写在前面的话

本篇blog实现了GridView的拖拽功能。方法和上一篇自定义ListView实现拖拽ListItem项交换位置一个原理。只是在交换位置上记录了X轴的相关坐标，计算了X轴的相关变量。

实现效果图如下

说明：

本篇给出实现代码，但是不做任何说明。如需了解请看上一篇blog：自定义ListView实现拖拽ListItem项交换位置

文件代码：

1、MainActivity.java

复制代码 代码如下:

package com.jay.draggridview;

import java.lang.reflect.Field;

import java.util.ArrayList;

import java.util.List;

import android.os.Bundle;

import android.app.Activity;

import android.content.Context;

import android.util.Log;

import android.view.LayoutInflater;

import android.view.Menu;

import android.view.View;

import android.view.ViewGroup;

import android.widget.ArrayAdapter;

import android.widget.ImageView;

public class MainActivity extends Activity {

private static List<String> list = null;

//自定义适配器

private DragGridAdapter adapter = null;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

//初始化数据

initData();

//后面用到的自定义GridView

DragGridView dragGridView = (DragGridView)findViewById(R.id.drag_grid);

adapter = new DragGridAdapter(this, list);

dragGridView.setAdapter(adapter);

}

public void initData(){

list = new ArrayList<String>();

for(int i= 0 ; i < 12 ; i++){

list.add("grid_"+i%12);

}

}

public static class DragGridAdapter extends ArrayAdapter<String>{

public DragGridAdapter(Context context, List<String> objects) {

super(context, 0, objects);

}

public List<String> getList(){

return list;

}

@Override

public View getView(int position, View convertView, ViewGroup parent) {

View view = convertView;

if(view==null){

view = LayoutInflater.from(getContext()).inflate(R.layout.drag_grid_item, null);

}

try {

Log.v("item", "------"+getItem(position));

//根据文件名获取资源文件夹中的图片资源

Field f= (Field)R.drawable.class.getDeclaredField(getItem(position));

int i=f.getInt(R.drawable.class);

ImageView imageview= (ImageView)view.findViewById(R.id.drag_grid_item_image);

imageview.setImageResource(i);

} catch (SecurityException e) {

e.printStackTrace();

} catch (NoSuchFieldException e) {

e.printStackTrace();

} catch (IllegalArgumentException e) {

e.printStackTrace();

} catch (IllegalAccessException e) {

e.printStackTrace();

}

return view;

}

}

}

2、DragGridView.java

复制代码 代码如下:

package com.jay.draggridview;

import com.jay.draggridview.MainActivity.DragGridAdapter;

import android.content.Context;

import android.graphics.Bitmap;

import android.graphics.PixelFormat;

import android.util.AttributeSet;

import android.view.Gravity;

import android.view.MotionEvent;

import android.view.View;

import android.view.ViewGroup;

import android.view.WindowManager;

import android.widget.AdapterView;

import android.widget.GridView;

import android.widget.ImageView;

import android.widget.Toast;

public class DragGridView extends GridView{

//定义基本的成员变量

private ImageView dragImageView;

private int dragSrcPosition;

private int dragPosition;

//x,y坐标的计算

private int dragPointX;

private int dragPointY;

private int dragOffsetX;

private int dragOffsetY;

private WindowManager windowManager;

private WindowManager.LayoutParams windowParams;

private int scaledTouchSlop;

private int upScrollBounce;

private int downScrollBounce;

public DragGridView(Context context, AttributeSet attrs) {

super(context, attrs);

}

@Override

public boolean onInterceptTouchEvent(MotionEvent ev) {

if(ev.getAction()==MotionEvent.ACTION_DOWN){

int x = (int)ev.getX();

int y = (int)ev.getY();

dragSrcPosition = dragPosition = pointToPosition(x, y);

if(dragPosition==AdapterView.INVALID_POSITION){

return super.onInterceptTouchEvent(ev);

}

ViewGroup itemView = (ViewGroup) getChildAt(dragPosition-getFirstVisiblePosition());

dragPointX = x - itemView.getLeft();

dragPointY = y - itemView.getTop();

dragOffsetX = (int) (ev.getRawX() - x);

dragOffsetY = (int) (ev.getRawY() - y);

View dragger = itemView.findViewById(R.id.drag_grid_item_drag);

//如果选中拖动图标

if(dragger!=null&&dragPointX>dragger.getLeft()&&dragPointX<dragger.getRight()&&dragPointY>dragger.getTop()&&dragPointY<dragger.getBottom()+20){

upScrollBounce = Math.min(y-scaledTouchSlop, getHeight()/4);

downScrollBounce = Math.max(y+scaledTouchSlop, getHeight()*3/4);

itemView.setDrawingCacheEnabled(true);

Bitmap bm = Bitmap.createBitmap(itemView.getDrawingCache());

startDrag(bm, x, y);

}

return false;

}

return super.onInterceptTouchEvent(ev);

}

@Override

public boolean onTouchEvent(MotionEvent ev) {

if(dragImageView!=null&&dragPosition!=INVALID_POSITION){

int action = ev.getAction();

switch(action){

case MotionEvent.ACTION_UP:

int upX = (int)ev.getX();

int upY = (int)ev.getY();

stopDrag();

onDrop(upX,upY);

break;

case MotionEvent.ACTION_MOVE:

int moveX = (int)ev.getX();

int moveY = (int)ev.getY();

onDrag(moveX,moveY);

break;

default:break;

}

return true;

}

return super.onTouchEvent(ev);

}

public void startDrag(Bitmap bm, int x, int y){

stopDrag();

windowParams = new WindowManager.LayoutParams();

windowParams.gravity = Gravity.TOP|Gravity.LEFT;

windowParams.x = x - dragPointX + dragOffsetX;

windowParams.y = y - dragPointY + dragOffsetY;

windowParams.width = WindowManager.LayoutParams.WRAP_CONTENT;

windowParams.height = WindowManager.LayoutParams.WRAP_CONTENT;

windowParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE

| WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE

| WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON

| WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN;

windowParams.format = PixelFormat.TRANSLUCENT;

windowParams.windowAnimations = 0;

ImageView imageView = new ImageView(getContext());

imageView.setImageBitmap(bm);

windowManager = (WindowManager)getContext().getSystemService("window");

windowManager.addView(imageView, windowParams);

dragImageView = imageView;

}

public void onDrag(int x, int y){

if(dragImageView!=null){

windowParams.alpha = 0.8f;

windowParams.x = x - dragPointX + dragOffsetX;

windowParams.y = y - dragPointY + dragOffsetY;

windowManager.updateViewLayout(dragImageView, windowParams);

}

int tempPosition = pointToPosition(x, y);

if(tempPosition!=INVALID_POSITION){

dragPosition = tempPosition;

}

//滚动

if(y<upScrollBounce||y>downScrollBounce){

//使用setSelection来实现滚动

setSelection(dragPosition);

}

}

public void onDrop(int x, int y){

//为了避免滑动到分割线的时候，返回-1的问题

int tempPosition = pointToPosition(x, y);

if(tempPosition!=INVALID_POSITION){

dragPosition = tempPosition;

}

//超出边界处理

if(y<getChildAt(0).getTop()){

//超出上边界

dragPosition = 0;

}else if(y>getChildAt(getChildCount()-1).getBottom()||(y>getChildAt(getChildCount()-1).getTop()&&x>getChildAt(getChildCount()-1).getRight())){

//超出下边界

dragPosition = getAdapter().getCount()-1;

}

//数据交换

if(dragPosition!=dragSrcPosition&&dragPosition>-1&&dragPosition<getAdapter().getCount()){

DragGridAdapter adapter = (DragGridAdapter)getAdapter();

String dragItem = adapter.getItem(dragSrcPosition);

adapter.remove(dragItem);

adapter.insert(dragItem, dragPosition);

Toast.makeText(getContext(), adapter.getList().toString(), Toast.LENGTH_SHORT).show();

}

}

/***

* 停止拖动，去掉拖动时候的影像

*/

public void stopDrag(){

if(dragImageView != null){

windowManager.removeView(dragImageView);

dragImageView = null;

}

}

}

3、activity_main.xml

复制代码 代码如下:

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:orientation="vertical"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:background="#ffffff"

android:padding="10dip"

>

<com.jay.draggridview.DragGridView

android:id="@+id/drag_grid"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:cacheColorHint="#00000000"

android:numColumns="3"

android:stretchMode="columnWidth"

android:verticalSpacing="5dip"

android:horizontalSpacing="20dip"

android:background="#ffffff"/>

</LinearLayout>

4、drag_grid_item.xml

复制代码 代码如下:

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:paddingLeft="5dip"

android:paddingRight="5dip">

<ImageView android:id="@+id/drag_grid_item_image"

android:layout_margin="5dip"

android:layout_alignParentTop="true"

android:layout_width="fill_parent"

android:layout_height="60dip"/>

<ImageView android:id="@+id/drag_grid_item_drag"

android:src="@drawable/p32_24_1"

android:layout_alignParentTop="true"

android:layout_alignParentRight="true"

android:layout_width="wrap_content"

android:layout_height="wrap_content"/>

</RelativeLayout>

源码下载