水平ListView类

package com.hztbc.android.HorizontalListView;

/*
 * HorizontalListView.java v1.5
 *
 *
 * The MIT License
 * Copyright (c) 2011 Paul Soucy ([e-mail])
 *
 * 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.util.Log;
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;

/**
 *水平ListView类. 
 * @author lsq
 *
 */
public class HorizontalListView extends AdapterView<ListAdapter> {

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<View> mRemovedViewQueue = new LinkedList<View>();
 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;
    autoScroll = true;
   }
   invalidate();
   requestLayout();
  }

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

};

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

@Override
 public View getSelectedView() {
  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) {
  // scrollTo(position);
 }

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);// 进行控件的位置定位，确定在显示窗体的位置，默认不要修改这里
  if (mAdapter == null) {
   return;
  }

if (mDataChanged) {
   int oldCurrentX = mCurrentX;
   initView();// 初始化计算位置的相关变量
   removeAllViewsInLayout();// 移除全部view，准备重新渲染
   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);// 移除不可见的item
  fillList(dx);
  positionItems(dx);// 进行每个item的位置的确定！--开始以为是在这里面进行控制，实际不是。
  scrollToRight();
  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);
  }
 }

// 自动计算每个显示出来的item的位置！自动根据屏幕大小计算出来的！
 private void positionItems(final int dx) {
  if (getChildCount() > 0) {
   // getChildCount()的结果不是全部选择图片的数量，而是这里水平listView显示出现的item的数量.
   mDisplayOffset += dx;
   int left = mDisplayOffset;
   for (int i = 0; i < getChildCount(); i++) {
    View child = getChildAt(i);
    int childWidth = child.getMeasuredWidth();
    child.layout(left, 0, left + childWidth,
      child.getMeasuredHeight());
    left += childWidth;
   }

}
 }

private boolean autoScroll = true;

public synchronized void scrollToRight() {
  if (autoScroll) {
   int maxCount = (int)Math.floor(getWidth()/45.0);
   if (mAdapter.getCount() >=maxCount) {
    mScroller.setFinalX(45 * (mAdapter.getCount()-maxCount));
   } else
    mScroller.setFinalX(0);
   requestLayout();
  }
 }

@Override
 public boolean dispatchTouchEvent(MotionEvent ev) {
  autoScroll = false;
  boolean handled = super.dispatchTouchEvent(ev);
  handled |= mGesture.onTouchEvent(ev);
  return handled;
 }

protected boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
   float velocityY) {
  synchronized (HorizontalListView.this) {
   mScroller.fling(mNextX, 0, (int) -velocityX, 0, 0, mMaxX, 0, 0);
  }
  requestLayout();

return true;
 }

protected boolean onDown(MotionEvent e) {
  mScroller.forceFinished(true);
  return true;
 }

private OnGestureListener mOnGesture = new GestureDetector.SimpleOnGestureListener() {

@Override
  public boolean onDown(MotionEvent e) {
   return HorizontalListView.this.onDown(e);
  }

@Override
  public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
    float velocityY) {
   return HorizontalListView.this
     .onFling(e1, e2, velocityX, velocityY);
  }

@Override
  public boolean onScroll(MotionEvent e1, MotionEvent e2,
    float distanceX, float distanceY) {
   synchronized (HorizontalListView.this) {
    mNextX += (int) distanceX;
   }
   requestLayout();

return true;
  }

@Override
  public boolean onSingleTapConfirmed(MotionEvent e) {
   for (int i = 0; i < getChildCount(); i++) {
    View child = getChildAt(i);
    if (isEventWithinView(e, child)) {
     if (mOnItemClicked != null) {
      mOnItemClicked.onItemClick(HorizontalListView.this,
        child, mLeftViewIndex + 1 + i,
        mAdapter.getItemId(mLeftViewIndex + 1 + i));
     }
     if (mOnItemSelected != null) {
      mOnItemSelected.onItemSelected(HorizontalListView.this,
        child, mLeftViewIndex + 1 + i,
        mAdapter.getItemId(mLeftViewIndex + 1 + i));
     }
     break;
    }

}
   return true;
  }

@Override
  public void onLongPress(MotionEvent e) {
   int childCount = getChildCount();
   for (int i = 0; i < childCount; i++) {
    View child = getChildAt(i);
    if (isEventWithinView(e, child)) {
     if (mOnItemLongClicked != null) {
      mOnItemLongClicked.onItemLongClick(
        HorizontalListView.this, child, mLeftViewIndex
          + 1 + i,
        mAdapter.getItemId(mLeftViewIndex + 1 + i));
     }
     break;
    }

}
  }

private boolean isEventWithinView(MotionEvent e, View child) {
   Rect viewRect = new Rect();
   int[] childPosition = new int[2];
   child.getLocationOnScreen(childPosition);
   int left = childPosition[0];
   int right = left + child.getWidth();
   int top = childPosition[1];
   int bottom = top + child.getHeight();
   viewRect.set(left, top, right, bottom);
   return viewRect.contains((int) e.getRawX(), (int) e.getRawY());
  }
 };
}