android studio数据库增删查改源码

以下是一个简单的Android Studio数据库增删查改的示例代码：

1. 首先，在你的项目中创建一个DatabaseHelper类，继承自SQLiteOpenHelper。

public class DatabaseHelper extends SQLiteOpenHelper {

    private static final String DATABASE_NAME = "mydatabase.db";
    private static final int DATABASE_VERSION = 1;

    //构造方法
    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

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

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

2. 创建一个数据访问类StudentDAO，封装增删查改操作。

public class StudentDAO {

    private static final String TABLE_NAME = "student";

    //插入数据
    public static long insert(Context context, ContentValues values) {
        DatabaseHelper dbHelper = new DatabaseHelper(context);
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        long id = db.insert(TABLE_NAME, null, values);
        db.close();
        return id;
    }

    //删除数据
    public static int delete(Context context, String whereClause, String[] whereArgs) {
        DatabaseHelper dbHelper = new DatabaseHelper(context);
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        int count = db.delete(TABLE_NAME, whereClause, whereArgs);
        db.close();
        return count;
    }

    //更新数据
    public static int update(Context context, ContentValues values, String whereClause, String[] whereArgs) {
        DatabaseHelper dbHelper = new DatabaseHelper(context);
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        int count = db.update(TABLE_NAME, values, whereClause, whereArgs);
        db.close();
        return count;
    }

    //查询数据
    public static List<Student> query(Context context, String selection, String[] selectionArgs) {
        List<Student> list = new ArrayList<>();
        DatabaseHelper dbHelper = new DatabaseHelper(context);
        SQLiteDatabase db = dbHelper.getReadableDatabase();
        Cursor cursor = db.query(TABLE_NAME, null, selection, selectionArgs, 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"));
            String gender = cursor.getString(cursor.getColumnIndex("gender"));
            Student student = new Student(id, name, age, gender);
            list.add(student);
        }
        cursor.close();
        db.close();
        return list;
    }
}

3. 在你的Activity中使用StudentDAO类进行增删查改操作。

//插入数据
ContentValues values = new ContentValues();
values.put("name", "张三");
values.put("age", 18);
values.put("gender", "男");
long id = StudentDAO.insert(this, values);

//删除数据
String whereClause = "name=?";
String[] whereArgs = {"张三"};
int count = StudentDAO.delete(this, whereClause, whereArgs);

//更新数据
ContentValues values = new ContentValues();
values.put("name", "李四");
String whereClause = "name=?";
String[] whereArgs = {"张三"};
int count = StudentDAO.update(this, values, whereClause, whereArgs);

//查询数据
String selection = "age=?";
String[] selectionArgs = {"18"};
List<Student> list = StudentDAO.query(this, selection, selectionArgs);