SYSTEM_ALERT_WINDOW选项变灰（不可更改）

Question

I'm working on an App that is uses the SYSTEM_ALERT_WINDOW permission. I've added the permission to the Manifest.

In my activity, I've added the following code to ask permission at runtime.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    Button button = (Button) findViewById(R.id.button);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                Intent myIntent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION, Uri.parse("package:" + getPackageName()));
                startActivityForResult(myIntent, 5469);
            }
        }
    });
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    switch (requestCode) {
        case 5469: {
            Toast.makeText(this,"Permission Granted!",Toast.LENGTH_SHORT).show();
            return;
        }
    }
}

But, as the "Draw over other Apps" setting page is opened, the 'switch button' to allow the permission is greyed out(not clickable).

Given below is the screenshot :

Code for Manifest :

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.graphics.unlockbrtest">

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

    <receiver
        android:name=".UnlockReceiver"
        android:enabled="true">
        <intent-filter>
            <action android:name="android.intent.action.USER_PRESENT" />
        </intent-filter>
    </receiver>

    <activity
        android:name=".FloatingActivity"
        android:theme="@android:style/Theme.Dialog" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

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

</application>

What am I doing wrong that the option is greyed out? Thanks in advance!

Answer 1

将<uses-permission>元素移动为<manifest>的直接子元素，在<application>元素之外。