简单拖动效果(带Cache,需要完善)

如何去实现一个具有幻象的拖拽效果？
所谓”幻象“就是当你按下去拖动一个View时，View本身不动，拖动的是这个View的复制品，当抬起时真正的View才显示到拖动的地方。
复制品很容易解决，2句代码就可以了：
v.setDrawingCacheEnabled(true);
Bitmap bitmap = Bitmap.createBitmap(v.getDrawingCache());

package com.ql.app;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.ImageView;
import android.widget.FrameLayout.LayoutParams;

/**
 * 参考：http://techdroid.kbeanie.com/2010/04/simple-drag-n-drop-on-android.html
 * @author admin
 *
 */
public class App extends Activity implements OnTouchListener{
	private final static int START_DRAGGING = 0;
	private final static int STOP_DRAGGING = 1;

	private Button btn;
	private FrameLayout layout;
	private int status;
	private LayoutParams params;

	private ImageView image;

	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);

		layout = (FrameLayout) findViewById(R.id.layout);
		// layout.setOnTouchListener(this);

		btn = (Button) findViewById(R.id.btn);
		btn.setDrawingCacheEnabled(true);
		btn.setOnTouchListener(this);

		params = new LayoutParams(LayoutParams.WRAP_CONTENT,
				LayoutParams.WRAP_CONTENT);

	}

	@Override
	public boolean onTouch(View view, MotionEvent me) {
		switch (me.getAction()) {
		case MotionEvent.ACTION_DOWN:
			status = START_DRAGGING;
			image = new ImageView(this);
			image.setImageBitmap(btn.getDrawingCache());
			layout.addView(image, params);
			break;
		case MotionEvent.ACTION_MOVE:
			if (status == START_DRAGGING) {
				image.setPadding((int) me.getRawX(), (int) me.getRawY(), 0, 0);
				image.invalidate();
			}
			break;
		case MotionEvent.ACTION_UP:
			status = STOP_DRAGGING;
			Log.i("Drag", "Stopped Dragging");
			
//			layout.removeView(image);
			break;

		default:
			break;
		}
		return false;
	}
}

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
	android:layout_width="fill_parent" 
	android:layout_height="fill_parent"
	android:id="@+id/layout"
	>

	<Button android:layout_width="wrap_content"
		android:layout_height="wrap_content" 
		android:id="@+id/btn"
		android:text="Drag Me"
		/>
</FrameLayout>

Android Drag and Drop
http://www.vogella.com/tutorials/AndroidDragAndDrop/article.html