Android中GridView拖拽的效果

2022-11-16 16:21:41

最近看到联想，摩托罗拉等，手机launcher中有个效果，进入mainmenu后，里面的应用程序的图标可以拖来拖去，所以我也参照网上给的代码，写了一个例子。还是很有趣的，实现的流畅度没有人家的那么好，我只是模仿这种效果，我写的这个拖拽是两个图标之间进行交换，所以，当从一行的某个位置，换到下一行的另一列的时候，发现有好几个图标都改变位置了，因为是相邻两个交换位置，所以每经过相邻的图标的时候都改变位置。先弄个雏形，以后再更新优化。

转载请标明出处：http://blog.csdn.net/wdaming1986/article/details/7436881

先看几张效果图，再来研究代码：

横行拖拽：

纵向拖拽的效果图：

下面贴上代码---->在GragGridViewApp-4-7这个工程里面：

1、在包com.cn.daming.adapter中，有三个类----->

1.1、DragAdapter.java这个类中的代码如下：

package com.cn.daming.adapter;
import java.util.ArrayList;
import java.util.Collections;
import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
public abstract class DragAdapter extends BaseAdapter {
protected Context mContext;
protected ArrayList<DragMessage> mlist;
public DragAdapter(Context mContext, ArrayList<DragMessage> mlist) {
this.mContext = mContext;
this.mlist = mlist;
}
public int getCount() {
if (this.mlist != null) {
return this.mlist.size();
}
return 0;
}
public DragMessage getItem(int position) {
return (DragMessage)this.mlist.get(position);
}
public long getItemId(int position) {
return 0;
}
public void addMsg(DragMessage msg){
this.mlist.add(msg);
}
final void reFlag(){
for (DragMessage msg : this.mlist) {
msg.flag = 0;
}
notifyDataSetChanged();
}
final void swap(int srcPosition, int dragPosition){
Collections.swap(this.mlist, srcPosition, dragPosition);
notifyDataSetChanged();
}
final void setFlag(int position, int flag){
getItem(position).flag = flag;
notifyDataSetChanged();
}
public abstract View getView(int position, View convertView, ViewGroup parent);
}

1.2、DragMessage.java这个类中的代码如下：

package com.cn.daming.adapter;
public class DragMessage {
public static final int MOVE_FLAG = 1;
public static final int STATIC_FLAG = 0;
public int flag = 0;
}

1.3、GragGridView.java核心类中的代码如下：

package com.cn.daming.adapter;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Color;
import android.graphics.PixelFormat;
import android.graphics.drawable.Drawable;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.util.AttributeSet;
import android.util.Log;
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;
public class GragGridView extends GridView{
private ImageView dragImageView;//拖动item的preview
private WindowManager windowManager;
private WindowManager.LayoutParams windowParams;
private int dragSrcPosition; //开始拖拽的位置
private int dragPosition; // 结束拖拽的位置
private int dragPointX;//相对于item的x坐标
private int dragPointY;//相对于item的y坐标
private int dragOffsetX;
private int dragOffsetY;
private int dragImageId;
private int itemHeight;
private int itemWidth;
private int moveHeight = 0;
private int upScrollBounce;
private int downScrollBounce;
private int dragColor = Color.GRAY;
private int changePosition = -1;
private long scrollDelayMillis = 10L;
private int middleX;
private int middleY;
private boolean isDrag = false;
private RefreshHandler scrollDelayUp = new RefreshHandler(Looper.getMainLooper(), true);
private RefreshHandler scrollDelayDown = new RefreshHandler(Looper.getMainLooper(), false);
private int scrollHeight = 4;
private int maxSH = 20;
private int minSH = 4;
public void setMoveHeight(int height) {
this.moveHeight = height;
}
public void setDragColor(int color) {
this.dragColor = color;
}
public void setDragImageId(int id) {
this.dragImageId = id;
}
public GragGridView(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();
this.dragSrcPosition = this.dragPosition = pointToPosition(x, y);
if (this.dragPosition == -1) {
return super.onInterceptTouchEvent(ev);
}
ViewGroup itemView = (ViewGroup)getChildAt(this.dragPosition -
getFirstVisiblePosition());
//得到当前点在item内部的偏移量即相对于item左上角的坐标
this.itemHeight = itemView.getHeight();
this.dragPointX = (x - itemView.getLeft());
this.dragPointY = (y - itemView.getTop());
this.dragOffsetX = (int)(ev.getRawX() - x);
this.dragOffsetY = (int)(ev.getRawY() - y);
View dragger = itemView.findViewById(this.dragImageId);
if ((dragger != null) && (x > dragger.getLeft()&& x < dragger.getRight()) &&
(y > dragger.getTop() && y < dragger.getBottom())) {
if(this.moveHeight <= 0 || (this.moveHeight >= getHeight()/2)) {
this.upScrollBounce = (getHeight() / 3);
this.downScrollBounce = (getHeight() * 2 / 3);
} else {
this.upScrollBounce = this.moveHeight;
this.downScrollBounce = (getHeight() - this.moveHeight);
}
//解决问题3
//每次都销毁一次cache，重新生成一个bitmap
itemView.destroyDrawingCache();
itemView.setDrawingCacheEnabled(true);
Drawable background = itemView.getBackground();
itemView.setBackgroundColor(this.dragColor);
Bitmap bitmap = Bitmap.createBitmap(itemView.getDrawingCache());
itemView.setBackgroundDrawable(background);
//建立item的缩略图
startDrag(bitmap, x, y);
}
return false;
}
return super.onInterceptTouchEvent(ev);
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
if ((this.dragImageView != null) && (this.dragPosition != -1)) {
int action = ev.getAction();
int moveY = (int)ev.getY();
int moveX = (int)ev.getX();
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:
if (moveX <= 0)
this.middleX = 0;
else if (moveX >= getWidth())
this.middleX = getWidth();
else {
this.middleX = moveX;
}
if (moveY <= 0)
this.middleY = 0;
else if (moveY >= getHeight())
this.middleY = getHeight();
else {
this.middleY = moveY;
}
dragPositionChanged();
onDrag(moveX, moveY);
}
return true;
}
return super.onTouchEvent(ev);
}
private void onDrag(int x, int y) {
if (this.dragImageView != null) {
this.windowParams.alpha = 0.8F;
if (this.middleX - this.dragPointX <= 0)
this.windowParams.x = this.dragOffsetX;
else if (this.middleX - this.dragPointX >= getWidth() - this.itemWidth)
this.windowParams.x = (getWidth() - this.itemWidth + this.dragOffsetX);
else {
this.windowParams.x = (this.middleX - this.dragPointX + this.dragOffsetX);
}
if (this.middleY - this.dragPointY <= 0)
this.windowParams.y = this.dragOffsetY;
else if (this.middleY - this.dragPointY >= getHeight() - this.itemHeight)
this.windowParams.y = (getHeight() - this.itemHeight + this.dragOffsetY);
else {
this.windowParams.y = (this.middleY - this.dragPointY + this.dragOffsetY);
}
this.windowManager.updateViewLayout(this.dragImageView, this.windowParams);
}
int tempPosition = pointToPosition(this.middleX, this.middleY);
Log.v("daming", "GragGridView ---> 177 tempPosition == "+tempPosition);
if (tempPosition != -1) {
this.dragPosition = tempPosition;
}
if ((y >= this.upScrollBounce) && (y <= this.downScrollBounce)) {
this.isDrag = false;
return;
}
if (y < this.upScrollBounce) {
float a = this.upScrollBounce - this.middleY;
float b = this.upScrollBounce;
float c = a / b;
this.scrollHeight = (int)(c * (this.maxSH - this.minSH) + this.minSH);
this.isDrag = true;
this.scrollDelayUp.sleep(0L);
} else if (y > this.downScrollBounce) {
float a = this.middleY - this.downScrollBounce;
float b = this.upScrollBounce;
float c = a / b;
this.scrollHeight = (int)(c * (this.maxSH - this.minSH) + this.minSH);
this.isDrag = true;
this.scrollDelayDown.sleep(0L);
}
}
private void startDrag(Bitmap bm, int x, int y) {
stopDrag();
this.windowParams = new WindowManager.LayoutParams();
//Gravity.TOP|Gravity.LEFT;这个必须加
this.windowParams.gravity = Gravity.TOP|Gravity.LEFT;
//得到preview左上角相对于屏幕的坐标
this.windowParams.x = (x - this.dragPointX + this.dragOffsetX);
this.windowParams.y = (y - this.dragPointY + this.dragOffsetY);
//设置拖拽item的宽和高
this.windowParams.width = WindowManager.LayoutParams.WRAP_CONTENT;
this.windowParams.height = WindowManager.LayoutParams.WRAP_CONTENT;
this.windowParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
| WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE
| WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
| WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN;
this.windowParams.format = PixelFormat.TRANSLUCENT;
this.windowParams.windowAnimations = 0;
ImageView imageView = new ImageView(getContext());
imageView.setImageBitmap(bm);
this.windowManager = ((WindowManager)getContext().getSystemService(Context.WINDOW_SERVICE));//“window”
this.windowManager.addView(imageView, this.windowParams);
this.dragImageView = imageView;
}
private void stopDrag() {
if (this.dragImageView != null) {
this.windowManager.removeView(this.dragImageView);
this.dragImageView = null;
}
this.changePosition = -1;
this.isDrag = false;
}
private void dragPositionChanged(){
DragAdapter adapter = (DragAdapter)getAdapter();
if (this.changePosition != this.dragPosition) {
if (this.changePosition == -1)
{
this.changePosition = this.dragPosition;
adapter.setFlag(this.changePosition, 1);
return;
}
adapter.swap(this.changePosition, this.dragPosition);
this.changePosition = this.dragPosition;
}
}
public void setMaxSH(int sh){
this.maxSH = sh;
}
public void setMinSH(int sh){
this.minSH = sh;
}
private 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()){
DragAdapter adapter = (DragAdapter)getAdapter();
adapter.reFlag();
}
// DragAdapter adapter = (DragAdapter)getAdapter();
// adapter.reFlag();
}
private void actDown(){
int tempPosition = pointToPosition(this.middleX, this.middleY);
if (tempPosition != AdapterView.INVALID_POSITION) {
this.dragPosition = tempPosition;
}
dragPositionChanged();
}
private void actUp(){
int tempPosition = pointToPosition(this.middleX, this.middleY);
if (tempPosition != AdapterView.INVALID_POSITION) {
this.dragPosition = tempPosition;
}
dragPositionChanged();
}
class RefreshHandler extends Handler {
boolean isUp;
public RefreshHandler(Looper looper, boolean isUp){
super(looper);
this.isUp = isUp;
}
public RefreshHandler(Looper l) {
super(l);
}
public void handleMessage(Message msg){
if (GragGridView.this.isDrag) {
if (this.isUp)
GragGridView.this.actUp();
else {
GragGridView.this.actDown();
}
sleep(GragGridView.this.scrollDelayMillis);
}
}
public void sleep(long delayMillis) {
sendMessageDelayed(obtainMessage(0), delayMillis);
}
}
}