I before I started the game I'm currently working on, I built the following logic to handle pausing. Everything works perfectly in there, or so I thought. In the test app that logic still works, which means I broke it somewhere else along the line. Based on the logic below and the LogCat messages, can you point me in the direction that I should be looking? I don't know how to interpret the errors below. Any help would be very welcome. I can't exactly require the game to be restarted if it ever goes to sleep.
Thanks!
MainGamePanel.java
public void pause() {
mSensorManager.unregisterListener(this);
}
public void resume(Context context) {
mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_FASTEST);
}
public void destroy() {
thread.setRunning(false);
if (thread != null)
{
Thread killThread = thread;
thread = null;
killThread.interrupt();
}
}
@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;
}
}
Main Activity:
//Restarts the accelerometer after onPause
protected void onResume() {
super.onResume();
viewPanel.resume(this);
}
//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() {
super.onPause();
viewPanel.pause();
}
protected void onDestroy() {
super.onDestroy();
viewPanel.destroy();
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
// do something on back.
viewPanel.backHit();
return true;
}
return super.onKeyDown(keyCode, event);
}
And my MainThread.java file:
package com.petronicarts.stormthecastle;
import com.petronicarts.stormthecastle.MainGamePanel;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.view.SurfaceHolder;
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;
Matrix matrix = new Matrix();
matrix.preScale(gamePanel.getScaleX(), gamePanel.getScaleY());
long startTime, elapsedTime;
startTime = System.currentTimeMillis();
elapsedTime = System.currentTimeMillis() - startTime;
while (running) {
if(!pleaseWait) {
canvas = null;
// try locking the canvas for exclusive pixel editing on the surface
try {
canvas = this.surfaceHolder.lockCanvas();
canvas.setMatrix(matrix);
synchronized (surfaceHolder) {
// update game state
startTime = System.currentTimeMillis();
this.gamePanel.update(elapsedTime);
// draws the canvas on the panel
this.gamePanel.onDraw(canvas);
elapsedTime = System.currentTimeMillis() - startTime;
}
} 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) { }
}
}
}
}
}
The LogCat Errors:
06-07 15:56:45.852: E/AndroidRuntime(3374): FATAL EXCEPTION: main
06-07 15:56:45.852: E/AndroidRuntime(3374): java.lang.NullPointerException
06-07 15:56:45.852: E/AndroidRuntime(3374): at com.petronicarts.stormthecastle.MainGamePanel.surfaceDestroyed(MainGamePanel.java:312)
06-07 15:56:45.852: E/AndroidRuntime(3374): at android.view.SurfaceView.reportSurfaceDestroyed(SurfaceView.java:600)
06-07 15:56:45.852: E/AndroidRuntime(3374): at android.view.SurfaceView.updateWindow(SurfaceView.java:486)
06-07 15:56:45.852: E/AndroidRuntime(3374): at android.view.SurfaceView.onWindowVisibilityChanged(SurfaceView.java:213)
06-07 15:56:45.852: E/AndroidRuntime(3374): at android.view.View.dispatchDetachedFromWindow(View.java:6232)
06-07 15:56:45.852: E/AndroidRuntime(3374): at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:1248)
06-07 15:56:45.852: E/AndroidRuntime(3374): at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:1248)
06-07 15:56:45.852: E/AndroidRuntime(3374): at android.view.ViewRoot.dispatchDetachedFromWindow(ViewRoot.java:1868)
06-07 15:56:45.852: E/AndroidRuntime(3374): at android.view.ViewRoot.doDie(ViewRoot.java:2958)
06-07 15:56:45.852: E/AndroidRuntime(3374): at android.view.ViewRoot.die(ViewRoot.java:2928)
06-07 15:56:45.852: E/AndroidRuntime(3374): at android.view.WindowManagerImpl.removeViewImmediate(WindowManagerImpl.java:254)
06-07 15:56:45.852: E/AndroidRuntime(3374): at android.view.Window$LocalWindowManager.removeViewImmediate(Window.java:445)
06-07 15:56:45.852: E/AndroidRuntime(3374): at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:3201)
06-07 15:56:45.852: E/AndroidRuntime(3374): at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3306)
06-07 15:56:45.852: E/AndroidRuntime(3374): at android.app.ActivityThread.access$1600(ActivityThread.java:132)
06-07 15:56:45.852: E/AndroidRuntime(3374): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1055)
06-07 15:56:45.852: E/AndroidRuntime(3374): at android.os.Handler.dispatchMessage(Handler.java:99)
06-07 15:56:45.852: E/AndroidRuntime(3374): at android.os.Looper.loop(Looper.java:150)
06-07 15:56:45.852: E/AndroidRuntime(3374): at android.app.ActivityThread.main(ActivityThread.java:4312)
06-07 15:56:45.852: E/AndroidRuntime(3374): at java.lang.reflect.Method.invokeNative(Native Method)
06-07 15:56:45.852: E/AndroidRuntime(3374): at java.lang.reflect.Method.invoke(Method.java:507)
06-07 15:56:45.852: E/AndroidRuntime(3374): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:849)
06-07 15:56:45.852: E/AndroidRuntime(3374): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
06-07 15:56:45.852: E/AndroidRuntime(3374): at dalvik.system.NativeStart.main(Native Method)
You should probably not synchronize on the thread variable (doing that in surfaceDestroyed). It's set to null elsewhere (in destroy).
Actually, in general, it's always a bad idea to synchronize on a non final object reference.