SQLite数据库事务之银行转账

数据库事物：执行一段逻辑 要么同时成功 要么同时失败

需求：张三给李四转账，点击转账，进行扣款

1，创建数据库表account，存有张三和李四的金额

    public MyOpenHelper(Context context) {
        super(context, "Account.db", null, 1);
    }

    //当数据库第一次创建的时候调用 特别适合做表结构的初始化 
    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table info (_id integer primary key autoincrement,name varchar(20),phone varchar(20),money varchar(20))");
        db.execSQL("insert into info ('name','phone','money') values ('张三','138888','2000')");
        db.execSQL("insert into info ('name','phone','money') values ('李四','139999','5000')");
        
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }

}

2，点击转账 开启数据库事务

3，转账结束 结束事务

public class MainActivity extends Activity {

    private MyOpenHelper myOpenHelper;

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

        myOpenHelper = new MyOpenHelper(getApplicationContext());

    }

    // 点击按钮进行转账的逻辑
    public void click(View v) {
        SQLiteDatabase db = myOpenHelper.getReadableDatabase();
        // 使用事物进行转账
        db.beginTransaction(); // 开启事物
        try {
            // 实现转账的逻辑 实际上就写sql语句

            db.execSQL("update info set money = money - 100 where name = ?",
                    new Object[] { "张三" });

            int i = 10 / 0;

            db.execSQL("update info set money = money + 100 where name = ?",
                    new Object[] { "李四" });

            // 给当前事物设置一个成功的标记
            db.setTransactionSuccessful();
        } catch (Exception e) {

            Toast.makeText(getApplicationContext(), "服务器忙,请稍后再转", 1).show();
        }

        finally {
            db.endTransaction(); // 关闭事物
        }

    }

}