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我正在嘗試在已有的RecyclerView中實現粘性頭文件，該頭文件包含頭文件但不包含粘性頭文件。 SuperSLiM看起來很有希望，但我無法將庫集成到我現有的代碼中。源代碼後面的示例運行良好，我嘗試了適應此操作以及遵循SuperSLiM wiki上的步驟。無法使用超級鏈接來獲取粘性頭文件
我的RecyclerView最初是空的。我遇到的問題是當我第一次添加項目到我的適配器，並呼籲這些項目Adapter.notifyItemChanged()。我這樣做後，我被扔進LayoutManager.onItemsUpdated()。該方法是這樣的：
public void onItemsUpdated(RecyclerView recyclerView, int positionStart, int itemCount)
{
super.onItemsUpdated(recyclerView, positionStart, itemCount);
View first = this.getChildAt(0); // null
View last = this.getChildAt(this.getChildCount() - 1); // null
if(positionStart + itemCount > this.getPosition(first)) // NullPointerException
{
if(positionStart <= this.getPosition(last))
{
this.requestLayout();
}
}
}
在這裏，既first和last成爲null，因此NullPointerException拋出下面的線。請注意，onItemsUpdated()未在示例應用程序中調用，所以此錯誤不會在此處發生。我不知道爲什麼; Adapter.notifyItemChanged()也在示例應用程序中調用。
可能是什麼問題？
我的片段類：
注意切換回代碼正常RecyclerView.LayoutManager下面讓一切工作，因爲它一般不會。在崩潰時
public class MyFragment extends Fragment
{
private MyRecyclerView mRecyclerView;
private MyAdapter mAdapter;
// private RecyclerView.LayoutManager mLayoutManager; // Normal RecyclerView.LayoutManager working just fine
private LayoutManager mLayoutManager; // SuperSLiM LayoutManager crashing
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
View rootView = inflater.inflate(R.layout.my_fragment, container, false);
MyActivity myActivity = (MyActivity) rootView.getContext();
mRecyclerView = (MyRecyclerView) rootView.findViewById(R.id.my_recyclerview);
// mLayoutManager = new LinearLayoutManager(myActivity); // Normal RecyclerView.LayoutManager
mLayoutManager = new LayoutManager(myActivity); // SuperSLiM LayoutManager
mAdapter = new MyAdapter(myActivity);
mRecyclerView.setLayoutManager(mLayoutManager);
mRecyclerView.setAdapter(mAdapter);
myActivity.onShoppingListCreated();
return rootView;
}
public void onDataSetChanged()
{
if (mAdapter == null)
{
return;
}
mAdapter.notifyDataSetChanged();
}
// This is called multiple times after a button press at some point.
// Thereafter, if it is the SuperSLiM LayoutManager that is in play,
// the error explained above occurs.
public void onItemChanged(int position)
{
if (mAdapter == null)
{
return;
}
mAdapter.notifyItemChanged(position);
}
}
堆棧跟蹤：
java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.ViewGroup$LayoutParams android.view.View.getLayoutParams()' on a null object reference
at android.support.v7.widget.RecyclerView$LayoutManager.getPosition(RecyclerView.java:6097)
at com.tonicartos.superslim.LayoutManager.onItemsUpdated(LayoutManager.java:542)
at android.support.v7.widget.RecyclerView$5.dispatchUpdate(RecyclerView.java:665)
at android.support.v7.widget.RecyclerView$5.onDispatchSecondPass(RecyclerView.java:675)
at android.support.v7.widget.AdapterHelper.consumeUpdatesInOnePass(AdapterHelper.java:547)
at android.support.v7.widget.RecyclerView.processAdapterUpdatesAndSetAnimationFlags(RecyclerView.java:2530)
at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:2318)
at android.view.View.measure(View.java:17547)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:875)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:17547)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1488)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
at android.view.View.measure(View.java:17547)
at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:727)
at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:463)
at android.view.View.measure(View.java:17547)
at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:868)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
at android.support.v7.internal.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:124)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2615)
at android.view.View.measure(View.java:17547)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2015)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1173)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1379)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1061)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5885)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
at android.view.Choreographer.doCallbacks(Choreographer.java:580)
at android.view.Choreographer.doFrame(Choreographer.java:550)
at android.view.Choreographer$FrameDisplayEventRe
是的，我在該庫看起來爲好。我不相信我可以使用它，因爲它的文檔指出：*標題視圖被繪製到畫布上，而實際上並不是視圖層次結構的一部分。因此，他們不能有觸摸狀態，並且如果您嘗試異步加載圖像，可能會遇到問題。在我的情況下，除了純文本以外，標題還需要有一些狀態和附加視圖（例如一個小按鈕）。我想這個圖書館是不可能的。如果我錯了，請糾正我。 –
@Krøllebølle，你是完全正確的，的確我在我的https://github.com/davideas/FlexibleAdapter項目中使用了相同的timehop機制，並且我正在尋找幫助，使用自定義LayoutManager以良好的方式製作粘性標題，沒有龐大的編碼，因爲SuperSlim項目已經完成（只有3400行的部分和粘頭只有！？） – Davidea