用Android编写新闻列表

编写新闻列表的过程大致如下：

1. 定义数据模型：首先需要定义一个News类，包含新闻的标题、内容、发布时间等信息。

2. 获取数据：从网络或本地数据库中获取新闻数据。网络数据可以使用Android自带的HttpURLConnection或第三方库如OkHttp进行请求，本地数据库可以使用SQLite。

3. 创建列表视图：使用Android提供的RecyclerView控件来展示新闻列表，并创建一个ViewHolder来显示每个新闻项的视图。

4. 绑定数据：将数据绑定到ViewHolder中，更新新闻项的视图。

5. 实现点击事件：为每个新闻项添加点击事件，跳转到新闻详情页。

具体实现过程如下：

1. 定义News类

public class News {
    private String title;
    private String content;
    private String time;

    public News(String title, String content, String time) {
        this.title = title;
        this.content = content;
        this.time = time;
    }

    public String getTitle() {
        return title;
    }

    public String getContent() {
        return content;
    }

    public String getTime() {
        return time;
    }
}

2. 获取数据

网络请求：

public class NewsApi {
    private static final String TAG = "NewsApi";

    private static final String BASE_URL = "https://newsapi.org/v2/";
    private static final String API_KEY = "YOUR_API_KEY";

    public static List<News> getNews() throws IOException, JSONException {
        String urlString = BASE_URL + "top-headlines?country=us&apiKey=" + API_KEY;

        URL url = new URL(urlString);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("GET");
        connection.connect();

        InputStream inputStream = connection.getInputStream();
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
        StringBuffer stringBuffer = new StringBuffer();
        String line;
        while ((line = bufferedReader.readLine()) != null) {
            stringBuffer.append(line);
        }
        String responseString = stringBuffer.toString();

        JSONObject responseJson = new JSONObject(responseString);
        JSONArray articles = responseJson.getJSONArray("articles");

        List<News> newsList = new ArrayList<>();
        for (int i = 0; i < articles.length(); i++) {
            JSONObject article = articles.getJSONObject(i);
            String title = article.getString("title");
            String content = article.getString("description");
            String time = article.getString("publishedAt");
            News news = new News(title, content, time);
            newsList.add(news);
        }

        return newsList;
    }
}

本地数据库：

public class NewsDbHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "news.db";
    private static final int DATABASE_VERSION = 1;

    private static final String SQL_CREATE_ENTRIES =
            "CREATE TABLE " + NewsEntry.TABLE_NAME + " (" +
                    NewsEntry._ID + " INTEGER PRIMARY KEY," +
                    NewsEntry.COLUMN_NAME_TITLE + " TEXT," +
                    NewsEntry.COLUMN_NAME_CONTENT + " TEXT," +
                    NewsEntry.COLUMN_NAME_TIME + " TEXT)";

    private static final String SQL_DELETE_ENTRIES =
            "DROP TABLE IF EXISTS " + NewsEntry.TABLE_NAME;

    public NewsDbHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    public void onCreate(SQLiteDatabase db) {
        db.execSQL(SQL_CREATE_ENTRIES);
    }

    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL(SQL_DELETE_ENTRIES);
        onCreate(db);
    }

    public void addNews(News news) {
        SQLiteDatabase db = getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(NewsEntry.COLUMN_NAME_TITLE, news.getTitle());
        values.put(NewsEntry.COLUMN_NAME_CONTENT, news.getContent());
        values.put(NewsEntry.COLUMN_NAME_TIME, news.getTime());
        db.insert(NewsEntry.TABLE_NAME, null, values);
        db.close();
    }

    public List<News> getNews() {
        SQLiteDatabase db = getReadableDatabase();
        String[] projection = {
                NewsEntry._ID,
                NewsEntry.COLUMN_NAME_TITLE,
                NewsEntry.COLUMN_NAME_CONTENT,
                NewsEntry.COLUMN_NAME_TIME
        };
        Cursor cursor = db.query(
                NewsEntry.TABLE_NAME,
                projection,
                null,
                null,
                null,
                null,
                null
        );

        List<News> newsList = new ArrayList<>();
        while (cursor.moveToNext()) {
            String title = cursor.getString(cursor.getColumnIndexOrThrow(NewsEntry.COLUMN_NAME_TITLE));
            String content = cursor.getString(cursor.getColumnIndexOrThrow(NewsEntry.COLUMN_NAME_CONTENT));
            String time = cursor.getString(cursor.getColumnIndexOrThrow(NewsEntry.COLUMN_NAME_TIME));
            News news = new News(title, content, time);
            newsList.add(news);
        }
        cursor.close();
        db.close();

        return newsList;
    }

    public static class NewsEntry implements BaseColumns {
        public static final String TABLE_NAME = "news";
        public static final String COLUMN_NAME_TITLE = "title";
        public static final String COLUMN_NAME_CONTENT = "content";
        public static final String COLUMN_NAME_TIME = "time";
    }
}

3. 创建列表视图

在布局文件中添加RecyclerView控件：

<androidx.recyclerview.widget.RecyclerView
    android:id="@+id/recycler_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="16dp"
    app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
    tools:listitem="@layout/item_news" />

在Activity中获取RecyclerView并设置Adapter：

public class NewsListActivity extends AppCompatActivity {
    private RecyclerView recyclerView;
    private NewsAdapter newsAdapter;

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

        recyclerView = findViewById(R.id.recycler_view);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        newsAdapter = new NewsAdapter(new ArrayList<>());
        recyclerView.setAdapter(newsAdapter);

        // 获取新闻数据并更新列表
        List<News> newsList = getNews();
        newsAdapter.updateNews(newsList);
    }

    private List<News> getNews() {
        // 获取新闻数据
        return null;
    }
}

4. 绑定数据

创建ViewHolder来显示新闻项的视图：

public class NewsViewHolder extends RecyclerView.ViewHolder {
    private TextView titleTextView;
    private TextView contentTextView;
    private TextView timeTextView;

    public NewsViewHolder(@NonNull View itemView) {
        super(itemView);
        titleTextView = itemView.findViewById(R.id.title_text_view);
        contentTextView = itemView.findViewById(R.id.content_text_view);
        timeTextView = itemView.findViewById(R.id.time_text_view);
    }

    public void bind(News news) {
        titleTextView.setText(news.getTitle());
        contentTextView.setText(news.getContent());
        timeTextView.setText(news.getTime());
    }
}

创建Adapter来管理新闻列表的视图：

public class NewsAdapter extends RecyclerView.Adapter<NewsViewHolder> {
    private List<News> newsList;

    public NewsAdapter(List<News> newsList) {
        this.newsList = newsList;
    }

    public void updateNews(List<News> newsList) {
        this.newsList = newsList;
        notifyDataSetChanged();
    }

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

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

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

5. 实现点击事件

在ViewHolder中为新闻项添加点击事件：

public class NewsViewHolder extends RecyclerView.ViewHolder {
    private TextView titleTextView;
    private TextView contentTextView;
    private TextView timeTextView;

    public NewsViewHolder(@NonNull View itemView) {
        super(itemView);
        titleTextView = itemView.findViewById(R.id.title_text_view);
        contentTextView = itemView.findViewById(R.id.content_text_view);
        timeTextView = itemView.findViewById(R.id.time_text_view);

        itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // 跳转到新闻详情页
            }
        });
    }

    public void bind(News news) {
        titleTextView.setText(news.getTitle());
        contentTextView.setText(news.getContent());
        timeTextView.setText(news.getTime());
    }
}