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.<!-- height of a normal list item in edit playlist mode -->
<dimen name="normal_height">48dip</dimen>
<!-- height of an expanded list item in edit playlist mode -->
<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>