read40.md

Intent Filters

Allowing Other Apps to Start Your Activity

To allow other apps to start your activity in this way, you need to add an <intent-filter> element in your manifest file for the corresponding <activity> element.

Add an Intent Filter

• Action A string naming the action to perform. Usually one of the platform-defined values such as ACTION_SEND or ACTION_VIEW. Specify this in your intent filter with the <action> element.
• Data A description of the data associated with the intent. Specify this in your intent filter with the <data> element.
• Category There are several different categories supported by the system, but most are rarely used. Specify this in your intent filter with the <category> element.

For example, here's an activity with an intent filter that handles the ACTION_SEND intent when the data type is either text or an image:

 <activity android:name="ShareActivity">
  <intent-filter>
    <action android:name="android.intent.action.SEND"/>
    <category android:name="android.intent.category.DEFAULT"/>
    <data android:mimeType="text/plain"/>
    <data android:mimeType="image/*"/>
  </intent-filter>
 </activity>

For example, suppose your activity handles both text and images for both the ACTION_SEND and ACTION_SENDTO intents.

 <activity android:name="ShareActivity">
  <!-- filter for sending text; accepts SENDTO action with sms URI schemes -->
   <intent-filter>
    <action android:name="android.intent.action.SENDTO"/>
    <category android:name="android.intent.category.DEFAULT"/>
    <data android:scheme="sms" />
    <data android:scheme="smsto" />
  </intent-filter>
  <!-- filter for sending text or images; accepts SEND action and text or image data -->
  <intent-filter>
    <action android:name="android.intent.action.SEND"/>
    <category android:name="android.intent.category.DEFAULT"/>
    <data android:mimeType="image/*"/>
    <data android:mimeType="text/plain"/>
   </intent-filter>
 </activity>

Handle the Intent in Your Activity

• Call getIntent() to retrieve the Intent that started the activity. For example:

  @Override
  protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
  
   setContentView(R.layout.main);
  
   // Get the intent that started this activity
   Intent intent = getIntent();
   Uri data = intent.getData();
  
   // Figure out what to do based on the intent type
   if (intent.getType().indexOf("image/") != -1) {
    // Handle intents with image data ...
   } else if (intent.getType().equals("text/plain")) {
    // Handle intents with text ...
  }
  

  }

Return a Result

• Call setResult() to specify the result code and result Intent. When your operation is done and the user should return to the original activity, call finish() to close (and destroy) your activity. For example:

  // Create intent to deliver some kind of result data
  Intent result = new Intent("com.example.RESULT_ACTION", Uri.parse("content://result_uri"));
  setResult(Activity.RESULT_OK, result);
  finish();