为了增加复用性和灵活性，我们还是定义一个接口来做监听滚动到底部的回调，这样你就可以把它用在listview，scrollView中去。
OnBottomListener
package kale.com.waterfall; /**
* @author Jack Tony
* @brief
* @date 2015/4/6
*/
public interface OnBottomListener {
public void onBottom();
}
接着，我们来重写RecyclerView.OnScrollListener
package kale.com.waterfall.extra.RecyclerView; import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.StaggeredGridLayoutManager; import kale.com.waterfall.OnBottomListener; /**
* @author Jack Tony
* @brief recyle view 滚动监听器
* @date 2015/4/6
*/
public class OnRcvScrollListener extends RecyclerView.OnScrollListener implements OnBottomListener { private String TAG = getClass().getSimpleName(); public static enum LAYOUT_MANAGER_TYPE {
LINEAR,
GRID,
STAGGERED_GRID
} /**
* layoutManager的类型（枚举）
*/
protected LAYOUT_MANAGER_TYPE layoutManagerType; /**
* 最后一个的位置
*/
private int[] lastPositions; /**
* 最后一个可见的item的位置
*/
private int lastVisibleItemPosition;
/* *//**
* 是否正在加载
*//*
private boolean isLoadingMore = false;*/ /**
* 当前滑动的状态
*/
private int currentScrollState = 0; @Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy); RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
// int lastVisibleItemPosition = -1;
if (layoutManagerType == null) {
if (layoutManager instanceof LinearLayoutManager) {
layoutManagerType = LAYOUT_MANAGER_TYPE.LINEAR;
} else if (layoutManager instanceof GridLayoutManager) {
layoutManagerType = LAYOUT_MANAGER_TYPE.GRID;
} else if (layoutManager instanceof StaggeredGridLayoutManager) {
layoutManagerType = LAYOUT_MANAGER_TYPE.STAGGERED_GRID;
} else {
throw new RuntimeException(
"Unsupported LayoutManager used. Valid ones are LinearLayoutManager, GridLayoutManager and StaggeredGridLayoutManager");
}
} switch (layoutManagerType) {
case LINEAR:
lastVisibleItemPosition = ((LinearLayoutManager) layoutManager)
.findLastVisibleItemPosition();
break;
case GRID:
lastVisibleItemPosition = ((GridLayoutManager) layoutManager)
.findLastVisibleItemPosition();
break;
case STAGGERED_GRID:
StaggeredGridLayoutManager staggeredGridLayoutManager
= (StaggeredGridLayoutManager) layoutManager;
if (lastPositions == null) {
lastPositions = new int[staggeredGridLayoutManager.getSpanCount()];
}
staggeredGridLayoutManager.findLastVisibleItemPositions(lastPositions);
lastVisibleItemPosition = findMax(lastPositions);
break;
} } @Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
currentScrollState = newState;
RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
int visibleItemCount = layoutManager.getChildCount();
int totalItemCount = layoutManager.getItemCount();
if ((visibleItemCount > 0 && currentScrollState == RecyclerView.SCROLL_STATE_IDLE &&
(lastVisibleItemPosition) >= totalItemCount - 1)) {
//Log.d(TAG, "is loading more");
onBottom();
}
} @Override
public void onBottom() {
//Log.d(TAG, "is onBottom");
} private int findMax(int[] lastPositions) {
int max = lastPositions[0];
for (int value : lastPositions) {
if (value > max) {
max = value;
}
}
return max;
}
}
在之后的使用中，我们就可以像下方这样监听回调方法了：
waterFallRcv.setOnScrollListener(new OnRcvScrollListener(){
@Override
public void onBottom() {
super.onBottom();
// 到底部自动加载
if (!isLoadingData){
Log.d(TAG, "loading old data");
adapter.loadOldData();
isLoadingData = true;
}
}
});