java - RecyclerView 根本不显示。我找不到错误。我该如何解决？

Question

我正在尝试使用 ViewPageAdapter 将我的 recyclerview 构建为多个 fragment 。我对 Android Studio 还很陌生，我不知道如何处理我遇到的错误。我的回收 View 没有显示，在运行时，我遇到的唯一问题似乎是“跳帧”类型的问题。这通常小于 100 帧(而且我的模拟器很慢，所以我不知道应用程序是否真的占用了这么多时间)。

我尝试修复它的事情:我尝试使用 AsyncTask 类，但我仍然不确定如果它减慢了应用程序的速度，如何正确实现它。该平台上的一些人建议您需要翻转回收器 View 适配器和布局管理器的设置顺序，但这根本没有帮助。

注意:我还没有时间为 ViewPageAdapter 创建新的 fragment 类。目前只有一个 fragment 类，但我打算在 ViewPager 上将多个 fragment 表示为多个页面。 (另外，我不想分享我团队项目背后的总体想法。我想保持匿名，但如果您发现有必要了解该项目的主要想法，我绝对可以发送消息更多详细信息。)

我设置 RecyclerView 适配器的 fragment

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import java.util.ArrayList;
import java.util.List;

public class Fragment_new extends Fragment {

    View v;
    private RecyclerView myRecyclerView;
    private List<new_prescription> list_prescriptions;

    public View onCreateNewView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        v = inflater.inflate(R.layout.new_fragment, container, false);
        myRecyclerView = v.findViewById(R.id.recyclerview_obj);
        recyclerViewAdapter recycleAdapter = new recyclerViewAdapter(getContext(), list_prescriptions);
        myRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        myRecyclerView.setAdapter(recycleAdapter);
        return v;

    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        list_prescriptions = new ArrayList<>();
        list_prescriptions.add(new new_prescription("Some Medication #1", "6:30-9:30", 5));
        list_prescriptions.add(new new_prescription("Some Medication #2", "1:30-4:30", 5));
    }
}

ViewPageAdapter 为不同的 fragment 创建 View

import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentPagerAdapter;

import java.util.ArrayList;
import java.util.List;

public class ViewPageAdapter extends FragmentPagerAdapter {


    private final List<Fragment> pager_list = new ArrayList<>();
    private final List<String>   string_List = new ArrayList<>();

    public ViewPageAdapter(FragmentManager manager) {
        super(manager);

    }

    @Override
    public Fragment getItem(int position) {
        return pager_list.get(position);
    }

    @Override
    public int getCount() {
        return string_List.size();
    }

    public CharSequence elementString(int position) {
        return string_List.get(position);
    }

    public void addFragment(Fragment fragment, String title) {
        pager_list.add(fragment);
        string_List.add(title);

    }


}

我的 RecyclerView 的普通 RecyclerViewAdapter

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import java.util.List;

public class recyclerViewAdapter extends RecyclerView.Adapter<recyclerViewAdapter.MyViewHolder> {

    Context data;
    List<new_prescription> new_list;

    public recyclerViewAdapter(Context data, List<new_prescription> new_list) {
        this.data = data;
        this.new_list = new_list;
    }

    public recyclerViewAdapter() {
    }

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(data).inflate(R.layout.new_fragment_items, parent, false);
        MyViewHolder view = new MyViewHolder(v);
        return view;
    }

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

        holder.new_name.setText(new_list.get(position).getName());
        holder.new_quantity.setText(new_list.get(position).getTime());

    }

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

    public static class MyViewHolder extends RecyclerView.ViewHolder {

        private TextView new_name;
        private TextView new_quantity;
        private ImageView new_image;
        private TextView  new_time;

        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
            new_name = itemView.findViewById(R.id.prescription_name);
            new_image = itemView.findViewById(R.id.new_image);
            new_quantity = itemView.findViewById(R.id.quantity_items);
            new_time = itemView.findViewById(R.id.new_time);

        }

    }
    }

主要 Activity 类

import android.os.Bundle;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager.widget.ViewPager;

import com.google.android.material.tabs.TabLayout;

public class Main_Activity_Frags extends AppCompatActivity {

   private TabLayout layout;
   private ViewPager viewpager;
   private ViewPageAdapter adapter;


   public Main_Activity_Frags() {
   }

   @Override
   protected void onCreate(@Nullable Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main_2);

       layout = findViewById(R.id.tab_layout_id);
       viewpager = findViewById(R.id.viewpager_id);
       adapter = new ViewPageAdapter(getSupportFragmentManager());


       adapter.addFragment(new Fragment_new(),"Prescriptions For Today");
       adapter.addFragment(new Secondary_Fragment(),"Quantity");
       adapter.addFragment(new Fragment_final(), "Time");


       viewpager.setAdapter(adapter);
       layout.setupWithViewPager(viewpager);
       layout.getTabAt(0).setIcon(R.drawable.baseline_today_black_18dp);
       layout.getTabAt(1).setIcon(R.drawable.baseline_history_black_18dp);


   }



}

这是我用来实例化添加到 RecyclerView Arraylist 的 new_prescription 对象的类。

public class new_prescription {

    private String Name;
    private String Time;
    private int Frequency;

    public new_prescription() {
    }

    public new_prescription(String name, String time, int frequency) {
        Name = name;
        Time = time;
        Frequency = frequency;
    }

    public String getTime() {
        return Time;
    }

    public String getName() {
        return Name;
    }

    public int getFrequency() {
        return Frequency;
    }
}

Answer 1

我认为这是可行的，试试这个:

public class Fragment_new extends Fragment {

            private RecyclerView myRecyclerView;
            private List<new_prescription> list_prescriptions;


            @Override
            public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
                v = inflater.inflate(R.layout.new_fragment, container, false);
                myRecyclerView = v.findViewById(R.id.recyclerview_obj);
                list_prescriptions = new ArrayList<>();
                list_prescriptions.add(new new_prescription("Some Medication #1", "6:30-9:30", 5));
                list_prescriptions.add(new new_prescription("Some Medication #2", "1:30-4:30", 5));

                recyclerViewAdapter recycleAdapter = new recyclerViewAdapter(getContext(), list_prescriptions);
                myRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
                myRecyclerView.setAdapter(recycleAdapter);
                return v;

            }


        }