Question

我想要的东西-我已经分类了recyclerview和quoteList recyclerview。当用户单击任何类别时，它应显示/动画该类别的报价。

问题-1.现在，我尝试设置从类别适配器到报价适配器的列表，但是它给了我空指针执行。 2.我已经实现了DiffUtils，但是同样它不会更新数据，而是返回nullpointer。

问题-如何从OnBindViewHolder类别更新Recyclerview报价？

这是代码...

类别适配器

public class category_adapter extends RecyclerView.Adapter<category_ViewHolder>{

private ArrayList<CategoryModel> categoryList;

public category_adapter(ArrayList<CategoryModel> categoryList) {
    this.categoryList = categoryList;
}

@NonNull
@Override
public category_ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.category_recyclerview, parent, false);
    return new category_ViewHolder(view);
}

@Override
public void onBindViewHolder(@NonNull category_ViewHolder holder, int position) {

    ArrayList<FirebaseModel> quoteList = new ArrayList<>();
    TextView item = holder.item;
    item.setText(categoryList.get(position).getCategoryName());

    holder.categoryLayout.setOnClickListener(v -> {
        FirebaseFirestore db = FirebaseFirestore.getInstance();

        Query first = db.collection("quotes")
                .whereGreaterThanOrEqualTo("Tag",categoryList.get(position).getCategoryName())
                .orderBy("Tag")
                .limit(10);

        first.get()
            .addOnCompleteListener(task -> {
                if (task.isSuccessful()) {
                    for (QueryDocumentSnapshot document : Objects.requireNonNull(task.getResult())) {

                        quoteList.add(new FirebaseModel(
                                document.getData().get("id").toString(),
                                document.getData().get("Quote").toString(),
                                document.getData().get("Author").toString(),
                                Integer.parseInt(document.getData().get("Likes").toString()),
                                document.getData().get("Tag").toString())
                        );
                        new MainActivity().setQupteAdapter(quoteList);

                    }
                } else {
                    Log.d("FIRESTORE", "Error getting documents: ", task.getException());
                }
            });
    });
}

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

new MainActivity（）。setQupteAdapter（quoteList）;

在上面的代码中，我尝试将适配器公开，并用于更新适配器。但是不起作用，我尝试使用method。:(不起作用..

报价适配器

public class quoteAdapter extends RecyclerView.Adapter<quoteViewHolder>{

ArrayList<FirebaseModel> quoteList;

public void setList(ArrayList<FirebaseModel> newList) {
    ArrayList<FirebaseModel> oldList = this.quoteList;
    DiffUtil.DiffResult diffResult = DiffUtil.calculateDiff(new quoteAdapterDiffUtil(newList, oldList), true);
    this.quoteList = newList;
    diffResult.dispatchUpdatesTo(this);
}

public quoteAdapter(ArrayList<FirebaseModel> quoteList) {
    this.quoteList = quoteList;
}

@NonNull
@Override
public quoteViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.quote_recycler_item, parent, false);
    return new quoteViewHolder(view);
}

@Override
public void onBindViewHolder(@NonNull final quoteViewHolder holder, final int position) {
    holder.autherName.setText("- " + quoteList.get(position).getAuthor());
    holder.quote.setText(quoteList.get(position).getQuote());
}

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

帮我找到更新报价清单recyclerview的方法。

Answer 1

以下内容将使您的代码以最小的更改工作

创建界面

interface QuoteUpdate {
    void updateAdapter(ArrayList<FirebaseModel> quoteList);
}

在 category_adapter

中

private ArrayList<CategoryModel> categoryList;
private QuoteUpdate quoteUpdate;

public category_adapter(ArrayList<CategoryModel> categoryList, QuoteUpdate quoteUpdate) {
    this.categoryList = categoryList;
    this.quoteUpdate = quoteUpdate;
}

//..

将MainActivity().setQupteAdapter(quoteList);替换为quoteUpdate.update(quoteList);

在 MainActivity

中

category_adapter adapter = new category_adapter(categoryList, new QuoteUpdate {
    @Override
    public void updateAdapter(ArrayList<FirebaseModel> quoteList) {
        setQupteAdapter(quoteList);
    }
});

Answer 2

我要实现的方式是：

每个RecyclerView的实现项目单击侦听器

如何实现项目单击侦听器，以便当从RecyclerView收到事件时，“活动/片段”可以采取行动：Click Here

现在两个RecyclerViews都有一个项目单击侦听器，共享活动/片段可以采取以下行动：

活动/片段：

@Override
public void onCategoryItemClickListener(int position) {
    //updateItem() is a function inside your adapter that updates data at 
    //the specified index
    quoteAdapter.updateItem(position, newData)
    quoteAdapter.notifyItemChanged(position)
}

//implement the same for onQuoteItemClickListener

从其他适配器更新recyclerview适配器

2 个答案: