Question

I have a app that allows users to drag shapes on the screen. I use a custom surface view for the dragging. Every time the surface view gets a OnTouchEvent, it changes the postion of the graphic image and calls OnDraw to update the screen.

So the bitmap image does not get drawn until a touchevent happens. I tried to invalidate the Costume surface view, but according to the debugger, OnDraw never gets called.

So right now my screen is blank until some one touches the screen

// code

public class cPlay extends  cBase  implements OnClickListener {
    /** Called when the activity is first created. */
    // sound
    private SoundPool soundPool;
    private int soundID;
    boolean loaded = false;  

    @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
      //      setContentView(R.layout.play);


            int w=getWindowManager().getDefaultDisplay().getWidth();
            int h=getWindowManager().getDefaultDisplay().getHeight();

            BallView ballView=new BallView(this,w,h);
            setContentView(ballView);

            // Does not update screen??????
            ballView.invalidate();
                 ....
...
....} // end of class

public class BallView  extends SurfaceView implements SurfaceHolder.Callback {
    private Bitmap bitmap ;
    private int x=20,y=20;int width,height;
    cShapeParent MyShapes;   
    cTarget MyTargetShapes;
    Context context;
    int counter=0;   

    // sound
    private SoundPool soundPool;
    private int soundID;
    boolean loaded = false;

    public BallView(Context InContext,int w,int h) {
        super(InContext);

        context=InContext;
        int counter=0;
        int Page=0;
        width=w;
        height=h;
        getHolder().addCallback(this);
        setFocusable(true);
        MyShapes=new cShapeParent(context,w,h);
        MyTargetShapes= new cTarget(context,w,h);
        MyShapes.SetTargets(  MyTargetShapes );
        // load in bitmaps



    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);




        bitmap =BitmapFactory.decodeResource(getResources(), R.drawable.ball_green);
        canvas.drawColor(Color.BLUE);//To make background 
  //      canvas.drawBitmap(bitmap,x-(bitmap.getWidth()/2),y-(bitmap.getHeight()/2),null);

        // See if we shoyld drag it
        for(int i=MyShapes.Amount-1; i>=0; i--)
        {
          if (MyShapes.Intersect(i,x,y))        
          {
             // see if we can drag it
              if ( MyShapes.getDragFlag(i)==false)
                 break;

              // yes drag this image
              MyShapes.SetCenter(i, x, y);

              // if the target was found
              // make it so we can no loner drag it
              if (MyShapes.CheckTarget(i))
              {
                  MyShapes.SetDrag(i,false);
                  MyShapes.SetToTarget(i);
                  if (++counter>2)
                      DisplayNextScreen();
              }
              break;
          } 
        }     

        // Draw target shapes
        // NOTE: draw these first so they are on the bottom
        for(int i=0; i<MyShapes.Amount;i++)
        {
            int x=MyTargetShapes.GetX(i);
            int y=MyTargetShapes.GetY(i);
            int w=MyTargetShapes.GetW(i);
            int h=MyTargetShapes.GetH(i);

            Rect br=new Rect( x, y,w+x,  h+y);
            Bitmap m= MyTargetShapes.MyImages[i];
            canvas.drawBitmap(m, null, br, null);
        }      

        // Draw shapes that can be dragged
        for(int i=0; i<MyShapes.Amount;i++)
        {
            int x=MyShapes.GetX(i);
            int y=MyShapes.GetY(i);
            int w=MyShapes.GetW(i);
            int h=MyShapes.GetH(i);
            Rect br=new Rect( x, y, x+w,y+h);
            Bitmap m= MyShapes.MyImages[i];
            canvas.drawBitmap(m, null, br, null);
        }




    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        x=(int)event.getX();
        y=(int)event.getY();

        if(x<25)
            x=25;
        if(x> width)   
            x=width;
        if(y <25)
            y=25;
        if(y > height)
            y=height;

        updateBall();

        return true;
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,int height) {
        // TODO Auto-generated method stub
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        // TODO Auto-generated method stub
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        // TODO Auto-generated method stub
    }

    private void updateBall() {
        Canvas canvas = null;
        try {
            canvas = getHolder().lockCanvas(null);
            synchronized (getHolder()) {
                this.onDraw(canvas);
            }
        }
        finally {
            if (canvas != null) {
                getHolder().unlockCanvasAndPost(canvas);
            }
        }
    }   

  void  DisplayNextScreen()
    {
           /////////////////////////////////////
        // call up dialog
        final Dialog dialog = new Dialog(context);
        dialog.setContentView(R.layout.custom);
        dialog.setTitle("Title...");

        // set the custom dialog components - text, image and button
        TextView text = (TextView) dialog.findViewById(R.id.text);
        text.setText("Android custom dialog example!");
        ImageView image = (ImageView) dialog.findViewById(R.id.image);
        image.setImageResource(R.drawable.ic_launcher);

        Button dialogButton = (Button) dialog.findViewById(R.id.dialogButtonOK);
        // if button is clicked, close the custom dialog

        dialogButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                dialog.dismiss();
                MyTargetShapes.SetUp(1);
                MyShapes.SetUp(1);
                MyShapes.SetTargets(  MyTargetShapes );
                counter =0;
            }
        });

        dialog.show();
    } // end methed


  void StartSound(int soundID )
  {
       AudioManager audioManager = (AudioManager) context.getSystemService("audio");
        float actualVolume = (float) audioManager
                .getStreamVolume(AudioManager.STREAM_MUSIC);
        float maxVolume = (float) audioManager
                .getStreamMaxVolume(AudioManager.STREAM_MUSIC);
        float volume = actualVolume / maxVolume;
        // Is the sound loaded already?

            soundPool.play(soundID, volume, volume, 1, 0, 1f);
        //  Log.e("Test", "Playe");

  } 

} // end class

Answer 1

I faced a similar issue in my app. invalidate() does not redraw the shape. So the solution which i found was to extract the shape into the class displaying the components on UI and then to update the component from the main activity by accessing it from the UI class.

SurfaceView Class:

@Override
public void onDraw(Canvas canvas) {

    Log.d("check","="+color);
    Log.e("check","after set:"+buf);
    Log.i("new view ", " on draw ");
    paint.setStyle(Paint.Style.STROKE);
    paint.setStrokeWidth(5);
    paint.setColor(Color.WHITE);

    path = new Path();
    path.moveTo(0, 30);                             /*For Borders*/
    path.lineTo(30, 0);
    path.lineTo(-30, 0);
    path.close();
    path.offset(20, -5);
    canvas.drawPath(path, paint);

UI class:

public void show(View anchor,int color) {
preShow();

    int xPos, yPos, arrowPos;

    mDidAction = false;
    }

    showArrow(((onTop) ? R.id.arrow_down : R.id.arrow_up), arrowPos,color);

    setAnimationStyle(screenWidth, anchorRect.centerX(), onTop);
    mWindow.showAtLocation(anchor, Gravity.NO_GRAVITY, xPos, yPos);


}

R.id.arrow_down is the shape drawn using the NewView class.

In the main activity on the event call the function like this:

    btn1 = (Button) this.findViewById(R.id.btn1);
    btn1.setOnClickListener(new View.OnClickListener() {

        public void onClick(View v) {


            Log.d("In","View");
            quickAction.show(v,Color.BLUE);


        }
    });

This will update the view as required.
Hope This Helps