Android和onTouch

我有绘画形象的课。这是代码：Android和onTouch

public class CanvasdrawActivity extends Activity implements OnTouchListener { 
     ImageView imageView; 
     Bitmap bitmap; 
     Bitmap bitmap2; 
     Canvas canvas; 
     Paint paint; 
     boolean oneClick=true; 
     float downx = 0,downy = 0,upx = 0,upy = 0; 

     @Override 
     public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 
     imageView = (ImageView) this.findViewById(R.id.imageView1); 
     Display currentDisplay = getWindowManager().getDefaultDisplay(); 
     float dw = currentDisplay.getWidth(); 
     float dh = currentDisplay.getHeight(); 

     bitmap = Bitmap.createBitmap((int) dw, (int) dh, 
      Bitmap.Config.ARGB_8888); 
     bitmap2=BitmapFactory.decodeResource(getResources(), 
       R.drawable.star_bez_nog); 

     canvas = new Canvas(bitmap); 

     imageView.setImageBitmap(bitmap); 
     imageView.setOnTouchListener(this); 
     } 

     public boolean onTouch(View v, MotionEvent event) { 
     int action = event.getAction(); 
     switch (action) { 
     case MotionEvent.ACTION_DOWN: 
      if(oneClick){ 
      downx = event.getX(); 
      downy = event.getY(); 
      canvas.drawBitmap(bitmap2, downx, downy, null); 
      imageView.invalidate(); 
      oneClick=false; 
      } 
      break; 

     } 
     return true; 
     } 
    }

当我点击第一次绘制图像。当我在其他地方点击这张旧图片失踪和新绘图时，我该怎么做？

来源

2012-04-02 edi233

你缺少的的onDraw机制的东西，检查重复链接：你必须重写onDraw来每次更新你的绘图。 OnTouch将更改绘制内容的数据，但绘图作业必须在onDraw中执行。 – Snicolas 2012-04-02 06:56:47

[Override onDraw改变绘图发生的方式（Android）]的可能的重复]（http://stackoverflow.com/questions/2763572/override-ondraw-to-change-how-the-drawing-occurs-android） – Snicolas 2012-04-02 06:56:55

在ontouch清除画布每一次这样的..

Paint paint = new Paint(); 
paint.setXfermode(new PorterDuffXfermode(Mode.CLEAR)); 
canvas.drawPaint(paint); 
paint.setXfermode(new PorterDuffXfermode(Mode.SRC));

在此之后绘制位图在居民点

canvas.drawBitmap(bitmap2, downx, downy, null);

来源

2012-04-02 07:15:19 5hssba

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