Facebook deep linking on Android

问题:

I'm trying to implement Facebook's Deep Linking feature on my app and encountered the following scenario:

I have an activity called MainActivity which is declared like so:

    <activity
        android:name="com.mypackage.android.MainActivity">

        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

This activity + my package name are also declared in my app's settings on facebook developer website.

Once a link gets clicked on Facebook's app, I'm supposed to handle this event via the onCreate method of my activity. The following code handle the event:

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Uri target = getIntent().getData();

        if (target != null){
          // got here via Facebook deep link
          // once I'm done parsing the URI and deciding
          // which part of my app I should point the client to
          // I fire an intent for a new activity and
          // call finish() the current activity (MainActivity)
        }else{
          // activity was created in a normal fashion
        }
    }

All goes according to plan except for the following scenario:

1. User launched my app
2. MainActivity created
3. SecondaryActivity created
4. MainActivity finished
5. App goes to background via the device home button
6. Deep link gets clicked on Facebook's app

In this case my app goes to foreground again, but MainActivity's onCreate / onNewIntent don't get called, instead SecondaryActivity's onResume() gets called and restored to it's last state.

Note: I've tested this issue on a Samsung Nexus with Android 4.2.1 and got to this result, though when tested on Galaxy S1 with Android 2.3.5 it worked as I initially expected.

Any help would be greatly appreciated, Thank you.

回答1:

Facebook is starting your app from their own app by explicitly start your "MainActivity" (the one your provided them in the developer page).

by that - Android's default behavior is: if the application already runs, then calling again to startActivity() won't start new task from scratch, but only restore to foreground the already running task.

but the good news are that you can change this default behavior by adding to your MainActivity the android:launchMode="singleTask". it definition is:

the system creates a new task and instantiates the activity at the root of the new task. However, if an instance of the activity already exists in a separate task, the system routes the intent to the existing instance through a call to its onNewIntent() method, rather than creating a new instance. Only one instance of the activity can exist at a time.

from this point you could always respond to the starting intent, and from that point you can always navigate back to the task that already was in background(if exists) by restarting activity with both flags Intent.FLAG_ACTIVITY_SINGLE_TOP && Intent.FLAG_ACTIVITY_CLEAR_TOP combination

回答2:

See http://developer.android.com/guide/topics/manifest/activity-element.html

You can play with:

android:clearTaskOnLaunch
android:noHistory
android:launchMode

回答3:

You need to have more information in your intent filter:

<intent-filter>
   <action android:name="android.intent.action.VIEW"></action>
   <category android:name="android.intent.category.DEFAULT"></category>
   <category android:name="android.intent.category.BROWSABLE"></category>
   <data android:host="www.yoursite.com" android:scheme="http"></data>
</intent-filter>

This will capture links going to your site (make sure to change the URL), and direct them to whatever Activity you define this intent filter under.