将列表作为 ParcelableArrayList 传递 [英] Passing a List through as a ParcelableArrayList

问题描述

嘿伙计们，我在处理一些代码时遇到了一些问题.我正在实施parcelables.基本上我有一个全局启动的项目列表

So hey guys, Im having some trouble with some code. Im implementing parcelables. Basically I have an List of items initiated globally as

private List<Movie> mMovieList = new ArrayList<>();

并且我希望将其作为可分块传递以在旋转时保存实例状态.我实现了 saveOnInstanceState 方法和 onCreate

and I wish to pass this in as a parcellable to save the instance state upon rotation. I implement the saveOnInstanceState method and onCreate

public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putParcelableArrayList(MOVIE_KEY, (ArrayList< ? extends Parcelable >)mMovieList);
}

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setHasOptionsMenu(true);
    if (savedInstanceState != null)
    {
        mMovieList = (List<Movie>)savedInstanceState.get(MOVIE_KEY);
    }
}

唯一的问题是它抛出一个错误并且错误指向 outstate.putParcelableArrayList 行.

Only problem is it throws an error and the error points to the outstate.putParcelableArrayList line.

java.lang.ClassCastException: java.util.Arrays$ArrayList cannot be cast to java.util.ArrayList

有人知道解决方法或解决方法吗?我尝试使用谷歌搜索并查看其他 stackoverflow 答案，但找不到有效的答案.

Does anyone know of a fix or a way around this? I tried googling and looking at other stackoverflow answers but couldnt find one that worked.

这里是该项目的 GitHub 链接，如果有人想查看它的全部内容，上面提到的方法尚未提交.https://github.com/Rykuno/Flix-Viewer

Here is the GitHub link to the project if anyone wants to look at its entirety, the methods mention above have not been committed yet. https://github.com/Rykuno/Flix-Viewer

推荐答案

遗憾的是，Android 不会针对界面编程".如果 List 不是 ArrayList，那么您别无选择，只能创建一个新的 ArrayList.这没什么大不了的，可以通过编程来完成.

Sadly Android doesn't "program to the interface". If the List is not an ArrayList then you'll have no choice but to create a new ArrayList. This isn't a big deal and can be done programmatically.

public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    ArrayList<Movie> toSave = mMovieList instanceof ArrayList ?
        (ArrayList<Movie>)mMovieList : new ArrayList<Movie>(mMovieList);
    outState.putParcelableArrayList(MOVIE_KEY, toSave);
}

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