自定义GridView并且实现拖拽(附源码)

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

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

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

<?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

<?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