Android开发入门之在SQLite中使用事务

银行转账

1)update person set amount=amount-10 where personid=1;

2)update person set amount=amount+10 where personid=2;

以上个例子为基础，修改DBOpenHelper类，增加amount字段升级数据库

package cn.leigo.service;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;public class DBOpenHelper extends SQLiteOpenHelper {public DBOpenHelper(Context context) {super(context, "leigo.db", null, 3);  //<包>/databases/}@Overridepublic void onCreate(SQLiteDatabase db) {// 数据库第一次被创建的时候调用的db.execSQL("CREATE TABLE person (personid integer primary key autoincrement, name varchar(20))");}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {db.execSQL("ALTER TABLE person ADD amount integer");}}

在Person类中增加amount变量:

package cn.leigo.domain;public class Person {private Integer id;private String name;private String phone;private Integer amount;public Person() {}public Person(String name, String phone, Integer amount) {this.name = name;this.phone = phone;this.amount = amount;}public Person(Integer id, String name, String phone, Integer amount) {this.id = id;this.name = name;this.phone = phone;this.amount = amount;}public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getPhone() {return phone;}public void setPhone(String phone) {this.phone = phone;}public Integer getAmount() {return amount;}public void setAmount(Integer amount) {this.amount = amount;}@Overridepublic String toString() {return "Person [id=" + id + ", name=" + name + ", phone=" + phone+ ", amount=" + amount + "]";}}

修改报错的类

更新数据

public void testUpdateAmount() throws Exception {PersonService service = new PersonService(getContext());Person person1 = service.find(1);Person person2 = service.find(2);person1.setAmount(100);person2.setAmount(50);service.update(person1);service.update(person2);}

public void payment() {SQLiteDatabase db = dbOpenHelper.getWritableDatabase();// 开启事务db.beginTransaction();db.execSQL("UPDATE person SET amount=amount-10 where personid=1");//System.out.println(1/0);db.execSQL("UPDATE person SET amount=amount+10 where personid=2");db.setTransactionSuccessful();// 结束事务，有两种情况:commit、rollback// 事务的提交或者回滚是由事务的标识决定的，如果事务的标识为true,事务就会提交否则回滚，默认情况下事务的标识为falsedb.endTransaction();db.close();}

public void testPayment() throws Exception {PersonService service = new PersonService(getContext());service.payment();}

将

System.out.println(1/0);

前的注释去掉，重新测试，测试失败，数据未修改。