基于Android SQLiteOpenHelper && CRUD 的使用

public class dbopenhelper extends sqliteopenhelper {
 // 类没有实例化，不能用作父类构造器的参数，必须声明为静态
 public dbopenhelper(context context, int version) {
  super(context, "sqlite.db", null, version);
  // 第三个参数cursorfactory指定在执行查询时获得一个游标实例的工厂类，设置为null代表使用系统默认的游标工厂;
 }
 @override
 public void oncreate(sqlitedatabase db) {// 数据库第一次被创建的时候被调用，最开始创建数据库时赋的版本号值是0
  // sqlitedatabase用于生成数据库表;数据库存放路径:<package name>/databases/
  db.execsql("create table person(personid integer primary key autoincrement, name varchar(20))");
 }
 @override
 public void onupgrade(sqlitedatabase db, int oldversion, int newversion) {// 版本号升级的时候进行调用；如果数据库不存在就不调用
  db.execsql("alter table person add phone varchar(12) null");// 往表中增加一列
 }
}
dbopenhelper dbopenhelper = new dbopenhelper(getcontext(), 1);
dbopenhelper.getwritabledatabase();// 会create数据库表or/open数据库表

public class personservice {
 private dbopenhelper dbopenhelper;
 public personservice(context context) {
  super();
  this.dbopenhelper = new dbopenhelper(context, 2);
 }
 public void save(person person) {
  sqlitedatabase db = dbopenhelper.getwritabledatabase();
  // sqlitedatabase db2 = dbopenhelper.getwritabledatabase();有缓存的功能，同一个helper用此方法得到的对象为db;
  db.execsql("insert into person(name,phone) values(?,?)", new object[] {person.getname(), person.getphone() });
 }
 public void delete(integer id) {
  sqlitedatabase db = dbopenhelper.getwritabledatabase();
  db.execsql("delete from person where personid=?", new object[] { id });
 }
 public void update(person person) {
  sqlitedatabase db = dbopenhelper.getwritabledatabase();
  db.execsql("update person set name=?,phone=? where personid=?",new object[] { person.getname(), person.getphone(),person.getid() });
 }
 public person find(integer id) {
  sqlitedatabase db = dbopenhelper.getreadabledatabase();
  // 如果数据库磁盘空间未满，得到的实例即为getwritabledatabase()得到的对象；因为此方法会调用getwritabledatabase方法；
  cursor cursor = db.rawquery("select * from person where personid=?",new string[] { id.tostring() });
  if (cursor.movetofirst()) {
   int personid = cursor.getint(cursor.getcolumnindex("personid"));
   string name = cursor.getstring(cursor.getcolumnindex("name"));
   string phone = cursor.getstring(cursor.getcolumnindex("phone"));
   return new person(personid, name, phone);
  }
  cursor.close();
  return null;
 }
 /*
  * 获取分页数据
  */
 public list getscolldata(int offest, int maxresult) {
  list persons = new arraylist();
  sqlitedatabase db = dbopenhelper.getreadabledatabase();
  cursor cursor = db.rawquery("select * from person order by personid asc limit ?,?",new string[] { string.valueof(offest),string.valueof(maxresult) });
  while (cursor.movetonext()) {
   int personid = cursor.getint(cursor.getcolumnindex("personid"));
   string name = cursor.getstring(cursor.getcolumnindex("name"));
   string phone = cursor.getstring(cursor.getcolumnindex("phone"));
   persons.add(new person(personid, name, phone));
  }
  cursor.close();
  return persons;
 }
 public long getcount() {
  sqlitedatabase db = dbopenhelper.getreadabledatabase();
  cursor cursor = db.rawquery("select count(*) from person", null);
  cursor.movetofirst();
  long result = cursor.getlong(0);
  return result;
 }
}

public class otherpersonservice {
 private dbopenhelper dbopenhelper;
 public otherpersonservice(context context) {
  super();
  this.dbopenhelper = new dbopenhelper(context, 2);
 }
 public void save(person person) {
  sqlitedatabase db = dbopenhelper.getwritabledatabase();
  contentvalues values = new contentvalues();// contentvalues 专门用于保存字段的值
  values.put("name", person.getname());
  values.put("phone", person.getphone());
  db.insert("person", null, values);// 第三个参数为字段值,第二个参数为空值字段，如果第三个参数为null
 }
 public void delete(integer id) {
  sqlitedatabase db = dbopenhelper.getwritabledatabase();
  db.delete("person", "personid=?", new string[] { id.tostring() });
 }
 public void update(person person) {
  sqlitedatabase db = dbopenhelper.getwritabledatabase();
  contentvalues values = new contentvalues();
  values.put("name", person.getname());
  values.put("phone", person.getphone());
  db.update("person", values, "personid=?", new string[] { person.getid().tostring() });
 }
 public person find(integer id) {
  sqlitedatabase db = dbopenhelper.getreadabledatabase();
  cursor cursor = db.query("person", null, "personid=?",new string[] { id.tostring() }, null, null, null);
  if (cursor.movetofirst()) {
   int personid = cursor.getint(cursor.getcolumnindex("personid"));
   string name = cursor.getstring(cursor.getcolumnindex("name"));
   string phone = cursor.getstring(cursor.getcolumnindex("phone"));
   return new person(personid, name, phone);
  }
  cursor.close();
  return null;
 }
 /*
  * 获取分页数据
  */
 public list getscolldata(int offest, int maxresult) {
  list persons = new arraylist();
  sqlitedatabase db = dbopenhelper.getreadabledatabase();
  cursor cursor = db.query("person", null, null, null, null, null,"personid asc", offest + "," + maxresult);
                //db.query(table, columns, selection, selectionargs, groupby, having, orderby, limit);
  while (cursor.movetonext()) {
   int personid = cursor.getint(cursor.getcolumnindex("personid"));
   string name = cursor.getstring(cursor.getcolumnindex("name"));
   string phone = cursor.getstring(cursor.getcolumnindex("phone"));
   persons.add(new person(personid, name, phone));
  }
  cursor.close();
  return persons;
 }
 public long getcount() {
  sqlitedatabase db = dbopenhelper.getreadabledatabase();
  cursor cursor = db.query("person", new string[] { "count(*)" }, null, null, null, null, null);
                //db.query(table, columns, selection, selectionargs, groupby, having, orderby);
  cursor.movetofirst();
  long result = cursor.getlong(0);
  return result;
 }
}