| page.title=Checkboxes |
| |
| @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.CheckBox}</li> |
| </ol> |
| </div> |
| </div> |
| |
| <p>Checkboxes allow the user to select one or more options from a set. Typically, you should |
| present each checkbox option in a vertical list.</p> |
| |
| <img src="{@docRoot}images/ui/checkboxes.png" alt="" /> |
| |
| <p>To create each checkbox option, create a {@link android.widget.CheckBox} in your layout. Because |
| a set of checkbox options allows the user to select multiple items, each checkbox is managed |
| separately and you must register a click listener for each one.</p> |
| |
| <h2 id="HandlingEvents">Responding to Click Events</h2> |
| |
| <p>When the user selects a checkbox, the {@link android.widget.CheckBox} object receives an |
| on-click event.</p> |
| |
| <p>To define the click event handler for a checkbox, add the <code><a |
| href="/reference/android/R.attr.html#onClick">android:onClick</a></code> attribute to the |
| <code><CheckBox></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.CheckBox} objects in a list:</p> |
| |
| <pre> |
| <?xml version="1.0" encoding="utf-8"?> |
| <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" |
| android:orientation="vertical" |
| android:layout_width="fill_parent" |
| android:layout_height="fill_parent"> |
| <CheckBox android:id="@+id/checkbox_meat" |
| android:layout_width="wrap_content" |
| android:layout_height="wrap_content" |
| android:text="@string/meat" |
| android:onClick="onCheckboxClicked"/> |
| <CheckBox android:id="@+id/checkbox_cheese" |
| android:layout_width="wrap_content" |
| android:layout_height="wrap_content" |
| android:text="@string/cheese" |
| android:onClick="onCheckboxClicked"/> |
| </LinearLayout> |
| </pre> |
| |
| <p>Within the {@link android.app.Activity} that hosts this layout, the following method handles the |
| click event for both checkboxes:</p> |
| |
| <pre> |
| public void onCheckboxClicked(View view) { |
| // Is the view now checked? |
| boolean checked = ((CheckBox) view).isChecked(); |
| |
| // Check which checkbox was clicked |
| switch(view.getId()) { |
| case R.id.checkbox_meat: |
| if (checked) |
| // Put some meat on the sandwich |
| else |
| // Remove the meat |
| break; |
| case R.id.checkbox_cheese: |
| if (checked) |
| // Cheese me |
| else |
| // I'm lactose intolerant |
| break; |
| // TODO: Veggie sandwich |
| } |
| } |
| </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> |