For the need of my application, I need to display a message on the screen even if the lockscreen is enabled, then wait 3 seconds, than I have to lock again the phone as I don't want it to make unwanted phone calls in your pockets.

First part is easy:

if (PreferenceManager.getDefaultSharedPreferences(
    getBaseContext()).getBoolean("wake", false)) {
    KeyguardManager kgm = (KeyguardManager) getSystemService(Context.KEYGUARD_SERVICE);
    boolean isKeyguardUp = kgm.inKeyguardRestrictedInputMode();
    WakeLocker.acquire(ProtoBenService.this);
    Intent myIntent = new Intent(ProtoBenService.this,LockActivity.class);
    myIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

    if (isKeyguardUp) {
        ProtoBenService.this.startActivity(myIntent);
    } else
    Toast.makeText(ProtoBenService.this.getBaseContext(), intention, Toast.LENGTH_LONG).show();

    WakeLocker.release();
}

With this class:

public abstract class WakeLocker {
    private static PowerManager.WakeLock wakeLock;

    public static void acquire(Context ctx) {
        if (wakeLock != null) wakeLock.release();

        PowerManager pm = (PowerManager) ctx.getSystemService(Context.POWER_SERVICE);
        wakeLock = pm.newWakeLock(PowerManager.FULL_WAKE_LOCK |
                PowerManager.ACQUIRE_CAUSES_WAKEUP |
                PowerManager.ON_AFTER_RELEASE, "CobeIm");
        wakeLock.acquire();
    }

    public static void release() {
        if (wakeLock != null) wakeLock.release(); wakeLock = null;
    }
}

And the Activity:

public class LockActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Window window = getWindow();
        window.addFlags(WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD);
        window.addFlags(WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON);
        window.addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
        TextView tv = new TextView(this);
        tv.setText("This is working!");
        tv.setTextSize(45);
        setContentView(tv);

        Runnable mRunnable;
        Handler mHandler = new Handler();
        mRunnable = new Runnable() {
            @Override
            public void run() {
                LockActivity.this.finish();
            }
        };
        mHandler.postDelayed(mRunnable, 3 * 1000);
    }
}

So, this is nice, the phone can display my text!

The only problem comes when I want to lock again the phone, it seems that locking the phone is protected by the system...

• Programmatically turning off the screen and locking the phone
• how to lock the android programatically

I think that my users won't understand the Device Admin and won't be able to activate it. Is there any workaround to lock the screen without the Device Admin stuff?