Overlay Windows draw over the apps 

Tato Kutalia tatocaster tatocaster.me github.com/tatocaster twitter.com/@tatokutalia 

SYSTEM OVERLAY WINDOW 

SYSTEM OVERLAY WINDOW • SYSTEM_ALERT_WINDOW permission • extend Service class • add view to Window Manager 

SYSTEM_ALERT_WINDOW • granted automatically if installed from Play Store for 6.0 and up 

SYSTEM_ALERT_WINDOW • Settings -> Apps -> Draw over other apps below 6.0 OR new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION, Uri.parse("package:" + packageName)); 

Service Class • extend service • inflate or use custom / compound views • add to window manager service getSystemService(Context.WINDOW_SERVICE) • service stops immediately after activity destroy 

persistent service • return START_STICKY; always • and startForeground(int FOREGROUND_ID, Notification notification); those parameters allow to stay service alive and no matter what will persist over the top of apps // this will cause to show notification in status bar as long as the service retains. you can set pendingIntent to bind some actions on it 

some things to know we should pass WindowManager.LayoutParams along the actual view to the window manager service. WindowManager.LayoutParams windowLayoutParams = new WindowManager.LayoutParams(
 CANVAS_WIDTH,
 CANVAS_HEIGHT,
 WindowManager.LayoutParams.TYPE_PHONE,
 WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
 PixelFormat.TRANSLUCENT);
 windowLayoutParams.gravity = Gravity.BOTTOM | Gravity.END;
 with incorrect parameters, service may block touch events for lower app in view hierarchy (because our service is on top), even keyboard will not work. https://developer.android.com/reference/android/view/ WindowManager.LayoutParams.html 

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Some Examples https://github.com/tatocaster/SnowViewChatHead https://github.com/tatocaster/BuildNumberOverlay