Sarnoth, I appreciate you taking the time to comment.
Does that matter - if the thread isn't different?
Just in case there were problems with the thread, I rewrote the
program not to use a second thread and just execute the drawing loop
in the view.
In the code sample, I also changed draw() to drawSprites(), as I
described in an earlier post. Neither of these things helped.
====== Begin Code ======
package com.baltz.scorched;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.util.AttributeSet;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
class ScorchedView extends SurfaceView implements
SurfaceHolder.Callback {
private Context context;
private SurfaceHolder holder;
private Bitmap backgroundImage;
private Bitmap foregroundImage;
private Bitmap spriteImage;
private Resources resources;
private ScorchedTerrain terrain;
private Engine engine;
public ScorchedView(Context c, AttributeSet attrs) {
super(c, attrs);
// register our interest in hearing about changes to our
surface
holder = getHolder();
holder.addCallback(this);
context = c;
resources = context.getResources();
// load background image as a Bitmap instead of a Dable b/c
// we don't need to transform it and it's faster to d this way
backgroundImage = BitmapFactory.decodeResource(resources,
R.drawable.earthrise);
foregroundImage = BitmapFactory.decodeResource(resources,
R.drawable.foreground1);
spriteImage = BitmapFactory.decodeResource(resources,
R.drawable.sprite1);
terrain = new ScorchedTerrain(foregroundImage);
engine = new Engine();
Body body;
body = new Body(spriteImage);
body.setLocation(50, 50);
engine.addBody(body);
body = new Body(spriteImage);
body.setLocation(40, 100);
engine.addBody(body);
}
/* Callback invoked when the surface dimensions change. */
public void surfaceChanged(SurfaceHolder h, int format, int width,
int height) {
holder = h;
}
/*
* Callback invoked when the Surface has been created and is ready
to be
* used.
*/
public void surfaceCreated(SurfaceHolder h) {
holder = h;
gameLoop();
}
/*
* 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!
*/
public void surfaceDestroyed(SurfaceHolder holder) {
}
private void gameLoop(){
Canvas canvas;
int i=0;
while(i<30){
canvas = null;
try {
canvas = holder.lockCanvas(null);
engine.update();
drawSprites(canvas);
} finally {
// do this in a finally so that if an exception is thrown
// during the above, we don't leave the Surface in an
// inconsistent state
if (canvas != null) {
Log.w("dbg", "unlocking canvas" + i);
holder.unlockCanvasAndPost(canvas);
}
}
try{
Thread.currentThread().sleep(300);
}
catch(Exception e){
}
i++;
}
}
/**
* Draws the sprites and background to the provided
* Canvas.
*/
public void drawSprites(Canvas canvas) {
// Draw the background image. Operations on the Canvas
accumulate
// so this is like clearing the screen.
canvas.drawBitmap(backgroundImage, 0, 0, null);
//draw the up-to-date, deformed foreground
terrain.draw(canvas);
//draw all bodies (players, projectiles, etc) on the screen
engine.drawAll(canvas);
}
}
On Apr 15, 4:47 pm, Sarnoth <[email protected]> wrote:
> I can't really say without seeing more of the code, but based on your
> description of the problem I wonder if your thread is in fact a
> separate thread or if the run method is simply being executed in the
> main UI thread. Something worth checking. You can log
> Thread.currentThread().getName() from inside your run method and from
> inside your activity's onCreate method to make sure they are
> different.
>
> On Apr 15, 9:57 am, Warren <[email protected]> wrote:
>
> > I may have found my problem.
>
> > The SurfaceView class implements a function called draw(Canvas).
>
> > I unwittingly created my own function draw() with the same signature,
> > overriding the original. I'm guessing that the SurfaceView probably
> > calls draw() duringunlockCanvasAndPost(). But instead of executing
> > its original draw() method and doing what it is supposed to do, it
> > calls my function - simply overwriting the canvas buffer without
> > affecting the Surface at all... thus theblackscreen. I'm still
> > confused about why it eventually shows. Perhaps some final cleanup
> > code...
>
> > I will test this tonight when I have access to my development computer
> > and post my findings.
>
> > On Apr 15, 8:48 am, Warren <[email protected]> wrote:
>
> > > Thanks for the comment ellipsoidmobile.
>
> > > If I remove the sleep, I still don't see anything until the very end.
> > > I don't need that sleep in there for the application. I only put it in
> > > so that, hopefully, I could see what was happening a little better.
>
> > > Also, I thought that the SurfaceView allowed you to write to the
> > >screenat your own pace, whatever that may be. So in this case, there
> > > would be nothing "from the outside" that's causing ascreenrefresh.
> > > Thescreenshould stay how I left it until I post a new canvas. Am I
> > > misunderstanding this?
>
> > > What really confuses me is why the last call tounlockCanvasAndPost()
> > > does work. It seems like if an error prevented the first calls from
> > > functioning, then it would also prevent the last.
>
> > > On Apr 15, 3:09 am, "[email protected]"
>
> > > <[email protected]> wrote:
> > > > The problem is your line Thread.currentThread().sleep(1000);//sleep
> > > > for 1000 ms
>
> > > > I believe with SurfaceView you have to draw your whole view on
> > > > everyscreenrefresh. You just need to loop as fast as possible and the
> > > > system will throttle the speed in the calls to lockCanvas(). By
> > > > sleeping for 1 second you are failing to provide a canvas for every
> > > > refresh so thescreenappears blank.
>
> > > > What I don't know is whether there is any guidance on how quickly you
> > > > have to get through your loop, i.e. what the maximum refresh rate is
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