一个支持下拉自动加载的recycleview

最新推荐文章于 2020-02-25 09:32:34 发布

原创最新推荐文章于 2020-02-25 09:32:34 发布 · 470 阅读

CC 4.0 BY-SA版权

本文介绍了一个自定义RecyclerView的滚动监听器，用于实现加载更多功能。监听器能够根据不同类型的LayoutManager（如LinearLayoutManager、GridLayoutManager和StaggeredGridLayoutManager）确定何时加载更多数据。

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public class RecyclerViewOnScroll extends RecyclerView.OnScrollListener {
RecyclerView.Adapter mMyadputer;
LodeMoreCallBack mLodeMoreCallBack;
int lastVisibleItem = 0;
int firstVisibleItem = 0;

public RecyclerViewOnScroll(RecyclerView.Adapter mMyadputer, LodeMoreCallBack mLodeMoreCallBack) {
this.mMyadputer = mMyadputer;
this.mLodeMoreCallBack = mLodeMoreCallBack;
}

@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
int totalItemCount = layoutManager.getItemCount();
if (layoutManager instanceof LinearLayoutManager) {
LinearLayoutManager linearLayoutManager = ((LinearLayoutManager) layoutManager);
lastVisibleItem = linearLayoutManager.findLastVisibleItemPosition();
firstVisibleItem = linearLayoutManager.findFirstCompletelyVisibleItemPosition();
} else if (layoutManager instanceof GridLayoutManager) {
GridLayoutManager gridLayoutManager = ((GridLayoutManager) layoutManager);
//通过LayoutManager找到当前显示的最后的item的position
lastVisibleItem = gridLayoutManager.findLastVisibleItemPosition();
firstVisibleItem = gridLayoutManager.findFirstCompletelyVisibleItemPosition();
} else if (layoutManager instanceof StaggeredGridLayoutManager) {
StaggeredGridLayoutManager staggeredGridLayoutManager = ((StaggeredGridLayoutManager) layoutManager);
//因为StaggeredGridLayoutManager的特殊性可能导致最后显示的item存在多个，所以这里取到的是一个数组
//得到这个数组后再取到数组中position值最大的那个就是最后显示的position值了
int[] lastPositions = new int[((StaggeredGridLayoutManager) layoutManager).getSpanCount()];
staggeredGridLayoutManager.findLastVisibleItemPositions(lastPositions);
lastVisibleItem = findMax(lastPositions);
firstVisibleItem = staggeredGridLayoutManager.findFirstVisibleItemPositions(lastPositions)[0];
}

}

@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
//获取总的适配器的数量
int totalCount = mMyadputer.getItemCount();
Log.e("总的数目", totalCount + "");
Log.e("滚动的状态", newState + "");
//这个就是判断当前滑动停止了，并且获取当前屏幕最后一个可见的条目是第几个，当前屏幕数据已经显示完毕的时候就去加载数据
if (newState == RecyclerView.SCROLL_STATE_IDLE && lastVisibleItem + 1 == mMyadputer.getItemCount()) {
//回调加载更多
mLodeMoreCallBack.LodeMore();
}
}
//找到数组中的最大值

private int findMax(int[] lastPositions) {

int max = lastPositions[0];
for (int value : lastPositions) {
// int max = Math.max(lastPositions,value);
if (value > max) {
max = value;
}
}
return max;
}
}