Android 6.0+ 請求 SYSTEM_ALERT_WINDOW權限

Reference:

http://stackoverflow.com/questions/32652533/android-system-overlay-window
http://caiyao.name/2016/03/02/Android-6-0%E8%BF%90%E8%A1%8C%E6%97%B6%E6%9D%83%E9%99%90%E5%B0%8F%E7%BB%93/

Error message:

Unable to add window android.view.ViewRoot$W@XXXXXXXX — permission denied for this window type

Code snippet:

在 Android 6.0+ (SDK 23+) 用 TYPE_SYSTEM_ALERT，即使在 Manifest裡有宣告 permission

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

依舊會出現上面的 Error message.
這時候要先透過 Settings.canDrawOverlays檢查 app是否有權限，如果沒有的話，發出 Settings.ACTION_MANAGE_OVERLAY_PERMISSION 的 Intent，讓使用者打開權限

@Overrideprotected void onResume() {
    super.onResume();

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
        if(!Settings.canDrawOverlays(this)){
            requestAlertWindowPermission();
        } else{
            // do something
        }
    } else{
        // do something
    }
}

private static final int REQUEST_CODE = 1;
private  void requestAlertWindowPermission() {
    Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION);
    intent.setData(Uri.parse("package:" + getPackageName()));
    startActivityForResult(intent, REQUEST_CODE);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == REQUEST_CODE) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (Settings.canDrawOverlays(this)) {
                Log.i(TAG, "onActivityResult granted");
                // do something
            } else{
                Log.i(TAG, "onActivityResult not granted");
            }
        }
    }
}