ImageView问题

Question

我在绘制ImageView时遇到了一些问题 当我按下按钮（调用函数zxc（））时，程序会在错误的位置绘制 为什么呢？

屏幕直至您按下：http://s52.radikal.ru/i137/1401/51/c084b1b955d9.png
之后：http://s020.radikal.ru/i718/1401/b6/bec1187422ca.png

代码：

   package com.example.asd;

   import android.app.Activity;
   import android.content.Context;
   import android.content.res.Resources;
   import android.graphics.Bitmap;
   import android.graphics.Canvas;
   import android.graphics.drawable.Drawable;
   import android.os.Bundle;
   import android.view.View;
   import android.widget.ImageView;

   public class MainActivity extends Activity {
 Bitmap myBitmap;
ImageView myImageView;
Canvas myCanvas;
Resources myResources;
Context myContext;
 @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    myImageView=(ImageView)findViewById(R.id.imageView1);
    myBitmap=Bitmap.createBitmap(1000, 1000, Bitmap.Config.ARGB_8888);
    myImageView.setImageBitmap(myBitmap);
    for(int i=0;i<1000;i++)
        for(int j=0;j<1000;j++)
            myBitmap.setPixel(i, j, 0xffff4000);

      myContext=getWindow().getContext();
      myResources=myContext.getResources();

    Drawable myDrawable=myResources.getDrawable(R.drawable.qwe1);
    myDrawable.setBounds(10, 10, 100, 100);

     myCanvas=new Canvas(myBitmap);


    myImageView.setImageDrawable(myDrawable);
    myImageView.draw(myCanvas);
    myImageView.setImageBitmap(myBitmap);

         Drawable my_second_draw=myResources.getDrawable(R.drawable.qwe1);
         my_second_draw.setBounds(900, 900, 1000, 1000);
         myImageView.setImageDrawable(my_second_draw);
         myImageView.draw(myCanvas);
         myImageView.setImageBitmap(myBitmap);

 }
 public void zxc(View v)
 {   

     Drawable my_second_draw=myResources.getDrawable(R.drawable.ic_launcher);
     my_second_draw.setBounds(500, 500, 1000, 1000);
     myImageView.setImageDrawable(my_second_draw);
     myImageView.draw(myCanvas);
     myImageView.setImageBitmap(myBitmap); 
 } 
}