findFirstVisibleItemPositions不适合recycleview机器人工作
我有这样的代码:findFirstVisibleItemPositions不适合recycleview机器人工作
mRecycleView.setOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int[] firstVisibleItemPositions = new int[getResources().getInteger(R.integer.news_numbers_column)];
int pastVisiblesItems = ((StaggeredGridLayoutManager)getLayoutManager()).findFirstVisibleItemPositions(firstVisibleItemPositions)[0];
}
});
当我滚动我recycleview我得到这个错误:
java.lang.NullPointerException: Attempt to invoke virtual method 'int android.support.v7.widget.OrientationHelper.getStartAfterPadding()' on a null object reference
at android.support.v7.widget.StaggeredGridLayoutManager$Span.findOneVisibleChild(StaggeredGridLayoutManager.java:2177)
at android.support.v7.widget.StaggeredGridLayoutManager$Span.findFirstVisibleItemPosition(StaggeredGridLayoutManager.java:2153)
at android.support.v7.widget.StaggeredGridLayoutManager.findFirstVisibleItemPositions(StaggeredGridLayoutManager.java:806)
at info.lanouvelletribune.apps.android.ui.fragments.NewsFragment$1.onScrollStateChanged(NewsFragment.java:90)
at android.support.v7.widget.RecyclerView.setScrollState(RecyclerView.java:751)
at android.support.v7.widget.RecyclerView.onInterceptTouchEvent(RecyclerView.java:1535)
at com.github.ksoichiro.android.observablescrollview.ObservableRecyclerView.onInterceptTouchEvent(ObservableRecyclerView.java:188)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2060)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2431)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2173)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2431)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2173)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2431)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2173)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2431)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2173)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2431)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2173)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2431)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2173)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2431)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2173)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2431)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2173)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2431)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2173)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2431)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2173)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2431)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2173)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2431)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2173)
at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2390)
at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1741)
at android.app.Activity.dispatchTouchEvent(Activity.java:2826)
at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2351)
at android.view.View.dispatchPointerEvent(View.java:8590)
at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4098)
at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3964)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3488)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3541)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3507)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3515)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3488)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3541)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3507)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3617)
at android
我该怎么做才能处理此错误,并得到第一个可见的项目位置?
我这个代码,测试它,我用循环视图参数正常工作与我
int positionView = ((LinearLayoutManager)recyclerView.getLayoutManager()).findFirstVisibleItemPosition();
。
很好的答案 – 2015-08-31 16:01:32
你救了我,爽! – 2017-08-03 12:55:17
试试这个:
int position = layoutManager.findFirstVisibleItemPositions(null)[0];
其中layoutManager
是你在你的recyclerview
设置。
例如,
layoutManager = new StaggeredGridLayoutManager(2,StaggeredGridLayoutManager.VERTICAL);
mrecyclerView.setLayoutManager(layoutManager);
此解决方案适用于我。请告诉我解决方案中是否有问题。 layoutManager.findFirstVisibleItemPositions(null)将返回一个新的数组。 [link](https://developer.android.com/reference/android/support/v7/widget/StaggeredGridLayoutManager.html#findFirstVisibleItemPositions(int [])) – 2015-04-09 11:01:23
这是RecyclerView StaggeredGridLayoutManager了一个错误:
https://code.google.com/p/android/issues/detail?id=180521
https://code.google.com/p/android/issues/detail?id=181461
一种解决方法是尝试/捕获异常:
try {
((StaggeredGridLayoutManager)getLayoutManager()).findFirstVisibleItemPositions(firstVisibleItemPositions);
} catch (NullPointerException ex) {
// workaround for RecyclerView bug. assume not laid out, so no items visible
firstVisibleItemPositions[0] = RecyclerView.NO_POSITION;
firstVisibleItemPositions[1] = RecyclerView.NO_POSITION;
}
您可以使用此:
int[] firstVisibleItemPositions = new int[yourNumberOfColumns];
int pastVisiblesItems = layoutManager.findFirstVisibleItemPositions(firstVisibleItemPositions)[0];
如果您正在使用StaggeredGridLayoutManager你可以找到findLastVisibleItemPositions象下面这样:
int visibleThreshold =1;
final StaggeredGridLayoutManager linearLayoutManager = (StaggeredGridLayoutManager) mRecyclerViewAllPost.getLayoutManager();
mRecyclerViewAllPost.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int[] lastVisibleItemPositions = linearLayoutManager.findLastVisibleItemPositions(null);
int lastVisibleItem = getLastVisibleItem(lastVisibleItemPositions);
int totalItemCount = linearLayoutManager.getItemCount();
if (!isLoading && totalItemCount <= (lastVisibleItem + visibleThreshold)) {
print("load more item ");
isLoading = true;
}
}
});
和getLastVisibleItem方法如下:
public int getLastVisibleItem(int[] lastVisibleItemPositions) {
int maxSize = 0;
for (int i = 0; i < lastVisibleItemPositions.length; i++) {
if (i == 0) {
maxSize = lastVisibleItemPositions[i];
}
else if (lastVisibleItemPositions[i] > maxSize) {
maxSize = lastVisibleItemPositions[i];
}
}
return maxSize;
}
我想它在第一次初始化时发生。 现在,请在调用findFirstVisible之前检查它是否有任何孩子,如果您可以在b.android.com上创建一个错误报告,那也是很好的。 – yigit 2015-04-07 04:42:56