Thank you for your suggestions, however according to the API, there is
no way to pause or resume threads. Only start them, then join them
(which eventually kills it). All related methods for pausing and
resuming have been deprecated it seems.
On Mar 31, 11:07 pm, Streets Of Boston <flyingdutc...@gmail.com>
wrote:
> I haven't read through all your code, but you should not call
> thread.start() in your surfaceCreated method.
> Instead, create and start your thread asap and have it paused when
> necessary.
>
> When 'onPause()' or when surfaceDestroyed is called, pause your thread
> (CupThread).
> When 'onResume()' or surfaceCreated is called, resume your thread.
> Only stop and terminate your thread when 'onDestroy()' is called.
>
> Take a look at the OpenGL Cube example from the API demos.
> I think the class is called RenderThread.
> It creates and starts the thread when the activity is created, stops
> it when the activity is destroyed.
> It pauses the thread on surfaceDestroyed, it resumes it on
> surfaceCreated. This also makes sure that your CupThread does not eat
> CPU-cycles when your app moves to the background. If you don't pause
> the thread when your app is in the background, your phone will eat a
> lot of CPU cycles basically doing nothing --> battery drain -->
> unhappy customers.
>
> Pausing and resuming threads should be done using synchronized blocks,
> wait() statements and notify() statements.
>
> On Mar 31, 10:35 pm, kbeal10 <kbea...@gmail.com> wrote:
>
> > This is where the thread variable is declared.
>
> > private Context mContext;
> > /** The thread that actually draws teh animations. */
> > private CupThread thread;
> > private TextView mStatusText;
>
> > public CupView(Context context, AttributeSet attrs){
> > super(context,attrs);
>
> > //register our interest in hearing about changes to our
> > surface
> > SurfaceHolder holder = getHolder();
> > holder.addCallback(this);
> > mContext = context;
> > setFocusable(true);
> > // create thread only; it's started in surfaceCreated()
> > }
>
> > I'm sorry for the confusion about "exiting" in rollDice(). Indeed, I
> > am not exiting here, but starting another Activity.
>
> > I believe, as you mentioned, this is a case where the original
> > activity is still there, and then being re-displayed. However,
> > CupView's surfaceDestroyed() is called when I start the other Activity
> > in rollDice(). This means that when the Activity holding CupView
> > resumes I should be able to create a new thread and start it. I am
> > aware you can't call start() on the same thread twice, but since
> > surfaceDestroyed() is called that thread is terminated with the .join
> > () call. A new thread is then created and started in surfaceCreated().
>
> > I will post the full code to both the Activity holding the CupView, as
> > well as the CupView in the following post.
>
> > On Mar 31, 10:17 pm, Dianne Hackborn <hack...@android.com> wrote:
>
> > > I don't think you've included enough code. Where is this 'thread'
> > > variable
> > > defined? Where do you clear it after finishing the thread?
>
> > > I am also confused by the comment saying you "exiting" the activity in
> > > rollDice -- you aren't calling finish, you are just starting another
> > > activity, so the original activity is still there, and its window will
> > > just
> > > be re-displayed when it is shown again.
>
> > > The only thing I can think of is that you aren't handling the case where
> > > your window is hidden and then shown again, causing surfaceCreated to be
> > > called a second time on the same SurfaceView, but again there isn't enough
> > > code here to really tell what is happening.
>
> > > Also you do know that you can only call Thread.start() once on a
> > > particular
> > > thread object, right?
>
> > >http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Thread.html#start()
>
> > > On Tue, Mar 31, 2009 at 6:46 PM, kbeal10 <kbea...@gmail.com> wrote:
>
> > > > I'm writing a game using two different SurfaceView's (RollView and
> > > > CupView) in two different activities. Both SurfaceView's heavily
> > > > resemble the LunarLander demo.
>
> > > > The RollView SurfaceView is working fine. When leaving the Activity,
> > > > RollView's surfaceDestroyed() is called, killing the thread. If I then
> > > > re-enter that Activity, the thread is recreated in RollView's
> > > > constructor and then started in surfaceCreated().
>
> > > > However in CupView the thread never seems to go away. SurfaceDestroyed
> > > > is being called, but upon reentering the Activity I get the following
> > > > error:
>
> > > > java.lang.IllegalThreadStateException: Thread already started.
>
> > > > This thrown is in surfaceCreated() at the thread.start() call.
>
> > > > The difference between the two, and apparently the problem, is that in
> > > > the RollView Activity I call finish() when done. When leaving the
> > > > CupView Activity, I'm doing a startActivityForResult
> > > > (i,ClassWithRollView.class);......not calling finish().
>
> > > > This is because after leaving the RollView, I want to return to the
> > > > CupView. Below is relevant code:
>
> > > > /** This where I'm exiting the Activity with the CupView **/
> > > > private void rollDice(){
> > > > if (mMode==IN_PROGRESS){
> > > > // create a new intent for the roll dice view
> > > > Intent i = new Intent(this,RollDice.class);
> > > > mRollCount = mRollCount + 1;
> > > > if (mRollCount == 3){
> > > > mTurnCount += 1;
> > > > }
> > > > if (mTurnCount == 13){
> > > > setState(GAME_OVER);
> > > > }
> > > > i.putExtra("my.package.RollCount", mRollCount);
> > > > i.putExtra("my.package.GameID",mGameID);
> > > > startActivityForResult(i,ROLL_DICE_ACTIVITY);
> > > > }
> > > > }
>
> > > > /** This is CupView's surfaceCreated/Destroyed **/
>
> > > > //-------------------------------------------------------------------------
> > > > --------------------
> > > > /* Callback invoked when the Surface has been created and is
> > > > read to
> > > > be used. */
> > > > public void surfaceCreated(SurfaceHolder holder){
> > > > // start the thread here so that we don't busy-wait in
> > > > run()
> > > > // waiting for the surface to be created
> > > > Log.d("MyApp","cup view surface created");
> > > > thread.setRunning(true);
> > > > thread.start();
> > > > }
>
> > > > //-------------------------------------------------------------------------
> > > > --------------------
> > > > /* Callback invoked when the Surface has been destroyed and must
> > > > no
> > > > longer be touched.
> > > > * WARNING: after this method returns, the Surface/Canvas must
> > > > never
> > > > be touched again!
> > > > * (Unless its REALLY asking for it.)
> > > > */
> > > > public void surfaceDestroyed(SurfaceHolder holder){
> > > > // we have to tell thread to shut down & wait for it to
> > > > finish, or
> > > > else it might touch
> > > > // the Surface(wouldn't want that!) after we return and
> > > > explode
> > > > (ahhh!).
> > > > Log.d("MyApp","cup view surface destroyed");
> > > > boolean retry = true;
> > > > thread.setRunning(false);
> > > > while (retry){
> > > > try{
> > > > thread.join();
> > > > retry = false;
> > > > }catch(InterruptedException e){
>
> > > > }
> > > > }
> > > > }
>
> > > > So why is the thread saying its already started when surfaceDestroyed
> > > > () has been called?
>
> > > > A possible workaround is to call finish() on the CupView Activity in
> > > > the rollDice() method above. This doesn't seem to follow common
> > > > paradigm though. Any other solutions, comments? All help is
> > > > appreciated.
>
> > > --
> > > Dianne Hackborn
> > > Android framework engineer
> > > hack...@android.com
>
> > > Note: please don't send private questions to me, as I don't have time to
> > > provide private support. All such questions should be posted on public
> > > forums, where I and others can see and answer them.- Hide quoted text -
>
> > - Show quoted text -
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