CODEWITHSUNDEEP
javaandroidsurfaceview
Shaquil Hansford
Shaquil Hansford

Reputation: 383

bitmap being drawn multiple times on surfaceview

I'm just trying to draw a circle on the spot where I touch the screen. When I touch the screen, a circle is drawn there, but then when I touch the screen somewhere else a new circle is drawn (the old one is supposed to appear there, not a new one). Does anyone understand why this is happening? Code:

Thread class: 

public class GameThread extends Thread{
    private SurfaceHolder sHolder;
    private DrawingSurface dSurface;

    private boolean okToRun;

    Paint redPaint = new Paint();

    public int x, y;

    boolean myTouchEvent(MotionEvent event){
        int touch = event.getAction();
        switch(touch){
            case MotionEvent.ACTION_DOWN:
            x = (int) event.getX();
            y = (int) event.getY();
        }
        return true;
    }

    public GameThread(SurfaceHolder holder, DrawingSurface surface){
        sHolder = holder;
        dSurface = surface;
        redPaint.setARGB(255, 255, 0, 0);
    }//GameThread()

    public void setOkToRun(boolean status){
        okToRun = status;
    }//setOkToRun()

    public void run(){
        while(okToRun){//gameloop
            Canvas canvas = null;
            try{
                canvas = sHolder.lockCanvas(null);
                synchronized(sHolder){
                    try{
                        canvas.drawCircle(x, y, 60, redPaint);
                    } catch (Exception e){
                    }
                }
                } finally {
                if (canvas != null) {
                    sHolder.unlockCanvasAndPost(canvas);
                }
            }
        }
    }//run()
}

Here are the relevant methods of my surfaceview class:

@Override
public boolean onTouchEvent(MotionEvent event) {
    return drawingThread.onTouchEvent(event);
}

@Override
public void surfaceCreated(SurfaceHolder holder) {
        drawingThread = new GameThread(getHolder(), this);
        drawingThread.start();
        drawingThread.setOkToRun(true);
}

@Override
public void surfaceDestroyed(SurfaceHolder arg0) {
    radius += 10;
    drawingThread.setOkToRun(false);
    try {
        drawingThread.join();
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

TO BE CLEAR: I want to draw a single circle, and have it appear wherever I tap the screen. It does not do that. Can you tell why that is the case in this code?

Upvotes: 0

Views: 457

Answers (1)

tomasbuzek
tomasbuzek

Reputation: 526

I hope I am right that you need to draw a circle at the place where the screen was touched and the problem is that circles from previous touches still appear on the screen. In this case the problem is, that you are drawing circles on canvas without clearing it. Canvas is represented in a memory as a array. When you call Canvas.drawCircle() part of memory is rewritten by an image of circle. When you do it repeatedly, the canvas contains more circles which are being drawn on the screen. You need to repaint the whole canvas before you draw a new circle. It can be done by calling the method Canvas.drawColor() before calling the method Canvas.drawCircle(). It clears the whole Canvas with selected color.

Upvotes: 2

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