Restoring Unity3d Android application with another activity on top

Question

I need the following problem to be resolved:

From the UnityPlayerNativeActivity I am starting a standard Android activity (may be mine, may be with an ad from the ad network - nevermind). When the game is being hidden with this activity on top (not the Unity one) by pressing the home button, as a user I have two ways of restoring it:

• from the Recently used apps screen - the app is being restored to the same state, when it was minimized (that is what I expect to happen);
• from the launcher, what causes the game's UnityPlayerNativeActivity is being restored with losing all other activities, that have been opened on top of it.

These activities are lost somehow (in a way I don't exactly know, what has happened with them). My game's logic depends on the result of the processes happening there, ie. I need to know, that this particular activity has been exited in any specific way (give a callback for example).

Do you know how I can bring this Unity activity back from launcher with all activities above it, as it was while minimizing it?

I want to understand the difference between the ways of restoring the app from Recently used screen and the launcher. I guess it is related to the intent-filter section within AndroidManifest.xml file, which is included within UnityPlayerNativeActivity entry.

Answer 1

The solution turned out to be quite simple, but not so obvious.

It has turned out, that the AndroidManifest.xml configuration that is being produced by Unity by default is causing this problem. For the main activity that is being started from launcher the following parameters are defined (taken from decompiled app):

    <activity 
        android:alwaysRetainTaskState="true"
        android:clearTaskOnLaunch="true"
        android:configChanges="locale|fontScale|keyboard|keyboardHidden|mcc|mnc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|touchscreen|uiMode" 
        android:label="@string/app_name" 
        android:launchMode="singleTask" 
        android:name="com.unity3d.player.UnityPlayerNativeActivity" 
        android:screenOrientation="fullSensor" 
        launchMode="singleTask">

        <meta-data android:name="unityplayer.ForwardNativeEventsToDalvik" android:value="true"/>

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

The problematic behaviour is being caused by these 2 parameters:

    android:clearTaskOnLaunch="true"
    android:launchMode="singleTask"

When the I change them to:

    android:clearTaskOnLaunch="false"
    android:launchMode="standard"

Then the app is resuming fine from the launcher.

The correct parameters should be set as follows:

    <activity 
        android:alwaysRetainTaskState="true" 
        android:clearTaskOnLaunch="false"
        android:configChanges="locale|fontScale|keyboard|keyboardHidden|mcc|mnc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|touchscreen|uiMode" 
        android:label="@string/app_name" 
        android:launchMode="standard" 
        android:name="com.unity3d.player.UnityPlayerNativeActivity" 
        android:screenOrientation="fullSensor" 
        launchMode="standard">

        <meta-data android:name="unityplayer.ForwardNativeEventsToDalvik" android:value="true"/>

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

Note: While I am able to set the value android:clearTaskOnLaunch="false" for this activity explicitly, the launchMode parameter will be forced by Unity3d and set to "singleTask". I managed to change and check it by decompiling the app and rebuilding from these changed resources. I wonder if there is any elegant way to set this value.