android - 如何使用 MVVM 在 fragment 内运行的 RecyclerView 中显示项目？

Question

我正在尝试使用 MVVM 在 fragment 中实现 recyclerview，但项目未加载到屏幕上。这是代码:

空白 fragment .java:

package com.phunware.example.mvvmrecyclerviewblog;

import android.content.Context;
import android.databinding.DataBindingUtil;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.widget.DividerItemDecoration;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.phunware.example.mvvmrecyclerviewblog.databinding.FragmentBlankBinding;
import com.phunware.example.mvvmrecyclerviewblog.viewmodel.DataViewModel;

import static android.support.v7.widget.LinearLayoutManager.VERTICAL;

public class BlankFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        FragmentBlankBinding binding = DataBindingUtil.inflate(inflater, R.layout.fragment_blank, container, false);
        binding.setViewModel(new DataViewModel());

        binding.executePendingBindings();

        RecyclerView recyclerView = binding.getRoot().findViewById(R.id.data_recycler_view);
        recyclerView.setLayoutManager(new LinearLayoutManager(recyclerView.getContext()));
        recyclerView.addItemDecoration(new DividerItemDecoration(recyclerView.getContext(), VERTICAL));

        new DataViewModel().setUp();

//       initRecyclerView(binding.getRoot());
        return binding.getRoot();
    }
}

fragment_blank.xml:

<layout xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>

        <variable
            name="viewModel"
            type="com.phunware.example.mvvmrecyclerviewblog.viewmodel.DataViewModel"/>
    </data>

    <android.support.v7.widget.RecyclerView
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:id="@+id/data_recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@android:color/black"
        app:adapter="@{viewModel.adapter}"
        app:data="@{viewModel.data}"
        tools:context="com.phunware.example.mvvmrecyclerviewblog.view.MainActivity"/>
</layout>

DataViewModel.java:

package com.phunware.example.mvvmrecyclerviewblog.viewmodel;

import android.databinding.BaseObservable;
import android.databinding.Bindable;

import com.phunware.example.mvvmrecyclerviewblog.BR;
import com.phunware.example.mvvmrecyclerviewblog.adapter.DataAdapter;
import com.phunware.example.mvvmrecyclerviewblog.model.DataModel;

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

/**
 * Created by Gregory Rasmussen on 7/26/17.
 */
public class DataViewModel extends BaseObservable {
    private static final String TAG = "DataViewModel";
    private DataAdapter adapter;
    private List<DataModel> data;

    public DataViewModel() {
        data = new ArrayList<>();
        adapter = new DataAdapter();
    }

    public void setUp() {
        // perform set up tasks, such as adding listeners, data population, etc.
        populateData();
    }

    public void tearDown() {
        // perform tear down tasks, such as removing listeners
    }

    @Bindable
    public List<DataModel> getData() {
        return this.data;
    }

    @Bindable
    public DataAdapter getAdapter() {
        return this.adapter;
    }

    private void populateData() {
        // populate the data from the source, such as the database.
        for (int i = 0; i < 50; i++) {
            DataModel dataModel = new DataModel();
            dataModel.setTitle(String.valueOf(i));
            data.add(dataModel);
        }
        notifyPropertyChanged(BR.data);
    }
}

我已经尝试从 Fragment 的几乎每个生命周期方法中调用 setup()，但它不起作用。如果您想要更多项目文件，那么我可以上传，或者您可以从 this 观看项目文件的其余部分。 github repo 。请帮助我解决这个问题，或者接受任何其他实现方式。

编辑:如果我们在 Activity 而不是 fragment 上使用这种方法，那么这段代码可以正常工作，您可以在原始存储库中看到这一点。

Answer 1

首先你确实用这段代码绑定(bind)了你的数据

binding.setViewModel(new DataViewModel());

它没有得到用 new 关键字创建的对象然后你又调用了

new DataViewModel().setUp();

所以绑定(bind)的 viewModel 对象是别的东西，你调用了 viewModel.setup();在其他一些对象上，因此您没有在 recyclerView 中获取数据