Re: [android-developers] Simple drawing sample, I seem to miss something

Can anyone help me to understand this ?
It's as if something clears the screen inbetween my drawing calls.

I can get similar incomplete drawings with other sequences too :-(

Is there a way to figure out which events are on the queue for the UI
thread while debugging ?

Danny

On Sat, 2010-06-19 at 11:54 +0200, Danny Backx wrote:
> Hi,
>
> I must be misunderstanding something. I am trying to draw some simple
> stuff, and things appear to clear (so not to display) in moments I don't
> expect it. The sample included is a simplified version of a larger
> application I'm porting to Android.
>
> What I would expect is a circle in green, with a geometry (looking like
> a rather silly satelite) composed out of three red polygons, drawn in
> the circle.
>
> Can anyone tell my why this is not happening ?
>
> Thanks,
>
> Danny
>
> package info.backx.testdraw1;
>
> import android.app.Activity;
> import android.content.Context;
> import android.graphics.Canvas;
> import android.graphics.Color;
> import android.graphics.Paint;
> import android.graphics.Path;
> import android.os.Bundle;
> import android.util.Log;
> import android.view.SurfaceHolder;
> import android.view.SurfaceView;
> import android.view.View;
> import android.view.View.OnClickListener;
> import android.widget.Button;
> import android.widget.LinearLayout;
>
> public class DrawActivity extends Activity {
> public DrawActivity thiz;
> Panel p;
>
> @Override
> public void onCreate(Bundle savedInstanceState) {
> super.onCreate(savedInstanceState);
>
> thiz = this;
>
> LinearLayout ll = new LinearLayout(this);
> ll.setOrientation(LinearLayout.VERTICAL);
>
> Button quit = new Button(this);
> quit.setOnClickListener(mDoitClick);
> quit.setText("Do it");
> ll.addView(quit);
>
> p = new Panel(this);
> ll.addView(p);
>
> setContentView(ll);
> }
>
> OnClickListener mDoitClick = new OnClickListener() {
> public void onClick(View v) {
> Log.e("Test", "DoitClick");
>
> p.erase();
> p.DrawPolygon(1, 4, new float[] {10, 95, 17, 88, 20, 95,
> 18, 97});
> p.DrawPolygon(1, 4, new float[] {25, 100, 32, 103, 25,
> 110, 22, 103});
> p.DrawPolygon(1, 4, new float[] {25, 90, 30, 95, 20,
> 105, 15, 100});
> }
> };
>
>
> public class Panel extends SurfaceView implements
> SurfaceHolder.Callback {
> public Panel(Context context) {
> super(context);
> getHolder().addCallback(this);
> }
>
> @Override
> public void surfaceChanged(SurfaceHolder arg0, int arg1, int
> arg2, int arg3) {
> }
>
> @Override
> public void surfaceCreated(SurfaceHolder arg0) {
> }
>
> @Override
> public void surfaceDestroyed(SurfaceHolder arg0) {
> }
>
> public void DrawPolygon(int filled, int count, float[] points)
> {
> int i;
> Path path = new Path();
> Paint paint = new Paint();
> paint.setColor(Color.RED);
> paint.setStyle(Paint.Style.FILL_AND_STROKE);
>
> Canvas canvas = getHolder().lockCanvas();
> path.moveTo(points[0], points[1]);
> for (i=1; i<count; i++) {
> path.lineTo(points[i*2], points[i*2+1]);
> }
> path.close();
> canvas.drawPath(path, paint);
> getHolder().unlockCanvasAndPost(canvas);
> }
>
> public void erase() {
> Canvas canvas = getHolder().lockCanvas();
> Paint paint = new Paint();
> paint.setColor(Color.GREEN);
> canvas.drawCircle(20, 100, 15, paint);
> getHolder().unlockCanvasAndPost(canvas);
> }
> }
> }
>
> --
> Danny Backx ; danny.backx - at - scarlet.be ; http://danny.backx.info
>
>
>

--
Danny Backx ; danny.backx - at - scarlet.be ; http://danny.backx.info

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