尝试在空对象引用上调用虚拟方法“void androidx.recyclerview.widget.RecyclerView.removeViewAt(int)”答案

【问题标题】：Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.removeViewAt(int)' on a null object reference尝试在空对象引用上调用虚拟方法“void androidx.recyclerview.widget.RecyclerView.removeViewAt(int)”
【发布时间】：2023-03-13 18:37:01
【问题描述】：

错误：

     java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.removeViewAt (int)' on a null object reference
     W / System.err: at com.arvicapps.geomitric_wallpapers.FavoriteFullImageActivity $ 5.onFavoriteChanged (FavoriteFullImageActivity.java:533)
             at com.github.ivbaranov.mfb.MaterialFavoriteButton.updateFavoriteButton (MaterialFavoriteButton.java:324)
             at com.github.ivbaranov.mfb.MaterialFavoriteButton.setFavorite (MaterialFavoriteButton.java:257)
             at com.github.ivbaranov.mfb.MaterialFavoriteButton.toggleFavorite (MaterialFavoriteButton.java:292)
     W / System.err: at com.github.ivbaranov.mfb.MaterialFavoriteButton $ 1.onClick (MaterialFavoriteButton.java:152)
             at android.view.View.performClick (View.java:6659)
             at android.view.View.performClickInternal (View.java:6631)
             at android.view.View.access $ 3100 (View.java:790)
             at android.view.View $ PerformClick.run (View.java:26187)
             at android.os.Handler.handleCallback (Handler.java:907)

以下是来自 FavoriteFullImageActivity.java 的部分代码：

@Override protected void onCreate (Bundle savedInstanceState) {super.onCreate (savedInstanceState);  setContentView (R.layout.activity_favorite_full_image);  getSupportActionBar (). hide ();  RecyclerView recyclerView = findViewById (R.id.FavoriteCategoryView);  }

 try {
  recyclerView.removeViewAt (position);  recyclerView.notifyAll ();
 myDbHelper.closeDb ();
 myDbHelper.close ();
 myDbHelper.notifyAll ();
 } catch (NullPointerException nullPointerException) {nullPointerException.printStackTrace ();
  }

如何解决？

【问题讨论】：

欢迎来到stackoverflow。你把the tour读了how to ask a good question了吗？

标签： java android android-recyclerview

【解决方案1】：

您正在尝试访问 child view 而不对其进行膨胀，或者该子视图不存在。将适配器设置为回收站视图

recyclerView.adapter=adapter

【讨论】：

【解决方案2】：

java.lang.NullPointerException: Attempt to invoke virtual method 'void 
androidx.recyclerview.widget.RecyclerView.removeViewAt (int)' on a null 
object reference

这意味着recyclerView的属性在你使用之前没有被初始化。对此，您需要更仔细地检查代码。

【讨论】：