Avoid Activity resuming when app goes in background

Question

In my application I have three activities:

    <activity
        android:name="com.example.myapp.SplashScreenActivity"
        android:exported="true"
        android:launchMode="singleInstance"
        android:noHistory="true"
        android:screenOrientation="sensorLandscape" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name="com.example.myapp.MainActivity"
        android:exported="false"
        android:launchMode="singleInstance"
        android:screenOrientation="sensorLandscape" >
    </activity>
    <activity
        android:name="com.example.myapp.ListActivity"
        android:exported="false"
        android:launchMode="singleTop"
        android:screenOrientation="sensorLandscape" >
        <meta-data
            android:name="android.support.PARENT_ACTIVITY"
            android:value="com.example.myapp.MainActivity" />
    </activity>

The first one is the LAUNCHER , SplashScreenActivity , which is a splash screen that disappears quite soon and it's not shown in recent activities, it starts MainActivity . In MainActivity users can select a category and ListActivity shows the items belonging to the given category. This is done with the following code:

Intent i = new Intent(getActivity(),ListActivity.class);
i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
i.putExtra("category",mCategory);
startActivity(i);

In ListActivity the onResume method checks for the "category" extra and shows data accordingly. Since Activity launchMode is singleTop, I've also overridden the onNewIntent method to set the new Intent of the Activity .

This works properly if the app doesn't go in background: in this case, when I restart MainActivity and select a category, ListActivity resumes the old Activity showing data belonging to the previously chosen category.

How should I fix flags/launchMode in such way that my app doesn't resume ListActivity with the old data loaded?

Answer 1

You should not use the special launch modes. These are rarely required and only in very specific circumstances. Remove all the launchMode specifiers from your manifest. You also don't need to use these flags when launching ListActivity from MainActivity :

i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);

Your use of singleInstance launch mode is causing you all these problems.

Answer 2

Assuming you would ditch all the launchModes and Flags, then activity lifecycle gives you all the information needed to implement application as you have described - maybe there is somethings you have not added?

Once application goes to background, then ListActivity will be allowed to save its state, even if system will kill your process (lack of memory etc.), then still - launching back your app will first bring back ListActivity with previously saved instance state. So you will not have behaviour as you describe : when I restart MainActivity and select a category, ListActivity resumes the old Activity showing data belonging to the previously chosen category.

Still, if you need to keep to your current design, then you should somehow inform ListActivity of new data changes, question is if ListActivity.onNewIntent is being called at all in the case your describe? Have you tried adding Intent.FLAG_ACTIVITY_SINGLE_TOP : as per this blog entry: http://www.acnenomor.com/1094151p2/bug-onnewintent-not-called-for-singletop-activity-with-intentflagactivitynewtask ?