Receiving Content from Other Apps

Just as your application can send data to other applications, so too can it easily receive data from applications. Think about how users interact with your application, and what data types you want to receive from other applications. For example, a social networking application would likely be interested in receiving text content, like an interesting web URL, from another app. The Google+ Android application accepts both text and single or multiple images. With this app, a user can easily start a new Google+ post with photos from the Android Gallery app.

Update Your Manifest

Intent filters inform the system what intents an application component is willing to accept. Similar to how you constructed an intent with action ACTION_SEND in the Send Content to Other Apps Using Intents lesson, you create intent filters in order to be able to receive intents with this action. You define an intent filter in your manifest, using the <intent-filter> element. For example, if your application handles receiving text content, a single image of any type, or multiple images of any type, your manifest would look like:

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

Note: For more information on intent filters and intent resolution please read Intents and Intent Filters

When another application tries to share any of these things by constructing an intent and passing it to startActivity(), your application will be listed as an option in the intent chooser. If the user selects your application, the corresponding activity (.ui.MyActivity in the example above) will be started. It is then up to you to handle the content appropriately within your code and UI.

Handle the Incoming Content

To handle the content delivered by an Intent, start by calling getIntent() to get Intent object. Once you have the object, you can examine its contents to determine what to do next. Keep in mind that if this activity can be started from other parts of the system, such as the launcher, then you will need to take this into consideration when examining the intent.

void onCreate (Bundle savedInstanceState) {
    ...
    // Get intent, action and MIME type
    Intent intent = getIntent();
    String action = intent.getAction();
    String type = intent.getType();
    if (Intent.ACTION_SEND.equals(action) && type != null) {
        if ("text/plain".equals(type)) {
            handleSendText(intent); // Handle text being sent
        } else if (type.startsWith("image/")) {
            handleSendImage(intent); // Handle single image being sent
        }
    } else if (Intent.ACTION_SEND_MULTIPLE.equals(action) && type != null) {
        if (type.startsWith("image/")) {
            handleSendMultipleImages(intent); // Handle multiple images being sent
        }
    } else {
        // Handle other intents, such as being started from the home screen
    }
    ...
}
void handleSendText(Intent intent) {
    String sharedText = intent.getStringExtra(Intent.EXTRA_TEXT);
    if (sharedText != null) {
        // Update UI to reflect text being shared
    }
}
void handleSendImage(Intent intent) {
    Uri imageUri = (Uri) intent.getParcelableExtra(Intent.EXTRA_STREAM);
    if (imageUri != null) {
        // Update UI to reflect image being shared
    }
}
void handleSendMultipleImages(Intent intent) {
    ArrayList<Uri> imageUris = intent.getParcelableArrayListExtra(Intent.EXTRA_STREAM);
    if (imageUris != null) {
        // Update UI to reflect multiple images being shared
    }
}

Caution: Take extra care to check the incoming data, you never know what some other application may send you. For example, the wrong MIME type might be set, or the image being sent might be extremely large. Also, remember to process binary data in a separate thread rather than the main ("UI") thread.

Updating the UI can be as simple as populating an EditText, or it can be more complicated like applying an interesting photo filter to an image. It's really specific to your application what happens next.