Android studio 实现新闻界面，并实现增删改查新闻具体代码

以下是一个简单的实现新闻列表界面，并实现增删改查新闻的代码示例，供参考：

1. 布局文件 `activity_main.xml`：

<?xml version="1.0" encoding="utf-8"?>
<androidx.recyclerview.widget.RecyclerView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/news_list"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

2. 新闻类 `News.java`：

public class News {
    private String title;
    private String summary;
    private String publishTime;

    public News(String title, String summary, String publishTime) {
        this.title = title;
        this.summary = summary;
        this.publishTime = publishTime;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getSummary() {
        return summary;
    }

    public void setSummary(String summary) {
        this.summary = summary;
    }

    public String getPublishTime() {
        return publishTime;
    }

    public void setPublishTime(String publishTime) {
        this.publishTime = publishTime;
    }
}

3. 接口类 `NewsService.java`：

public interface NewsService {
    @GET("news")
    Call<List<News>> getNewsList();
}

4. 适配器类 `NewsAdapter.java`：

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

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

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.news_item, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        holder.title.setText(newsList.get(position).getTitle());
        holder.summary.setText(newsList.get(position).getSummary());
        holder.publishTime.setText(newsList.get(position).getPublishTime());
    }

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

    static class ViewHolder extends RecyclerView.ViewHolder {
        TextView title;
        TextView summary;
        TextView publishTime;

        ViewHolder(View itemView) {
            super(itemView);
            title = itemView.findViewById(R.id.news_title);
            summary = itemView.findViewById(R.id.news_summary);
            publishTime = itemView.findViewById(R.id.news_publish_time);
        }
    }
}

5. 新闻列表界面 `MainActivity.java`：

public class MainActivity extends AppCompatActivity {
    private RecyclerView recyclerView;
    private NewsAdapter newsAdapter;
    private List<News> newsList = new ArrayList<>();

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

        recyclerView = findViewById(R.id.news_list);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        newsAdapter = new NewsAdapter(newsList);
        recyclerView.setAdapter(newsAdapter);

        // 请求服务器端的新闻数据
        NewsService newsService = RetrofitClient.getRetrofit().create(NewsService.class);
        Call<List<News>> call = newsService.getNewsList();
        call.enqueue(new Callback<List<News>>() {
            @Override
            public void onResponse(Call<List<News>> call, Response<List<News>> response) {
                newsList.addAll(response.body());
                newsAdapter.notifyDataSetChanged();
            }

            @Override
            public void onFailure(Call<List<News>> call, Throwable t) {
                Toast.makeText(MainActivity.this, "请求失败：" + t.getMessage(), Toast.LENGTH_SHORT).show();
            }
        });
    }
}

6. 数据库帮助类 `DatabaseHelper.java`：

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

    private static final String TABLE_NAME = "news";
    private static final String COLUMN_ID = "_id";
    private static final String COLUMN_TITLE = "title";
    private static final String COLUMN_CONTENT = "content";
    private static final String COLUMN_PUBLISH_TIME = "publish_time";

    private static final String CREATE_TABLE = "CREATE TABLE " + TABLE_NAME + "("
            + COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
            + COLUMN_TITLE + " TEXT NOT NULL, "
            + COLUMN_CONTENT + " TEXT NOT NULL, "
            + COLUMN_PUBLISH_TIME + " TEXT NOT NULL)";

    private static final String DROP_TABLE = "DROP TABLE IF EXISTS " + TABLE_NAME;

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

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_TABLE);
    }

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

7. 内容提供器类 `NewsProvider.java`：

public class NewsProvider extends ContentProvider {
    private static final String AUTHORITY = "com.example.news.provider";
    private static final String TABLE_NAME = "news";
    private static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/" + TABLE_NAME);
    private static final int NEWS_DIR = 1;
    private static final int NEWS_ITEM = 2;

    private DatabaseHelper databaseHelper;
    private SQLiteDatabase db;

    private static final UriMatcher uriMatcher;
    static {
        uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        uriMatcher.addURI(AUTHORITY, TABLE_NAME, NEWS_DIR);
        uriMatcher.addURI(AUTHORITY, TABLE_NAME + "/#", NEWS_ITEM);
    }

    @Override
    public boolean onCreate() {
        databaseHelper = new DatabaseHelper(getContext());
        db = databaseHelper.getWritableDatabase();
        return true;
    }

    @Nullable
    @Override
    public Cursor query(@NonNull Uri uri, @Nullable String[] projection,
                        @Nullable String selection, @Nullable String[] selectionArgs,
                        @Nullable String sortOrder) {
        Cursor cursor = null;
        switch (uriMatcher.match(uri)) {
            case NEWS_DIR:
                cursor = db.query(TABLE_NAME, projection, selection, selectionArgs,
                        null, null, sortOrder);
                break;
            case NEWS_ITEM:
                String newsId = uri.getPathSegments().get(1);
                cursor = db.query(TABLE_NAME, projection, COLUMN_ID + "=?",
                        new String[] { newsId }, null, null, sortOrder);
                break;
            default:
                throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        return cursor;
    }

    @Nullable
    @Override
    public String getType(@NonNull Uri uri) {
        switch (uriMatcher.match(uri)) {
            case NEWS_DIR:
                return "vnd.android.cursor.dir/vnd." + AUTHORITY + "." + TABLE_NAME;
            case NEWS_ITEM:
                return "vnd.android.cursor.item/vnd." + AUTHORITY + "." + TABLE_NAME;
            default:
                throw new IllegalArgumentException("Unknown URI: " + uri);
        }
    }

    @Nullable
    @Override
    public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
        Uri uriReturn = null;
        switch (uriMatcher.match(uri)) {
            case NEWS_DIR:
            case NEWS_ITEM:
                long newId = db.insert(TABLE_NAME, null, values);
                uriReturn = Uri.parse("content://" + AUTHORITY + "/" + TABLE_NAME + "/" + newId);
                break;
            default:
                throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        return uriReturn;
    }

    @Override
    public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
        int deletedRows = 0;
        switch (uriMatcher.match(uri)) {
            case NEWS_DIR:
                deletedRows = db.delete(TABLE_NAME, selection, selectionArgs);
                break;
            case NEWS_ITEM:
                String newsId = uri.getPathSegments().get(1);
                deletedRows = db.delete(TABLE_NAME, COLUMN_ID + "=?",
                        new String[] { newsId });
                break;
            default:
                throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        return deletedRows;
    }

    @Override
    public int update(@NonNull Uri uri, @Nullable ContentValues values,
                      @Nullable String selection, @Nullable String[] selectionArgs) {
        int updatedRows = 0;
        switch (uriMatcher.match(uri)) {
            case NEWS_DIR:
                updatedRows = db.update(TABLE_NAME, values, selection, selectionArgs);
                break;
            case NEWS_ITEM:
                String newsId = uri.getPathSegments().get(1);
                updatedRows = db.update(TABLE_NAME, values, COLUMN_ID + "=?",
                        new String[] { newsId });
                break;
            default:
                throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        return updatedRows;
    }
}

8. 在 `AndroidManifest.xml` 中注册内容提供器：

<manifest ...>
    <application ...>
        <provider
            android:name=".NewsProvider"
            android:authorities="com.example.news.provider"
            android:exported="true" />
    </application>
</manifest>

以上是一个简单的实现新闻列表界面，并实现增删改查新闻的代码示例，具体实现还需根据实际需求进行调整和完善。