | android.bluetooth.BluetoothServerSocket#accept()} will |
| 559 | return a connected {@link android.bluetooth.BluetoothSocket}.</p> |
| 560 | </li> |
| 561 | |
| 562 | <li>Unless you want to accept additional connections, call |
| 563 | {@link android.bluetooth.BluetoothServerSocket#close()}. |
| 564 | <p>This releases the server socket and all its resources, but does <em>not</em> close the |
| 565 | connected {@link android.bluetooth.BluetoothSocket} that's been returned by {@link |
| 566 | android.bluetooth.BluetoothServerSocket#accept()}. Unlike TCP/IP, RFCOMM only allows one |
| 567 | connected client per channel at a time, so in most cases it makes sense to call {@link |
| 568 | android.bluetooth.BluetoothServerSocket#close()} on the {@link |
| 569 | android.bluetooth.BluetoothServerSocket} immediately after accepting a connected |
| 570 | socket.</p> |
| 571 | </li> |
| 572 | </ol> |
| 573 | |
| 574 | <p>The {@link android.bluetooth.BluetoothServerSocket#accept()} call should not |
| 575 | be executed in the main activity UI thread because it is a blocking call and |
| 576 | will prevent any other interaction with the application. It usually makes |
| 577 | sense to do all work with a {@link android.bluetooth.BluetoothServerSocket} or {@link |
| 578 | android.bluetooth.BluetoothSocket} in a new |
| 579 | thread managed by your application. To abort a blocked call such as {@link |
| 580 | android.bluetooth.BluetoothServerSocket#accept()}, call {@link |
| 581 | android.bluetooth.BluetoothServerSocket#close()} on the {@link |
| 582 | android.bluetooth.BluetoothServerSocket} (or {@link |
| 583 | android.bluetooth.BluetoothSocket}) from another thread and the blocked call will |
| 584 | immediately return. Note that all methods on a {@link |
| 585 | android.bluetooth.BluetoothServerSocket} or {@link android.bluetooth.BluetoothSocket} |
| 586 | are thread-safe.</p> |
| 587 | |
| 588 | <h4>Example</h4> |
| 589 | |
| 590 | <p>Here's a simplified thread for the server component that accepts incoming |
| 591 | connections:</p> |
| 592 | <pre> |
| 593 | private class AcceptThread extends Thread { |
| 594 | private final BluetoothServerSocket mmServerSocket; |
| 595 | |
| 596 | public AcceptThread() { |
| 597 | // Use a temporary object that is later assigned to mmServerSocket, |
| 598 | // because mmServerSocket is final |
| 599 | BluetoothServerSocket tmp = null; |
| 600 | try { |
| 601 | // MY_UUID is the app's UUID string, also used by the client code |
| 602 | tmp = mBluetoothAdapter.listenUsingRfcommWithServiceRecord(NAME, MY_UUID); |
| 603 | } catch (IOException e) { } |
| 604 | mmServerSocket = tmp; |
| 605 | } |
| 606 | |
| 607 | public void run() { |
| 608 | BluetoothSocket socket = null; |
| 609 | // Keep listening until exception occurs or a socket is returned |
| 610 | while (true) { |
| 611 | try { |
| 612 | socket = mmServerSocket.accept(); |
| 613 | } catch (IOException e) { |
| 614 | break; |
| 615 | } |
| 616 | // If a connection was accepted |
| 617 | if (socket != null) { |
| 618 | // Do work to manage the connection (in a separate thread) |
| 619 | manageConnectedSocket(socket); |
| 620 | mmServerSocket.close(); |
| 621 | break; |
| 622 | } |
| 623 | } |
| 624 | } |
| 625 | |
| 626 | /** Will cancel the listening socket, and cause the thread to finish */ |
| 627 | public void cancel() { |
| 628 | try { |
| 629 | mmServerSocket.close(); |
| 630 | } catch (IOException e) { } |
| 631 | } |
| 632 | } |
| 633 | </pre> |
| 634 | |
| 635 | <p>In this example, only one incoming connection is desired, so as soon as a |
| 636 | connection is accepted and the {@link android.bluetooth.BluetoothSocket} is |
| 637 | acquired, the application |
| 638 | sends the acquired {@link android.bluetooth.BluetoothSocket} to a separate |
| 639 | thread, closes the |
| 640 | {@link android.bluetooth.BluetoothServerSocket} and breaks the loop.</p> |
| 641 | |
| 642 | <p>Note that when {@link android.bluetooth.BluetoothServerSocket#accept()} |
| 643 | returns the {@link android.bluetooth.BluetoothSocket}, the socket is already |
| 644 | connected, so you should <em>not</em> call {@link |
| 645 | android.bluetooth.BluetoothSocket#connect()} (as you do from the |
| 646 | client-side).</p> |
| 647 | |
| 648 | <p><code>manageConnectedSocket()</code> is a fictional method in the application |
| 649 | that will |
| 650 | initiate the thread for transferring data, which is discussed in the section |
| 651 | about <a href="#ManagingAConnection">Managing a Connection</a>.</p> |
| 652 | |
| 653 | <p>You should usually close your {@link android.bluetooth.BluetoothServerSocket} |
| 654 | as soon as you are done listening for incoming connections. In this example, {@link |
| 655 | android.bluetooth.BluetoothServerSocket#close()} is called as soon |
| 656 | as the {@link android.bluetooth.BluetoothSocket} is acquired. You may also want |
| 657 | to provide a public method in your thread that can close the private {@link |
| 658 | android.bluetooth.BluetoothSocket} in the event that you need to stop listening on the |
| 659 | server socket.</p> |
| 660 | |
| 661 | |
| 662 | <h3 id="ConnectingAsAClient">Connecting as a client</h3> |
| 663 | |
| 664 | <p>In order to initiate a connection with a remote device (a device holding an |
| 665 | open |
| 666 | server socket), you must first obtain a {@link |
| 667 | android.bluetooth.BluetoothDevice} object that represents the remote device. |
| 668 | (Getting a {@link android.bluetooth.BluetoothDevice} is covered in the above |
| 669 | section about <a |
| 670 | href="#FindingDevices">Finding Devices</a>.) You must then use the |
| 671 | {@link android.bluetooth.BluetoothDevice} to acquire a {@link |
| 672 | android.bluetooth.BluetoothSocket} and initiate the connection.</p> |
| 673 | |
| 674 | <p>Here's the basic procedure:</p> |
| 675 | |
| 676 | <ol> |
| 677 | <li>Using the {@link android.bluetooth.BluetoothDevice}, get a {@link |
| 678 | android.bluetooth.BluetoothSocket} by calling {@link |
| 679 | android.bluetooth.BluetoothDevice#createRfcommSocketToServiceRecord(UUID)}. |
| 680 | <p>This initializes a {@link android.bluetooth.BluetoothSocket} that will |
| 681 | connect to the {@link android.bluetooth.BluetoothDevice}. The UUID passed here |
| 682 | must match the UUID used by the server device when it opened its |
| 683 | {@link android.bluetooth.BluetoothServerSocket} (with {@link |
| 684 | android.bluetooth.BluetoothAdapter#listenUsingRfcommWithServiceRecord(String, |
| 685 | UUID)}). Using the same UUID is simply a matter of hard-coding the UUID string |
| 686 | into your application and then referencing it from both the server and client |
| 687 | code.</p> |
| 688 | </li> |
| 689 | |
| 690 | <li>Initiate the connection by calling {@link |
| 691 | android.bluetooth.BluetoothSocket#connect()}. |
| 692 | <p>Upon this call, the system will perform an SDP lookup on the remote device in |
| 693 | order to match the UUID. If the lookup is successful and the remote device |
| 694 | accepts the connection, it will share the RFCOMM channel to use during the |
| 695 | connection and {@link |
| 696 | android.bluetooth.BluetoothSocket#connect()} will return. This method is a |
| 697 | blocking call. If, for |
| 698 | any reason, the connection fails or the {@link |
| 699 | android.bluetooth.BluetoothSocket#connect()} method times out (after about |
| 700 | 12 seconds), then it will throw an exception.</p> |
| 701 | <p>Because {@link |
| 702 | android.bluetooth.BluetoothSocket#connect()} is a blocking call, this connection |
| 703 | procedure should always be performed in a thread separate from the main activity |
| 704 | thread.</p> |
| 705 | <p class="note">Note: You should always ensure that the device is not performing |
| 706 | device discovery when you call {@link |
| 707 | android.bluetooth.BluetoothSocket#connect()}. If discovery is in progress, then |
| 708 | the |
| 709 | connection attempt will be significantly slowed and is more likely to fail.</p> |
| 710 | </li> |
| 711 | </ol> |
| 712 | |
| 713 | <h4>Example</h4> |
| 714 | |
| 715 | <p>Here is a basic example of a thread that initiates a Bluetooth |
| 716 | connection:</p> |
| 717 | <pre> |
| 718 | private class ConnectThread extends Thread { |
| 719 | private final BluetoothSocket mmSocket; |
| 720 | private final BluetoothDevice mmDevice; |
| 721 | |
| 722 | public ConnectThread(BluetoothDevice device) { |
| 723 | // Use a temporary object that is later assigned to mmSocket, |
| 724 | // because mmSocket is final |
| 725 | BluetoothSocket tmp = null; |
| 726 | mmDevice = device; |
| 727 | |
| 728 | // Get a BluetoothSocket to connect with the given BluetoothDevice |
| 729 | try { |
| 730 | // MY_UUID is the app's UUID string, also used by the server code |
| 731 | tmp = device.createRfcommSocketToServiceRecord(MY_UUID); |
| 732 | } catch (IOException e) { } |
| 733 | mmSocket = tmp; |
| 734 | } |
| 735 | |
| 736 | public void run() { |
| 737 | // Cancel discovery because it will slow down the connection |
| 738 | mBluetoothAdapter.cancelDiscovery(); |
| 739 | |
| 740 | try { |
| 741 | // Connect the device through the socket. This will block |
| 742 | // until it succeeds or throws an exception |
| 743 | mmSocket.connect(); |
| 744 | } catch (IOException connectException) { |
| 745 | // Unable to connect; close the socket and get out |
| 746 | try { |
| 747 | mmSocket.close(); |
| 748 | } catch (IOException closeException) { } |
| 749 | return; |
| 750 | } |
| 751 | |
| 752 | // Do work to manage the connection (in a separate thread) |
| 753 | manageConnectedSocket(mmSocket); |
| 754 | } |
| 755 | |
| 756 | /** Will cancel an in-progress connection, and close the socket */ |
| 757 | public void cancel() { |
| 758 | try { |
| 759 | mmSocket.close(); |
| 760 | } catch (IOException e) { } |
| 761 | } |
| 762 | } |
| 763 | </pre> |
| 764 | |
| 765 | <p>Notice that {@link android.bluetooth.BluetoothAdapter#cancelDiscovery()} is called |
| 766 | before the connection is made. You should always do this before connecting and it is safe |
| 767 | to call without actually checking whether it is running or not (but if you do want to |
| 768 | check, call {@link android.bluetooth.BluetoothAdapter#isDiscovering()}).</p> |
| 769 | |
| 770 | <p><code>manageConnectedSocket()</code> is a fictional method in the application |
| 771 | that will initiate the thread for transferring data, which is discussed in the section |
| 772 | about <a href="#ManagingAConnection">Managing a Connection</a>.</p> |
| 773 | |
| 774 | <p>When you're done with your {@link android.bluetooth.BluetoothSocket}, always |
| 775 | call {@link android.bluetooth.BluetoothSocket#close()} to clean up. |
| 776 | Doing so will immediately close the connected socket and clean up all internal |
| 777 | resources.</p> |
| 778 | |
| 779 | |
| 780 | <h2 id="ManagingAConnection">Managing a Connection</h2> |
| 781 | |
| 782 | <p>When you have successfully connected two (or more) devices, each one will |
| 783 | have a connected {@link android.bluetooth.BluetoothSocket}. This is where the fun |
| 784 | begins because you can share data between devices. Using the {@link |
| 785 | android.bluetooth.BluetoothSocket}, the general procedure to transfer arbitrary data is |
| 786 | simple:</p> |
| 787 | <ol> |
| 788 | <li>Get the {@link java.io.InputStream} and {@link java.io.OutputStream} that |
| 789 | handle transmissions through the socket, via {@link |
| 790 | android.bluetooth.BluetoothSocket#getInputStream()} and |
| 791 | {@link android.bluetooth.BluetoothSocket#getOutputStream}, respectively.</li> |
| 792 | |
| 793 | <li>Read and write data to the streams with {@link |
| 794 | java.io.InputStream#read(byte[])} and {@link java.io.OutputStream#write(byte[])}.</li> |
| 795 | </ol> |
| 796 | |
| 797 | <p>That's it.</p> |
| 798 | |
| 799 | <p>There are, of course, implementation details to consider. First and foremost, |
| 800 | you should use a dedicated thread for all stream reading and writing. This is |
| 801 | important because both {@link java.io.InputStream#read(byte[])} and {@link |
| 802 | java.io.OutputStream#write(byte[])} methods are blocking calls. {@link |
| 803 | java.io.InputStream#read(byte[])} will block until there is something to read |
| 804 | from the stream. {@link java.io.OutputStream#write(byte[])} does not usually |
| 805 | block, but can block for flow control if the remote device is not calling {@link |
| 806 | java.io.InputStream#read(byte[])} quickly enough and the intermediate buffers are full. |
| 807 | So, your main loop in the thread should be dedicated to reading from the {@link |
| 808 | java.io.InputStream}. A separate public method in the thread can be used to initiate |
| 809 | writes to the {@link java.io.OutputStream}.</p> |
| 810 | |
| 811 | <h4>Example</h4> |
| 812 | |
| 813 | <p>Here's an example of how this might look:</p> |
| 814 | <pre> |
| 815 | private class ConnectedThread extends Thread { |
| 816 | private final BluetoothSocket mmSocket; |
| 817 | private final InputStream mmInStream; |
| 818 | private final OutputStream mmOutStream; |
| 819 | |
| 820 | public ConnectedThread(BluetoothSocket socket) { |
| 821 | mmSocket = socket; |
| 822 | InputStream tmpIn = null; |
| 823 | OutputStream tmpOut = null; |
| 824 | |
| 825 | // Get the input and output streams, using temp objects because |
| 826 | // member streams are final |
| 827 | try { |
| 828 | tmpIn = socket.getInputStream(); |
| 829 | tmpOut = socket.getOutputStream(); |
| 830 | } catch (IOException e) { } |
| 831 | |
| 832 | mmInStream = tmpIn; |
| 833 | mmOutStream = tmpOut; |
| 834 | } |
| 835 | |
| 836 | public void run() { |
| 837 | byte[] buffer = new byte[1024]; // buffer store for the stream |
| 838 | int bytes; // bytes returned from read() |
| 839 | |
| 840 | // Keep listening to the InputStream until an exception occurs |
| 841 | while (true) { |
| 842 | try { |
| 843 | // Read from the InputStream |
| 844 | bytes = mmInStream.read(buffer); |
| 845 | // Send the obtained bytes to the UI activity |
| 846 | mHandler.obtainMessage(MESSAGE_READ, bytes, -1, buffer) |
| 847 | .sendToTarget(); |
| 848 | } catch (IOException e) { |
| 849 | break; |
| 850 | } |
| 851 | } |
| 852 | } |
| 853 | |
| 854 | /* Call this from the main activity to send data to the remote device */ |
| 855 | public void write(byte[] bytes) { |
| 856 | try { |
| 857 | mmOutStream.write(bytes); |
| 858 | } catch (IOException e) { } |
| 859 | } |
| 860 | |
| 861 | /* Call this from the main activity to shutdown the connection */ |
| 862 | public void cancel() { |
| 863 | try { |
| 864 | mmSocket.close(); |
| 865 | } catch (IOException e) { } |
| 866 | } |
| 867 | } |
| 868 | </pre> |
| 869 | |
| 870 | <p>The constructor acquires the necessary streams and once executed, the thread |
| 871 | will wait for data to come through the InputStream. When {@link |
| 872 | java.io.InputStream#read(byte[])} returns with |
| 873 | bytes from the stream, the data is sent to the main activity using a member |
| 874 | Handler from the parent class. Then it goes back and waits for more bytes from |
| 875 | the stream.</p> |
| 876 | |
| 877 | <p>Sending outgoing data is as simple as calling the thread's |
| 878 | <code>write()</code> method from the main activity and passing in the bytes to |
| 879 | be sent. This method then simply calls {@link |
| 880 | java.io.OutputStream#write(byte[])} to send the data to the remote device.</p> |
| 881 | |
| 882 | <p>The thread's <code>cancel()</code> method is important so that the connection |
| 883 | can be |
| 884 | terminated at any time by closing the {@link android.bluetooth.BluetoothSocket}. |
| 885 | This should always be called when you're done using the Bluetooth |
| 886 | connection.</p> |
| 887 | |
| 888 | <div class="special"> |
| 889 | <p>For a demonstration of using the Bluetooth APIs, see the <a |
| 890 | href="{@docRoot}resources/samples/BluetoothChat/index.html">Bluetooth Chat sample app</a>.</p> |
| 891 | </div> |
| 892 | |
| 893 | <h2 id="Profiles">Working with Profiles</h2> |
| 894 | |
| 895 | <p>Starting in Android 3.0, the Bluetooth API includes support for working with |
| 896 | Bluetooth profiles. A <em>Bluetooth profile</em> is a wireless interface |
| 897 | specification for Bluetooth-based communication between devices. An example |
| 898 | is the Hands-Free profile. For a mobile phone to connect to a wireless headset, |
| 899 | both devices must support the Hands-Free profile. </p> |
| 900 | |
| 901 | <p>You can implement the interface {@link android.bluetooth.BluetoothProfile} to write |
| 902 | your own classes to support a particular Bluetooth profile. The Android |
| 903 | Bluetooth API provides implementations for the following Bluetooth |
| 904 | profiles:</p> |
| 905 | <ul> |
| 906 | |
| 907 | <li><strong>Headset</strong>. The Headset profile provides support for |
| 908 | Bluetooth headsets to be used with mobile phones. Android provides the {@link |
| 909 | android.bluetooth.BluetoothHeadset} class, which is a proxy for controlling the |
| 910 | Bluetooth Headset Service via interprocess communication (<a |
| 911 | href="{@docRoot}guide/components/processes-and-threads.html#IPC">IPC</a |
| 912 | >). This includes both Bluetooth Headset and Hands-Free (v1.5) profiles. The |
| 913 | {@link android.bluetooth.BluetoothHeadset} class includes support for AT commands. |
| 914 | For more discussion of this topic, see <a href="#AT-Commands">Vendor-specific AT commands</a></li> |
| 915 | |
| 916 | <li><strong>A2DP</strong>. The Advanced Audio Distribution Profile (A2DP) |
| 917 | profile defines how high quality audio can be streamed from one device to |
| 918 | another over a Bluetooth connection. Android provides the {@link |
| 919 | android.bluetooth.BluetoothA2dp} class, which is a proxy for controlling |
| 920 | the Bluetooth A2DP Service via IPC.</li> |
| 921 | |
| 922 | <li><strong>Health Device</strong>. Android 4.0 (API level 14) introduces |
| 923 | support for the Bluetooth Health Device Profile (HDP). This lets you create |
| 924 | applications that use Bluetooth to communicate with health devices that support |
| 925 | Bluetooth, such as heart-rate monitors, blood meters, thermometers, scales, and |
| 926 | so on. For a list of supported devices and their corresponding device data |
| 927 | specialization codes, refer to <strong>Bluetooth Assigned Numbers</strong> at <a |
| 928 | href="http://www.bluetooth.org">www.bluetooth.org</a>. Note that these values |
| 929 | are also referenced in the ISO/IEEE 11073-20601 [7] specification as |
| 930 | MDC_DEV_SPEC_PROFILE_* in the Nomenclature Codes Annex. For more discussion of |
| 931 | HDP, see <a href="#HDP">Health Device Profile</a>.</li> |
| 932 | |
| 933 | </ul> |
| 934 | |
| 935 | <p>Here are the basic steps for working with a profile:</p> |
| 936 | <ol> |
| 937 | |
| 938 | <li>Get the default adapter, as described in |
| 939 | <a href="{@docRoot}guide/topics/connectivity/bluetooth.html#SettingUp">Setting Up |
| 940 | Bluetooth</a>.</li> |
| 941 | |
| 942 | <li>Use {@link |
| 943 | android.bluetooth.BluetoothAdapter#getProfileProxy(android.content.Context, |
| 944 | android.bluetooth.BluetoothProfile.ServiceListener, int) getProfileProxy()} to |
| 945 | establish a connection to the profile proxy object associated with the profile. |
| 946 | In the example below, the profile proxy object is an instance of {@link |
| 947 | android.bluetooth.BluetoothHeadset}. </li> |
| 948 | |
| 949 | <li>Set up a {@link android.bluetooth.BluetoothProfile.ServiceListener}. This |
| 950 | listener notifies {@link android.bluetooth.BluetoothProfile} IPC clients when |
| 951 | they have been connected to or disconnected from the service.</li> |
| 952 | |
| 953 | <li>In {@link |
| 954 | android.bluetooth.BluetoothProfile.ServiceListener#onServiceConnected(int, |
| 955 | android.bluetooth.BluetoothProfile) onServiceConnected()}, get a handle |
| 956 | to the profile proxy object.</li> |
| 957 | |
| 958 | <li>Once you have the profile proxy object, you can use it to monitor the |
| 959 | state of the connection and perform other operations that are relevant to that |
| 960 | profile.</li> |
| 961 | </ol> |
| 962 | |
| 963 | <p> For example, this code snippet shows how to connect to a {@link |
| 964 | android.bluetooth.BluetoothHeadset} proxy object so that you can control the |
| 965 | Headset profile:</p> |
| 966 | |
| 967 | <pre>BluetoothHeadset mBluetoothHeadset; |
| 968 | |
| 969 | // Get the default adapter |
| 970 | BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter(); |
| 971 | |
| 972 | // Establish connection to the proxy. |
| 973 | mBluetoothAdapter.getProfileProxy(context, mProfileListener, BluetoothProfile.HEADSET); |
| 974 | |
| 975 | private BluetoothProfile.ServiceListener mProfileListener = new BluetoothProfile.ServiceListener() { |
| 976 | public void onServiceConnected(int profile, BluetoothProfile proxy) { |
| 977 | if (profile == BluetoothProfile.HEADSET) { |
| 978 | mBluetoothHeadset = (BluetoothHeadset) proxy; |
| 979 | } |
| 980 | } |
| 981 | public void onServiceDisconnected(int profile) { |
| 982 | if (profile == BluetoothProfile.HEADSET) { |
| 983 | mBluetoothHeadset = null; |
| 984 | } |
| 985 | } |
| 986 | }; |
| 987 | |
| 988 | // ... call functions on mBluetoothHeadset |
| 989 | |
| 990 | // Close proxy connection after use. |
| 991 | mBluetoothAdapter.closeProfileProxy(mBluetoothHeadset); |
| 992 | </pre> |
| 993 | |
| 994 | |
| 995 | |
| 996 | <h3 id="AT-Commands">Vendor-specific AT commands</h3> |
| 997 | |
| 998 | <p>Starting in Android 3.0, applications can register to receive system |
| 999 | broadcasts of pre-defined vendor-specific AT commands sent by headsets (such as |
| 1000 | a Plantronics +XEVENT command). For example, an application could receive |
| 1001 | broadcasts that indicate a connected device's battery level and could notify the |
| 1002 | user or take other action as needed. Create a broadcast receiver for the {@link |
| 1003 | android.bluetooth.BluetoothHeadset#ACTION_VENDOR_SPECIFIC_HEADSET_EVENT} intent |
| 1004 | to handle vendor-specific AT commands for the headset.</p> |
| 1005 | |
| 1006 | <h3 id="HDP">Health Device Profile</h3> |
| 1007 | |
| 1008 | <p>Android 4.0 (API level 14) introduces support for the Bluetooth Health Device |
| 1009 | Profile (HDP). This lets you create applications that use Bluetooth to |
| 1010 | communicate with health devices that support Bluetooth, such as heart-rate |
| 1011 | monitors, blood meters, thermometers, and scales. The Bluetooth Health API |
| 1012 | includes the classes {@link android.bluetooth.BluetoothHealth}, {@link |
| 1013 | android.bluetooth.BluetoothHealthCallback}, and {@link |
| 1014 | android.bluetooth.BluetoothHealthAppConfiguration}, which are described in <a |
| 1015 | href="#TheBasics">The Basics</a>. </p> |
| 1016 | |
| 1017 | <p>In using the Bluetooth Health API, it's helpful to understand these key HDP concepts:</p> |
| 1018 | <table> |
| 1019 | <tr> |
| 1020 | <th>Concept</th> |
| 1021 | <th>Description</th> |
| 1022 | </tr> |
| 1023 | <tr> |
| 1024 | <td><strong>Source</strong></td> |
| 1025 | |
| 1026 | <td>A role defined in HDP. A <em>source</em> is a health device that |
| 1027 | transmits medical data (weight scale, glucose meter, thermometer, etc.) to a |
| 1028 | smart device such as an Android phone or tablet. </td> |
| 1029 | </tr> |
| 1030 | <tr> |
| 1031 | <td><strong>Sink</strong></td> |
| 1032 | |
| 1033 | <td>A role defined in HDP. In HDP, a <em>sink</em> is the smart device that |
| 1034 | receives the medical data. In an Android HDP application, the sink is |
| 1035 | represented by a {@link android.bluetooth.BluetoothHealthAppConfiguration} |
| 1036 | object.</td> |
| 1037 | </tr> |
| 1038 | <tr> |
| 1039 | <td><strong>Registration</strong></td> |
| 1040 | <td>Refers to registering a sink for a particular health device.</td> |
| 1041 | </tr> |
| 1042 | <tr> |
| 1043 | <td><strong>Connection</strong></td> |
| 1044 | |
| 1045 | <td>Refers to opening a channel between a health device and a smart device |
| 1046 | such as an Android phone or tablet.</td> |
| 1047 | </tr> |
| 1048 | </table> |
| 1049 | |
| 1050 | <h4>Creating an HDP Application</h4> |
| 1051 | |
| 1052 | <p>Here are the basic steps involved in creating an Android HDP application:</p> |
| 1053 | <ol> |
| 1054 | |
| 1055 | <li>Get a reference to the {@link android.bluetooth.BluetoothHealth} proxy |
| 1056 | object. <p>Similar to regular headset and A2DP profile devices, you must call |
| 1057 | {@link android.bluetooth.BluetoothAdapter#getProfileProxy getProfileProxy()} |
| 1058 | with a {@link android.bluetooth.BluetoothProfile.ServiceListener} and the {@link |
| 1059 | android.bluetooth.BluetoothProfile.ServiceListener#HEALTH} profile type to |
| 1060 | establish a connection with the profile proxy object.</p> </li> |
| 1061 | |
| 1062 | <li>Create a {@link android.bluetooth.BluetoothHealthCallback} and register an |
| 1063 | application configuration |
| 1064 | ({@link android.bluetooth.BluetoothHealthAppConfiguration}) |
| 1065 | that acts as a health |
| 1066 | sink.</li> |
| 1067 | |
| 1068 | <li>Establish a connection to a health device. Some devices will initiate the |
| 1069 | connection. It is unnecessary to carry out this step for those devices.</li> |
| 1070 | |
| 1071 | <li>When connected successfully to a health device, read/write to the health |
| 1072 | device using the file descriptor. <p>The received data needs to be interpreted |
| 1073 | using a health manager which implements the IEEE 11073-xxxxx |
| 1074 | specifications.</p></li> |
| 1075 | |
| 1076 | <li>When done, close the health channel and unregister the application. The |
| 1077 | channel also closes when there is extended inactivity.</li> |
| 1078 | </ol> |
| 1079 | |
| 1080 | <p>For a complete code sample that illustrates these steps, see <a |
| 1081 | href="{@docRoot}resources/samples/BluetoothHDP/index.html">Bluetooth HDP (Health |
| 1082 | Device Profile)</a>. </p> |