RecyclerView 没有迭代布局[重复]

Question

我正在为我的 android 应用程序创建一个 RecyclerView，其中包含一些具有两组数据的虚拟数据。但是布局没有迭代两次，而是正确显示了第一个数据。

public class HomeScreenFragment extends Fragment {

    private ArrayList<String> flags = new ArrayList<>();
    private ArrayList<String> leagues = new ArrayList<>();
    private ArrayList<String> dates = new ArrayList<>();

    private Context context;

    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View root = inflater.inflate(R.layout.fragment_home, container, false);
        return root;
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {

        initData();

    }

    private void initData() {
        leagues.add("Indian premiere league");
        dates.add("03-Dec");

        leagues.add("Srilankan Premiere league");
        dates.add("04-Dec");

        initRecyclerView();
    }

    private void initRecyclerView() {
        RecyclerView recyclerView = getView().findViewById(R.id.homeRecyclerView);
        HomeScreenRVAdapter adapter = new HomeScreenRVAdapter(flags,leagues,dates,context);
        recyclerView.setAdapter(adapter);
        recyclerView.setLayoutManager(new LinearLayoutManager(context));
    }
}

回收站视图

public class HomeScreenRVAdapter extends RecyclerView.Adapter<HomeScreenRVAdapter.ViewHolder> {
    private static final String TAG = "HomeScreenRVAdapter";

    private String BASE_URL, API_KEY;

    private ArrayList<String> flags = new ArrayList<>();
    private ArrayList<String> leagues = new ArrayList<>();
    private ArrayList<String> dates = new ArrayList<>();
    private Context context;

    public HomeScreenRVAdapter(ArrayList<String> flags, ArrayList<String> leagues, ArrayList<String> dates, Context context) {
        this.flags = flags;
        this.leagues = leagues;
        this.dates = dates;
        this.context = context;
    }

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

    @Override
    public void onBindViewHolder(@NonNull final ViewHolder holder, final int position) {
        holder.league.setText(leagues.get(position));
        holder.date.setText(dates.get(position));
    }

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

    public class ViewHolder extends RecyclerView.ViewHolder {

        // HEADER WIDGETS
        ExpansionHeader expansionHeader;
        ImageView flag;
        TextView league, date;

        // LAYOUT WIDGETS
        ExpansionLayout expansionLayout;
        TextView minutes, local, visitor, localScore, visitorScore;
        ImageView favourite;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);

            expansionHeader = itemView.findViewById(R.id.expansionHeader);
            flag = itemView.findViewById(R.id.headerFlag);
            league = itemView.findViewById(R.id.expansionHeaderLeague);
            date = itemView.findViewById(R.id.expansionHeaderDate);

        }
    }
}

我想让应用在数据到来时迭代布局 (layout_home) 的次数。但它不是迭代的。否则无论如何只迭代扩展布局？

Answer 1

您的代码看起来不错。 layout_home 中很可能存在问题。确保 android:layout_height 设置为 wrap_content。

此外，您可以实现自定义对象ArrayList，而不是创建三个单独的对象。自定义对象将保存每个项目的属性。但是，这是一个建议，我认为这不是您面临的错误的原因。

Answer 2

接受的答案是正确的答案，但我为您制定了另一种方法和良好的编码实践。

首先，我们需要初始化RecyclerView

@Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {

        RecyclerView recyclerView = getView().findViewById(R.id.homeRecyclerView);
        recyclerView.setLayoutManager(new LinearLayoutManager(context));
        HomeScreenRVAdapter adapter = new HomeScreenRVAdapter();
        recyclerView.setAdapter(adapter);

    }

然后创建名为HomeScreenRVAdapter.java

的recyclerView Adapter

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

    private List<League> leagues = new ArrayList<>();

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

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        League league = leagues.get(position);
        holder.league.setText(league.getLeague());
        holder.date.setText(league.getDate());
    }

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

    void setList(List<League> list) {
        this.leagues = list;
        notifyDataSetChanged();
    }


    class ViewHolder extends RecyclerView.ViewHolder {
        ImageView flag;
        TextView league, date;

        ViewHolder(@NonNull View itemView) {
            super(itemView);
            flag = itemView.findViewById(R.id.headerFlag);
            league = itemView.findViewById(R.id.expansionHeaderLeague);
            date = itemView.findViewById(R.id.expansionHeaderDate);
        }
    }
}

创建名为 League.java

的 getter 和 setter 类

class League {
    private String flag;
    private String league;
    private String date;

    public League(String flag, String league, String date) {
        this.flag = flag;
        this.league = league;
        this.date = date;
    }

    public String getFlag() {
        return flag;
    }

    public String getLeague() {
        return league;
    }

    public String getDate() {
        return date;
    }
}

然后在你的 onViewCreated() 中像这样添加你的数据。

@Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {

        ...

        List<League> leagues = new ArrayList<>();
        leagues.add(new League("Flag1","Indian premiere league","03-Dec"));
        leagues.add(new League("Flag2","Srilankan Premiere league","04-Dec"));

        adapter.setList(leagues);
    }

notifyDataSetChanged();

非常重要。数据更改后不要忘记添加。