基于基于Android SQLiteOpenHelper CRUD 的使用的使用
代码如下:
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()) {
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