Android - onPause and WidgetLocker

Question

I am writing a basic application to test the behavior of the accelerometer. Currently I am registering and unregistering the accelerometer like this:

public void pause() {
    mSensorManager.unregisterListener(this);
}

public void resume(Context context) {
    mSensorManager.registerListener(this, mAccelerometer,     
            SensorManager.SENSOR_DELAY_FASTEST);        
}

I have the pause and resume methods triggered by the Activity, as the accelerometer is running in a child class. When I lock the screen the screen, the program breaks. I actually have to end the process to get the program to work again. I am currently using WidgetLocker. The program works fine with the stock lockscreen. My assumption is that resume is never being run.

Is there a way to make sure that the sensor will be reregisterd? I don't want my program to break if they are using anything outside of the normal lockscreen.

EDIT: Full Source Added. The main logic regarding this issue takes place at the bottom of MainGamePanel.java

TiltBallActivity.java

package com.tornquist.nathan;

import android.app.Activity;
import android.content.pm.ActivityInfo;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;

public class TiltBallActivity extends Activity{
    /** Called when the activity is first created. */
    MainGamePanel viewPanel;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        //Window state functions.
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);

        //This works without declaring a viewPanel instance here.
        //The instance declaration is needed to pass the 
        //onPause and onResume commands though.
        viewPanel = new MainGamePanel(this);
        setContentView(viewPanel);
    }

    //Restarts the accelerometer after onPause
    protected void onResume() {

        viewPanel.resume(this);
        super.onResume();
    }

    //Standard Method run when the Application loses focus.
    //This runs the pause() function in the viewPanel so that
    //the accelerometer can be paused.
    protected void onPause() {

        viewPanel.pause();
        super.onPause(); 
    }
}

MainThread.java

package com.tornquist.nathan;

import com.tornquist.nathan.MainGamePanel;
import android.graphics.Canvas;
import android.view.SurfaceHolder;

public class MainThread extends Thread {

    private SurfaceHolder surfaceHolder;
    private MainGamePanel gamePanel;
    private boolean running;
    public void setRunning(boolean running) {
        this.running = running;
    }

    public MainThread(SurfaceHolder surfaceHolder, MainGamePanel gamePanel) {
        super();
        this.surfaceHolder = surfaceHolder;
        this.gamePanel = gamePanel;
    }

    @Override
    public void run() 
    {
        Canvas canvas;
        while (running) {
            canvas = null;
            // try locking the canvas for exclusive pixel editing on the surface
            try {
                canvas = this.surfaceHolder.lockCanvas();
                synchronized (surfaceHolder) {
                    // update game state
                    this.gamePanel.update();

                    // draws the canvas on the panel
                    this.gamePanel.onDraw(canvas);
                }
            } finally {
                // in case of an exception the surface is not left in
                // an inconsistent state
                if (canvas != null) {
                    surfaceHolder.unlockCanvasAndPost(canvas);
                }
            }   // end finally
        }
    }
}

MainGamePanel.java

package com.tornquist.nathan;

import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.view.Display;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

public class MainGamePanel extends SurfaceView implements SensorEventListener, SurfaceHolder.Callback 
{
    //Variable Declarations.
    private MainThread thread;
    public int xColor;
    public int yColor;
    public int zColor;

    public float xPos;
    public float yPos;
    public float oldXPos;
    public float oldYPos;

    public int screenWidth;
    public int screenHeight;

    private SensorManager mSensorManager;
    private Sensor mAccelerometer;    

    Paint paint;

    public MainGamePanel(Context context)
    {
        //Standard Initialization
        super(context);

        //This line adds a callback for the touch screen.  
        //This allows you to actually capture touch input.
        getHolder().addCallback(this);

        thread = new MainThread(getHolder(),this);

        xColor = 100;
        yColor = 100;
        zColor = 100;

        paint = new Paint();
        paint.setAntiAlias(true);

        Display display = ((Activity) context).getWindowManager().getDefaultDisplay(); 
        screenWidth = display.getWidth();
        screenHeight = display.getHeight();

        yPos = screenHeight/2;
        xPos = screenWidth/2;
        oldYPos = yPos;
        oldXPos = xPos;

        //This registers the accelerometer.  Without registering it, the onSensorChanged
        //event will never be called, and you cannot get the accelerometer values.
        mSensorManager = (SensorManager) context.getSystemService(Context.SENSOR_SERVICE);

        mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);

        mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_FASTEST);

        //Also required for touch input.
        setFocusable(true);
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
            int height) {
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        // at this point the surface is created and
        // we can safely start the game loop
        thread.setRunning(true);
        thread.start();
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        boolean retry = true;
        while (retry) {
            try {
                thread.join();
                retry = false;
            } catch (InterruptedException e) {
                // try again shutting down the thread
            }
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (event.getAction() == MotionEvent.ACTION_DOWN) {
                        // check if in the lower part of the screen we exit
            if (event.getY() > getHeight() - 50) {
                thread.setRunning(false);
                ((Activity)getContext()).finish();
            }

            if (xColor < 235)
                xColor = xColor + 20;
            else
                xColor = 0;
            if (yColor < 235)
                yColor = yColor + 20;
            else
                yColor = 0;
            if (zColor < 235)
                zColor = zColor + 20;
            else
                zColor = 0;

            yPos = event.getY();
            xPos = event.getX();
        }
        return true;
    }

    @Override
    protected void onDraw(Canvas canvas) 
    {
        //canvas.drawColor(Color.CYAN);
        canvas.drawColor(Color.rgb(xColor, yColor, zColor));
        int xInvert = (int) (255 - xColor);
        int yInvert = (int) (255 - yColor);
        int zInvert = (int) (255 - zColor);

        paint.setColor(Color.rgb(xInvert, yInvert, zInvert));
        paint.setStyle(Style.FILL);
        canvas.drawCircle(xPos, yPos, 50, paint);
    }

    public void update() {
    }

    @Override
    public void onAccuracyChanged(Sensor sensor, int accuracy) {        
    }

    @Override
    public void onSensorChanged(SensorEvent event) {

        oldYPos = yPos;
        oldXPos = xPos;

        xColor = (int) (255 + (event.values[0])*11);
        if (xColor > 255)
            xColor = 255;
        if (xColor < 0)
            xColor = 0;

        yColor = (int) (255 + (event.values[1])*11);
        if (yColor > 255)
            yColor = 255;
        if (yColor < 0)
            yColor = 0;

        zColor = (int) (255 + (event.values[2])*11);
        if (zColor > 255)
            zColor = 255;
        if (zColor < 0)
            zColor = 0;

        xPos = xPos + -1*(event.values[0])*5;
        yPos = yPos + event.values[1]*5;

        if (xPos < 50)
            xPos = 50;
        if (xPos > screenWidth - 50)
            xPos = screenWidth - 50;
        if (yPos < 50)
            yPos = 50;
        if (yPos > screenHeight - 50)
            yPos = screenHeight - 50;

        if ((oldYPos == yPos) && (oldXPos == xPos))
        {
            invalidate();
        }

    }

    public void pause() {
        mSensorManager.unregisterListener(this);

        //thread.setRunning(false);
        //((Activity)getContext()).finish();
    }

    public void resume(Context context) {
        //mSensorManager = (SensorManager) context.getSystemService(Context.SENSOR_SERVICE);

        //mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);

        mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_FASTEST);      
    }


}

Do you use `pause` and `resume`, or `onPause` and `onResume`? — asaelr, Jan 17 '12 at 00:47
onPause and onResume. pause and resume are in a child class. They are executed by the onPause and onResume methods. As I said above, this works perfectly when I am not using WidgetLocker. I need to program for any situation though. — Nathan Tornquist, Jan 17 '12 at 00:50

tungi52 · Accepted Answer · 2012-01-22T15:30:39.233

I think you could use the ACTION_SCREEN_ON and ACTION_SCREEN_OFF Intent actions and you don't have to deal with onPause and onResume thing. So something like this:

mReceiver = new BroadcastReceiver() {
     public void onReceive(Context context, Intent intent) {
    String action = intent.getAction();
    if (Intent.ACTION_SCREEN_OFF.equals(action)) {
        //deregister
    }
    else if (Intent.ACTION_SCREEN_ON.equals(action)) {
        //register
    }
}};

IntentFilter filter = new IntentFilter(Intent.ACTION_SCREEN_ON);
registerReceiver(mReceiver, filter); 

filter = new IntentFilter(Intent.ACTION_SCREEN_OFF);
registerReceiver(mReceiver, filter);

and deregister this receiver in the onDestroy() method

Ok I think I found a solution. The thread.join part in the onSurfaceDestroyed method code blocks the activity somehow. I made a few modifications on your code and this works for me:

public MainGamePanel(Context context)
{
    ...

    //Also required for touch input.
    setFocusable(true);

    //start thread
    thread.setRunning(true);
    thread.start();
}

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
        int height) {
}

@Override
public void surfaceCreated(SurfaceHolder holder) {
    //continue the thread
    synchronized (thread) {
        thread.pleaseWait = false;
        thread.notifyAll();
    }
}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
    //pause the thread
    synchronized (thread) {
        thread.pleaseWait = true;
    }
}

And the thread class

public class MainThread extends Thread {

private SurfaceHolder surfaceHolder;
private MainGamePanel gamePanel;
private boolean running;
public boolean pleaseWait = true;
public void setRunning(boolean running) {
    this.running = running;
}

public MainThread(SurfaceHolder surfaceHolder, MainGamePanel gamePanel) {
    super();
    this.surfaceHolder = surfaceHolder;
    this.gamePanel = gamePanel;
}

@Override
public void run() 
{
    Canvas canvas;
    while (running) {
        if(!pleaseWait) {
            canvas = null;
            // try locking the canvas for exclusive pixel editing on the surface
            try {
                canvas = this.surfaceHolder.lockCanvas();
                synchronized (surfaceHolder) {
                    // update game state
                    this.gamePanel.update();

                    // draws the canvas on the panel
                    this.gamePanel.onDraw(canvas);
                }
            } finally {
                // in case of an exception the surface is not left in
                // an inconsistent state
                if (canvas != null) {
                    surfaceHolder.unlockCanvasAndPost(canvas);
                }
            }   // end finally            
        }
        else {
            synchronized (this) {
                try {
                    wait();
                } catch (Exception e) { }
            }
        }
    }
}
}

And destroy the thread in the onDestroy method

I will certainly try that, but ultimately that doesn't solve the problem. If someone switches applications, my app will continue to be a drain on the battery. The only way this would solve the problem is if they always locked the screen from my app, and unlocked the screen to return directly to it. — Nathan Tornquist, Jan 22 '12 at 05:12
I debug your code: i think the battery drain problem is because of the thread. I think you should pause it. One more think, when I debug you code, the onResume doesn't fire for me. — tungi52, Jan 22 '12 at 11:01
The onResume not firing is the whole problem I'm asking about. — Nathan Tornquist, Jan 22 '12 at 13:31
That seems to work perfectly. Can you try to explain what was actually wrong though? The thread wasn't getting paused and ultimately pausing half the app broke it? And is the onDestroy method something I need to add? --- EDIT: Can I just use thread = null; in the onDestroy() method? — Nathan Tornquist, Jan 22 '12 at 21:27
Yes, the main problem with your code is the thread.join part. The onSurfaceDestroy will fire always after the onPause and your code blocks the process of the activity because you don't call thread.setRunning(false). This not solve your problem because you have to reinitialize the thread in the onSurfaceCreate. A more elegant solution is if you pause the thread and continue it. In the onDestroy: create a stop method in the MainGamePanel and copy your thread stopping code in there but set the running field to false. You cannot set the thread to null because the thread will continue the execution — tungi52, Jan 23 '12 at 09:34
Okay, I set the stopping system up like the one shown here: http://stackoverflow.com/questions/680180/where-to-stop-destroy-threads-in-android-service-class so I do this: public void destroy() { thread.setRunning(false); if (thread != null) { Thread killThread = thread; thread = null; killThread.interrupt(); } } ---- Is that correct? The program seems to work. — Nathan Tornquist, Jan 24 '12 at 00:09

score 0 · Answer 2 · answered Jan 20 '12 at 08:33

0

I think, if you use onCreate() for register and onDestroy() to unregister, that ill solve your problem. Becoz your onDestory wont be called while your screen locked and that might solve your problem.

answered Jan 20 '12 at 08:33

Ravi Bhojani

1,032
1
13
24

I need to unregister the accelerometer when the screen is locked. Otherwise the battery will drain really fast. – Nathan Tornquist Jan 20 '12 at 16:23

Android - onPause and WidgetLocker

2 Answers2