Android Lollipop - Bypass lock screen for popup activity

Question

I have Activity1 which is a list screen of items. Each item can be viewed in a separate Activity2 which is displayed as a popup. Activity1 can be launched from the background and displayed even when the screen is locked. Activity1 may also choose to automatically display the contents of an item in the list screen by starting Activity2. We can bypass the lock screen because both activities have the WindowManagerFlags.DismissKeyguard enabled in the OnCreate method.

Before Android Lollipop everything worked as expected. But now the popup Activity2 is not visible unless the device is manually unlocked. If I change Activity2 to be a full screen Activity then everything seems to work (Except transitioning from one activity to another will briefly display the lock screen). Any ideas on how to fix this cleanly?

Also, I have only tried the Galaxy S6/S6 Edge devices which have this new Knox security feature on them.

Edit I have changed Activity2 to be a DialogFragment instead of an Activity. This worked for me best because the suggested answer used code that is deprecated or obsolete depending on the target sdk. Activity1 is using the following flags to bypass the lock screen when needed.

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

Since Activity2 is now just a DialogFragment, it uses the window flags of the parent Activity1. I also remove those flags on the "android.intent.action.SCREEN_OFF" action so that the activity bypasses the lock screen only when launched as a notification and not every time the activity is at the top of the stack. Permissions mentioned in the answer are required.

Answer 1

For sure this snippet should help You (works with Lollipop):

        PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
        wl = pm.newWakeLock(PowerManager.FULL_WAKE_LOCK | PowerManager.ACQUIRE_CAUSES_WAKEUP, "My Tag");
        wl.acquire();

        KeyguardManager keyguardManager = (KeyguardManager) getSystemService(Context.KEYGUARD_SERVICE);
        keyguardLock = keyguardManager.newKeyguardLock("TAG");
        keyguardLock.disableKeyguard();

and when leaving Your activity (i.e. onStop(), onPause() and onDestroy()):

keyguardLock.reenableKeyguard();

Also, don't forget about permissions:

    <uses-permission android:name="android.permission.WAKE_LOCK" />
    <uses-permission android:name="android.permission.DISABLE_KEYGUARD" />