1

I want to simply lock the screen. Here's what I did:

public class MainActivity : ActionBarActivity() {
    var dpm: DevicePolicyManager? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        dpm = getSystemService(Context.DEVICE_POLICY_SERVICE) as DevicePolicyManager
    }

    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
        getMenuInflater()?.inflate(R.menu.menu_main, menu)
        dpm?.lockNow()
        return true
    }
}

It's in Kotlin but those who Java will understand it.

And manifest:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="android.me.com.app123" >
    <uses-permission
        android:name="android.permission.USES_POLICY_FORCE_LOCK">
    </uses-permission>

    <application
        android:allowBackup="true"

The error is:

android.me.com.app123 E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: android.me.com.app123, PID: 22964
    java.lang.SecurityException: No active admin owned by uid 10121 for policy #3
            at android.os.Parcel.readException(Parcel.java:1472)

Haven't I gotten enough permissions when I said "android.permission.USES_POLICY_FORCE_LOCK"? If not how to fix it?

Incerteza
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    It isn't clear if the answers below helped you or not with this question, because you did not accept the answer nor leave any comments. Can you review the answers so that it is clear whether this is helpful answer or if you still need help? – Jayson Minard Jan 02 '16 at 02:47

3 Answers3

2

In order to be able to lock the screen, you need to add a Device Admin as described here.

Second: If you got any properties, which you cant assign a value in the constructor, use the notNull-Delegate.

var dpm: DevicePolicyManager by Delegates.notNull()

When you access dpm before it is set, a NPE is thrown. If not, you wont have to check dpm for null all the time.

D3xter
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2

(previous answer links the correct tutorial)

Your received error because your app not enabled as Device Admin.

Key points for the (pof) implementation:

Policy definition resource (res/xml/....):

<device-admin>
    <uses-policies>
        <force-lock />
    </uses-policies>
</device-admin>

Broadcast receiver:

<receiver android:name="your.LockDeviceAdminReceiver" 
        android:permission="android.permission.BIND_DEVICE_ADMIN">
    <meta-data android:name="android.app.device_admin"
        android:resource="@xml/device_admin" />
    <intent-filter>
        <action android:name="android.app.action.DEVICE_ADMIN_ENABLED" />
    </intent-filter>
</receiver>

Check enabled state of your Admin (and start activity if not and handle the result):

val devicePolicyManager = getSystemService(Context.DEVICE_POLICY_SERVICE) 
    as DevicePolicyManager
val deviceAdminReceiver = ComponentName(context, 
    LockDeviceAdminReceiver::class.java)

if (devicePolicyManager.isAdminActive(deviceAdminReceiver)) {
   devicePolicyManager.lockNow()
} else {
    val intent = Intent(DevicePolicyManager.ACTION_ADD_DEVICE_ADMIN)
    intent.putExtra(DevicePolicyManager.EXTRA_DEVICE_ADMIN, 
        deviceAdminReceiver))
    startActivityForResult(intent, ENABLE_ADMIN_REQUEST_CODE);
}
Ferenc Boldog
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0

You would need 3 thing to do :

  1. add <receiver> to AndroidManifest
  2. make new xml file for <device-admin>
  3. make new .kt file for DeviceAdminReceiver

Here is an answer I already did (with code in Kotlin) : stackoverflow.com

QuartZ
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