idsIterator.remove() 抛出 IllegalStateException

Question

我正在尝试使用 listIterator 的 remove 方法。但是，我收到 IllegalStateException

这是我的代码：

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$SimpleListIterator.remove(AbstractList.java:67)
        at com.example.clients.someoneplatform.ui.categories.list.ListCategoriesFragment.findDescendantsOfCurrentCategory(ListCategoriesFragment.java:186)
        at com.example.clients.someoneplatform.ui.categories.list.ListCategoriesFragment.startAddEditCategoryForModification(ListCategoriesFragment.java:154)
        at com.example.clients.someoneplatform.ui.categories.list.ListCategoriesFragment.access0(ListCategoriesFragment.java:39)
        at com.example.clients.someoneplatform.ui.categories.list.ListCategoriesFragment.onCategoryModifyButtonClicked(ListCategoriesFragment.java:124)
        at com.example.clients.someoneplatform.ui.categories.list.ListCategoriesAdapter$ViewHolder.onModifyButtonClicked(ListCategoriesAdapter.java:134)
        at com.example.clients.someoneplatform.ui.categories.list.ListCategoriesAdapter$ViewHolder_ViewBinding.doClick(ListCategoriesAdapter$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

ListIterator 上的文档 (https://docs.oracle.com/javase/7/docs/api/java/util/ListIterator.html#remove()) 介绍了删除方法："It can be made only if add(E) has not been called after the last call to next or previous."

所以你基本上必须在调用 remove

之前重写你不使用 add 函数的代码

idsIterator.remove() 抛出 IllegalStateException

idsIterator.remove() throws IllegalStateException

java

illegalstateexception

listiterator