java - Android System overlay window

Question

I'm trying to create a system overlay. But I keep getting "permission denied". I'm using SDK version 23.

My manifest file:

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

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

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name=".activity.MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

</manifest>

The code I use to create the overlay:

    //mView = new HUDView(this);
    mButton = new Button(this);
    mButton.setText("Overlay button");
    mButton.setOnTouchListener(this);

    WindowManager.LayoutParams params = new WindowManager.LayoutParams(
            WindowManager.LayoutParams.WRAP_CONTENT,
            WindowManager.LayoutParams.WRAP_CONTENT,
            WindowManager.LayoutParams.TYPE_SYSTEM_ALERT,
            WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH,
            PixelFormat.TRANSLUCENT);
    params.gravity = Gravity.RIGHT | Gravity.TOP;
    params.setTitle("Load Average");
    WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);
    wm.addView(mButton, params);

Answer 1

First, there is no permission named SYSTEM_OVERLAY_WINDOW. It is SYSTEM_ALERT_WINDOW.

Second, if your targetSdkVersion is 23 or higher, and you are running on Android 6.0+ devices, your app will not get this permission at the outset. Call Settings.canDrawOverlays() to see if you have the permission, and use ACTION_MANAGE_OVERLAY_PERMISSION to lead the user over to Settings if you do not.