findFirstVisibleItemPositions不適合recycleview機器人工作

我有這樣的代碼：findFirstVisibleItemPositions不適合recycleview機器人工作

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]; 
    } 
});

當我滾動我recycleview我得到這個錯誤：

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

我該怎麼做才能處理此錯誤，並得到第一個可見的項目位置？

來源

2015-04-05 user3535747

我想它在第一次初始化時發生。現在，請在調用findFirstVisible之前檢查它是否有任何孩子，如果您可以在b.android.com上創建一個錯誤報告，那也是很好的。 – yigit 2015-04-07 04:42:56

我這個代碼，測試它，我用循環視圖參數正常工作與我

int positionView = ((LinearLayoutManager)recyclerView.getLayoutManager()).findFirstVisibleItemPosition();

。

來源

2015-04-06 08:56:23 zed007

很好的答案 – 2015-08-31 16:01:32

你救了我，爽！ – 2017-08-03 12:55:17

試試這個：

int position = layoutManager.findFirstVisibleItemPositions(null)[0];

其中layoutManager是你在你的recyclerview設置。

例如，

layoutManager = new StaggeredGridLayoutManager(2,StaggeredGridLayoutManager.VERTICAL); 
mrecyclerView.setLayoutManager(layoutManager);

來源

2015-04-09 04:43:44

此解決方案適用於我。請告訴我解決方案中是否有問題。 layoutManager.findFirstVisibleItemPositions（null）將返回一個新的數組。 [link]（https://developer.android.com/reference/android/support/v7/widget/StaggeredGridLayoutManager.html#findFirstVisibleItemPositions（int []）） – 2015-04-09 11:01:23

這是RecyclerView StaggeredGridLayoutManager了一個錯誤：

https://code.google.com/p/android/issues/detail?id=180521

https://code.google.com/p/android/issues/detail?id=181461

一種解決方法是嘗試/捕獲異常：

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; 
}

來源

2016-01-19 04:37:32 TalkLittle

您可以使用此：

int[] firstVisibleItemPositions = new int[yourNumberOfColumns]; 
int pastVisiblesItems = layoutManager.findFirstVisibleItemPositions(firstVisibleItem‌Positions)[0];

來源

2016-11-26 19:12:55 user3793358

如果您正在使用StaggeredGridLayoutManager你可以找到findLastVisibleItemPositions象下面這樣：

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; 
}

來源

2017-08-19 07:19:51

findFirstVisibleItemPositions不適合recycleview機器人工作

回答

相關問題