androidstudio增删改查代码

以下是 Android Studio 中使用 SQLite 数据库进行增删改查的示例代码：

1. 建立数据库帮助类

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

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

    @Override
    public void onCreate(SQLiteDatabase db) {
        String sql = "CREATE TABLE IF NOT EXISTS mytable " +
                     "(id INTEGER PRIMARY KEY AUTOINCREMENT, " +
                     "name TEXT, " +
                     "age INTEGER)";
        db.execSQL(sql);
    }

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

2. 插入数据

public void insertData(String name, int age) {
    SQLiteDatabase db = getWritableDatabase();
    ContentValues values = new ContentValues();
    values.put("name", name);
    values.put("age", age);
    db.insert("mytable", null, values);
    db.close();
}

3. 查询数据

public ArrayList<String> queryData() {
    ArrayList<String> data = new ArrayList<>();
    SQLiteDatabase db = getReadableDatabase();
    String[] columns = {"id", "name", "age"};
    Cursor cursor = db.query("mytable", columns, null, null, null, null, null);
    while (cursor.moveToNext()) {
        int id = cursor.getInt(cursor.getColumnIndex("id"));
        String name = cursor.getString(cursor.getColumnIndex("name"));
        int age = cursor.getInt(cursor.getColumnIndex("age"));
        data.add(id + " " + name + " " + age);
    }
    cursor.close();
    db.close();
    return data;
}

4. 更新数据

public void updateData(int id, String name, int age) {
    SQLiteDatabase db = getWritableDatabase();
    ContentValues values = new ContentValues();
    values.put("name", name);
    values.put("age", age);
    db.update("mytable", values, "id=?", new String[]{String.valueOf(id)});
    db.close();
}

5. 删除数据

public void deleteData(int id) {
    SQLiteDatabase db = getWritableDatabase();
    db.delete("mytable", "id=?", new String[]{String.valueOf(id)});
    db.close();
}

注意：以上代码仅为示例，实际使用时需要根据具体情况进行修改。