idsIterator.remove（）抛出IllegalStateException

Question

我想使用listIterator的remove方法。不过，我得到一个IllegalStateException

这里是我的代码：

private List<Category> findDescendantsOfCurrentCategory() { 
    List<Category> categoryList = new ArrayList<>(mCategoryList); 

    List<Category> descendantCategories = new ArrayList<>(); 

    Stack<String> categoriesIds = new Stack<>(); 
    categoriesIds.push(mCategoryId); 

    ListIterator<Category> categoryListIterator = categoryList.listIterator(); 

    ListIterator<String> idsIterator = categoriesIds.listIterator(); 

    while (idsIterator.hasNext()) { 
     String parentId = idsIterator.next(); 

     while (categoryListIterator.hasNext()) { 
      Category category = categoryListIterator.next(); 

      if (category.getParentId().equals(parentId)) { 
       idsIterator.add(category.getId()); 

       descendantCategories.add(category); 
      } 

      categoryListIterator.remove(); 
     } 

     idsIterator.remove(); 
    } 

    return descendantCategories; 
} 

堆栈跟踪：

03-09 23:11:33.160 25298-25298/com.example.clients.someoneplatform.dev E/AndroidRuntime: FATAL EXCEPTION: main 
       Process: com.example.clients.someoneplatform.dev, PID: 25298 
       java.lang.IllegalStateException 
     at java.util.AbstractList$SimpleListIterator.remove(AbstractList.java:67) 
     at com.example.clients.someoneplatform.ui.categories.list.ListCategoriesFragment.findDescendantsOfCurrentCategory(ListCategoriesFragment.java:186) 
     at com.example.clients.someoneplatform.ui.categories.list.ListCategoriesFragment.startAddEditCategoryForModification(ListCategoriesFragment.java:154) 
     at com.example.clients.someoneplatform.ui.categories.list.ListCategoriesFragment.access$200(ListCategoriesFragment.java:39) 
     at com.example.clients.someoneplatform.ui.categories.list.ListCategoriesFragment$1.onCategoryModifyButtonClicked(ListCategoriesFragment.java:124) 
     at com.example.clients.someoneplatform.ui.categories.list.ListCategoriesAdapter$ViewHolder.onModifyButtonClicked(ListCategoriesAdapter.java:134) 
     at com.example.clients.someoneplatform.ui.categories.list.ListCategoriesAdapter$ViewHolder_ViewBinding$2.doClick(ListCategoriesAdapter$ViewHolder_ViewBinding.java:47) 
     at butterknife.internal.DebouncingOnClickListener.onClick(DebouncingOnClickListener.java:22) 
     at android.view.View.performClick(View.java:5201) 
     at android.view.View$PerformClick.run(View.java:21209) 
     at android.os.Handler.handleCallback(Handler.java:739) 
     at android.os.Handler.dispatchMessage(Handler.java:95) 
     at android.os.Looper.loop(Looper.java:148) 
     at android.app.ActivityThread.main(ActivityThread.java:5525) 
     at java.lang.reflect.Method.invoke(Native Method) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620) 

Answer 1

上的ListIterator的文档（https://docs.oracle.com/javase/7/docs/api/java/util/ListIterator.html#remove()）说，有关remove方法：“它可以是只有在最后一次调用next或previous之后没有调用add（E）时才进行。“

所以你基本上必须重写你的代码，你不使用添加功能，然后调用删除