android listivew 下拉回弹刷新

该效果是一名国外工程师（johannilsson）的代码，拿来研究了下，自己整合了一下，现在拿出来，跟大家一起分享。

再次感谢这位国外工程师（johannilsson），谢谢！

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）

下面，就亮出关键代码：

**** 自定义 listivew （关键代码）

public class PullToRefreshListView extends ListView implements OnScrollListener {

private static final int TAP_TO_REFRESH = 1; // 初始状态
private static final int PULL_TO_REFRESH = 2; //拉动刷新
private static final int RELEASE_TO_REFRESH = 3; //释放刷新
private static final int REFRESHING = 4; //正在刷新

private static final String TAG = "PullToRefreshListView";
//刷新接口
private OnRefreshListener mOnRefreshListener;

//箭头图片
private static int REFRESHICON = R.drawable.goicon;

/**
* listview 滚动监听器
*/
private OnScrollListener mOnScrollListener;

//视图索引器
private LayoutInflater mInflater;
/**
* 头部视图 内容 -- start
*/
private RelativeLayout mRefreshView;
private TextView mRefreshViewText;
private ImageView mRefreshViewImage;
private ProgressBar mRefreshViewProgress;
private TextView mRefreshViewLastUpdated;
/**
* 头部视图 内容 -- end
*/
//当前listivew 的滚动状态
private int mCurrentScrollState;

//当前listview 的刷新状态
private int mRefreshState;

//动画效果
//变为向下的箭头
private RotateAnimation mFlipAnimation;
//变为逆向的箭头
private RotateAnimation mReverseFlipAnimation;
//头视图的高度
private int mRefreshViewHeight;
//头视图 原始的 top padding 属性值
private int mRefreshOriginalTopPadding;
//
private int mLastMotionY;
//是否反弹
private boolean mBounceHack;

public PullToRefreshListView(Context context) {
super(context);
init(context);
}

public PullToRefreshListView(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}

public PullToRefreshListView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
init(context);
}

private void init(Context context) {
// Load all of the animations we need in code rather than through XML
//初始化动画
//
mFlipAnimation = new RotateAnimation(0, -180,
RotateAnimation.RELATIVE_TO_SELF, 0.5f,
RotateAnimation.RELATIVE_TO_SELF, 0.5f);
mFlipAnimation.setInterpolator(new LinearInterpolator());
mFlipAnimation.setDuration(250);
mFlipAnimation.setFillAfter(true);



mReverseFlipAnimation = new RotateAnimation(-180, 0,
RotateAnimation.RELATIVE_TO_SELF, 0.5f,
RotateAnimation.RELATIVE_TO_SELF, 0.5f);
mReverseFlipAnimation.setInterpolator(new LinearInterpolator());
mReverseFlipAnimation.setDuration(250);
mReverseFlipAnimation.setFillAfter(true);

mInflater = (LayoutInflater) context.getSystemService(
Context.LAYOUT_INFLATER_SERVICE);

mRefreshView = (RelativeLayout) mInflater.inflate(R.layout.pull_to_refresh_header, this, false);//(R.layout.pull_to_refresh_header, null);
mRefreshViewText =
(TextView) mRefreshView.findViewById(R.id.pull_to_refresh_text);
mRefreshViewImage =
(ImageView) mRefreshView.findViewById(R.id.pull_to_refresh_image);
mRefreshViewProgress =
(ProgressBar) mRefreshView.findViewById(R.id.pull_to_refresh_progress);
mRefreshViewLastUpdated =
(TextView) mRefreshView.findViewById(R.id.pull_to_refresh_updated_at);

mRefreshViewImage.setMinimumHeight(50);
mRefreshView.setOnClickListener(new OnClickRefreshListener());
mRefreshOriginalTopPadding = mRefreshView.getPaddingTop();

mRefreshState = TAP_TO_REFRESH;

addHeaderView(mRefreshView);

super.setOnScrollListener(this);

measureView(mRefreshView);
mRefreshViewHeight = mRefreshView.getMeasuredHeight(); //获取头文件的测量高度
}

@Override
protected void onAttachedToWindow() {
setSelection(1);
}

@Override
public void setAdapter(ListAdapter adapter) {
super.setAdapter(adapter);

setSelection(1);
}

/**
* Set the listener that will receive notifications every time the list
* scrolls.
*
* @param l The scroll listener.
*/
@Override
public void setOnScrollListener(AbsListView.OnScrollListener l) {
mOnScrollListener = l;
}

/**
* Register a callback to be invoked when this list should be refreshed.
*
* @param onRefreshListener The callback to run.
*/
public void setOnRefreshListener(OnRefreshListener onRefreshListener) {
mOnRefreshListener = onRefreshListener;
}

/**
* Set a text to represent when the list was last updated.
* @param lastUpdated Last updated at.
*/
public void setLastUpdated(CharSequence lastUpdated) {
if (lastUpdated != null) {
mRefreshViewLastUpdated.setVisibility(View.VISIBLE);
mRefreshViewLastUpdated.setText(lastUpdated);
} else {
mRefreshViewLastUpdated.setVisibility(View.GONE);
}
}

@Override
public boolean onTouchEvent(MotionEvent event) {
//当前手指的Y值
final int y = (int) event.getY();

//Log.i(TAG, "触屏的Y值"+y);
mBounceHack = false; //不反弹

switch (event.getAction()) {
case MotionEvent.ACTION_UP:
//将垂直滚动条设置为可用状态
if (!isVerticalScrollBarEnabled()) {
setVerticalScrollBarEnabled(true);
}

//如果头部刷新条出现，并且不是正在刷新状态
if (getFirstVisiblePosition() == 0 && mRefreshState != REFRESHING) {
if ((mRefreshView.getBottom() >= mRefreshViewHeight
|| mRefreshView.getTop() >= 0)
&& mRefreshState == RELEASE_TO_REFRESH) { //如果头部视图处于拉离顶部的情况
// Initiate the refresh
mRefreshState = REFRESHING; //将标量设置为，正在刷新
prepareForRefresh(); //准备刷新
onRefresh(); //刷新
} else if (mRefreshView.getBottom() < mRefreshViewHeight
|| mRefreshView.getTop() <= 0) {
// Abort refresh and scroll down below the refresh view
// 停止刷新，并且滚动到头部刷新视图的下一个视图
resetHeader();
setSelection(1); //定位在第二个列表项
}
}
break;
case MotionEvent.ACTION_DOWN:
mLastMotionY = y; //跟踪手指的Y值
break;

case MotionEvent.ACTION_MOVE:
//更行头视图的toppadding 属性
applyHeaderPadding(event);
break;
}
return super.onTouchEvent(event);
}

/****
* 不断的头部的top padding 属性
* @param ev
*/
private void applyHeaderPadding(MotionEvent ev) {
//获取累积的动作数
int pointerCount = ev.getHistorySize();
// Log.i(TAG, "获取累积的动作数"+pointerCount);
for (int p = 0; p < pointerCount; p++) {
if (mRefreshState == RELEASE_TO_REFRESH) { //如果是释放将要刷新状态
if (isVerticalFadingEdgeEnabled()) {
setVerticalScrollBarEnabled(false);
}
//历史累积的高度
int historicalY = (int) ev.getHistoricalY(p);
//Log.i(TAG, "单个动作getHistoricalY值："+historicalY);
// Calculate the padding to apply, we divide by 1.7 to
// simulate a more resistant effect during pull.
int topPadding = (int) (((historicalY - mLastMotionY)
- mRefreshViewHeight) / 1.7);

mRefreshView.setPadding(
mRefreshView.getPaddingLeft(),
topPadding,
mRefreshView.getPaddingRight(),
mRefreshView.getPaddingBottom());
}
}
}

/**
* Sets the header padding back to original size.
* 使头部视图的 toppadding 恢复到初始值
*/
private void resetHeaderPadding() {
mRefreshView.setPadding(
mRefreshView.getPaddingLeft(),
mRefreshOriginalTopPadding,
mRefreshView.getPaddingRight(),
mRefreshView.getPaddingBottom());
}

/**
* Resets the header to the original state.
* 初始化头部视图 状态
*/
private void resetHeader() {
if (mRefreshState != TAP_TO_REFRESH) {
mRefreshState = TAP_TO_REFRESH; //初始刷新状态
//使头部视图的 toppadding 恢复到初始值
resetHeaderPadding();
// Set refresh view text to the pull label
//将文字初始化
mRefreshViewText.setText(R.string.pull_to_refresh_tap_label);
// Replace refresh drawable with arrow drawable
//设置初始图片
mRefreshViewImage.setImageResource(REFRESHICON);
// Clear the full rotation animation
// 清除动画
mRefreshViewImage.clearAnimation();
// Hide progress bar and arrow.
//隐藏头视图
mRefreshViewImage.setVisibility(View.GONE);
//隐藏进度条
mRefreshViewProgress.setVisibility(View.GONE);
}
}

//测量视图的高度
private void measureView(View child) {
//获取头部视图属性
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;

//不懂MeasureSpec------------------------------------------------------------------------------------------
if (lpHeight > 0) { //如果视图的高度大于0
childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight, MeasureSpec.EXACTLY);
} else {
childHeightSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
}
child.measure(childWidthSpec, childHeightSpec);
//不懂MeasureSpec------------------------------------------------------------------------------------------
}

/****
* 滑动事件
*/
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
// When the refresh view is completely visible, change the text to say
// "Release to refresh..." and flip the arrow drawable.
if (mCurrentScrollState == SCROLL_STATE_TOUCH_SCROLL //如果是接触滚动状态,并且不是正在刷新的状态
&& mRefreshState != REFRESHING) {
if (firstVisibleItem == 0) { //如果显示出来了第一个列表项
//显示刷新图片
mRefreshViewImage.setVisibility(View.VISIBLE);
if ((mRefreshView.getBottom() >= mRefreshViewHeight + 20
|| mRefreshView.getTop() >= 0)
&& mRefreshState != RELEASE_TO_REFRESH) { //如果下拉了listiview,则显示上拉刷新动画
mRefreshViewText.setText(R.string.pull_to_refresh_release_label);
mRefreshViewImage.clearAnimation();
mRefreshViewImage.startAnimation(mFlipAnimation);
mRefreshState = RELEASE_TO_REFRESH;

Log.i(TAG, "现在处于下拉状态");

} else if (mRefreshView.getBottom() < mRefreshViewHeight + 20
&& mRefreshState != PULL_TO_REFRESH) { //如果没有到达，下拉刷新距离，则回归原来的状态
mRefreshViewText.setText(R.string.pull_to_refresh_pull_label);
if (mRefreshState != TAP_TO_REFRESH) {
mRefreshViewImage.clearAnimation();
mRefreshViewImage.startAnimation(mReverseFlipAnimation);

Log.i(TAG, "现在处于回弹状态");

}
mRefreshState = PULL_TO_REFRESH;
}
} else {
mRefreshViewImage.setVisibility(View.GONE); //隐藏刷新图片
resetHeader(); //初始化，头部
}
} else if (mCurrentScrollState == SCROLL_STATE_FLING //如果是自己滚动状态+ 第一个视图已经显示 + 不是刷新状态
&& firstVisibleItem == 0
&& mRefreshState != REFRESHING) {
setSelection(1);
mBounceHack = true; //状态为回弹
Log.i(TAG, "现在处于自由滚动到顶部的状态");
} else if (mBounceHack && mCurrentScrollState == SCROLL_STATE_FLING) {
setSelection(1);
Log.i(TAG, "现在处于自由滚动到顶部的状态");
}

if (mOnScrollListener != null) {
mOnScrollListener.onScroll(view, firstVisibleItem,
visibleItemCount, totalItemCount);
}
}

//滚动状态改变
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
mCurrentScrollState = scrollState;

if (mCurrentScrollState == SCROLL_STATE_IDLE) { //如果滚动停顿
mBounceHack = false;
}

if (mOnScrollListener != null) {
mOnScrollListener.onScrollStateChanged(view, scrollState);
}
}

//准备刷新
public void prepareForRefresh() {
resetHeaderPadding(); //初始化，头部文件

mRefreshViewImage.setVisibility(View.GONE);
// We need this hack, otherwise it will keep the previous drawable.
mRefreshViewImage.setImageDrawable(null);
mRefreshViewProgress.setVisibility(View.VISIBLE);

// Set refresh view text to the refreshing label
mRefreshViewText.setText(R.string.pull_to_refresh_refreshing_label);

mRefreshState = REFRESHING;
}

//刷新
public void onRefresh() {
Log.d(TAG, "执行刷新");

if (mOnRefreshListener != null) {
mOnRefreshListener.onRefresh();
}
}

/**
* 刷新完成 的回调函数
* Resets the list to a normal state after a refresh.
* @param lastUpdated Last updated at.
*/
public void onRefreshComplete(CharSequence lastUpdated) {
setLastUpdated(lastUpdated);
onRefreshComplete();
}

/**
* 刷新完成回调函数
* Resets the list to a normal state after a refresh.
*/
public void onRefreshComplete() {
Log.d(TAG, "onRefreshComplete");

resetHeader();

// If refresh view is visible when loading completes, scroll down to
// the next item.
if (mRefreshView.getBottom() > 0) {
invalidateViews(); //重绘视图
setSelection(1);
}
}

/**
* Invoked when the refresh view is clicked on. This is mainly used when
* there's only a few items in the list and it's not possible to drag the
* list.
*/
private class OnClickRefreshListener implements OnClickListener {

@Override
public void onClick(View v) {
if (mRefreshState != REFRESHING) {
//准备刷新
prepareForRefresh();
//刷新
onRefresh();
}
}

}

/**
* 刷新方法接口
*/
public interface OnRefreshListener {

public void onRefresh();
}

* 如果你还是没有弄明白的话，那就点击下面的链接，来下载整个demo项目:

http://download.csdn.net/detail/zjl5211314/3775209

原作者：johannilsson

选自：https://github.com/johannilsson/android-pulltorefresh

评论

1 楼 lkf871224 2011-12-02  

bug多多！