Android lock screen multiple activities (a.k.a basic kiosk mode)

Question

I try to implement a kiosk mode application. I was able to lock down most of the possibilities to close the app or access system functions. Now, I was wondering, if it is possible have multiple activities in a lock screen. If I switch between multiple activities of my app, the default lock screen is shown for a short moment and then the app re-appears. If I just replace fragments, the app works like a charm.

I have the following code:

@Override
public void onAttachedToWindow() {
    getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG|WindowManager.LayoutParams.FLAG_FULLSCREEN);
    super.onAttachedToWindow();
}

and:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    getWindow().addFlags(WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED);
    getWindow().addFlags(WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD);
}

Does anyone has some hints how to improve the lock down without flickering?

Answer 1

Ok, this is how I solved the problem with kiosk mode in front of the keyguard.

First of all, I had to accept that the flag FLAG_SHOW_WHEN_LOCKED does not work well with multiple activities. So, we have to reduce the app to one single activity. But this implies another drawback: startActivity will still start new activities and causes the app to flicker.

To avoid that, I rewrote all Activities and made them Fragments. The MainActivity now keeps control over replacing the fragments when needed. It is declared in the Manifest as SingleTop:

<activity android:name="com.example.DashboardActivity"
        android:screenOrientation="landscape"
        android:launchMode="singleTop"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
            <category android:name="android.intent.category.DEFAULT" />
            <category android:name="android.intent.category.HOME"/>
        </intent-filter>
        ...
        <intent-filter>
            <action android:name="android.intent.action.VIEW" />
            <data android:scheme="video" />
            <category android:name="android.intent.category.BROWSABLE"/>
            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
        ...
    </activity>

The intents are handled with:

@Override
public void onNewIntent(Intent intent){
    super.onResume();
    dispatchIntent(intent);
}

public void dispatchIntent(Intent intent) {
    Log.d(TAG, "Intent:" + intent);

    Bundle extras = intent.getExtras();
    String action = intent.getAction();
    if(extras == null) { 
        extras = new Bundle();
    }
    Fragment fragment = null;

    if (Intent.ACTION_VIEW.equals(action)) {

        extras.putParcelable("uri", intent.getData());
        fragment = new VideoplayerFragment();

    } else {

        fragment = new DashboardFragment();

    }

    addOrReplaceFragment(fragment, extras);
}

private void addOrReplaceFragment(Fragment fragment, Bundle arguments) {
    if (fragment != null && findViewById(CONTENT_CONTAINERVIEW_ID) != null) {
        if(arguments != null) {
            fragment.setArguments(arguments);
        }

        FragmentTransaction ft = getFragmentManager().beginTransaction();
        String tag = fragment.getClass().getSimpleName();

        ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE)
          .addToBackStack(tag);

        if(getFragmentManager().findFragmentByTag(fragment.getClass().getSimpleName()) != null) {
            ft.replace(CONTENT_CONTAINERVIEW_ID, fragment, tag);
        } else {
            ft.add(CONTENT_CONTAINERVIEW_ID, fragment, tag);
        }

        ft.commit();

    }
}

Additionally, you should register for SCREEN_ON and SCREEN_OFF intents to launch the activity, if it was stopped due any reason.

Hope it helps someone.