android 拖动imageview 如果没有拖动到指定的位置 返回到起点怎么实现

点击imageview,加一个边框，再点击，取消边框。拖动imageview,可以停在移动结束之后的位置上，而不是弹回移动之前的位置。

请问有什么好的实现办法。

public class MainActivity extends Activity {

private int screenWidth;
private int screenHeight;
private ImageView bgview;
private ImageView photoview;

private TextView txtview;

int top, right, bottom, left;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

DisplayMetrics dm = getResources().getDisplayMetrics();

screenWidth = dm.widthPixels;
screenHeight = dm.heightPixels - 50;

bgview = (ImageView) findViewById(R.id.bgview);
photoview = (ImageView) findViewById(R.id.photoview);

photoview.setOnTouchListener(new TouchHandler());
photoview.setOnClickListener(new ClickHandler());

}

class TouchHandler implements OnTouchListener{

int lastX , lastY, dx, dy;

@Override
public boolean onTouch(View v, MotionEvent event) {
switch(event.getAction()){
case MotionEvent.ACTION_DOWN:

// if(mode == NONE)
// if(dx < 2 && dy < 2)
{
lastX = (int) event.getRawX();
lastY = (int) event.getRawY();
}
break;

case MotionEvent.ACTION_MOVE:
dx = (int) event.getRawX() - lastX;
dy = (int) event.getRawY() - lastY;

// if(mode == DRAG)
{

// photoview.setBackgroundResource(R.drawable.img_border);

left = v.getLeft() + dx;
top = v.getTop() + dy;
right = v.getRight() + dx;
bottom = v.getBottom() + dy;

if(left < 0)
{
left = 0;
right = left + v.getWidth();
}

if(right > screenWidth)
{
right = screenWidth;
left = right - v.getWidth();
}

if(top < 0)
{
top = 0;
bottom = top + v.getHeight();
}

if(bottom > screenHeight)
{
bottom = screenHeight;
top = bottom - v.getHeight();
}

v.layout(left, top, right, bottom);
lastX = (int) event.getRawX();
lastY = (int) event.getRawY();

}
break;

case MotionEvent.ACTION_UP:

break;
}
if(dx < 2 && dy < 2)
{
return false;
}

return true;

}

}

class ClickHandler implements OnClickListener{

@Override
public void onClick(View v) {
switch(v.getId())
{
case R.id.photoview:
if( null == photoview.getBackground())
{
photoview.setBackgroundResource(R.drawable.img_border);

}else{
photoview.setBackgroundDrawable(null);

}
break;

}
v.layout(left, top, right, bottom);
System.out.println("left===" + left);
System.out.println("top===" + top);
}

}
}

scaletype属性用FITXY 就是把图片布满View，固定了，我想问你怎样ImageView的拖动效果和点击事件