package com.itheima.transtation;
import com.itheima.transtation.db.BankOpenHelper;
import android.os.Bundle;
import android.app.Activity;
import android.database.sqlite.SQLiteDatabase;
import android.view.Menu;
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
  }
 }
}

package com.itheima.transtation.db;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
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
 }
}

<?xml version="1.0"?>
-<RelativeLayout tools:context=".MainActivity" android:paddingTop="@dimen/activity_vertical_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingBottom="@dimen/activity_vertical_margin" android:layout_height="match_parent" android:layout_width="match_parent" xmlns:tools="http://schemas.android.com/tools" xmlns:android="http://schemas.android.com/apk/res/android">
<Button android:layout_height="wrap_content" android:layout_width="fill_parent" android:text="@string/transtation" android:onClick="transtation" android:layout_centerInParent="true"/>
</RelativeLayout>

//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
 }
}