首屏Fragment中Retrofit加载RecyclerView报数组越界问题求助

问题根源 #

• 初始化UsersAdapter时硬编码传入size=4，且getItemCount()直接返回该固定值，完全忽略了usersModel集合的实际状态。
• 首屏加载时网络请求尚未完成，usersModel是空集合，RecyclerView会根据getItemCount()返回的4条数据尝试绑定，调用usersModel.get(position)时触发数组越界异常。
• 切换Fragment后再切回时，网络请求已完成，usersModel已有数据，因此不会触发异常。

修复方案 #

1. 修复Adapter核心逻辑 #

删除硬编码的size参数，根据usersModel的实际大小返回item数量，同时处理集合为null的情况：

public class UsersAdapter extends RecyclerView.Adapter<UsersAdapter.UsersHolder> {
    Context mContext;
    List<UsersModel> usersModel;

    // 移除size参数，初始化时处理空集合
    public UsersAdapter(Context mContext, List<UsersModel> usersModel) {
        this.mContext = mContext;
        this.usersModel = usersModel != null ? usersModel : new ArrayList<>();
    }

    public void setUsersList(List<UsersModel> usersModel) {
        // 更新数据时同样处理null情况
        this.usersModel = usersModel != null ? usersModel : new ArrayList<>();
        notifyDataSetChanged();
    }

    @NonNull
    @Override
    public UsersAdapter.UsersHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(mContext).inflate(R.layout.recycler_view_users, parent, false);
        return new UsersHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull UsersAdapter.UsersHolder holder, int position) {
        UsersModel model = usersModel.get(position);
        holder.name.setText(model.getName());
        holder.description.setText(model.getDescription());
        Glide.with(holder.itemView.getContext().getApplicationContext())
             .load(model.getLogo())
             .into(holder.logo);
    }

    @Override
    public int getItemCount() {
        // 返回集合实际大小，而非固定值
        return usersModel.size();
    }

    public static class UsersHolder extends RecyclerView.ViewHolder {
        private final ImageView logo;
        private final TextView name, description;

        public UsersHolder(@NonNull View itemView) {
            super(itemView);
            logo = itemView.findViewById(R.id.logo);
            name = itemView.findViewById(R.id.title);
            description = itemView.findViewById(R.id.description);
        }
    }
}

2. 优化Fragment初始化与网络请求逻辑 #

• 初始化usersList为非空的空集合，避免传递null给Adapter
• 处理网络返回数据为null的情况

// 初始化空集合，避免传递null
List<UsersModel> usersList = new ArrayList<>();

binding.recyclerViewUser.setLayoutManager(new LinearLayoutManager(getContext(), LinearLayoutManager.VERTICAL, false));
binding.recyclerViewUser.setOverScrollMode(View.OVER_SCROLL_NEVER);
// 不再传入size参数
usersAdapter = new UsersAdapter(mContext, usersList);
binding.recyclerViewUser.setAdapter(usersAdapter);

Call<List<UsersModel>> getUersData = RetrofitClient.getInstance().getApi().getUsersData();
getUersData.enqueue(new Callback<>() {
    @Override
    public void onResponse(@NonNull Call<List<UsersModel>> call, @NonNull Response<List<UsersModel>> response) {
        if (response.isSuccessful() && response.body() != null) {
            usersList = response.body();
            usersAdapter.setUsersList(usersList);
            
            Log.d("Retrofit success", "Yeah!");
            long requestTime = response.raw().sentRequestAtMillis();
            long responseTime = response.raw().receivedResponseAtMillis();
            long apiTime =  responseTime - requestTime;
            Log.d("Retrofit time", apiTime + "ms");
        } else {
            Log.d("Retrofit info", "No data returned");
            usersAdapter.setUsersList(null);
        }
    }

    @Override
    public void onFailure(@NonNull Call<List<UsersModel>> call, @NonNull Throwable t) {
        Log.d("Retrofit error", t.getMessage());
        usersAdapter.setUsersList(null);
    }
});

3. 可选：添加空状态提示 #

如果需要在无数据时给用户明确提示，可以在Fragment布局中添加空状态View，根据数据情况显示/隐藏：

// 在更新Adapter数据后执行
if (usersList == null || usersList.isEmpty()) {
    binding.emptyView.setVisibility(View.VISIBLE);
    binding.recyclerViewUser.setVisibility(View.GONE);
} else {
    binding.emptyView.setVisibility(View.GONE);
    binding.recyclerViewUser.setVisibility(View.VISIBLE);
}

内容的提问来源于stack exchange，提问作者zigg-zigg