java - 在不同的片段中添加和显示项目到 RecyclerView

Question

我正在创建一个具有 3 个选项卡的应用程序，每个选项卡都有不同的工作。例如，在Employee选项卡中，有 EditText 用于获取 emolyee 的姓名和姓氏，而 Button 用于将项目添加到其 RecyclerView。城市选项卡与员工选项卡相同，只是采用城市名称。最后一个选项卡只有一个按钮，用于分发员工和城市的条目并显示给用户。

我的问题是，我找不到如何将项目添加到 RecyclerView 并将其显示给用户。

这是我的代码。我只发送 Tab1 的片段和布局。其他都是一样的。

这是Fragment1 类：

public class Fragment1 extends Fragment {

    private RecyclerView employeeRecyclerView;
    private RecyclerViewAdapter employeeRecyclerViewAdapter;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        return inflater.inflate(R.layout.name_employee, container, false);

    }
}

这是RecyclerViewAdapter 类：

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

    private List<String> mData;
    private LayoutInflater mInflater;

    RecyclerViewAdapter(Context context, List<String> data) {
        this.mInflater = LayoutInflater.from(context);
        this.mData = data;
    }

    @NonNull
    @Override
    public RecyclerViewAdapter.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = mInflater.inflate(R.layout.fragment_main, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull RecyclerViewAdapter.ViewHolder holder, int position) {
        String x = mData.get(position);
        holder.myTextView.setText(x);
    }


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


    public class ViewHolder extends RecyclerView.ViewHolder{
        TextView myTextView;

        ViewHolder(View itemView) {
            super(itemView);
            myTextView = itemView.findViewById(R.id.section_label);
        }

    }
}

和Employee.xml文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">

    <EditText
        android:id="@+id/employeeField"
        android:hint="Name and Surname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal" />

    <Button
        android:id="@+id/cityAdd"
        android:text="addEmployee"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal" />

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/employees"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

</LinearLayout>

和fragment_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/constraintLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ui.main.PlaceholderFragment">

    <TextView
        android:id="@+id/section_label"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

更新我上传其他课程。有 Fragment2 和 Fragment3 类，但它们与 Fragment1 相同。

PlaceHolderFragment.class

public class PlaceholderFragment extends Fragment {

    private static final String ARG_SECTION_NUMBER = "section_number";

    private PageViewModel pageViewModel;

    public static PlaceholderFragment newInstance(int index) {
        PlaceholderFragment fragment = new PlaceholderFragment();
        Bundle bundle = new Bundle();
        bundle.putInt(ARG_SECTION_NUMBER, index);
        fragment.setArguments(bundle);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        pageViewModel = ViewModelProviders.of(this).get(PageViewModel.class);
        int index = 1;
        if (getArguments() != null) {
            index = getArguments().getInt(ARG_SECTION_NUMBER);
        }
        pageViewModel.setIndex(index);
    }

    @Override
    public View onCreateView(
            @NonNull LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View root = inflater.inflate(R.layout.fragment_main, container, false);
        final TextView textView = root.findViewById(R.id.section_label);
        pageViewModel.getText().observe(this, new Observer<String>() {
            @Override
            public void onChanged(@Nullable String s) {
                textView.setText(s);
            }
        });
        return root;
    }
}

SectionsPagerAdapter.class

public class SectionsPagerAdapter extends FragmentPagerAdapter {

    @StringRes
    private static final int[] TAB_TITLES = new int[]{R.string.tab_text_1, R.string.tab_text_2, R.string.tab_text_3};
    private final Context mContext;

    public SectionsPagerAdapter(Context context, FragmentManager fm) {
        super(fm);
        mContext = context;
    }

    @Override
    public Fragment getItem(int position) {
        Fragment fragment = null;

        switch (position){
            case 0:
                fragment = new Fragment1();
                break;
            case 1:
                fragment = new Fragment2();
                break;
            case 2:
                fragment = new Fragment3();
                break;
        }
        return fragment;


    }

    @Nullable
    @Override
    public CharSequence getPageTitle(int position) {
        return mContext.getResources().getString(TAB_TITLES[position]);
    }

    @Override
    public int getCount() {

        return 3;
    }
}

和 PageViewModel.class

public class PageViewModel extends ViewModel {

    private MutableLiveData<Integer> mIndex = new MutableLiveData<>();
    private LiveData<String> mText = Transformations.map(mIndex, new Function<Integer, String>() {
        @Override
        public String apply(Integer input) {
            return "Hello world from section: " + input;
        }
    });

    public void setIndex(int index) {
        mIndex.setValue(index);
    }

    public LiveData<String> getText() {
        return mText;
    }
}

标签： javaandroidxmlandroid-fragmentsandroid-recyclerview