利用java实现《第一行代码》中Fragment一个简易版的新闻应用android

好的，我们可以按照以下步骤实现一个简易版的新闻应用：

1. 创建一个新的 Android 项目，并在 MainActivity 中添加用于显示 Fragment 的布局：

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
}

<!-- activity_main.xml -->
<FrameLayout
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

2. 创建 NewsFragment 类，并在其中添加用于显示新闻列表的 RecyclerView：

public class NewsFragment extends Fragment {
    private RecyclerView mRecyclerView;
    private NewsAdapter mAdapter;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_news, container, false);
        mRecyclerView = view.findViewById(R.id.recycler_view);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        mAdapter = new NewsAdapter();
        mRecyclerView.setAdapter(mAdapter);
        return view;
    }

    private class NewsHolder extends RecyclerView.ViewHolder {
        private TextView mTitleTextView;
        private TextView mDateTextView;

        public NewsHolder(LayoutInflater inflater, ViewGroup parent) {
            super(inflater.inflate(R.layout.list_item_news, parent, false));
            mTitleTextView = itemView.findViewById(R.id.news_title);
            mDateTextView = itemView.findViewById(R.id.news_date);
        }

        public void bind(News news) {
            mTitleTextView.setText(news.getTitle());
            mDateTextView.setText(news.getDate());
        }
    }

    private class NewsAdapter extends RecyclerView.Adapter<NewsHolder> {
        private List<News> mNewsList = new ArrayList<>();

        public void setNewsList(List<News> newsList) {
            mNewsList = newsList;
        }

        @Override
        public NewsHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            LayoutInflater layoutInflater = LayoutInflater.from(getActivity());
            return new NewsHolder(layoutInflater, parent);
        }

        @Override
        public void onBindViewHolder(NewsHolder holder, int position) {
            News news = mNewsList.get(position);
            holder.bind(news);
        }

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

<!-- fragment_news.xml -->
<androidx.recyclerview.widget.RecyclerView
    android:id="@+id/recycler_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

<!-- list_item_news.xml -->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="16dp">

    <TextView
        android:id="@+id/news_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textAppearance="?android:textAppearanceLarge" />

    <TextView
        android:id="@+id/news_date"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textAppearance="?android:textAppearanceSmall" />

</LinearLayout>

3. 创建 News 类，用于保存新闻的标题和日期：

public class News {
    private String mTitle;
    private String mDate;

    public News(String title, String date) {
        mTitle = title;
        mDate = date;
    }

    public String getTitle() {
        return mTitle;
    }

    public String getDate() {
        return mDate;
    }
}

4. 在 MainActivity 中添加用于显示 NewsFragment 的代码：

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        FragmentManager fm = getSupportFragmentManager();
        Fragment fragment = fm.findFragmentById(R.id.container);

        if (fragment == null) {
            fragment = new NewsFragment();
            fm.beginTransaction()
              .add(R.id.container, fragment)
              .commit();
        }
    }
}

5. 在 NewsFragment 中添加一个用于生成假数据的方法，并在 onCreateView 方法中调用它：

public class NewsFragment extends Fragment {
    // ...

    private void generateNewsList() {
        List<News> newsList = new ArrayList<>();
        newsList.add(new News("Title 1", "2021-01-01"));
        newsList.add(new News("Title 2", "2021-01-02"));
        newsList.add(new News("Title 3", "2021-01-03"));
        newsList.add(new News("Title 4", "2021-01-04"));
        newsList.add(new News("Title 5", "2021-01-05"));
        mAdapter.setNewsList(newsList);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_news, container, false);
        mRecyclerView = view.findViewById(R.id.recycler_view);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        mAdapter = new NewsAdapter();
        mRecyclerView.setAdapter(mAdapter);
        generateNewsList();
        return view;
    }

    // ...
}

现在，我们可以运行应用程序，看到一个简单的新闻列表。这只是一个很简单的例子，但它展示了如何使用 Fragment 和 RecyclerView 构建一个 Android 应用程序。