6.對數據庫進行操作:
一下是對數據庫的操作代碼,包括添加,刪除,更新,查詢,和分頁,統計
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/DBSQLIte/src/com/credream/entity/Person.java
package com.credream.entity;
public class Person
{
private Integer id;
private String name;
private String phone;
public Person()
{
}
public Person(Integer id, String name, String phone)
{
this.id = id;
this.name = name;
this.phone = phone;
}
public Person(String name, String phone)
{
this.name = name;
this.phone = phone;
}
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;
}
@Override
public String toString()
{
return "Person [id=" + id + ", name=" + name + ", phone=" + phone + "]";
}
}
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/DBSQLIte/src/com/credream/service/DBOpenHelter.java
package com.credream.service;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
public class DBOpenHelter extends SQLiteOpenHelper
{
//父類沒有默認構造器,需要顯示調用
public DBOpenHelter(Context context)
{
super(context, "credream.db", null, 2);
//數據庫創建完成後,默認會保存在<包>/database/文件夾下
//當修改版本號時候,會觸發:onUpgrade方法
//第二個:指定數據庫名稱,
//第三個:遊標工廠,用來迭代,查詢後的結果集,null代表使用系統默認的
遊標工廠
//版本號,大於0
}
/**
* 這個方法是在數據庫第一次被創建的時候調用的
*/
@Override
public void onCreate(SQLiteDatabase db)
{
//SQLiteDatabase這個類,封裝瞭增刪改查操作,也叫做數據庫操作實例
db.execSQL("CREATE TABLE person (personid integer primary key
autoincrement, name varchar(20))");
//這裡也可以不寫name的數據類型,因為sqlite是數據類型無關的,就是寫
瞭varchar(20),也可以寫入超過20的內容
}
/**
* 當數據庫的版本號變更的時候被調用
*/
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
db.execSQL("alter table person add phone varchar(12) null");
}
}
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/DBSQLIte/src/com/credream/service/PersonService.java
package com.credream.service;
import java.util.ArrayList;
import java.util.List;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import com.credream.entity.Person;
public class PersonService
{
private DBOpenHelter dbOpenHelter;
public PersonService(Context context){
this.dbOpenHelter=new DBOpenHelter(context);
}
/**
* 添加記錄
* @param person
*/
public void save (Person person){
SQLiteDatabase db=dbOpenHelter.getWritableDatabase();
//SQLiteDatabase db2=dbOpenHelter.getWritableDatabase();
//這裡獲得的數據庫實例和db這個數據庫實例是一樣的,因為數據庫有緩存
功能
//在源碼裡進行瞭判斷,如果得到的數據庫實例不為null,並且已經打開,並
且是隻讀的,那麼
//就直接返回這個實例
//dbOpenHelter.getWritableDatabase().execSQL(sql);這裡和db.execSQL("作用
是一樣的
//db.execSQL("insert into person (name,phone) values
('"+person.getName()+"','"+person.getPhone()+"')");
//上面這種寫法是錯誤的,因為當用戶輸入cre'dream的時候那麼sql語句就成瞭
//insert into person (name,phone) values
('cre'dream','15066659146')這樣會出現sql語法錯誤
//所以,應該用轉義字符
db.execSQL("insert into person (name,phone) values(?,?)",new
Object[]{person.getName(),person.getPhone()});
//db.close();//數據庫也可以不關閉,因為這樣的話可以提升性能,因為不用頻繁的
開關數據庫
}
/**
* 刪除記錄
* @param person
*/
public void delete (Integer id){
SQLiteDatabase db=dbOpenHelter.getWritableDatabase();
db.execSQL("delete from person where personid=?",new Object[]
{id});
}
/**
* 更新記錄
* @param person
*/
public void update(Person person){
SQLiteDatabase db=dbOpenHelter.getWritableDatabase();
db.execSQL("update person set name=?,phone=? where
personid=?",new Object[]{person.getName(),person.getPhone(),person.getId()});
}
/**
* 查找記錄
* @param id
* @return
*/
public Person find (Integer id){
SQLiteDatabase db=dbOpenHelter.getReadableDatabase();
//getReadableDatabase();這個方法裡面調用瞭getWritableDatabase();
方法,來取得數據庫操作實例,隻有調用
//失敗的時候就會發現異常,當數據磁盤滿瞭,會拋出異常,這時候會打開這
個實例的數據庫
//然後開始讀取,這樣當磁盤滿的時候,
//當數據庫磁盤空間沒有滿的時候,返回的數據庫操作實例是一樣的:可讀
可寫,當數據庫磁盤滿瞭,返回的數據庫
//操作實例是隻讀的
Cursor cursor=db.rawQuery("select * from person where personid=?",new
String[]{id.toString()});
//遊標存放結果
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);
}//當有數據會返回true,否則為false
cursor.close();
return null;
}
//處理分頁
/**
* 分頁獲取記錄
* offset:跳過前面幾條記錄
* maxlength:獲取幾條
*/
public List<Person> getScrollData(int offset,int MaxResult){
List<Person> persons=new ArrayList<Person>();
SQLiteDatabase db=dbOpenHelter.getReadableDatabase();
Cursor cursor=db.rawQuery("select * from person order by personid asc
limit ?,?",
new String[]{String.valueOf(offset),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=dbOpenHelter.getReadableDatabase();
Cursor cursor=db.rawQuery("select count(*) from person " ,null);
//select count(*) from person註意這裡至少會獲得一條數據
cursor.moveToFirst();
long result=cursor.getLong(0);
return result;
}
}
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/DBSQLIte/src/com/credream/test/PersonServiceTest.java
package com.credream.test;
import java.util.List;
import com.credream.entity.Person;
import com.credream.service.DBOpenHelter;
import com.credream.service.PersonService;
import android.test.AndroidTestCase;
import android.util.Log;
public class PersonServiceTest extends AndroidTestCase
{
private static final String TAG="PersonServiceTest";
//創建數據庫,在<包>/database/
public void testCreateDB()throws Exception{
DBOpenHelter dbOpenHelter=new DBOpenHelter(getContext());
dbOpenHelter.getWritableDatabase();
}
public void testSave()throws Exception{
PersonService service=new PersonService(this.getContext());
for(int i=0;i<20;i++){
Person person=new Person("lidewei"+i,"15163245754"+i);
service.save(person);
}
}
public void testUpdate()throws Exception{
PersonService service=new PersonService(this.getContext());
Person person=service.find(1);
person.setName("credream");
service.update(person);
}
public void testDelete()throws Exception{
PersonService service=new PersonService(this.getContext());
service.delete(21);
}
public void testFind()throws Exception{
PersonService service=new PersonService(this.getContext());
Person person=service.find(1);
Log.i(TAG,person.toString());
}
public void testScrollData()throws Exception{
PersonService service=new PersonService(this.getContext());
List<Person> persons=
service.getScrollData(5, 5);
for(Person person :persons){
Log.i(TAG,person.toString());
}
//翻到第2頁
}
public void testCount()throws Exception{
PersonService service=new PersonService(this.getContext());
long result=service.getCount();
Log.i(TAG, result+"");
}
//除瞭以上的數據庫操作為,還為我們提供瞭專門方法:
}
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3.代碼寫完後在相應的方法上用android junit 進行測試