android - onTouch() 无法绘制画布

Question

onDraw(Canvas canvas) 自动工作。在这个视图中，onTouch() 方法监听触摸屏幕。单击屏幕时，我需要重新绘制矩形，但它没有绘制矩形画布。

public class Viewer extends View implements OnTouchListener{

    public Viewer(Context context) {
        super(context);

        .............
        ..............
        this.setOnTouchListener(this);              
    }

    @Override
    public void onDraw(Canvas canvas){  
        super .onDraw(canvas);
        drawBackGround(imgObj.bg01, canvas);    
    }

    @Override
    public boolean onTouch(View v,MotionEvent event) {
        // TODO Auto-generated method stub      

        Canvas c = new canvas();
        c.drawRect(.......);    //<------ It's work but it isn't redraw
        return true;
    }

Answer 1

尝试这个，

Canvas mCanvas;
 @Override
    public void onDraw(Canvas canvas){  

        mCanvas = canvas;
        drawBackGround(imgObj.bg01, mCanvas);
        super.onDraw(mCanvas);

    }

    @Override
    public boolean onTouch(View v,MotionEvent event) {
        // TODO Auto-generated method stub      

        mCanvas.drawRect(.......); 
        invalidate();
        return true;
    }