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

I'm working on an app where I need to display a window with some info ON the Lock Screen (KeyGuard) without unlocking the phone. I figured I could probably do it with WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG

But every time my app crashes with the following error:

android.view.WindowManager$BadTokenException: Unable to add window android.view.ViewRootImpl$W@40ec8528 -- permission denied for this window type

These posts (here, here and here) all give the same answer. To add the following permission in the Manifest file.

android.permission.SYSTEM_ALERT_WINDOW

Solution that I have implemented but I am still getting the same error. Any idea of what I'm doing wrong?

Here are the permissions in my manifest file:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.droidpilot.keyguardwindow" >

<uses-sdk
    android:minSdkVersion="16"
    android:targetSdkVersion="21" />

<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_PHONE_STATE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.VIBRATE" />

And this is the code I use to add the Window to the lock screen

WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);
    LayoutInflater mInflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    mView = mInflater.inflate(R.layout.lock_screen_notif, null);

    WindowManager.LayoutParams params = new WindowManager.LayoutParams(
            WindowManager.LayoutParams.WRAP_CONTENT,
            WindowManager.LayoutParams.WRAP_CONTENT,
            WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG,
            WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED
                    | WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON
                    | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON,
            PixelFormat.TRANSLUCENT
    );

    wm.addView(mView, params);

Anybody got any idea?

P.S. I'm testing on an HTC Desire 620 DS running Android 4.4.2

Solution

For what should be completely obvious reasons, ordinary Apps are not allowed to create arbitrary windows on top of the lock screen. What do you think I could do if I created a window on your lockscreen that could perfectly imitate the real lockscreen so you couldn't tell the difference?

The technical reason for your error is the use of the TYPE_KEYGUARD_DIALOG flag - it requires android.permission.INTERNAL_SYSTEM_WINDOW which is a signature-level permission. This means that only Apps signed with the same certificate as the creator of the permission can use it.

The creator of android.permission.INTERNAL_SYSTEM_WINDOW is the Android system itself, so unless your App is part of the OS, you don't stand a chance.

There are well defined and well documented ways of notifying the user of information from the lockscreen. You can create customised notifications which show on the lockscreen and the user can interact with them.