java.lang.SecurityException: No active admin owned by uid 10237 for policy #3

I tried to lock the device after my alarm is stopped through the following code.

mDevicePolicyManager = (DevicePolicyManager)getSystemService(Context.DEVICE_POLICY_SERVICE);
mComponentName = new ComponentName(this,AlarmAdminReceiver.class);
Intent adminIntent = new Intent(DevicePolicyManager.ACTION_ADD_DEVICE_ADMIN);
adminIntent.putExtra(DevicePolicyManager.EXTRA_DEVICE_ADMIN,mComponentName);
adminIntent.putExtra(DevicePolicyManager.EXTRA_ADD_EXPLANATION,description);
        startActivityForResult(adminIntent,1);


 mDevicePolicyManager.lockNow();

I have done entry in manifest file as follows :

    <receiver
        android:name=".AlarmAdminReceiver"
        android:permission="android.permission.BIND_DEVICE_ADMIN" >
        <meta-data
            android:name="device_admin"
            android:resource="@xml/device_admin" />

        <intent-filter>
            <action android:name="android.app.action.DEVICE_ADMIN_ENABLED" />
        </intent-filter>
    </receiver>

and device_admin.xml file is

<device-admin xmlns:android="http://ift.tt/nIICcg" >
    <uses-policies>
        <force-lock />
    </uses-policies>
</device-admin>

But when trying to lock the device exception is thrown:

05-04 16:42:06.046 E/AndroidRuntime(23159): Caused by: java.lang.SecurityException: No active admin owned by uid 10237 for policy #3 05-04 16:42:06.046 E/AndroidRuntime(23159): at android.os.Parcel.readException(Parcel.java:1540) 05-04 16:42:06.046 E/AndroidRuntime(23159): at android.os.Parcel.readException(Parcel.java:1493) 05-04 16:42:06.046 E/AndroidRuntime(23159): at android.app.admin.IDevicePolicyManager$Stub$Proxy.lockNow(IDevicePolicyManager.java:3509) 05-04 16:42:06.046 E/AndroidRuntime(23159): at android.app.admin.DevicePolicyManager.lockNow(DevicePolicyManager.java:1506)

Please guide me on this to proceed further. Am I using the correct way to get authority for device to lock ?