效果图
xiaoguo.gif
使用
布局文件
Activity代码
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_recycle_view);
mPullToRefreshView = findViewById(R.id.bfprv);
mRecyclerView = findViewById(R.id.rv);
mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
mBaseQuickAdapter = new BaseQuickAdapter(R.layout.item,DataUtils.generateData(0,20)) {
@Override
protected void convert(BaseViewHolder helper, String item) {
helper.setText(R.id.tv,item);
}
};
mRecyclerView.setAdapter(mBaseQuickAdapter);
mPullToRefreshView.setRefreshListener(new OnRefreshListener() { //下拉刷新
@Override
public void refreshListener(View view) {
mPullToRefreshView.postDelayed(new Runnable() {
@Override
public void run() {
mBaseQuickAdapter.setNewData(DataUtils.generateData(0,20));
mPullToRefreshView.setRefreshComplete();
}
},3000);
}
});
mPullToRefreshView.setLoadMoreListener(new OnLoadMoreListener() { //上拉加载更多
@Override
public void loadMoreListener(View v) {
mPullToRefreshView.postDelayed(new Runnable() {
@Override
public void run() {
mBaseQuickAdapter.addData(DataUtils.generateData(20,40));
mPullToRefreshView.setLoadMoreComplete();
}
},3000);
}
});
}
实现原理
yuanli.png
实现原理比较简单,BfPullToRefreshView由三部分组成,屏幕外的BfRefreshView,屏幕内的ListView/RecycleView等,屏幕外的BfLoadMoreView。当ListView/RecycleView滑动到顶部或者底部时拦截事件交由BfPullToRefreshView的处理,通过滚动BfPullToRefreshView来显示BfRefreshView/BfLoadMoreView
实现代码
定义接口
- 要实现下拉刷新上拉加载更多必然要提供2个回调,让外部处理下拉刷新和上拉加载更多。所以我们可以先定义这2个接口,如下:
public interface OnRefreshListener {
void refreshListener(View view);
}
public interface OnLoadMoreListener {
void loadMoreListener(View v);
}
- 我们要将上拉刷新/下拉加载更多的各个状态提供给BfRefreshView/BfLoadMoreView做出相应的操作,所以我们应提供以下接口
public interface IRefreshView {
void releaseToRefresh();
void refreshing();
void refreshComplete();
/**
* rate = 下拉距离/RealView.height
* @param rate
*/
void getPercentRage(float rate);
/**
* 获取真正的刷新view
* @return
*/
View getRealView();
}
public interface ILoadMoreView {
void preToLoadMore();
void releaseToLoadMore();
void loading();
void loadComplete();
/**
* rate = 下拉距离/RealView.height
* @param rate
*/
void getPercentage(float rate);
/**
* 获取真正的刷新view
* @return
*/
View getRealView();
}
基类BasePullToRefreshView主要代码
- 此处需要了解View的事件分发机制,这里简单介绍下,dispatchTouchEvent负责事件分发,当有touch事件到来时,首先调用dispatchTouchEvent进行事件分发,然后由onInterceptTouchEvent判断是否拦截事件,若拦截后续的事件将交由onTouchEvent处理,若不拦截则事件将会继续向下传递
private final static float SCROLL_RATIO = 0.6f; //阻尼系数
private final static int STATE_INIT = -1;
private final static int STATE_PULL_UP = 0; //上拉状态
private final static int STATE_PULL_DOWN = 1; //下拉状态
private final static int STATE_PRE_TO_REFRESH = 2; //准备开始刷新状态
private final static int STATE_RELEASE_TO_REFRESH = 3; //释放刷新
private final static int STATE_REFRESHING = 4; //正在刷新中
private final static int STATE_PRE_TO_LOAD_MORE = 5; //准备开始加载更多
private final static int STATE_RELEASE_TO_LOAD_MORE = 6; //释放加载更多
private final static int STATE_LOADING = 7; //正在加载更多
protected T mContentView; //中间的内容view ListView/RecycleView等
private IRefreshView mRefreshView;
private View mRealRefreshView;
private View mRealLoadMoreView;
private ILoadMoreView mLoadMoreView;
private OnLoadMoreListener mLoadMoreListener;
private OnRefreshListener mRefreshListener;
private int mPullState = STATE_INIT;
private int mRefreshState = STATE_INIT;
private int mLoadMoreState = STATE_INIT;
private boolean openLoadMore;
private boolean openPullToRefresh;
private int mLastY;
private Scroller mScroller;
/**
* 设置刷新View
* @param refreshView
*/
public void setRefreshView(IRefreshView refreshView){
mRefreshView = refreshView;
mRealRefreshView = mRefreshView.getRealView();
openPullToRefresh = true;
initContentView();
initLayoutParams(mRealRefreshView);
addView(mRealRefreshView,0);
post(new Runnable() {
@Override
public void run() {
hideRefreshView();//设置margin-top=-mRealRefreshView.height让其移除屏幕
}
});
}
/**
* 设置加载更多View
* @param loadMoreView
*/
public void setLoadMoreView(ILoadMoreView loadMoreView){
mLoadMoreView = loadMoreView;
mRealLoadMoreView = loadMoreView.getRealView();
openLoadMore = true;
initContentView();
initLayoutParams(mRealLoadMoreView);
addView(mRealLoadMoreView);
}
/**
* 设置刷新完成
*/
public void setRefreshComplete(){
resetState();
resetScrollPosition();
mRefreshView.refreshComplete();
}
/**
* 设置加载完成
*/
public void setLoadMoreComplete(){
resetState();
resetScrollPosition();
mLoadMoreView.loadComplete();
}
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
if (mPullState == STATE_REFRESHING || mLoadMoreState == STATE_LOADING){ //当处于正在刷新或者正在加载更多时,不对事件进行分发。
return true;
}
return super.dispatchTouchEvent(ev);
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
switch (ev.getAction()){
case MotionEvent.ACTION_DOWN:
mLastY = (int) ev.getY();
break;
case MotionEvent.ACTION_MOVE:
// deltaY > 0 是向下运动,< 0是向上运动
int deltaY = (int) (ev.getY() - mLastY);
Log.d(TAG,"deltaY=>"+deltaY);
if (deltaY >= -20 && deltaY <= 20){ //滚动距离过小，不拦截
return false;
}
setPullState(deltaY); //设置当前处于上拉还是下拉状态
if (isScrollToTopOrBottom()){ //判断当前是否滑动到顶部或者底部,是则拦截
return true;
}
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
break;
}
return super.onInterceptTouchEvent(ev);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
mLastY = (int) event.getY();
break;
case MotionEvent.ACTION_MOVE:
int deltaY = (int) (event.getY() - mLastY);
deltaY = (int)(deltaY * SCROLL_RATIO);
int scrollY = getScrollY();
Log.d(TAG,"getY()="+getScrollY());
if (openPullToRefresh && mPullState == STATE_PULL_DOWN){
prepareToRefresh(deltaY,scrollY,event); //准备刷新
}
if (openLoadMore && mPullState == STATE_PULL_UP){
prepareToLoadMore(deltaY,scrollY,event); //准备加载更多
}
mLastY = (int) event.getY();
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
if ((openPullToRefresh && mRefreshState == STATE_PRE_TO_REFRESH) || (openLoadMore && mLoadMoreState == STATE_PRE_TO_LOAD_MORE)){
//刷新View/加载更多View未完全显示出来
resetScrollPosition(); //复位
}
if (openPullToRefresh && mPullState == STATE_PULL_DOWN && mRefreshState == STATE_RELEASE_TO_REFRESH){
handleRefreshing(); // 处理正在刷新
}
if (openLoadMore && mPullState == STATE_PULL_UP && mLoadMoreState == STATE_RELEASE_TO_LOAD_MORE){
handleLoading(); // 处理正在加载更多
}
break;
}
return super.onTouchEvent(event);
}
private void prepareToRefresh(int deltaY,int scrollY) {
if (scrollY > 0){ //scrollY>0证明刷新view出现了并且是在向上滑动
mRefreshState = STATE_PRE_TO_REFRESH;
mContentView.onTouchEvent(event);
return;
}else {
scrollY = -scrollY;
}
final int height = mRealRefreshView.getHeight();
if (scrollY >= height){
Log.d(TAG,"STATE_RELEASE_TO_REFRESH");
//刷新View完全出现
mRefreshState = STATE_RELEASE_TO_REFRESH;
mRefreshView.releaseToRefresh();
mRefreshView.getPercentRage(1.0f);
}else {
mRefreshState = STATE_PRE_TO_REFRESH;
float rate = scrollY / (height * 1.0f);
mRefreshView.getPercentRage(rate);
}
scrollBy(0,-deltaY); //滚动内容
}
private void prepareToLoadMore(int deltaY,int scrollY) {
if (scrollY < 0){ //scrollY>0证明当前是在像下滑动
mLoadMoreState = STATE_PRE_TO_LOAD_MORE;
return;
}
final int height = mRealLoadMoreView.getHeight();
if (scrollY >= height){ //加载View完全出现
Log.d(TAG,"STATE_RELEASE_TO_LOAD_MORE");
mLoadMoreState = STATE_RELEASE_TO_LOAD_MORE;
mLoadMoreView.releaseToLoadMore();
mLoadMoreView.getPercentage(1.0f);
}else {
mLoadMoreState = STATE_PRE_TO_LOAD_MORE;
float rate = scrollY / (height * 1.0f);
mLoadMoreView.getPercentage(rate);
mLoadMoreView.preToLoadMore();
}
scrollBy(0,-deltaY); //滚动内容
}
private void resetScrollPosition(){
int sy = getScrollY();
Log.d(TAG,"sy=>"+sy);
mScroller.startScroll(0,sy,0,-sy,800);
invalidate();
}
private void handleRefreshing() {
Log.d(TAG,"refreshing");
mRefreshState = STATE_REFRESHING;
scrollToRefreshingPosition(); //使用scroller实现弹性回滚
mRefreshView.refreshing();
if (mRefreshListener != null){
mRefreshListener.refreshListener(this);
}
}
private void handleLoadMore() {
Log.d(TAG,"Loading");
mLoadMoreState = STATE_LOADING;
scrollToLoadingPosition();
mLoadMoreView.loading();
if (mLoadMoreListener != null){
mLoadMoreListener.loadMoreListener(this);
}
}
BfPullToRefreshView代码
public class BfPullToRefreshView extends BasePullToRefreshView{
public BfPullToRefreshView(Context context) {
super(context);
}
public BfPullToRefreshView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
}
public BfPullToRefreshView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
@Override
protected void onAttachedToWindow() {
super.onAttachedToWindow();
BfRefreshView bfRefreshView = new BfRefreshView(getContext());
bfRefreshView.setBackgroundColor(Color.BLUE);
bfRefreshView.setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
(int)TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,60,getResources().getDisplayMetrics())));
setRefreshView(bfRefreshView);
BfLoadMoreView loadMoreView = new BfLoadMoreView(getContext());
loadMoreView.setLayoutParams(new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
(int)TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,60,getResources().getDisplayMetrics())));
setLoadMoreView(loadMoreView);
}
@Override
protected View createContentView() {
return getChildAt(0);
}
}
BfRefreshView和BfLoadMoreView的代码在这里就不贴出来了,有兴趣的话可以自行查看github demo