AndroidUI使用HorizontalListView实现水平滑动

/* 
 * HorizontalListView.java v1.5 
 * 
 * 
 * The MIT License 
 * Copyright (c) 2011 Paul Soucy (paul@dev-smart.com) 
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy 
 * of this software and associated documentation files (the "Software"), to deal 
 * in the Software without restriction, including without limitation the rights 
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 
 * copies of the Software, and to permit persons to whom the Software is 
 * furnished to do so, subject to the following conditions: 
 * 
 * The above copyright notice and this permission notice shall be included in 
 * all copies or substantial portions of the Software. 
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 
 * THE SOFTWARE. 
 * 
 */
import java.util.LinkedList;
import java.util.Queue;

import android.content.Context;
import android.database.DataSetObserver;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.GestureDetector.OnGestureListener;
import android.view.MotionEvent;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.Scroller;

public class HorizontalListView extends AdapterView {

 public boolean mAlwaysOverrideTouch = true;
 protected ListAdapter mAdapter;
 private int mLeftViewIndex = -1;
 private int mRightViewIndex = 0;
 protected int mCurrentX;
 protected int mNextX;
 private int mMaxX = Integer.MAX_VALUE;
 private int mDisplayOffset = 0;
 protected Scroller mScroller;
 private GestureDetector mGesture;
 private Queue mRemovedViewQueue = new LinkedList();
 private OnItemSelectedListener mOnItemSelected;
 private OnItemClickListener mOnItemClicked;
 private OnItemLongClickListener mOnItemLongClicked;
 private boolean mDataChanged = false;


 public HorizontalListView(Context context, AttributeSet attrs) {
  super(context, attrs);
  initView();
 }

 private synchronized void initView() {
  mLeftViewIndex = -1;
  mRightViewIndex = 0;
  mDisplayOffset = 0;
  mCurrentX = 0;
  mNextX = 0;
  mMaxX = Integer.MAX_VALUE;
  mScroller = new Scroller(getContext());
  mGesture = new GestureDetector(getContext(), mOnGesture);
 }

 @Override
 public void setOnItemSelectedListener(AdapterView.OnItemSelectedListener listener) {
  mOnItemSelected = listener;
 }

 @Override
 public void setOnItemClickListener(AdapterView.OnItemClickListener listener){
  mOnItemClicked = listener;
 }

 @Override
 public void setOnItemLongClickListener(AdapterView.OnItemLongClickListener listener) {
  mOnItemLongClicked = listener;
 }

 private DataSetObserver mDataObserver = new DataSetObserver() {

  @Override
  public void onChanged() {
   synchronized(HorizontalListView.this){
    mDataChanged = true;
   }
   invalidate();
   requestLayout();
  }

  @Override
  public void onInvalidated() {
   reset();
   invalidate();
   requestLayout();
  }

 };

 @Override
 public ListAdapter getAdapter() {
  return mAdapter;
 }

 @Override
 public View getSelectedView() {
  //TODO: implement
  return null;
 }

 @Override
 public void setAdapter(ListAdapter adapter) {
  if(mAdapter != null) {
   mAdapter.unregisterDataSetObserver(mDataObserver);
  }
  mAdapter = adapter;
  mAdapter.registerDataSetObserver(mDataObserver);
  reset();
 }

 private synchronized void reset(){
  initView();
  removeAllViewsInLayout();
  requestLayout();
 }

 @Override
 public void setSelection(int position) {
  //TODO: implement
 }

 private void addAndMeasureChild(final View child, int viewPos) {
  LayoutParams params = child.getLayoutParams();
  if(params == null) {
   params = new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT);
  }

  addViewInLayout(child, viewPos, params, true);
  child.measure(MeasureSpec.makeMeasureSpec(getWidth(), MeasureSpec.AT_MOST),
    MeasureSpec.makeMeasureSpec(getHeight(), MeasureSpec.AT_MOST));
 }



 @Override
 protected synchronized void onLayout(boolean changed, int left, int top, int right, int bottom) {
  super.onLayout(changed, left, top, right, bottom);

  if(mAdapter == null){
   return;
  }

  if(mDataChanged){
   int oldCurrentX = mCurrentX;
   initView();
   removeAllViewsInLayout();
   mNextX = oldCurrentX;
   mDataChanged = false;
  }

  if(mScroller.computeScrollOffset()){
   int scrollx = mScroller.getCurrX();
   mNextX = scrollx;
  }

  if(mNextX <= 0){
   mNextX = 0;
   mScroller.forceFinished(true);
  }
  if(mNextX >= mMaxX) {
   mNextX = mMaxX;
   mScroller.forceFinished(true);
  }

  int dx = mCurrentX - mNextX;

  removeNonVisibleItems(dx);
  fillList(dx);
  positionItems(dx);

  mCurrentX = mNextX;

  if(!mScroller.isFinished()){
   post(new Runnable(){
    @Override
    public void run() {
     requestLayout();
    }
   });

  }
 }

 private void fillList(final int dx) {
  int edge = 0;
  View child = getChildAt(getChildCount()-1);
  if(child != null) {
   edge = child.getRight();
  }
  fillListRight(edge, dx);

  edge = 0;
  child = getChildAt(0);
  if(child != null) {
   edge = child.getLeft();
  }
  fillListLeft(edge, dx);


 }

 private void fillListRight(int rightEdge, final int dx) {
  while(rightEdge + dx < getWidth() && mRightViewIndex < mAdapter.getCount()) {

   View child = mAdapter.getView(mRightViewIndex, mRemovedViewQueue.poll(), this);
   addAndMeasureChild(child, -1);
   rightEdge += child.getMeasuredWidth();

   if(mRightViewIndex == mAdapter.getCount()-1) {
    mMaxX = mCurrentX + rightEdge - getWidth();
   }

   if (mMaxX < 0) {
    mMaxX = 0;
   }
   mRightViewIndex++;
  }

 }

 private void fillListLeft(int leftEdge, final int dx) {
  while(leftEdge + dx > 0 && mLeftViewIndex >= 0) {
   View child = mAdapter.getView(mLeftViewIndex, mRemovedViewQueue.poll(), this);
   addAndMeasureChild(child, 0);
   leftEdge -= child.getMeasuredWidth();
   mLeftViewIndex--;
   mDisplayOffset -= child.getMeasuredWidth();
  }
 }

 private void removeNonVisibleItems(final int dx) {
  View child = getChildAt(0);
  while(child != null && child.getRight() + dx <= 0) {
   mDisplayOffset += child.getMeasuredWidth();
   mRemovedViewQueue.offer(child);
   removeViewInLayout(child);
   mLeftViewIndex++;
   child = getChildAt(0);

  }

  child = getChildAt(getChildCount()-1);
  while(child != null && child.getLeft() + dx >= getWidth()) {
   mRemovedViewQueue.offer(child);
   removeViewInLayout(child);
   mRightViewIndex--;
   child = getChildAt(getChildCount()-1);
  }
 }

 private void positionItems(final int dx) {
  if(getChildCount() > 0){
   mDisplayOffset += dx;
   int left = mDisplayOffset;
   for(int i=0;i