用ontouch移动一张图片为什么图片不和ontouch触摸点在一起啊
     super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        ll=(LinearLayout) findViewById(R.id.ll);
        iv=(ImageView) findViewById(R.id.iv);
        iv.setOnTouchListener(this);
        
    }
public boolean onTouch(View v, MotionEvent event) {
    if(event.getAction()==MotionEvent.ACTION_MOVE){
                lp=(LayoutParams) iv.getLayoutParams();
                lp.leftMargin=(int) event.getRawX();
                lp.topMargin=(int) event.getRawY();
                iv.setLayoutParams(lp);
                
    }

return true;