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>