子 RecyclerView setadapter 在我的嵌套 RecyclerView 上不起作用 Android

Question

我有两个 RecyclerView。 Parent RecyclerView 工作完美，但父适配器中子项的 setadapter 不工作。

我试图在子适配器中创建一些日志消息，但它们甚至没有出现，因此适配器甚至没有启动

为了更好的理解，下面是一段代码。

MainFragment.java

        // Set up the RecyclerView.
        recyclerview = rootView.findViewById(R.id.recycler_view);
        adapter = new TodayAdapter(getContext());
        recyclerview.setLayoutManager(new LinearLayoutManager(getContext()));
        recyclerview.setAdapter(adapter);
        taskViewModel = new ViewModelProvider(requireActivity()).get(TaskViewModel.class);

        List<TaskList> categories = new ArrayList<>();

        TaskList completedTasks = new TaskList("Completed Tasks",null);
        TaskList incompletedTasks = new TaskList("Incompleted Tasks",null);
        List<Task> intask = new ArrayList<>();
        List<Task> comtask = new ArrayList<>();


        // Update the cached copy of the words in the adapter.
        // Get all the words from the database
        // and associate them to the adapter.
        taskViewModel.getAllTasks().observe( getActivity(), new Observer<List<Task>>() {
            @Override
            public void onChanged(List<Task> tasks) {
                for(Task task : tasks){
                    if(task.getState().equals("0")) {
                        intask.add(task);
                        incompletedTasks.setTasks(intask);
                    } else{
                        comtask.add(task);
                        completedTasks.setTasks(comtask);
                    }
                }

                categories.add(incompletedTasks);
                categories.add(completedTasks);

                adapter.setCategory(categories);
            }
        });

ParentAdapter.java

public class TodayAdapter extends RecyclerView.Adapter<TodayAdapter.TodayHolder>{
    private List<TaskList> categories;

    public TodayAdapter(List<TaskList> todayLists) {
        this.categories = todayLists;
    }

    public TodayAdapter(Context context) {
        LayoutInflater mInflater = LayoutInflater.from(context);
    }


    @NonNull
    @Override
    public TodayHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_item, parent, false);
        return new TodayAdapter.TodayHolder(itemView);    }

    @SuppressLint("NotifyDataSetChanged")
    @Override
    public void onBindViewHolder(@NonNull TodayHolder holder, int position) {
        Log.d("test", Integer.toString(categories.size()));
        if(categories!=null) {
            TaskList category = categories.get(position);
            holder.title.setText(category.getTitle());

            holder.tasks.setHasFixedSize(true);
            TaskAdapter taskAdapter = new TaskAdapter();
            taskAdapter.setTasks(category.getTasks());
            holder.tasks.setAdapter(taskAdapter);
            taskAdapter.notifyDataSetChanged();
        }
    }

    @Override
    public int getItemCount() {
        if(categories!=null)
            return categories.size();
        return 0;
    }

    public class TodayHolder extends RecyclerView.ViewHolder {
        private TextView title;
        private RecyclerView tasks;
        public TodayHolder(@NonNull View itemView) {
            super(itemView);
            title=itemView.findViewById(R.id.title);
            tasks=itemView.findViewById(R.id.tasks);
        }
    }

    //Associates a list of tasks with this adapter
    public void setCategory(List<TaskList> categories) {
        this.categories = categories;
        notifyDataSetChanged();
    }
}

ChildAdapter.java

/**
 * Adapter for the RecyclerView that displays a list of words.
 */

public class TaskAdapter extends RecyclerView.Adapter<TaskAdapter.TaskHolder> {

    private List<Task> tasks; // Cached copy of words
    private OnItemClickListener listener;

    public TaskAdapter(Context context) {
        LayoutInflater mInflater = LayoutInflater.from(context);
    }

    public TaskAdapter() {
    }

    @NonNull
    @Override
    public TaskHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        Log.d("test","rani fe task adapder");

        View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.task_item, parent, false);
        return new TaskHolder(itemView);
    }

    @SuppressLint("ResourceAsColor")
    @Override
    public void onBindViewHolder(@NonNull TaskHolder holder, int position) {
        Log.d("test","we are in =" +position);
        if (tasks != null) {
            Task currentTask = tasks.get(position);
            holder.textViewTitle.setText(currentTask.getTitle());
            holder.textViewDescription.setText(currentTask.getDescription());

            switch (currentTask.getCategory()) {
                case "1":
                    holder.layout.setBackgroundResource(R.color.button_beige);
                    if (currentTask.getState().equals("0")){
                        holder.view.setBackgroundResource(R.drawable.uncheck_beige);
                    holder.textViewTitle.setPaintFlags(0);
                    holder.textViewDescription.setPaintFlags(0);
                    }else{
                        holder.view.setBackgroundResource(R.drawable.check_beige);
                        holder.textViewTitle.setPaintFlags(holder.textViewTitle.getPaintFlags()
                                | Paint.STRIKE_THRU_TEXT_FLAG);
                        holder.textViewDescription.setPaintFlags(holder.textViewDescription.getPaintFlags()
                                | Paint.STRIKE_THRU_TEXT_FLAG);
                    }
                    break;
                case "2":
                    holder.layout.setBackgroundResource(R.color.button_blue);

                    if(currentTask.getState().equals("0")){
                        holder.view.setBackgroundResource(R.drawable.uncheck_blue);
                        holder.textViewTitle.setPaintFlags(0);
                        holder.textViewDescription.setPaintFlags(0);
                    }
                    else{
                        holder.view.setBackgroundResource(R.drawable.check_blue);
                        holder.textViewTitle.setPaintFlags(holder.textViewTitle.getPaintFlags()
                                | Paint.STRIKE_THRU_TEXT_FLAG);
                        holder.textViewDescription.setPaintFlags(holder.textViewDescription.getPaintFlags()
                                | Paint.STRIKE_THRU_TEXT_FLAG);
                    }
                    break;
                case "3":
                    holder.layout.setBackgroundResource(R.color.button_green);
                    if(currentTask.getState().equals("0")){
                        holder.view.setBackgroundResource(R.drawable.uncheck_green);
                        holder.textViewTitle.setPaintFlags(0);
                        holder.textViewDescription.setPaintFlags(0);
                    }
                    else{
                        holder.view.setBackgroundResource(R.drawable.check_green);
                        holder.textViewTitle.setPaintFlags(holder.textViewTitle.getPaintFlags()
                                | Paint.STRIKE_THRU_TEXT_FLAG);
                        holder.textViewDescription.setPaintFlags(holder.textViewDescription.getPaintFlags()
                                | Paint.STRIKE_THRU_TEXT_FLAG);
                    }                    break;
                case "4":
                    holder.layout.setBackgroundResource(R.color.button_pink);
                    if(currentTask.getState().equals("0")){
                        holder.view.setBackgroundResource(R.drawable.uncheck_pink);
                        holder.textViewTitle.setPaintFlags(0);
                        holder.textViewDescription.setPaintFlags(0);
                    }
                    else{
                        holder.view.setBackgroundResource(R.drawable.check_pink);
                        holder.textViewTitle.setPaintFlags(holder.textViewTitle.getPaintFlags()
                                | Paint.STRIKE_THRU_TEXT_FLAG);
                        holder.textViewDescription.setPaintFlags(holder.textViewDescription.getPaintFlags()
                                | Paint.STRIKE_THRU_TEXT_FLAG);
                    }
                    break;
                case "5":
                    holder.layout.setBackgroundResource(R.color.button_purple);
                    if(currentTask.getState().equals("0")){
                        holder.view.setBackgroundResource(R.drawable.uncheck_purple);
                        holder.textViewTitle.setPaintFlags(0);
                        holder.textViewDescription.setPaintFlags(0);
                    }
                    else{
                        holder.view.setBackgroundResource(R.drawable.check_purple);
                        holder.textViewTitle.setPaintFlags(holder.textViewTitle.getPaintFlags()
                                | Paint.STRIKE_THRU_TEXT_FLAG);
                        holder.textViewDescription.setPaintFlags(holder.textViewDescription.getPaintFlags()
                                | Paint.STRIKE_THRU_TEXT_FLAG);
                    }
                    break;
                default:
                    holder.layout.setBackgroundResource(R.color.black);
                    if(currentTask.getState().equals("0")){
                        holder.view.setBackgroundResource(R.drawable.uncheck_black);
                        holder.textViewTitle.setPaintFlags(0);
                        holder.textViewDescription.setPaintFlags(0);
                    }
                    else{
                        holder.view.setBackgroundResource(R.drawable.check_black);
                        holder.textViewTitle.setPaintFlags(holder.textViewTitle.getPaintFlags()
                                | Paint.STRIKE_THRU_TEXT_FLAG);
                        holder.textViewDescription.setPaintFlags(holder.textViewDescription.getPaintFlags()
                                | Paint.STRIKE_THRU_TEXT_FLAG);
                    }
                    break;
            }
        }
    }

    //getItemCount() is called many times, and when it is first called,
    //mWords has not been updated (means initially, it's null, and we can't return null).
    @Override
    public int getItemCount() {
        if (tasks != null)
            return tasks.size();
        return 0;
    }

    //Associates a list of tasks with this adapter
    public void setTasks(List<Task> tasks) {
        this.tasks = tasks;
        notifyDataSetChanged();
        if(tasks != null){
            Log.d("test","task size =" +this.tasks.size());
        }else Log.d("test","task size =" +0);
    }

    //to get the item from the id
    public Task getTaskAt(int position) {
        return tasks.get(position);
    }

    class TaskHolder extends RecyclerView.ViewHolder {
        private TextView textViewTitle;
        private TextView textViewDescription;
        private View view;
        private LinearLayout layout;
        private RelativeLayout EditLayout;

        public TaskHolder(@NonNull View itemView) {
            super(itemView);
            textViewTitle = itemView.findViewById(R.id.text_view_title);
            textViewDescription = itemView.findViewById(R.id.text_view_description);
            layout = itemView.findViewById(R.id.color);
            view = itemView.findViewById(R.id.image);
            EditLayout = itemView.findViewById(R.id.EditLayout);

            EditLayout.setOnClickListener(v -> {
                int position = getAdapterPosition();
                listener.onItemClick(tasks.get(position));
            });

            view.setOnClickListener(v -> {
                int position = getAdapterPosition();
                listener.onDoneClick(tasks.get(position));
            });
        }
    }

    public interface OnItemClickListener {
        void onItemClick(Task task);
        void onDoneClick(Task task);
    }

    public void setOnItemClickListener(OnItemClickListener listener) {
        this.listener = listener;
    }
}

Answer 1

这是因为您必须先预取子项，然后再使用以下方法创建其适配器：

layoutManager.setInitialPrefetchItemCount(parentItem, .size());

你可以在这里找到完整的教程

https://www.geeksforgeeks.org/how-to-create-a-nested-recyclerview-in-android/

Answer 2

我通过像这样添加线性布局管理器来修复它

holder.tasks.setHasFixedSize(true);
ChildAdapter childAdapter = new ChildAdapter();
childAdapter.setList(category.getLists());

LinearLayoutManager layoutManager = new LinearLayoutManager(mContext);
holder.tasks.setLayoutManager(layoutManager);

holder.tasks.setAdapter(childAdapter);
childAdapter.notifyDataSetChanged();

子 RecyclerView setadapter 在我的嵌套 RecyclerView 上不起作用 Android

Child RecyclerView setadapter doesn't work on my Nested RecyclerView Android

java

android

android-recyclerview

nestedrecyclerview