android listview拖拽，拖动item 改变位置

在packages/apps/Music/src/touchIncepter.java中

该类提供了listview的拖动效果，并提供接口，在程序接口中实现数据的交换即可。

package com.and.DragListview;import java.util.ArrayList;import java.util.List;import android.app.ListActivity;import android.content.Context;import android.os.Bundle;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.ImageView;import android.widget.TextView;public class DragListview extends ListActivity {       MyAdapter adapter;    TouchInterceptor list;    List<String> arrayText;        @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);                list = (TouchInterceptor) getListView();//(TouchInterceptor)findViewById(android.R.id.list);        getText();                adapter = new MyAdapter(this);        setListAdapter(adapter);               list.setDropListener(mDropListener);     //   list.setRemoveListener(mRemoveListener);          }    public void getText(){    arrayText = new ArrayList<String>();    arrayText.add("传奇");    arrayText.add("红豆");    arrayText.add("流年");    arrayText.add("棋子");    }        //交换listview的数据    private TouchInterceptor.DropListener mDropListener =        new TouchInterceptor.DropListener() {        public void drop(int from, int to) {        String item = arrayText.get(from);        arrayText.remove(item);//.remove(from);        arrayText.add(to, item);        adapter.notifyDataSetChanged();        }    };        private TouchInterceptor.RemoveListener mRemoveListener =        new TouchInterceptor.RemoveListener() {        public void remove(int which) {                  }    };        class MyAdapter extends BaseAdapter{    private LayoutInflater mInflater;    Context mContext;    public MyAdapter(Context c){    mInflater = LayoutInflater.from(c);    }public int getCount() {return arrayText.size();}public Object getItem(int arg0) {return arrayText.get(arg0);}public long getItemId(int arg0) {return arg0;}public View getView(int arg0, View contentView, ViewGroup arg2) {ImageView img;TextView text;if(contentView==null){contentView = mInflater.inflate(R.layout.list_layout, null); //contentView = mInflater.inflate(R.layout.list_layout,null);}img = (ImageView)contentView.findViewById(R.id.img);img.setBackgroundResource(R.drawable.icon);text = (TextView)contentView.findViewById(R.id.text);text.setText(arrayText.get(arg0).toString());return contentView;}        }}

源码中的类：

/* * Copyright (C) 2008 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * *      http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package com.and.DragListview;import android.content.Context;import android.content.SharedPreferences;import android.content.res.Resources;import android.graphics.Bitmap;import android.graphics.PixelFormat;import android.graphics.Rect;import android.util.AttributeSet;import android.view.GestureDetector;import android.view.Gravity;import android.view.MotionEvent;import android.view.View;import android.view.ViewConfiguration;import android.view.ViewGroup;import android.view.WindowManager;import android.view.GestureDetector.SimpleOnGestureListener;import android.widget.AdapterView;import android.widget.ImageView;import android.widget.ListView;public class TouchInterceptor extends ListView {        private ImageView mDragView;    private WindowManager mWindowManager;    private WindowManager.LayoutParams mWindowParams;    private int mDragPos;      // which item is being dragged    private int mFirstDragPos; // where was the dragged item originally    private int mDragPoint;    // at what offset inside the item did the user grab it    private int mCoordOffset;  // the difference between screen coordinates and coordinates in this view    private DragListener mDragListener;    private DropListener mDropListener;    private RemoveListener mRemoveListener;    private int mUpperBound;    private int mLowerBound;    private int mHeight;    private GestureDetector mGestureDetector;    private static final int FLING = 0;    private static final int SLIDE = 1;    private int mRemoveMode = -1;    private Rect mTempRect = new Rect();    private Bitmap mDragBitmap;    private final int mTouchSlop;    private int mItemHeightNormal;    private int mItemHeightExpanded;    private int mItemHeightHalf;    public TouchInterceptor(Context context, AttributeSet attrs) {        super(context, attrs);        SharedPreferences pref = context.getSharedPreferences("Music", 3);        mRemoveMode = pref.getInt("deletemode", -1);        mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();        Resources res = getResources();        mItemHeightNormal = 48;//res.getDimensionPixelSize(R.dimen.normal_height);        mItemHeightHalf = mItemHeightNormal / 2;        mItemHeightExpanded = 96;//res.getDimensionPixelSize(R.dimen.expanded_height);    }        @Override    public boolean onInterceptTouchEvent(MotionEvent ev) {        if (mRemoveListener != null && mGestureDetector == null) {            if (mRemoveMode == FLING) {                mGestureDetector = new GestureDetector(getContext(), new SimpleOnGestureListener() {                    @Override                    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,                            float velocityY) {                        if (mDragView != null) {                            if (velocityX > 1000) {                                Rect r = mTempRect;                                mDragView.getDrawingRect(r);                                if ( e2.getX() > r.right * 2 / 3) {                                    // fast fling right with release near the right edge of the screen                                    stopDragging();                                    mRemoveListener.remove(mFirstDragPos);                                    unExpandViews(true);                                }                            }                            // flinging while dragging should have no effect                            return true;                        }                        return false;                    }                });            }        }        if (mDragListener != null || mDropListener != null) {            switch (ev.getAction()) {                case MotionEvent.ACTION_DOWN:                    int x = (int) ev.getX();                    int y = (int) ev.getY();                    int itemnum = pointToPosition(x, y);                    if (itemnum == AdapterView.INVALID_POSITION) {                        break;                    }                    ViewGroup item = (ViewGroup) getChildAt(itemnum - getFirstVisiblePosition());                    mDragPoint = y - item.getTop();                    mCoordOffset = ((int)ev.getRawY()) - y;                    View dragger = item.findViewById(R.id.img);//..........................                    Rect r = mTempRect;                    dragger.getDrawingRect(r);                    // The dragger icon itself is quite small, so pretend the touch area is bigger                    if (x < r.right * 2) {                        item.setDrawingCacheEnabled(true);                        // Create a copy of the drawing cache so that it does not get recycled                        // by the framework when the list tries to clean up memory                        Bitmap bitmap = Bitmap.createBitmap(item.getDrawingCache());                        startDragging(bitmap, y);                        mDragPos = itemnum;                        mFirstDragPos = mDragPos;                        mHeight = getHeight();                        int touchSlop = mTouchSlop;                        mUpperBound = Math.min(y - touchSlop, mHeight / 3);                        mLowerBound = Math.max(y + touchSlop, mHeight * 2 /3);                        return false;                    }                    stopDragging();                    break;            }        }        return super.onInterceptTouchEvent(ev);    }        /*     * pointToPosition() doesn't consider invisible views, but we     * need to, so implement a slightly different version.     */    private int myPointToPosition(int x, int y) {        if (y < 0) {            // when dragging off the top of the screen, calculate position            // by going back from a visible item            int pos = myPointToPosition(x, y + mItemHeightNormal);            if (pos > 0) {                return pos - 1;            }        }        Rect frame = mTempRect;        final int count = getChildCount();        for (int i = count - 1; i >= 0; i--) {            final View child = getChildAt(i);            child.getHitRect(frame);            if (frame.contains(x, y)) {                return getFirstVisiblePosition() + i;            }        }        return INVALID_POSITION;    }        private int getItemForPosition(int y) {        int adjustedy = y - mDragPoint - mItemHeightHalf;        int pos = myPointToPosition(0, adjustedy);        if (pos >= 0) {            if (pos <= mFirstDragPos) {                pos += 1;            }        } else if (adjustedy < 0) {            // this shouldn't happen anymore now that myPointToPosition deals            // with this situation            pos = 0;        }        return pos;    }        private void adjustScrollBounds(int y) {        if (y >= mHeight / 3) {            mUpperBound = mHeight / 3;        }        if (y <= mHeight * 2 / 3) {            mLowerBound = mHeight * 2 / 3;        }    }    /*     * Restore size and visibility for all listitems     */    private void unExpandViews(boolean deletion) {        for (int i = 0;; i++) {            View v = getChildAt(i);            if (v == null) {                if (deletion) {                    // HACK force update of mItemCount                    int position = getFirstVisiblePosition();                    int y = getChildAt(0).getTop();                    setAdapter(getAdapter());                    setSelectionFromTop(position, y);                    // end hack                }                layoutChildren(); // force children to be recreated where needed                v = getChildAt(i);                if (v == null) {                    break;                }            }            ViewGroup.LayoutParams params = v.getLayoutParams();            params.height = mItemHeightNormal;            v.setLayoutParams(params);            v.setVisibility(View.VISIBLE);        }    }        /* Adjust visibility and size to make it appear as though     * an item is being dragged around and other items are making     * room for it:     * If dropping the item would result in it still being in the     * same place, then make the dragged listitem's size normal,     * but make the item invisible.     * Otherwise, if the dragged listitem is still on screen, make     * it as small as possible and expand the item below the insert     * point.     * If the dragged item is not on screen, only expand the item     * below the current insertpoint.     */    private void doExpansion() {        int childnum = mDragPos - getFirstVisiblePosition();        if (mDragPos > mFirstDragPos) {            childnum++;        }        View first = getChildAt(mFirstDragPos - getFirstVisiblePosition());        for (int i = 0;; i++) {            View vv = getChildAt(i);            if (vv == null) {                break;            }            int height = mItemHeightNormal;            int visibility = View.VISIBLE;            if (vv.equals(first)) {                // processing the item that is being dragged                if (mDragPos == mFirstDragPos) {                    // hovering over the original location                    visibility = View.INVISIBLE;                } else {                    // not hovering over it                    height = 1;                }            } else if (i == childnum) {                if (mDragPos < getCount() - 1) {                    height = mItemHeightExpanded;                }            }            ViewGroup.LayoutParams params = vv.getLayoutParams();            params.height = height;            vv.setLayoutParams(params);            vv.setVisibility(visibility);        }    }        @Override    public boolean onTouchEvent(MotionEvent ev) {        if (mGestureDetector != null) {            mGestureDetector.onTouchEvent(ev);        }        if ((mDragListener != null || mDropListener != null) && mDragView != null) {            int action = ev.getAction();             switch (action) {                case MotionEvent.ACTION_UP:                case MotionEvent.ACTION_CANCEL:                    Rect r = mTempRect;                    mDragView.getDrawingRect(r);                    stopDragging();                    if (mRemoveMode == SLIDE && ev.getX() > r.right * 3 / 4) {                        if (mRemoveListener != null) {                            mRemoveListener.remove(mFirstDragPos);                        }                        unExpandViews(true);                    } else {                        if (mDropListener != null && mDragPos >= 0 && mDragPos < getCount()) {                            mDropListener.drop(mFirstDragPos, mDragPos);                        }                        unExpandViews(false);                    }                    break;                                    case MotionEvent.ACTION_DOWN:                case MotionEvent.ACTION_MOVE:                    int x = (int) ev.getX();                    int y = (int) ev.getY();                    dragView(x, y);                    int itemnum = getItemForPosition(y);                    if (itemnum >= 0) {                        if (action == MotionEvent.ACTION_DOWN || itemnum != mDragPos) {                            if (mDragListener != null) {                                mDragListener.drag(mDragPos, itemnum);                            }                            mDragPos = itemnum;                            doExpansion();                        }                        int speed = 0;                        adjustScrollBounds(y);                        if (y > mLowerBound) {                            // scroll the list up a bit                            speed = y > (mHeight + mLowerBound) / 2 ? 16 : 4;                        } else if (y < mUpperBound) {                            // scroll the list down a bit                            speed = y < mUpperBound / 2 ? -16 : -4;                        }                        if (speed != 0) {                            int ref = pointToPosition(0, mHeight / 2);                            if (ref == AdapterView.INVALID_POSITION) {                                //we hit a divider or an invisible view, check somewhere else                                ref = pointToPosition(0, mHeight / 2 + getDividerHeight() + 64);                            }                            View v = getChildAt(ref - getFirstVisiblePosition());                            if (v!= null) {                                int pos = v.getTop();                                setSelectionFromTop(ref, pos - speed);                            }                        }                    }                    break;            }            return true;        }        return super.onTouchEvent(ev);    }        private void startDragging(Bitmap bm, int y) {        stopDragging();        mWindowParams = new WindowManager.LayoutParams();        mWindowParams.gravity = Gravity.TOP;        mWindowParams.x = 0;        mWindowParams.y = y - mDragPoint + mCoordOffset;        mWindowParams.height = WindowManager.LayoutParams.WRAP_CONTENT;        mWindowParams.width = WindowManager.LayoutParams.WRAP_CONTENT;        mWindowParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE                | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE                | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON                | WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN                | WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS;        mWindowParams.format = PixelFormat.TRANSLUCENT;        mWindowParams.windowAnimations = 0;                Context context = getContext();        ImageView v = new ImageView(context);//        int backGroundColor = context.getResources().getColor(R.color.dragndrop_background);//        v.setBackgroundColor(backGroundColor);        v.setImageBitmap(bm);        mDragBitmap = bm;        mWindowManager = (WindowManager)context.getSystemService("window");        mWindowManager.addView(v, mWindowParams);        mDragView = v;    }        private void dragView(int x, int y) {        if (mRemoveMode == SLIDE) {            float alpha = 1.0f;            int width = mDragView.getWidth();            if (x > width / 2) {                alpha = ((float)(width - x)) / (width / 2);            }            mWindowParams.alpha = alpha;        }        if (mRemoveMode == FLING) {            mWindowParams.x = x;        }        mWindowParams.y = y - mDragPoint + mCoordOffset;        mWindowManager.updateViewLayout(mDragView, mWindowParams);    }        private void stopDragging() {        if (mDragView != null) {            WindowManager wm = (WindowManager)getContext().getSystemService("window");            wm.removeView(mDragView);            mDragView.setImageDrawable(null);            mDragView = null;        }        if (mDragBitmap != null) {            mDragBitmap.recycle();            mDragBitmap = null;        }    }        public void setDragListener(DragListener l) {        mDragListener = l;    }        public void setDropListener(DropListener l) {        mDropListener = l;    }        public void setRemoveListener(RemoveListener l) {        mRemoveListener = l;    }    public interface DragListener {        void drag(int from, int to);    }    public interface DropListener {        void drop(int from, int to);    }    public interface RemoveListener {        void remove(int which);    }}

<com.and.DragListview.TouchInterceptor

android:id="@android:id/list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:textSize="18sp"
android:drawSelectorOnTop="false"
android:fastScrollEnabled="true" />

如果想要实现源码音乐播放器那种顺畅的拖动效果，则需注意2点：

1.
<dimen name="normal_height">48dip</dimen>

<dimen name="expanded_height">96dip</dimen>

后者的高度要为前者的2倍。

2.item对应的布局要在listview的item的bottom位置，即：

<?xml version="1.0" encoding="utf-8"?><RelativeLayout             xmlns:android="http://schemas.android.com/apk/res/android"    android:orientation="vertical"    android:layout_width="match_parent"    android:layout_height="48dip"><com.android.weather.CityListItemLayout android:id="@+id/item_layout"    android:orientation="horizontal"    android:layout_width="match_parent"    android:layout_height="48dip"          android:gravity="center_vertical"    android:layout_alignParentBottom="true">。。。</com.android.weather.CityListItemLayout></RelativeLayout>

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