java.lang.SecurityException: No active admin owned by uid 10034 for policy #3

public class tempActivity extends Activity {

	private static final String TAG = "tempActivity"; 

	private DevicePolicyManager policyManager;

	private ComponentName componentName;



	@Override

	protected void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		setContentView(R.layout.temp);

		Log.e(TAG, "Activity created~");

		policyManager = (DevicePolicyManager) getSystemService(Context.DEVICE_POLICY_SERVICE);

		componentName = new ComponentName(this, AdminReceiver.class);

		mylock();

	}



	private void mylock() {

		boolean active = policyManager.isAdminActive(componentName);

		if (!active) { // 若无权限

			Log.e(TAG, "没有权限~");

			activeManage(); // 去获得权限

			policyManager.lockNow(); // 并锁屏

		} else {

			Log.e(TAG, "已经有权限");

			policyManager.lockNow(); // 直接锁屏

		}

		this.finish();

	}



	private void activeManage() {

		Log.e(TAG, "activeManage");

		Intent intent = new Intent(DevicePolicyManager.ACTION_ADD_DEVICE_ADMIN);

		intent.putExtra(DevicePolicyManager.EXTRA_DEVICE_ADMIN, componentName);

		intent.putExtra(DevicePolicyManager.EXTRA_ADD_EXPLANATION, "developers：liushuaikobe");

		startActivityForResult(intent, 1);

	}

}