android listivew 下拉回弹刷新

原创

jdsjlzx 2022-12-16 16:22:23 博主文章分类：Android UI ©著作权

文章标签 android scroll listview null header 文章分类 运维

©著作权归作者所有：来自51CTO博客作者jdsjlzx的原创作品，请联系作者获取转载授权，否则将追究法律责任

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
//
new RotateAnimation(0, -180,
0.5f,
0.5f);
new LinearInterpolator());
250);
true);
new RotateAnimation(-180, 0,
0.5f,
0.5f);
new LinearInterpolator());
250);
true);
mInflater = (LayoutInflater) context.getSystemService(
Context.LAYOUT_INFLATER_SERVICE);
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);
50);
new OnClickRefreshListener());
mRefreshOriginalTopPadding = mRefreshView.getPaddingTop();
mRefreshState = TAP_TO_REFRESH;
addHeaderView(mRefreshView);
super.setOnScrollListener(this);
measureView(mRefreshView);
//获取头文件的测量高度
}
@Override
protected void onAttachedToWindow() {
1);
}
@Override
public void setAdapter(ListAdapter adapter) {
super.setAdapter(adapter);
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);
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()) {
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
0)
//如果头部视图处于拉离顶部的情况
// Initiate the refresh
//将标量设置为，正在刷新
//准备刷新
//刷新
else if (mRefreshView.getBottom() < mRefreshViewHeight
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();
1); //定位在第二个列表项
}
}
break;
case MotionEvent.ACTION_DOWN:
//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()) {
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)
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) {
//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);
}
}

[java] view plain copy

//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) {
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 {
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
0)
//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;
"现在处于下拉状态");
else if (mRefreshView.getBottom() < mRefreshViewHeight + 20
//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);
"现在处于回弹状态");
}
mRefreshState = PULL_TO_REFRESH;
}
else {
//隐藏刷新图片
//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
0
&& mRefreshState != REFRESHING) {
1);
true; //状态为回弹
"现在处于自由滚动到顶部的状态");
else if (mBounceHack && mCurrentScrollState == SCROLL_STATE_FLING) {
1);
"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
false;
}
if (mOnScrollListener != null) {
mOnScrollListener.onScrollStateChanged(view, scrollState);
}
}
//准备刷新
public void prepareForRefresh() {
//初始化，头部文件
mRefreshViewImage.setVisibility(View.GONE);
// We need this hack, otherwise it will keep the previous drawable.
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() {
"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() {
"onRefreshComplete");
resetHeader();
// If refresh view is visible when loading completes, scroll down to
// the next item.
if (mRefreshView.getBottom() > 0) {
//重绘视图
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();
}