如何锁定设备，但防止屏幕在android中关闭？

Question

I'm using DevicePolicyManager to lock the device while needed. what I want is to bring up the lock screen but using DevicePolicyManager and calling it's method lockNow() will lock the device and turn the screen off. how to prevent turning off the screen?

UPDATE: I have tried this:

public class LockMeNowActivity extends Activity {
protected PowerManager.WakeLock mWakeLock;
private DevicePolicyManager mgr = null;
private ComponentName cn = null;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(com.commonsware.android.lockme.R.layout.main);
    PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
    mWakeLock = pm.newWakeLock(PowerManager.SCREEN_DIM_WAKE_LOCK, "My Tag");
    cn = new ComponentName(this, AdminReceiver.class);
    mgr = (DevicePolicyManager) getSystemService(DEVICE_POLICY_SERVICE);
}

public void lockMeNow(View v) {
    if (mgr.isAdminActive(cn)) {

        mgr.lockNow();
    } else {
        Intent intent = new Intent(
                DevicePolicyManager.ACTION_ADD_DEVICE_ADMIN);
        intent.putExtra(DevicePolicyManager.EXTRA_DEVICE_ADMIN, cn);
        intent.putExtra(DevicePolicyManager.EXTRA_ADD_EXPLANATION,
                "For experimentation purposes only");
        startActivity(intent);
    }
}

public void pullWakeLock() {
    mWakeLock.acquire();
}

public void onPause() {
    super.onPause();
    pullWakeLock();
}

public void onResume() {
    super.onResume();
    releaseWakeLock();
}

public void releaseWakeLock() {
    mWakeLock.release();
}

}

Answer 1

Along with your lockNow(), add PowerManager.WakeLock :

Import

import android.os.PowerManager;

Global Variable

protected PowerManager.WakeLock mWakeLock;

Public Methods

    public void pullWakeLock() {
        final PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
        this.mWakeLock = pm.newWakeLock(PowerManager.SCREEN_DIM_WAKE_LOCK, "My Tag");
        this.mWakeLock.acquire();
    }

    public void releaseWakeLock() {
        this.mWakeLock.release();
    }

Use the follwing permission in manifest file :

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

Answer 2

I finally found a way for this problem. as I want to lock the device when onStop() happens I did:

    public void onStop() {
    mgr.lockNow();
    super.onStop();
    WakeLock screenLock = ((PowerManager) getSystemService(POWER_SERVICE))
            .newWakeLock(PowerManager.SCREEN_BRIGHT_WAKE_LOCK
                    | PowerManager.ACQUIRE_CAUSES_WAKEUP, "TAG");
    screenLock.acquire();
}

and it worked well. turning on the screen after locking it...