用android studio实现新闻收藏

好的，下面我来详细介绍一下如何用Android Studio实现新闻收藏功能。

1. 创建SQLite数据库

首先在Android Studio中创建一个新的Android工程，然后新建一个类用于创建SQLite数据库，并且定义好存储新闻的表结构。在这个类中，需要继承SQLiteOpenHelper类，并且重写onCreate()和onUpgrade()方法。onCreate()方法用于创建数据库和表，onUpgrade()方法用于升级数据库版本。

以下是一个示例的SQLiteOpenHelper类：

public class DBHelper extends SQLiteOpenHelper {

    private static final String DB_NAME = "news.db"; // 数据库名
    private static final int DB_VERSION = 1; // 数据库版本号

    // 新闻表
    private static final String TABLE_NEWS = "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_URL = "url";

    public DBHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String createTable = "CREATE TABLE " + TABLE_NEWS + "("
                + COLUMN_ID + " INTEGER PRIMARY KEY,"
                + COLUMN_TITLE + " TEXT,"
                + COLUMN_CONTENT + " TEXT,"
                + COLUMN_URL + " TEXT)";
        db.execSQL(createTable);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_NEWS);
        onCreate(db);
    }
}

2. 新闻收藏

在新闻详情页面中，添加一个收藏按钮，并且为这个按钮添加一个点击事件处理方法。在这个事件处理方法中，将新闻的标题、内容和URL等信息存储到SQLite数据库中。

以下是一个示例的新闻详情页面：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/news_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textAppearance="?android:textAppearanceLarge"
        android:text="News Title"
        android:padding="16dp"
        android:textStyle="bold"/>

    <TextView
        android:id="@+id/news_content"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textAppearance="?android:textAppearanceMedium"
        android:text="News Content"
        android:padding="16dp"/>

    <Button
        android:id="@+id/favorite_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="收藏"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:layout_marginRight="16dp"
        android:layout_marginBottom="16dp"/>

</RelativeLayout>

在新闻详情页面的Java代码中，为收藏按钮添加一个点击事件处理方法，将新闻的标题、内容和URL等信息存储到SQLite数据库中。以下是一个示例的Java代码：

public class NewsDetailActivity extends AppCompatActivity {

    private String newsTitle;
    private String newsContent;
    private String newsUrl;

    private Button favoriteButton;

    private DBHelper dbHelper;

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

        dbHelper = new DBHelper(this);

        newsTitle = getIntent().getStringExtra("title");
        newsContent = getIntent().getStringExtra("content");
        newsUrl = getIntent().getStringExtra("url");

        TextView newsTitleView = (TextView) findViewById(R.id.news_title);
        newsTitleView.setText(newsTitle);

        TextView newsContentView = (TextView) findViewById(R.id.news_content);
        newsContentView.setText(newsContent);

        favoriteButton = (Button) findViewById(R.id.favorite_button);
        favoriteButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                SQLiteDatabase db = dbHelper.getWritableDatabase();
                ContentValues values = new ContentValues();
                values.put(DBHelper.COLUMN_TITLE, newsTitle);
                values.put(DBHelper.COLUMN_CONTENT, newsContent);
                values.put(DBHelper.COLUMN_URL, newsUrl);
                db.insert(DBHelper.TABLE_NEWS, null, values);
                Toast.makeText(getApplicationContext(), "收藏成功", Toast.LENGTH_SHORT).show();
            }
        });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        dbHelper.close();
    }
}

3. 我的收藏

在应用中添加一个“我的收藏”页面，用于显示用户已经收藏的新闻列表。可以使用RecyclerView控件展示收藏的新闻列表，并且在列表中添加一个删除按钮，用于删除不需要的收藏。

以下是一个示例的“我的收藏”页面的布局文件：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/news_list"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scrollbars="vertical"/>

</RelativeLayout>

在Java代码中，使用SQLite数据库查询用户已经收藏的新闻，并且将这些新闻展示在RecyclerView中。在RecyclerView的适配器中，为列表项添加一个删除按钮，并且为这个按钮添加一个点击事件处理方法。

以下是一个示例的“我的收藏”页面的Java代码：

public class FavoriteActivity extends AppCompatActivity implements NewsAdapter.OnItemClickListener {

    private RecyclerView newsList;
    private NewsAdapter newsAdapter;
    private List<News> newsData = new ArrayList<>();

    private DBHelper dbHelper;

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

        dbHelper = new DBHelper(this);

        newsList = (RecyclerView) findViewById(R.id.news_list);
        newsList.setLayoutManager(new LinearLayoutManager(this));
        newsAdapter = new NewsAdapter(newsData);
        newsAdapter.setOnItemClickListener(this);
        newsList.setAdapter(newsAdapter);

        updateNewsList();
    }

    private void updateNewsList() {
        newsData.clear();
        SQLiteDatabase db = dbHelper.getReadableDatabase();
        Cursor cursor = db.query(DBHelper.TABLE_NEWS, null, null, null, null, null, null);
        if (cursor.moveToFirst()) {
            do {
                News news = new News();
                news.setTitle(cursor.getString(cursor.getColumnIndex(DBHelper.COLUMN_TITLE)));
                news.setContent(cursor.getString(cursor.getColumnIndex(DBHelper.COLUMN_CONTENT)));
                news.setUrl(cursor.getString(cursor.getColumnIndex(DBHelper.COLUMN_URL)));
                newsData.add(news);
            } while (cursor.moveToNext());
        }
        cursor.close();
        newsAdapter.notifyDataSetChanged();
    }

    @Override
    public void onItemClick(View view, int position) {
        News news = newsData.get(position);
        Intent intent = new Intent(this, NewsDetailActivity.class);
        intent.putExtra("title", news.getTitle());
        intent.putExtra("content", news.getContent());
        intent.putExtra("url", news.getUrl());
        startActivity(intent);
    }

    @Override
    public void onItemLongClick(View view, final int position) {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("提示");
        builder.setMessage("确定要删除这条收藏吗？");
        builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                SQLiteDatabase db = dbHelper.getWritableDatabase();
                News news = newsData.get(position);
                db.delete(DBHelper.TABLE_NEWS, DBHelper.COLUMN_TITLE + "=?", new String[]{news.getTitle()});
                newsData.remove(position);
                newsAdapter.notifyItemRemoved(position);
            }
        });
        builder.setNegativeButton("取消", null);
        builder.show();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        dbHelper.close();
    }
}

在适配器NewsAdapter中，为列表项添加一个删除按钮，并且为这个按钮添加一个点击事件处理方法。以下是一个示例的适配器代码：

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

    private List<News> newsData;
    private OnItemClickListener onItemClickListener;

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

    public void setOnItemClickListener(OnItemClickListener onItemClickListener) {
        this.onItemClickListener = onItemClickListener;
    }

    static class ViewHolder extends RecyclerView.ViewHolder {
        TextView newsTitleView;
        TextView newsContentView;
        Button deleteButton;

        public ViewHolder(View itemView) {
            super(itemView);
            newsTitleView = (TextView) itemView.findViewById(R.id.news_title);
            newsContentView = (TextView) itemView.findViewById(R.id.news_content);
            deleteButton = (Button) itemView.findViewById(R.id.delete_button);
        }
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.news_item, parent, false);
        final ViewHolder holder = new ViewHolder(view);
        holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int position = holder.getAdapterPosition();
                if (onItemClickListener != null) {
                    onItemClickListener.onItemClick(holder.itemView, position);
                }
            }
        });
        holder.deleteButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int position = holder.getAdapterPosition();
                if (onItemClickListener != null) {
                    onItemClickListener.onItemLongClick(holder.itemView, position);
                }
            }
        });
        return holder;
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        News news = newsData.get(position);
        holder.newsTitleView.setText(news.getTitle());
        holder.newsContentView.setText(news.getContent());
    }

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

    public interface OnItemClickListener {
        void onItemClick(View view, int position);

        void onItemLongClick(View view, int position);
    }
}

至此，我们完成了新闻收藏功能的实现。用户可以在新闻详情页面中点击收藏按钮，将新闻保存到SQLite数据库中。在“我的收藏”页面中，用户可以查看已经收藏的新闻，并且可以删除不需要的收藏。