多视图类型的IndexOutOfBoundsException在RecyclerAdapter中的应用

Question

当试图将视图类型作为数组中数据位置的函数返回时，我将获得一个IndexOutOfBoundsException。我有两个数据来源。一个是广告，另一个是名字和地点的列表。在RecyclerAdapter中处理数组之前，是否需要将数组组合成一个数组？我宁愿不这样做，尤其是在原则上它们可以是不同的类型，即图像和文本。我的getItemCount()方法正确地返回两个数组的总和大小。我为什么要得到这个例外？如何在两种不同的视图类型中显示来自两个不同源的数据？

我的主要活动：

public class MainActivity extends AppCompatActivity {

    private ArrayList<Object> getPresidentsArrayList() {
        ArrayList<Object> items = new ArrayList<>();
        items.add(new President("George Washington", "Mount Vernon"));
        items.add(new President("John Adams", "Braintree"));
        items.add(new President("Thomas Jefferson", "Monticello"));
        items.add(new President("James Madison", "Port Conway"));
        return items;
    }

    private ArrayList<Object> getAdsArrayList() {
        ArrayList<Object> ads = new ArrayList<>();
        ads.add(new Sponsored("Craft Beer 20% Off", "Budweiser"));
        ads.add(new Sponsored("Craft Beer 20% Off", "Budweiser"));
        ads.add(new Sponsored("Craft Beer 20% Off", "Budweiser"));
        ads.add(new Sponsored("Craft Beer 20% Off", "Budweiser"));
        return ads;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        bindDataToAdapter(recyclerView);

    }

    private void bindDataToAdapter(RecyclerView recyclerView) {
        recyclerView.setAdapter(new HeterogeneousRecyclerAdapter(getPresidentsArrayList(), getAdsArrayList()));
    }

}

我的回收器适配器允许多个视图：

public class HeterogeneousRecyclerAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    private List<Object> items;
    private List<Object> ads;
    private final int PRESIDENT = 0, SPONSORED = 1;

    public HeterogeneousRecyclerAdapter(List<Object> items, List<Object> ads) {
        this.items = items;
        this.ads = ads;
    }

    @Override
    public int getItemCount() {
        return (this.items.size() + this.ads.size());
    }

    @Override
    public int getItemViewType(int position) {
        if (items.get(position) instanceof President) {
            return PRESIDENT;
        } else if (ads.get(position) instanceof Sponsored) {
            return SPONSORED;
        }
        return -1;
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {

        RecyclerView.ViewHolder viewHolder;
        LayoutInflater inflater = LayoutInflater.from(viewGroup.getContext());

        switch (viewType) {
            case PRESIDENT:
                View v1 = inflater.inflate(R.layout.layout_viewholder1, viewGroup, false);
                viewHolder = new ViewHolder1(v1);
                break;
            case SPONSORED:
                View v2 = inflater.inflate(R.layout.layout_viewholder2, viewGroup, false);
                viewHolder = new ViewHolder2(v2);
                break;
            default:
                View v = inflater.inflate(android.R.layout.simple_list_item_1, viewGroup, false);
                viewHolder = new RecyclerViewSimpleTextViewHolder(v);
                break;
        }
        return viewHolder;
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder viewHolder, int position) {
        switch (viewHolder.getItemViewType()) {
            case PRESIDENT:
                ViewHolder1 vh1 = (ViewHolder1) viewHolder;
                configureViewHolder1(vh1, position);
                break;
            case SPONSORED:
                ViewHolder2 vh2 = (ViewHolder2) viewHolder;
                configureViewHolder2(vh2, position);
                break;
            default:
                RecyclerViewSimpleTextViewHolder vh = (RecyclerViewSimpleTextViewHolder) viewHolder;
                configureDefaultViewHolder(vh, position);
                break;
        }
    }

    private void configureDefaultViewHolder(RecyclerViewSimpleTextViewHolder vh, int position) {
        vh.getLabel().setText((CharSequence) items.get(position));
    }

    private void configureViewHolder1(ViewHolder1 vh1, int position) {
        President president = (President) items.get(position);
        if (president != null) {
            vh1.getLabel1().setText(president.getName());
            vh1.getLabel2().setText(president.getHometown());
        }
    }

    private void configureViewHolder2(ViewHolder2 vh2, int position) {
        Sponsored sponsored = (Sponsored) ads.get(position);
        if (sponsored != null) {
            vh2.getLabel1().setText(sponsored.getName());
            vh2.getLabel2().setText(sponsored.getCompany());
        }
    }
}

Answer 1

您需要创建一个公共列表，同时添加两个列表。做以下几件事-

    public HeterogeneousRecyclerAdapter(List<Object> items, List<Object> ads) {
        this.items = items;
        items.addAll(ads);
    }

现在更改get项目计数-

@Override
public int getItemCount() {
    return this.items.size();
}

希望它对你会很好:)

Answer 2

getItemCount的实现是错误的

 @Override
 public int getItemCount() {
     return (this.items.size() + this.ads.size());
 }

如果两者都不返回0，则返回的值大于两个集合的大小。这就是为什么你要得到一个ArrayIndexOutBoundException。请记住，position从0到getItemCount - 1，在您的示例中，items和ads都不包含getItemCount对象。

Answer 3

getItemViewType的实现是错误的。让我们假设您的items列表有4个条目，ads有3个广告对象。现在您的getItemViewType将返回7。现在系统将开始查找这7个对象的项目类型。让我们假设它希望在RecyclerView中找到第5行的类型。现在，在您的方法中，getItemViewType第1行本身抛出了这个异常，因为items列表的大小仅为4。

要么你必须将这两个列表合并在一个列表中，要么在回收商的视图中有一些订单，就像所有的广告都会出现在物品之前。在这种情况下，您还必须修改getItemViewType。

希望这能有所帮助。