Android Galaxy S4 -- Activity that is visible over lock screen

Question

A few years ago, I wrote an alarm app that worked on Android 2, and I'm now trying to upgrade it to work on Android 4. Specifically, on the Samsung Galaxy S4.

On Android 2, if the phone was sleeping, it would wake the phone up and display a "Snooze or Dismiss" screen over the lock screen.

On Android 4, it wakes the phone up, but you have to unlock it, then open the notifications area, then click the alarm's notification, before you can hit "Dismiss."

I have always been using this code to do the waking:

getWindow().addFlags(WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED
            | WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD
            | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
            | WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON);

I have read 8 different stackoverflow questions on this matter. Most of them give the code above, which worked for me years ago in Android 2 but doesn't work in Android 4. But none of them have helped me solve this problem. Here are the questions that I read and tried:

Android: remove or disable programmatically the Lock Screen on Samsung Galaxy S2 device

How to display a fullscreen TYPE_SYSTEM_ALERT window?

How do I create an Activity that is visible on top of the lock screen

How to start a dialog (like alarm dimiss /snooze) that can be clicked without unlocking the screen

Android activity over default lock screen

android device locked, yet want alarm to sound and dialog to appear

Android dialog over lock screen

Show dialog with touch events over lockscreen in Android 2.3

Does anyone have any ideas about what's changed in Android 4 that may have caused this?

EDIT: Here is one of the simplest examples I've seen of an alarm dialog that doesn't come up "minimized." It does not, as written, appear over the lockscreen, but you can fix that with WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED

http://wptrafficanalyzer.in/blog/setting-up-alarm-using-alarmmanager-and-waking-up-screen-and-unlocking-keypad-on-alarm-goes-off-in-android/

It's written with a FragmentActivity and a DialogFragment, but it still works as an Activity. It uses an AlertDialog.Builder to make the dialog, and if you try to do it with an XML layout, it won't work. Why?

Answer 1

I figured it out, and the answer was very different from what I expected.

This piece of code was included in the alarm clock sample from Android 2, in the AlarmAlert.java Activity:

@Override
protected void onStop() {
    super.onStop();
    // Don't hang around.
    finish();
}

For reference, you can see the file from the example code in Git's past right here, containing the above onStop function. It never caused a problem in Android 2.

But in Android 4, if the phone was off, this onStop would fire right before the phone woke up, effectively "minimizing" the Activity. Once I removed this function, it immediately worked again.

But I wonder, is this the problem that other people like @radley and @Guardanis are getting? It seems unlikely, but please let me know if this fixes your problems too.

If you're visiting this answer in the future, and you're getting this problem, what I would try is:

1. Take out any onStop functions.

2. Add this code to the Activity:

   getWindow().addFlags(WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED
           | WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD
           | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
           | WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON);
   

3. Make sure you're using a full screen theme, and not a dialog theme.

4. This didn't make a difference for me, but you could try setting showOnLockScreen explicitly in the manifest: <activity android:name="com.example.MyActivity" android:showOnLockScreen="true"/>

5. A second thing that didn't make a difference for me but you might try is adding the flag WindowManager.LayoutParams.FLAG_FULLSCREEN

I hope this helps other people!

Answer 2

In Kotlin,

For Api level 28 or less, you can simply add below method in your activity that needs to be opened:

override fun onAttachedToWindow() {
    super.onAttachedToWindow()
    toBeShownOnLockScreen()
}

private fun toBeShownOnLockScreen() {
    window.addFlags(
        WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD
                or WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
    )
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O_MR1) {
        setTurnScreenOn(true)
        setShowWhenLocked(true)
    } else {
        window.addFlags(
            WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON
                    or WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED
        )
    }
}

And to make it work on Android Pie and above, in additional to above step, we need to set in AndroidManifest as well:

<activity
    android:name=".view.activity.LockScreenActivity"
    android:showOnLockScreen="true"
    android:showWhenLocked="true"
    android:turnScreenOn="true" />

I have tested this code from Api level 21 to 29, and works like charm!

Answer 3

Not sure if this is the problem in all cases, but the documentation on ShowWhenLocked says it applies only to the top-most full-screen window. I had a window themed as a dialog which was not working, but it worked fine once I changed it to a regular full-screen window.

Answer 4

One of the questions you linked to has an answer that appeared to solve this issue for me.

This is the code I am using which appears to be working:

@Override
public void onAttachedToWindow() {
        Window window = getWindow();

        window.addFlags(WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON
                | WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED
                | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
                | WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD
                | WindowManager.LayoutParams.FLAG_FULLSCREEN);

        super.onAttachedToWindow();
    }

I'm also explicitly declaring this in the activity definition in the manifest:

<activity 
    android:name="com.example.MyActivity"
    android:label="@string/app_name"
    android:showOnLockScreen="true"
    >

Android activity over default lock screen

Answer 5

Right - So I have been struggling with this one recently but with a 5.0.2 Galaxy Tab A. Unsurprisingly what works on every other device does not work on Samsung (this has been the case since the first Samsung Galaxy device, they break something new each release!)

The general solution for showing an Activity over the lock screen for most devices is

//wake up device and show even when on lock screen
getWindow().addFlags(WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD |
        WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED |
        WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON |
        WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON |
        WindowManager.LayoutParams.FLAG_FULLSCREEN);

However this does not work for samsung devices. Removing FLAG_DISMISS_KEYGUARD however does this trick.

Looking at the docs for this flag we have

Window flag: when set the window will cause the keyguard to be dismissed, only if it is not a secure lock keyguard. Because such a keyguard is not needed for security, it will never re-appear if the user navigates to another window (in contrast to FLAG_SHOW_WHEN_LOCKED, which will only temporarily hide both secure and non-secure keyguards but ensure they reappear when the user moves to another UI that doesn't hide them). If the keyguard is currently active and is secure (requires an unlock pattern) than the user will still need to confirm it before seeing this window, unless FLAG_SHOW_WHEN_LOCKED has also been set.

and for FLAG_SHOW_WHEN_LOCKED we have

Window flag: special flag to let windows be shown when the screen is locked. This will let application windows take precedence over key guard or any other lock screens. Can be used with FLAG_KEEP_SCREEN_ON to turn screen on and display windows directly before showing the key guard window. Can be used with FLAG_DISMISS_KEYGUARD to automatically fully dismisss non-secure keyguards. This flag only applies to the top-most full-screen window.

You can see they can be used together but it seems samsung will not bother with FLAG_SHOW_WHEN_LOCKED if the device is locked and FLAG_DISMISS_KEYGUARD is present. My app requires a lock screen to be setup so removing the dismiss keyguard flag actually allows me to show full screen Activities over the lock screen. Yay for me, nay for samsung.