Android 数据库封装（SQLite）

以下是一个简单的Android SQLite数据库封装示例。这个例子展示了如何创建一个User表，并包含了基本的增删查改操作。

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
 
public class UserDbHelper extends SQLiteOpenHelper {
    private static final String DB_NAME = "user_database.db";
    private static final int DB_VERSION = 1;
    private static final String TABLE_NAME = "users";
 
    public UserDbHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }
 
    @Override
    public void onCreate(SQLiteDatabase db) {
        String CREATE_TABLE = "CREATE TABLE " + TABLE_NAME + "("
                + "id INTEGER PRIMARY KEY AUTOINCREMENT,"
                + "name TEXT,"
                + "email TEXT,"
                + "age INTEGER" + ")";
        db.execSQL(CREATE_TABLE);
    }
 
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        String DROP_TABLE = "DROP TABLE IF EXISTS " + TABLE_NAME;
        db.execSQL(DROP_TABLE);
        onCreate(db);
    }
 
    public boolean insertUser(User user) {
        SQLiteDatabase db = this.getWritableDatabase();
        db.beginTransaction();
        try {
            db.execSQL("INSERT INTO " + TABLE_NAME + " (name, email, age) VALUES (?, ?, ?)",
                    new Object[]{user.getName(), user.getEmail(), user.getAge()});
            db.setTransactionSuccessful();
            return true;
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        } finally {
            db.endTransaction();
            db.close();
        }
    }
 
    public boolean deleteUser(int id) {
        SQLiteDatabase db = this.getWritableDatabase();
        db.beginTransaction();
        try {
            db.execSQL("DELETE FROM " + TABLE_NAME + " WHERE id = ?", new Object[]{id});
            db.setTransactionSuccessful();
            return true;
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        } finally {
            db.endTransaction();
            db.close();
        }
    }
 
    public User getUser(int id) {
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery("SELECT * FROM " + TABLE_NAME + " WHERE id = ?", new String[]{String.valueOf(id)});
        if (cursor.moveToFirst()) {
            return new User(cur