android数据库学习_事务

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >

<Button
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:onClick="transtation"
android:text="@string/transtation" />

</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<resources>

<string name="app_name">1.数据库事务</string>
<string name="action_settings">Settings</string>
<string name="hello_world">Hello world!</string>
<string name="transtation">模拟银行转账</string>

</resources>

package com.itheima.transtation.db;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class BankOpenHelper extends SQLiteOpenHelper {

public BankOpenHelper(Context context) {
super(context, "bank.db", null, 1);
// TODO Auto-generated constructor stub
}

@Override
public void onCreate(SQLiteDatabase db) {

db.execSQL("create table account (_id integer primary key autoincrement,name varchar(20),money varchar(20))");
db.execSQL("insert into account ('name','money') values ('张三','2000')");
db.execSQL("insert into account ('name','money') values ('李四','5000')");

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub

}

}

package com.itheima.transtation;

import com.itheima.transtation.db.BankOpenHelper;
import com.zgs.sqlite.transtation.R;

import android.os.Bundle;
import android.app.Activity;
import android.database.sqlite.SQLiteDatabase;
import android.view.View;

public class MainActivity extends Activity {

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

//点击按钮执行该方法
public void transtation(View v){
//1.创建一个帮助类的对象
BankOpenHelper bankOpenHelper = new BankOpenHelper(this);
//2.调用数据库帮助类对象的getReadableDatabase创建数据库，初始化表数据，获取一个SqliteDatabase对象去做转账（sql语句）
SQLiteDatabase db = bankOpenHelper.getReadableDatabase();
//3.转账,将李四的钱减200，张三加200
db.beginTransaction();//开启一个数据库事务
try {
db.execSQL("update account set money= money-200 where name=?",new String[]{"李四"});
int i = 100/0;//模拟一个异常
db.execSQL("update account set money= money+200 where name=?",new String[]{"张三"});

db.setTransactionSuccessful();//标记事务中的sql语句全部成功执行
} finally {
db.endTransaction();//判断事务的标记是否成功，如果不成功，回滚错误之前执行的sql语句
}
}

}