| page.title=Radio Buttons |
| page.tags="radiobutton","radiogroup" |
| @jd:body |
| |
| <div id="qv-wrapper"> |
| <div id="qv"> |
| <h2>In this document</h2> |
| <ol> |
| <li><a href="#HandlingEvents">Responding to Click Events</a></li> |
| </ol> |
| |
| <h2>Key classes</h2> |
| <ol> |
| <li>{@link android.widget.RadioButton}</li> |
| <li>{@link android.widget.RadioGroup}</li> |
| </ol> |
| </div> |
| </div> |
| |
| <p>Radio buttons allow the user to select one option from a set. You should use radio buttons for |
| optional sets that are mutually exclusive if you think that the user needs to see all available |
| options side-by-side. If it's not necessary to show all options side-by-side, use a <a |
| href="{@docRoot}guide/topics/ui/controls/spinner.html">spinner</a> instead.</p> |
| |
| <img src="{@docRoot}images/ui/radiobuttons.png" alt="" /> |
| |
| <p>To create each radio button option, create a {@link android.widget.RadioButton} in your layout. |
| However, because radio buttons are mutually exclusive, you must group them together inside a |
| {@link android.widget.RadioGroup}. By grouping them together, the system ensures that only one |
| radio button can be selected at a time.</p> |
| |
| <h2 id="HandlingEvents">Responding to Click Events</h2> |
| |
| <p>When the user selects one of the radio buttons, the corresponding {@link |
| android.widget.RadioButton} object receives an on-click event.</p> |
| |
| <p>To define the click event handler for a button, add the <code><a |
| href="/reference/android/R.attr.html#onClick">android:onClick</a></code> attribute to the |
| <code><RadioButton></code> element in your XML |
| layout. The value for this attribute must be the name of the method you want to call in response |
| to a click event. The {@link android.app.Activity} hosting the layout must then implement the |
| corresponding method.</p> |
| |
| <p>For example, here are a couple {@link android.widget.RadioButton} objects:</p> |
| |
| <pre> |
| <?xml version="1.0" encoding="utf-8"?> |
| <RadioGroup xmlns:android="http://schemas.android.com/apk/res/android" |
| android:layout_width="fill_parent" |
| android:layout_height="wrap_content" |
| android:orientation="vertical"> |
| <RadioButton android:id="@+id/radio_pirates" |
| android:layout_width="wrap_content" |
| android:layout_height="wrap_content" |
| android:text="@string/pirates" |
| android:onClick="onRadioButtonClicked"/> |
| <RadioButton android:id="@+id/radio_ninjas" |
| android:layout_width="wrap_content" |
| android:layout_height="wrap_content" |
| android:text="@string/ninjas" |
| android:onClick="onRadioButtonClicked"/> |
| </RadioGroup> |
| </pre> |
| |
| <p class="note"><strong>Note:</strong> The {@link android.widget.RadioGroup} is a subclass of |
| {@link android.widget.LinearLayout} that has a vertical orientation by default.</p> |
| |
| <p>Within the {@link android.app.Activity} that hosts this layout, the following method handles the |
| click event for both radio buttons:</p> |
| |
| <pre> |
| public void onRadioButtonClicked(View view) { |
| // Is the button now checked? |
| boolean checked = ((RadioButton) view).isChecked(); |
| |
| // Check which radio button was clicked |
| switch(view.getId()) { |
| case R.id.radio_pirates: |
| if (checked) |
| // Pirates are the best |
| break; |
| case R.id.radio_ninjas: |
| if (checked) |
| // Ninjas rule |
| break; |
| } |
| } |
| </pre> |
| |
| <p>The method you declare in the {@link android.R.attr#onClick android:onClick} attribute |
| must have a signature exactly as shown above. Specifically, the method must:</p> |
| <ul> |
| <li>Be public</li> |
| <li>Return void</li> |
| <li>Define a {@link android.view.View} as its only parameter (this will be the {@link |
| android.view.View} that was clicked)</li> |
| </ul> |
| |
| <p class="note"><strong>Tip:</strong> If you need to change the radio button state |
| yourself (such as when loading a saved {@link android.preference.CheckBoxPreference}), |
| use the {@link android.widget.CompoundButton#setChecked(boolean)} or {@link |
| android.widget.CompoundButton#toggle()} method.</p> |