android拖动imageview实现复制效果

首先实现一个自定义的拖动阴影类，该类主要功能将ImageView控件中的图像放大50%后作为拖动阴影，拖动阴影实现如下

public class MyDragShadowBuilder extends DragShadowBuilder {

	// 拖动阴影的区域
	private static Drawable shadow;
	// 储存绘制的拖动阴影图像
	private static Bitmap newBitmap;

	public MyDragShadowBuilder(View arg0) {
		super(arg0);
		// TODO Auto-generated constructor stub
		shadow = new ColorDrawable(Color.LTGRAY);// 浅灰色
	}

	// 在该方法中绘制拖动阴影图像 实例化newBitmap变量
	@Override
	public void onProvideShadowMetrics(Point shadowSize, Point shadowTouchPoint) {
		// TODO Auto-generated method stub
		super.onProvideShadowMetrics(shadowSize, shadowTouchPoint);
		int width, heigth;
		// 设置拖动阴影的宽度/高度为原宽/高度的1.5倍
		width = (int) (getView().getWidth() * 1.5);
		heigth = (int) (getView().getHeight() * 1.5);
		// 设置拖动图像的绘制 区域
		shadow.setBounds(0, 0, width, heigth);
		// 设置拖动阴影图像的宽度和高度
		shadowSize.set(width, heigth);
		// 设置手指在拖动图像的位置 设置为中点
		shadowTouchPoint.set(width / 2, heigth / 2);

		if (getView() instanceof ImageView) {
			// getView()方法返回的值就是构造方法传入的arg0 参数
			ImageView imageView = (ImageView) getView();
			// 获取drawable对象
			Drawable drawable = imageView.getDrawable();
			// 获取imageview的bitmap
			Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();
			// 创建一个新的bitmap
			newBitmap = bitmap.createBitmap(width, heigth, Config.ARGB_8888);

			Canvas canvas = new Canvas(newBitmap);
			// 将图像绘制在画布上，但现在还没有正式将图像绘制在阴影图像上，目前只是将bitmap放大并绘制在newbitmap上
			canvas.drawBitmap(newBitmap, new Rect(0, 0, bitmap.getWidth(),
					bitmap.getHeight()), new Rect(0, 0, width, heigth), null);
		}

	}

	@Override
	public void onDrawShadow(Canvas canvas) {
		// TODO Auto-generated method stub
		super.onDrawShadow(canvas);
		// 将图像正式绘制在阴影图像上
		canvas.drawBitmap(newBitmap, 0, 0, new Paint());
	}

}

用来实现的主窗口

public class MainActivity extends Activity implements OnDragListener {

	private FrameLayout dragdropRegin;
	// 拖动到图像
	private ImageView imageView;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		dragdropRegin = (FrameLayout) findViewById(R.id.fl_dragdrop_region);
		imageView = (ImageView) findViewById(R.id.imageview);
		// 为目标设置拖动监听器
		imageView.setOnLongClickListener(new OnLongClickListener() {

			@Override
			public boolean onLongClick(View v) {
				// TODO Auto-generated method stub
				DragShadowBuilder mysBuilder = new MyDragShadowBuilder(
						imageView);
				// 开始拖动，方法中第一参数是ClipData类型的对象。用于传递剪切板数据，可以为null
				v.startDrag(null, mysBuilder, null, 0);
				return true;
			}
		});
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

	@Override
	public boolean onDrag(View v, DragEvent event) {
		// TODO Auto-generated method stub
		int action = event.getAction();
		switch (action) {
		// 开始拖动
		case DragEvent.ACTION_DRAG_STARTED:

			System.out.println("drag started");
			break;
		// 进入目标区域
		case DragEvent.ACTION_DRAG_ENTERED:
			System.out.println("drag entered");
			break;
		// 在目标区域移动
		case DragEvent.ACTION_DRAG_LOCATION:
			System.out.println("drag location x=" + event.getX() + " y ="
					+ event.getY());
			break;
		// 离开目标区域
		case DragEvent.ACTION_DRAG_EXITED:
			System.out.println("drage exited");
			break;
		// 在目标区域放下ImageView控件
		case DragEvent.ACTION_DROP:
			System.out.println("drag drop");
			ImageView imageView = (ImageView) getLayoutInflater().inflate(
					R.layout.image, null);
			LayoutParams layoutParams = new LayoutParams(
					LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
			// 由于framelayout 不能直接使用坐标设置子视图的位置 这里用左边距和顶边距
			layoutParams.leftMargin = (int) event.getX();
			layoutParams.topMargin = (int) event.getY();
			// 添加到视图中，完成复制
			dragdropRegin.addView(imageView, layoutParams);
			break;
		case DragEvent.ACTION_DRAG_ENDED:
			System.out.println("drag ended");
		default:
			return false;
		}
		return true;
	}
}

以及布局文件

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <FrameLayout
        android:id="@+id/fl_dragdrop_region"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >

        <ImageView
            android:id="@+id/imageview"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:src="@drawable/ic_launcher" />
    </FrameLayout>

</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<ImageView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:layout_marginTop="50dp"
    android:src="@drawable/ic_launcher" />