android之listivew实现下拉刷新



/** * 重写一个ListView,主要是添加一个下拉事件 *  * @author way *  */public class MyListView extends ListView implements OnScrollListener {private static final String TAG = "listview";private final static int RELEASE_To_REFRESH = 0; // 松开刷新状态private final static int PULL_To_REFRESH = 1;// 拉动刷新状态private final static int REFRESHING = 2;// 正在刷新状态private final static int DONE = 3;// 已经加载完毕状态private final static int LOADING = 4;// 正在加载数据状态private final static int RATIO = 3;// 实际的padding的距离与界面上偏移距离的比例private LayoutInflater inflater;private LinearLayout headView;// ListView头部的Viewprivate TextView tipsTextview;// 提示信息“下拉刷新”的TextViewprivate TextView lastUpdatedTextView;// 上次更新时间的TextViewprivate ImageView arrowImageView;// 箭头的图片private ProgressBar progressBar;// 刷新进度private RotateAnimation animation;// 箭头向下动画private RotateAnimation reverseAnimation;// 逆向箭头动画private boolean isRecored;// 用于保证startY的值在一个完整的touch事件中只被记录一次private int headContentWidth;// 头部View内容的宽度private int headContentHeight;// 头部view内容的高度private int startY;// 向下触屏事件时的手指起始y轴位置private int firstItemIndex;// ListView第一项的索引private int state;// 刷新状态private boolean isBack;// 是否反弹private OnRefreshListener refreshListener;// 给外面预留的刷新的接口private boolean isRefreshable;// 是否刷新的标志位/** * 第一个构造器 *  * @param context *            上下文对象 */public MyListView(Context context) {super(context);init(context);}/** * 第二个构造器 *  * @param context *            上下文对象 * @param attrs *            属性 */public MyListView(Context context, AttributeSet attrs) {super(context, attrs);init(context);}/** * 初始化数据 *  * @param context *            上下文对象 */private void init(Context context) {// setCacheColorHint(context.getResources().getColor(R.color.transparent));inflater = LayoutInflater.from(context);headView = (LinearLayout) inflater.inflate(R.layout.head, null);// 获取ListView头部的viewarrowImageView = (ImageView) headView.findViewById(R.id.head_arrowImageView);// 从头部的View获取箭头图片arrowImageView.setMinimumWidth(70);arrowImageView.setMinimumHeight(50);progressBar = (ProgressBar) headView.findViewById(R.id.head_progressBar);// 获取刷新进度条tipsTextview = (TextView) headView.findViewById(R.id.head_tipsTextView);// 提示信息的TextViewlastUpdatedTextView = (TextView) headView.findViewById(R.id.head_lastUpdatedTextView);// 最后刷新时间的TextViewmeasureView(headView);// 自己写的一个方法，没有很理解headContentHeight = headView.getMeasuredHeight();// 得到headView的原始高度headContentWidth = headView.getMeasuredWidth();headView.setPadding(0, -1 * headContentHeight, 0, 0);// 设置内容的内部偏移量headView.invalidate();Log.v("size", "width:" + headContentWidth + " height:"+ headContentHeight);addHeaderView(headView, null, false);// 加到ListView的头部view，ListView组件提供了两个很实用的功能，那就是可以在顶部和底部添加自定义的视图setOnScrollListener(this);// 箭头向下动画animation = new RotateAnimation(0, -180,RotateAnimation.RELATIVE_TO_SELF, 0.5f,RotateAnimation.RELATIVE_TO_SELF, 0.5f);animation.setInterpolator(new LinearInterpolator());animation.setDuration(250);animation.setFillAfter(true);// 逆向箭头动画reverseAnimation = new RotateAnimation(-180, 0,RotateAnimation.RELATIVE_TO_SELF, 0.5f,RotateAnimation.RELATIVE_TO_SELF, 0.5f);reverseAnimation.setInterpolator(new LinearInterpolator());reverseAnimation.setDuration(200);reverseAnimation.setFillAfter(true);state = DONE;// 第一次加载默认完成的状态isRefreshable = false;// 刷新标志位默认为false}/** * 滑动时被调用 */public void onScroll(AbsListView view, int firstVisiableItem,int visibleItemCount, int totalItemCount) {firstItemIndex = firstVisiableItem;// ListView第一个索引值为ListView数据中第一个可见项}/** * 滑动状态改变时被调用 */public void onScrollStateChanged(AbsListView view, int scrollState) {}/** * 触摸事件 */public boolean onTouchEvent(MotionEvent event) {if (isRefreshable) {// 如果刷新标志为trueswitch (event.getAction()) {case MotionEvent.ACTION_DOWN:// 向下if (firstItemIndex == 0 && !isRecored) {isRecored = true;startY = (int) event.getY();Log.v(TAG, "在down时候记录当前位置");}break;case MotionEvent.ACTION_UP:// 向上if (state != REFRESHING && state != LOADING) {if (state == DONE) {// 什么都不做}if (state == PULL_To_REFRESH) {// 下拉刷新state = DONE;changeHeaderViewByState();// 更新头部viewLog.v(TAG, "由下拉刷新状态，到done状态");}if (state == RELEASE_To_REFRESH) {// 释放刷新state = REFRESHING;changeHeaderViewByState();onRefresh();// 调用接口的方法，通知外面Log.v(TAG, "由松开刷新状态，到done状态");}}isRecored = false;isBack = false;break;case MotionEvent.ACTION_MOVE:// 手指移动int tempY = (int) event.getY();if (!isRecored && firstItemIndex == 0) {Log.v(TAG, "在move时候记录下位置");isRecored = true;startY = tempY;}if (state != REFRESHING && isRecored && state != LOADING) {// 保证在设置padding的过程中，当前的位置一直是在head，否则如果当列表超出屏幕的话，当在上推的时候，列表会同时进行滚动// 可以松手去刷新了if (state == RELEASE_To_REFRESH) {setSelection(0);// 往上推了，推到了屏幕足够掩盖head的程度，但是还没有推到全部掩盖的地步if (((tempY - startY) / RATIO < headContentHeight)&& (tempY - startY) > 0) {state = PULL_To_REFRESH;changeHeaderViewByState();Log.v(TAG, "由松开刷新状态转变到下拉刷新状态");}// 一下子推到顶了else if (tempY - startY <= 0) {state = DONE;changeHeaderViewByState();Log.v(TAG, "由松开刷新状态转变到done状态");}// 往下拉了，或者还没有上推到屏幕顶部掩盖head的地步else {// 不用进行特别的操作，只用更新paddingTop的值就行了}}// 还没有到达显示松开刷新的时候,DONE或者是PULL_To_REFRESH状态if (state == PULL_To_REFRESH) {setSelection(0);// 下拉到可以进入RELEASE_TO_REFRESH的状态if ((tempY - startY) / RATIO >= headContentHeight) {state = RELEASE_To_REFRESH;isBack = true;changeHeaderViewByState();Log.v(TAG, "由done或者下拉刷新状态转变到松开刷新");}// 上推到顶了else if (tempY - startY <= 0) {state = DONE;changeHeaderViewByState();Log.v(TAG, "由DOne或者下拉刷新状态转变到done状态");}}// done状态下if (state == DONE) {if (tempY - startY > 0) {state = PULL_To_REFRESH;changeHeaderViewByState();}}// 更新headView的sizeif (state == PULL_To_REFRESH) {headView.setPadding(0, -1 * headContentHeight+ (tempY - startY) / RATIO, 0, 0);}// 更新headView的paddingTopif (state == RELEASE_To_REFRESH) {headView.setPadding(0, (tempY - startY) / RATIO- headContentHeight, 0, 0);}}break;}}return super.onTouchEvent(event);}// 当状态改变时候，调用该方法，以更新界面private void changeHeaderViewByState() {switch (state) {case RELEASE_To_REFRESH:// 松开刷新状态arrowImageView.setVisibility(View.VISIBLE);// 显示箭头progressBar.setVisibility(View.GONE);// 移除进度条tipsTextview.setVisibility(View.VISIBLE);// 显示提示信息lastUpdatedTextView.setVisibility(View.VISIBLE);// 显示最后刷新时间arrowImageView.clearAnimation();// 先移除所有动画arrowImageView.startAnimation(animation);// 加载箭头向下动画tipsTextview.setText("松开刷新");Log.v(TAG, "当前状态，松开刷新");break;case PULL_To_REFRESH:// 下拉刷新状态progressBar.setVisibility(View.GONE);// 移除进度条tipsTextview.setVisibility(View.VISIBLE);// 显示提示信息lastUpdatedTextView.setVisibility(View.VISIBLE);// 显示最后刷新时间arrowImageView.clearAnimation();// 先移除所有动画arrowImageView.setVisibility(View.VISIBLE);// 箭头图片可见// 如果是由RELEASE_To_REFRESH状态转变来的，就加载动画if (isBack) {isBack = false;arrowImageView.clearAnimation();arrowImageView.startAnimation(reverseAnimation);tipsTextview.setText("下拉刷新");} else {tipsTextview.setText("下拉刷新");}Log.v(TAG, "当前状态，下拉刷新");break;case REFRESHING:// 正在刷新状态headView.setPadding(0, 0, 0, 0);// 无内部偏移progressBar.setVisibility(View.VISIBLE);// 进度条可见arrowImageView.clearAnimation();// 先清除动画arrowImageView.setVisibility(View.GONE);// 再移除箭头动画tipsTextview.setText("正在刷新...");// 提示信息变成正在刷新...lastUpdatedTextView.setVisibility(View.VISIBLE);// 最后刷新时间可见Log.v(TAG, "当前状态,正在刷新...");break;case DONE:// 完成状态headView.setPadding(0, -1 * headContentHeight, 0, 0);progressBar.setVisibility(View.GONE);arrowImageView.clearAnimation();arrowImageView.setImageResource(R.drawable.arrow_down);tipsTextview.setText("下拉刷新");lastUpdatedTextView.setVisibility(View.VISIBLE);Log.v(TAG, "当前状态，done");break;}}// 刷新完成public void onRefreshComplete() {state = DONE;SimpleDateFormat format = new SimpleDateFormat("yyyy年MM月dd日  HH:mm");String date = format.format(new Date());lastUpdatedTextView.setText("最近更新:" + date);changeHeaderViewByState();}/** * 一个下拉刷新的监听接口 *  */public interface OnRefreshListener {public void onRefresh();}// 监听方法public void setonRefreshListener(OnRefreshListener refreshListener) {this.refreshListener = refreshListener;isRefreshable = true;}// 正在刷新private void onRefresh() {if (refreshListener != null) {refreshListener.onRefresh();}}/** * 此方法是“估计”headView的width以及height *  * @param child *            传入进来的headView */private void measureView(View child) {ViewGroup.LayoutParams p = child.getLayoutParams();if (p == null) {p = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT,ViewGroup.LayoutParams.WRAP_CONTENT);}int childWidthSpec = ViewGroup.getChildMeasureSpec(0, 0 + 0, p.width);int lpHeight = p.height;int childHeightSpec;if (lpHeight > 0) {childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight,MeasureSpec.EXACTLY);} else {childHeightSpec = MeasureSpec.makeMeasureSpec(0,MeasureSpec.UNSPECIFIED);}child.measure(childWidthSpec, childHeightSpec);}// ListView添加Adapter方法public void setAdapter(BaseAdapter adapter) {SimpleDateFormat format = new SimpleDateFormat("yyyy年MM月dd日  HH:mm");String date = format.format(new Date());lastUpdatedTextView.setText("最近更新:" + date);super.setAdapter(adapter);}}

新浪微博，和QQ空间里面，都有那个下拉刷新的效果，另很多人眼前一亮，细细分析，原理原来如此。

在原作者的基础上，写了一些注释，和帮助大家更好的阅读理解，（可能其中有些地方注释不准，欢迎指正，谢谢）

源代码下载地址：http://download.csdn.net/detail/weidi1989/4588246

先来看一下效果图：