[android] Android: Unable to add window. Permission denied for this window type

I guess you should differentiate the target (before and after Oreo)

int LAYOUT_FLAG;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    LAYOUT_FLAG = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;
} else {
    LAYOUT_FLAG = WindowManager.LayoutParams.TYPE_PHONE;
}

params = new WindowManager.LayoutParams(
    WindowManager.LayoutParams.WRAP_CONTENT,
    WindowManager.LayoutParams.WRAP_CONTENT,
    LAYOUT_FLAG,
    WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE | WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
    PixelFormat.TRANSLUCENT);