Android开发之SQLite数据操作

这一节讲述一下Android中有关轻量级数据库SQLite的操作，主要正对该数据库的增删查改进行一些举例说明。

首先，得建一个数据库帮助类，用于建立数据库以及进行数据库方面的一些操作，该类必须继承自android.database.sqlite.SQLiteOpenHelper，重载两个方法，一个是onCreate()用于在数据库第一次创建的时候的操作，onUpgrade()用于在数据库版本更新时的操作

public class DBHelper extends
SQLiteOpenHelper {
public static final String
DB_NAME="yuchao";
public static final int DB_VERSION =
2;
public DBHelper(Context context)
{
super(context, DB_NAME, null,
DB_VERSION);
}
public void onCreate(SQLiteDatabase
db) {//创建数据库时的操作
db.execSQL("CREATE TABLE person(id
Integer primary key autoincrement,name varchar(20),amount
Integer)");
}
public void onUpgrade(SQLiteDatabase
db, int oldVersion, int newVersion) {
// 数据库版本号变更时执行
db.execSQL("drop table
person");
onCreate(db);
}
}

然后我们建立一个PersonbService类，用来说明增删查改时的具体操作

增

public void save(Person person)
{
SQLiteDatabase db =
dbHelper.getWritableDatabase();
db.execSQL("insert into
person(name,amount) values (?,?)",
new Object[] { person.getName(),
person.getAmount() });
}
删

public void delete(Integer id)
{
SQLiteDatabase db =
dbHelper.getWritableDatabase();
db.execSQL("delete from person where
id=?",
new Object[] { id.toString()
});
}
查

public Person find(Integer id)
{
Person person = null;
SQLiteDatabase db =
dbHelper.getWritableDatabase();
Cursor cursor = db.rawQuery("select
id,name from person where id=?",
new String[] { id.toString()
});
if (cursor.moveToFirst()) {
String name =
cursor.getString(cursor.getColumnIndex("name"));
person = new Person(id, name);
}
return person;
}
改

public void update(Person person)
{//包含事务的操作
SQLiteDatabase db =
dbHelper.getWritableDatabase();
db.beginTransaction();
try{
db.execSQL("update person set name=?
where id=?",
new Object[] { person.getName(),
person.getId().toString() });
db.setTransactionSuccessful();
}finally{
db.endTransaction();
}
}
查某一范围的人
返回游标

public Cursor getScollCursor(Integer
offset, Integer maxNum) {
SQLiteDatabase db =
dbHelper.getReadableDatabase();
Cursor cursor = db.rawQuery(
"select id as _id,name,amount from
person limit ?,?", new    
     
     
     
     
     
     
 String[] {offset.toString(), maxNum.toString()
});
return cursor;
}
返回所有人

public
List<Person> getScoll(Integer offset,
Integer maxNum) {

List<Person> persons = new
ArrayList<Person>();
SQLiteDatabase db =
dbHelper.getReadableDatabase();
Cursor cursor = db.rawQuery(
"select id,name,amount from person
limit ?,?", new String[] {
offset.toString(), maxNum.toString()
});
while (cursor.moveToNext()) {
int id =
cursor.getInt(cursor.getColumnIndex("id"));
String name =
cursor.getString(cursor.getColumnIndex("name"));
Integer amount =
cursor.getInt(cursor.getColumnIndex("amount"));
Person person = new Person(id,
name);
person.setAmount(amount);
persons.add(person);
}
return persons;
}
到此，有关数据库的大体操作已经实现!