Android中在GridView网格视图上实现item拖拽交换的方法

<?xml version="1.0" encoding="utf-8"?> <GridView  xmlns:android="http://schemas.android.com/apk/res/android"  android:id="@+id/gridview"  android:layout_width="fill_parent"  android:layout_height="fill_parent"  android:columnWidth="90dp"  android:numColumns="auto_fit"  android:horizontalSpacing="10dp"  android:verticalSpacing="10dp"  android:stretchMode="columnWidth"  android:gravity="center"> </GridView> 

public class HelloGridView extends Activity {   /** Called when the activity is first created. */   @Override   protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.main);     GridView gridView=(GridView)findViewById(R.id.gridview);     gridView.setAdapter(new ImageAdapter(this));     //单击GridView元素的响应     gridView.setOnItemClickListener(new OnItemClickListener() {        @Override       public void onItemClick(AdapterView<?> parent, View view,           int position, long id) {         //弹出单击的GridView元素的位置         Toast.makeText(HelloGridView.this,mThumbIds[position], Toast.LENGTH_SHORT).show();       }     });   }   private class ImageAdapter extends BaseAdapter{     private Context mContext;      public ImageAdapter(Context context) {       this.mContext=context;     }      @Override     public int getCount() {       return mThumbIds.length;     }      @Override     public Object getItem(int position) {       return mThumbIds[position];     }      @Override     public long getItemId(int position) {       // TODO Auto-generated method stub       return 0;     }      @Override     public View getView(int position, View convertView, ViewGroup parent) {       //定义一个ImageView,显示在GridView里       ImageView imageView;       if(convertView==null){         imageView=new ImageView(mContext);         imageView.setLayoutParams(new GridView.LayoutParams(85, 85));         imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);         imageView.setPadding(8, 8, 8, 8);       }else{         imageView = (ImageView) convertView;       }       imageView.setImageResource(mThumbIds[position]);       return imageView;     }              }   //展示图片   private Integer[] mThumbIds = {       R.drawable.sample_2, R.drawable.sample_3,       R.drawable.sample_4, R.drawable.sample_5,       R.drawable.sample_6, R.drawable.sample_7,       R.drawable.sample_0, R.drawable.sample_1,       R.drawable.sample_2, R.drawable.sample_3,       R.drawable.sample_4, R.drawable.sample_5,       R.drawable.sample_6, R.drawable.sample_7,       R.drawable.sample_0, R.drawable.sample_1,       R.drawable.sample_2, R.drawable.sample_3,       R.drawable.sample_4, R.drawable.sample_5,       R.drawable.sample_6, R.drawable.sample_7   }; } 

package com.example.draggridview;  import android.app.Activity; import android.content.Context; import android.graphics.Bitmap; import android.graphics.PixelFormat; import android.graphics.Rect; import android.os.Handler; import android.os.Vibrator; import android.util.AttributeSet; import android.view.Gravity; import android.view.MotionEvent; import android.view.View; import android.view.WindowManager; import android.widget.AdapterView; import android.widget.GridView; import android.widget.ImageView;  public class DragGridView extends GridView{   /**    * DragGridView的item长按响应的时间， 默认是1000毫秒，也可以自行设置    */   private long dragResponseMS = 1000;      /**    * 是否可以拖拽，默认不可以    */   private boolean isDrag = false;      private int mDownX;   private int mDownY;   private int moveX;   private int moveY;   /**    * 正在拖拽的position    */   private int mDragPosition;      /**    * 刚开始拖拽的item对应的View    */   private View mStartDragItemView = null;      /**    * 用于拖拽的镜像，这里直接用一个ImageView    */   private ImageView mDragImageView;      /**    * 震动器    */   private Vibrator mVibrator;      private WindowManager mWindowManager;   /**    * item镜像的布局参数    */   private WindowManager.LayoutParams mWindowLayoutParams;      /**    * 我们拖拽的item对应的Bitmap    */   private Bitmap mDragBitmap;      /**    * 按下的点到所在item的上边缘的距离    */   private int mPoint2ItemTop ;       /**    * 按下的点到所在item的左边缘的距离    */   private int mPoint2ItemLeft;      /**    * DragGridView距离屏幕顶部的偏移量    */   private int mOffset2Top;      /**    * DragGridView距离屏幕左边的偏移量    */   private int mOffset2Left;      /**    * 状态栏的高度    */   private int mStatusHeight;       /**    * DragGridView自动向下滚动的边界值    */   private int mDownScrollBorder;      /**    * DragGridView自动向上滚动的边界值    */   private int mUpScrollBorder;      /**    * DragGridView自动滚动的速度    */   private static final int speed = 20;      /**    * item发生变化回调的接口    */   private OnChanageListener onChanageListener;            public DragGridView(Context context) {     this(context, null);   }      public DragGridView(Context context, AttributeSet attrs) {     this(context, attrs, 0);   }    public DragGridView(Context context, AttributeSet attrs, int defStyle) {     super(context, attrs, defStyle);     mVibrator = (Vibrator) context.getSystemService(Context.VIBRATOR_SERVICE);     mWindowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);     mStatusHeight = getStatusHeight(context); //获取状态栏的高度        }      private Handler mHandler = new Handler();      //用来处理是否为长按的Runnable   private Runnable mLongClickRunnable = new Runnable() {          @Override     public void run() {       isDrag = true; //设置可以拖拽       mVibrator.vibrate(50); //震动一下       mStartDragItemView.setVisibility(View.INVISIBLE);//隐藏该item              //根据我们按下的点显示item镜像       createDragImage(mDragBitmap, mDownX, mDownY);     }   }; 

  /**    * 设置回调接口    * @param onChanageListener    */   public void setOnChangeListener(OnChanageListener onChanageListener){     this.onChanageListener = onChanageListener;   }      /**    * 设置响应拖拽的毫秒数，默认是1000毫秒    * @param dragResponseMS    */   public void setDragResponseMS(long dragResponseMS) {     this.dragResponseMS = dragResponseMS;   }    @Override   public boolean dispatchTouchEvent(MotionEvent ev) {     switch(ev.getAction()){     case MotionEvent.ACTION_DOWN:       mDownX = (int) ev.getX();       mDownY = (int) ev.getY();              //根据按下的X,Y坐标获取所点击item的position       mDragPosition = pointToPosition(mDownX, mDownY);                     if(mDragPosition == AdapterView.INVALID_POSITION){         return super.dispatchTouchEvent(ev);       }              //使用Handler延迟dragResponseMS执行mLongClickRunnable       mHandler.postDelayed(mLongClickRunnable, dragResponseMS);              //根据position获取该item所对应的View       mStartDragItemView = getChildAt(mDragPosition - getFirstVisiblePosition());              //下面这几个距离大家可以参考我的博客上面的图来理解下       mPoint2ItemTop = mDownY - mStartDragItemView.getTop();       mPoint2ItemLeft = mDownX - mStartDragItemView.getLeft();              mOffset2Top = (int) (ev.getRawY() - mDownY);       mOffset2Left = (int) (ev.getRawX() - mDownX);              //获取DragGridView自动向上滚动的偏移量，小于这个值，DragGridView向下滚动       mDownScrollBorder = getHeight() /4;       //获取DragGridView自动向下滚动的偏移量，大于这个值，DragGridView向上滚动       mUpScrollBorder = getHeight() * 3/4;                            //开启mDragItemView绘图缓存       mStartDragItemView.setDrawingCacheEnabled(true);       //获取mDragItemView在缓存中的Bitmap对象       mDragBitmap = Bitmap.createBitmap(mStartDragItemView.getDrawingCache());       //这一步很关键，释放绘图缓存，避免出现重复的镜像       mStartDragItemView.destroyDrawingCache();                     break;     case MotionEvent.ACTION_MOVE:       int moveX = (int)ev.getX();       int moveY = (int) ev.getY();              //如果我们在按下的item上面移动，只要不超过item的边界我们就不移除mRunnable       if(!isTouchInItem(mStartDragItemView, moveX, moveY)){         mHandler.removeCallbacks(mLongClickRunnable);       }       break;     case MotionEvent.ACTION_UP:       mHandler.removeCallbacks(mLongClickRunnable);       mHandler.removeCallbacks(mScrollRunnable);       break;     }     return super.dispatchTouchEvent(ev);   } 

  /**    * 是否点击在GridView的item上面    * @param itemView    * @param x    * @param y    * @return    */   private boolean isTouchInItem(View dragView, int x, int y){     if(dragView == null){       return false;     }     int leftOffset = dragView.getLeft();     int topOffset = dragView.getTop();     if(x < leftOffset || x > leftOffset + dragView.getWidth()){       return false;     }          if(y < topOffset || y > topOffset + dragView.getHeight()){       return false;     }          return true;   }          @Override   public boolean onTouchEvent(MotionEvent ev) {     if(isDrag && mDragImageView != null){       switch(ev.getAction()){       case MotionEvent.ACTION_MOVE:         moveX = (int) ev.getX();         moveY = (int) ev.getY();         //拖动item         onDragItem(moveX, moveY);         break;       case MotionEvent.ACTION_UP:         onStopDrag();         isDrag = false;         break;       }       return true;     }     return super.onTouchEvent(ev);   } 

  /**    * 创建拖动的镜像    * @param bitmap    * @param downX    *     按下的点相对父控件的X坐标    * @param downY    *     按下的点相对父控件的X坐标    */   private void createDragImage(Bitmap bitmap, int downX , int downY){     mWindowLayoutParams = new WindowManager.LayoutParams();     mWindowLayoutParams.format = PixelFormat.TRANSLUCENT; //图片之外的其他地方透明     mWindowLayoutParams.gravity = Gravity.TOP | Gravity.LEFT;     mWindowLayoutParams.x = downX - mPoint2ItemLeft + mOffset2Left;     mWindowLayoutParams.y = downY - mPoint2ItemTop + mOffset2Top - mStatusHeight;     mWindowLayoutParams.alpha = 0.55f; //透明度     mWindowLayoutParams.width = WindowManager.LayoutParams.WRAP_CONTENT;      mWindowLayoutParams.height = WindowManager.LayoutParams.WRAP_CONTENT;      mWindowLayoutParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE            | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE ;           mDragImageView = new ImageView(getContext());      mDragImageView.setImageBitmap(bitmap);      mWindowManager.addView(mDragImageView, mWindowLayoutParams);    }    

  /**    * 从界面上面移动拖动镜像    */   private void removeDragImage(){     if(mDragImageView != null){       mWindowManager.removeView(mDragImageView);       mDragImageView = null;     }   } 

  /**    * 拖动item，在里面实现了item镜像的位置更新，item的相互交换以及GridView的自行滚动    * @param x    * @param y    */   private void onDragItem(int moveX, int moveY){     mWindowLayoutParams.x = moveX - mPoint2ItemLeft + mOffset2Left;     mWindowLayoutParams.y = moveY - mPoint2ItemTop + mOffset2Top - mStatusHeight;     mWindowManager.updateViewLayout(mDragImageView, mWindowLayoutParams); //更新镜像的位置     onSwapItem(moveX, moveY);          //GridView自动滚动     mHandler.post(mScrollRunnable);   } 

  /**    * 当moveY的值大于向上滚动的边界值，触发GridView自动向上滚动    * 当moveY的值小于向下滚动的边界值，触犯GridView自动向下滚动    * 否则不进行滚动    */   private Runnable mScrollRunnable = new Runnable() {          @Override     public void run() {       int scrollY;       if(moveY > mUpScrollBorder){          scrollY = speed;          mHandler.postDelayed(mScrollRunnable, 25);       }else if(moveY < mDownScrollBorder){         scrollY = -speed;          mHandler.postDelayed(mScrollRunnable, 25);       }else{         scrollY = 0;         mHandler.removeCallbacks(mScrollRunnable);       }              //当我们的手指到达GridView向上或者向下滚动的偏移量的时候，可能我们手指没有移动，但是DragGridView在自动的滚动       //所以我们在这里调用下onSwapItem()方法来交换item       onSwapItem(moveX, moveY);                     smoothScrollBy(scrollY, 10);     }   }; 

  /**    * 交换item,并且控制item之间的显示与隐藏效果    * @param moveX    * @param moveY    */   private void onSwapItem(int moveX, int moveY){     //获取我们手指移动到的那个item的position     int tempPosition = pointToPosition(moveX, moveY);          //假如tempPosition 改变了并且tempPosition不等于-1,则进行交换     if(tempPosition != mDragPosition && tempPosition != AdapterView.INVALID_POSITION){       if(onChanageListener != null){         onChanageListener.onChange(mDragPosition, tempPosition);       }              getChildAt(tempPosition - getFirstVisiblePosition()).setVisibility(View.INVISIBLE);//拖动到了新的item,新的item隐藏掉       getChildAt(mDragPosition - getFirstVisiblePosition()).setVisibility(View.VISIBLE);//之前的item显示出来              mDragPosition = tempPosition;     }   } 

     /**    * 停止拖拽我们将之前隐藏的item显示出来，并将镜像移除    */   private void onStopDrag(){     View view = getChildAt(mDragPosition - getFirstVisiblePosition());     if(view != null){       view.setVisibility(View.VISIBLE);     }     ((DragAdapter)this.getAdapter()).setItemHide(-1);     removeDragImage();   } 

  /**    * 获取状态栏的高度    * @param context    * @return    */   private static int getStatusHeight(Context context){     int statusHeight = 0;     Rect localRect = new Rect();     ((Activity) context).getWindow().getDecorView().getWindowVisibleDisplayFrame(localRect);     statusHeight = localRect.top;     if (0 == statusHeight){       Class<?> localClass;       try {         localClass = Class.forName("com.android.internal.R$dimen");         Object localObject = localClass.newInstance();         int i5 = Integer.parseInt(localClass.getField("status_bar_height").get(localObject).toString());         statusHeight = context.getResources().getDimensionPixelSize(i5);       } catch (Exception e) {         e.printStackTrace();       }      }     return statusHeight;   } 

  /**    *    * @author xiaanming    *    */   public interface OnChanageListener{          /**      * 当item交换位置的时候回调的方法，我们只需要在该方法中实现数据的交换即可      * @param form      *     开始的position      * @param to      *     拖拽到的position      */     public void onChange(int form, int to);   } } 

首先看DragGridView的事件分发方法，不了解Android事件分发的可以先去了解下，Android事件分发对于自定义控件很重要，简单说下，当我们点击DragGridView的Item,先会去执行dispatchTouchEvent()方法将事件分发下去，所以我们要重写dispatchTouchEvent()方法在手指按下的时候根据pointToPosition()方法来获取我们按下的item的position,根据getChildAt()方法来获取该position上面所对应的View, 并且开启长按的定时器，默认时间为1000毫秒，如果在1000毫秒内手指抬起或者手指在屏幕上滑动出了该item，则取消长按定时器，否则就表示可以进行拖拽，手机友好的震动一下，隐藏我们长按的Item，屏幕调用createDragImage()方法来创建我们长按的item的镜像，创建Item的镜像使用的是WindowManager类，该类可以创建一个窗体显示在Activity之上，
再此之前大家先要理解这几个距离，理解这几个距离之前要首先知道getRawX(),getRawY()和getX(),getY()的区别，getRawX(),getRawY()是相对于屏幕的原点的距离，而getX(),getY()是相对于控件左上方的点的距离，为了方便大家理解我用Word简单的画了下图，画得不好，大家将就的看下，红色框框为我们的GridView

• mPoint2ItemTop 手指按下的点到该Item的上边缘的距离，如上图的1号线
• mPoint2ItemLeft 手指按下的点到该Item的左边缘的距离，如上图的2号线
• mOffset2Top  DragGridView的上边缘到屏幕上边缘的距离，如上图的3号线，这个距离包裹状态栏，标题栏，或者一些在DragGridView上面的布局的高度，这个很重要我们现实Item镜像需要用到
• mOffset2Left DragGridView的左边缘到屏幕左边缘的距离，如上图的4号线，我这个Demo的这个距离为0，因为我设置DragGridView的宽度为充满屏幕，但是我们要考虑假如DragGridView与屏幕左边缘设置了间隙或者左边有其他的布局的情形
• mDownScrollBorder 这个距离表示当DragGridView的item过多的时候，手机一屏显示不完全，我们拖动Item镜像到这个高度的时候，DragGridView自动向下滚动，如上图的5号线
• .mUpScrollBorder 这个和mDownScrollBorder相反，当我们大于这个高度的时候，DragGridView自动向上滚动，如上图的6号线

理解了这六个距离，我们就来看看创建Item镜像的方法里面，其他的我不多说，首先设置format为PixelFormat.TRANSLUCENT，表示除了我们显示图片和文字的其他地方为透明，之后就是x，y这两个距离的计算，计算的是item的左上角的坐标，理解了上面这六个距离我们很容易得出x,y的坐标，可是你会发现y的坐标减去了状态栏的高度，这点大家需要注意下，另外我们需要获取item的绘制缓存的Bitmap对象，然后将Bitmap设置到一个ImageView上面，为什么要这么做呢？如果调用addView()方法将item 直接添加到WindowManager里面，会有异常产生，因为item已经有了自己归属的父容器DragGridView，所有我们这里使用一个ImageView来代替item添加到WindowManager里面

<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" >    <com.example.draggridview.DragGridView     android:id="@+id/dragGridView"     android:listSelector="@android:color/transparent"     android:layout_width="match_parent"     android:layout_height="match_parent"     android:cacheColorHint="@android:color/transparent"     android:verticalSpacing="10dip"     android:horizontalSpacing="10dip"     android:stretchMode="columnWidth"      android:gravity="center"      android:numColumns="3" >   </com.example.draggridview.DragGridView>  </RelativeLayout> 

<?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:background="@android:color/transparent" >    <ImageView     android:id="@+id/item_image"     android:scaleType="centerCrop"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_centerHorizontal="true" >   </ImageView>    <TextView     android:id="@+id/item_text"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_below="@+id/item_image"     android:layout_centerHorizontal="true" >   </TextView>  </RelativeLayout> 

package com.example.draggridview;  import java.util.ArrayList; import java.util.Collections; import java.util.HashMap; import java.util.List;  import android.app.Activity; import android.os.Bundle; import android.widget.SimpleAdapter;  import com.example.draggridview.DragGridView.OnChanageListener; public class MainActivity extends Activity {   private List<HashMap<String, Object>> dataSourceList = new ArrayList<HashMap<String, Object>>();    @Override   protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.activity_main);      DragGridView mDragGridView = (DragGridView) findViewById(R.id.dragGridView);     for (int i = 0; i < 30; i++) {       HashMap<String, Object> itemHashMap = new HashMap<String, Object>();       itemHashMap.put("item_image",R.drawable.com_tencent_open_notice_msg_icon_big);       itemHashMap.put("item_text", "拖拽 " + Integer.toString(i));       dataSourceList.add(itemHashMap);     }           final SimpleAdapter mSimpleAdapter = new SimpleAdapter(this, dataSourceList,         R.layout.grid_item, new String[] { "item_image", "item_text" },         new int[] { R.id.item_image, R.id.item_text });          mDragGridView.setAdapter(mSimpleAdapter);          mDragGridView.setOnChangeListener(new OnChanageListener() {              @Override       public void onChange(int from, int to) {         HashMap<String, Object> temp = dataSourceList.get(from);         //直接交互item //       dataSourceList.set(from, dataSourceList.get(to)); //       dataSourceList.set(to, temp); //       dataSourceList.set(to, temp);                           //这里的处理需要注意下         if(from < to){           for(int i=from; i<to; i++){             Collections.swap(dataSourceList, i, i+1);           }         }else if(from > to){           for(int i=from; i>to; i--){             Collections.swap(dataSourceList, i, i-1);           }         }                  dataSourceList.set(to, temp);                  mSimpleAdapter.notifyDataSetChanged();                         }     });        }  } 

HashMap<String, Object> temp = dataSourceList.get(from);         //直接交互item //       dataSourceList.set(from, dataSourceList.get(to)); //       dataSourceList.set(to, temp);