在android中主要使用SQLite数据库进行对一些数据的存储,以下是相应的CRUD的实例。
[code]
package com.myclover.db.service;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
/**
*
* @author myclover SQLite3支持
* NULL、INTEGER、REAL(浮点数字)、TEXT(字符串文本)和BLOB(二进制对象)数据类型
* sqlite3也接受varchar(n)、char(n)、decimal(p,s) 等数据类型
*/
public class DBOpenHelper extends SQLiteOpenHelper {
private static final String DBNAME = "myclover.db";
private static final int VERSION = 1;
public DBOpenHelper(Context context) {
super(context, DBNAME, null, VERSION);
}
public DBOpenHelper(Context context, String name, CursorFactory factory,
int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table t_person (id integer primary key autoincrement , name varchar(30) , sex varchar(10) , age integer , amount real)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("drop table if exists t_person");
onCreate(db);
}
}
[/code]
[code]
package com.myclover.db.service;
import java.util.ArrayList;
import java.util.List;
import com.myclover.db.bean.Person;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
public class DBService {
@SuppressWarnings("unused")
private Context context;
private DBOpenHelper dbHelper;
public DBService(Context context) {
dbHelper = new DBOpenHelper(context);
}
/**
* 功能描述: 保存单个用户信息
*
* @param p
* 用户实例
*/
public void save(Person p) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
db.execSQL("insert into t_person (name , sex , age , amount) values (? , ? , ? , ?)",
new Object[] { p.getName(), p.getSex(), p.getAge(),
p.getAmount() });
}
/**
* 功能描述: 更新用户信息
*
* @param p
* 用户实例
*/
public void update(Person p) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
db.execSQL("update t_person set name = ? , sex = ? , age = ? , amount = ? where id = ? ",
new Object[] { p.getName(), p.getSex(), p.getAge(),
p.getAmount(), p.getId() });
}
/**
* 功能描述: 通过用户id查询用户信息
*
* @param id
* 用户id
* @return 返回值:如果存在,则返回用户实例,否则返回为null
*/
public Person findById(Integer id) {
SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cs = db.rawQuery("select * from t_person where id = ? ",
new String[] { String.valueOf(id) });
if (cs.moveToNext()) {
Person p = new Person();
p.setId(cs.getInt(cs.getColumnIndex("id")));
p.setName(cs.getString(cs.getColumnIndex("name")));
p.setSex(cs.getString(cs.getColumnIndex("sex")));
p.setAge(cs.getInt(cs.getColumnIndex("age")));
p.setAmount(cs.getFloat(cs.getColumnIndex("amount")));
cs.close();
return p;
}
return null;
}
/**
* 功能描述: 通过用户姓名查询用户信息
*
* @param name
* 用户姓名
* @return 返回值:如果存在,则返回用户实例,否则返回为null
*/
public Person findByName(String name) {
SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cs = db.rawQuery("select * from t_person where name = ? ",
new String[] { name });
if (cs.moveToNext()) {
Person p = new Person();
p.setId(cs.getInt(cs.getColumnIndex("id")));
p.setName(cs.getString(cs.getColumnIndex("name")));
p.setSex(cs.getString(cs.getColumnIndex("sex")));
p.setAge(cs.getInt(cs.getColumnIndex("age")));
p.setAmount(cs.getFloat(cs.getColumnIndex("amount")));
cs.close();
return p;
}
return null;
}
/**
* 功能描述: 通过用户id删除用户信息
*
* @param ids
* 用户id
*/
public void delete(Integer... ids) {
if (ids.length > 0) {
StringBuffer sb = new StringBuffer();
for (@SuppressWarnings("unused")
int id : ids) {
sb.append("?").append(",");
}
sb.deleteCharAt(sb.length() - 1);
SQLiteDatabase db = dbHelper.getWritableDatabase();
db.execSQL("delete from t_person where id in (" + sb + ")",(Object[]) ids);
}
}
/**
* 功能描述: 通过分页功能查询用户列表
*
* @param startNum
* 开始索引值
* @param perNum
* 每页显示的数目
* @return 返回值:返回用户列表信息
*/
public List
getPerosns(int startNum, int perNum) {
List lists = new ArrayList();
SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cs = db
.rawQuery("select * from t_person limit ? , ? ", new String[] {
String.valueOf(startNum), String.valueOf(perNum) });
while (cs.moveToNext()) {
Person p = new Person();
p.setId(cs.getInt(cs.getColumnIndex("id")));
p.setName(cs.getString(cs.getColumnIndex("name")));
p.setSex(cs.getString(cs.getColumnIndex("sex")));
p.setAge(cs.getInt(cs.getColumnIndex("age")));
p.setAmount(cs.getFloat(cs.getColumnIndex("amount")));
lists.add(p);
}
cs.close();
return lists;
}
/**
* 功能描述: 统计数据库中数据的数目
*
* @return 返回值:返回数据的条数
*/
public long getTotalCounts() {
SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cs = db.rawQuery("select count(*) from t_person ", null);
if (cs.moveToNext()) {
return cs.getLong(0);
}
return 0;
}
/**
* 功能描述: 使用事务进行控制两条信息的更新操作,从源用户转出指定金额到目的用户
*
* @param id
* 源用户id
* @param amount
* 转换金额
* @param tid
* 目的用户id
*/
public void transAmount(int id, float amount, int tid) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
// 开启事务
db.beginTransaction();
try {
if (findById(id) != null && findById(tid) != null) {
db.execSQL("update t_person set amount = amount - ? where id = ? ", new Object[] { amount, id });
db.execSQL("update t_person set amount = amount + ? where id = ? ", new Object[] { amount, tid });
// 设置事务的成功标志
db.setTransactionSuccessful();
}
} catch (SQLException e) {
} finally {
// 结束事务,如果设置事务是否成功标志为成功时,则此时先提交事务再结束,否则就是回滚事务并结束
db.endTransaction();
}
}
/**
* 功能描述:
* 关闭数据库资源
*/
public void closeDB(){
dbHelper.close();
}
}
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