Android学习---数据库的增删改查(sqlite CRUD)

上一篇文章介绍了sqlite数据库的创建,以及数据的访问,本文将主要介绍数据库的增删改查.

下面直接看代码:

MyDBHelper.java(创建数据库,添加一列phone)

package com.amos.android_database;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

/**
 * Created by amosli on 14-6-10.
 */
public class MyDBHelper extends SQLiteOpenHelper{
    /**
     * 创建数据库的构造方法
     * @param context 应用程序上下文
     * name 数据库的名字
     * factory 查询数据库的游标工厂一般情况下用sdk默认的
     * version 数据库的版本一般大于0
     */
    public MyDBHelper(Context context) {
        super(context, "test.db", null, 4);
    }
    private String tag = "MyDBHelper.class";
    /**
     * 在数据库第一次创建时会执行
     * @param db
     */
    @Override
    public void onCreate(SQLiteDatabase db) {
        Log.d(tag, "onCreate.....");
        //创建一个数据库
        db.execSQL("create table person (personid integer primary key autoincrement ,name varchar(30) )");

    }

    /**
     * 更新数据的时候调用的方法
     * @param db
     * @param oldVersion
     * @param newVersion
     */
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        Log.d(tag,"onUpgrade*******");
        //增加一列
        db.execSQL("alter table person add phone varchar(13) null");

    }

}

PersonDao.java(增删查改都在这了)

package com.amos.android_database.dao;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import com.amos.android_database.MyDBHelper;
import com.amos.android_database.domain.Person;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by amosli on 14-6-11.
 */
public class PersonDao {
    private MyDBHelper myDBHelper;
    public String tag = "PersonDao.class";

    //在new出来的时候就实现myDBHelper初始化
    public PersonDao(Context context) {
        myDBHelper = new MyDBHelper(context);
    }

    //增加
    public void addPerson(String name, String phone) {
        SQLiteDatabase database = myDBHelper.getWritableDatabase();
        //先判断数据库是否可用
        if (database.isOpen()) {
            //执行插入操作
            //database.execSQL("insert into person (name,phone) values('"+name+"','"+phone+"')");

            //推荐如下写法
            database.execSQL("insert into person (name,phone) values(?,?)", new Object[]{name, phone});
            database.close();
        }
    }

    //查找
    public boolean findPerson(String phone) {
        boolean result = false;
        SQLiteDatabase database = myDBHelper.getReadableDatabase();
        if (database.isOpen()) {
            //database.execSQL("select * from phone='"+phone+"'");

            Cursor cursor = database.rawQuery("select * from person where phone=?", new String[]{phone});
            if (cursor.moveToFirst()) {//游标是否移动到下一行,如果是,那说明有数据返回
                Log.d(tag, "count:" + cursor.getColumnCount());
                int nameIndex = cursor.getColumnIndex("name");
                Log.d(tag, "name:" + cursor.getString(nameIndex));
                cursor.close();
                result = true;
            } else {
                result = false;

            }
            database.close();
        }
        return result;
    }

    //删除一条数据
    public void deletePerson(String phone) {
        SQLiteDatabase database = myDBHelper.getWritableDatabase();
        if (database.isOpen()) {
            database.execSQL("delete from person where phone=?", new Object[]{phone});
        }
        database.close();
    }

    //更新一条数据
    public void updatePerson(String phone, String newName, String newPhone) {
        SQLiteDatabase database = myDBHelper.getWritableDatabase();
        if (database.isOpen()) {
            database.execSQL("update person set name=?,phone=? where phone=?", new Object[]{newName, newPhone, phone});
        }
        database.close();
    }

    //查找所有person
    public List<Person> findAllPerson(){
        List<Person> personList = new ArrayList<Person>();
        SQLiteDatabase database = myDBHelper.getReadableDatabase();
        if(database.isOpen()){
            Cursor cursor = database.rawQuery("select * from person ", null);
            while(cursor.moveToNext()){
                int nameIndex = cursor.getColumnIndex("name");
                int phoneIndex = cursor.getColumnIndex("phone");
                String name = cursor.getString(nameIndex);
                String phone = cursor.getString(phoneIndex);

                Person  person = new Person(name,phone);
                Log.d(tag,person.toString());

                personList.add(person);
            }

        }
        database.close();
        return personList;
    }

}

注:

１.由上面的方法可以看到,查找数据主要调用的是rawQuery方法,而增删改都是通过execSQL执行数据的

２.一定要注意,使用database前一定要判断是否可用,使用database.isOpen();

3.使用完database一定要注意关闭数据库,database.close();不然会报异常!

AndroidManifest.xml(配置测试环境,看加粗部分)

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          package="com.amos.android_database"
          android:versionCode="1"
          android:versionName="1.0">
    <instrumentation android:name="android.test.InstrumentationTestRunner"
                     android:targetPackage="com.amos.android_database"/>
    <uses-sdk android:minSdkVersion="7"/>
    <application android:label="@string/app_name">
        <uses-library android:name="android.test.runner"/>
        <activity android:name="MyActivity"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
    </application>
</manifest> 

测试类PersonDaoTest.java

package com.amos.android_database.test;

import android.test.AndroidTestCase;
import android.util.Log;
import com.amos.android_database.dao.PersonDao;
import com.amos.android_database.domain.Person;

/**
 * Created by amosli on 14-6-11.
 */
public class PersonDaoTest extends AndroidTestCase{
        private String tag = "PersonDaoTest.class";

        public void testAdd() throws Exception{
            PersonDao personDao = new PersonDao(getContext());
            for(int i=0;i<100;i++){
                personDao.addPerson("amsoli"+i,"131888870"+i);
            }
            Log.d(tag,"添加一些新用户");
        }
        public void testFind(){
            PersonDao personDao = new PersonDao(getContext());
            boolean result = personDao.findPerson("13188887776");
            assertEquals(true,result);
        }
        public void testDelete(){
            PersonDao personDao = new PersonDao(getContext());
            personDao.deletePerson("13188887778");
        }

        public void testUpdate(){
            PersonDao personDao = new PersonDao(getContext());
            personDao.updatePerson("13188887776","hi_amos","13188887775");
        }
        public void testFindAllPerson(){
            PersonDao personDao = new PersonDao(getContext());
            for (Person person : personDao.findAllPerson()) {
                System.out.println(person.toString());
            }
        }
}

由于要反复测试,所以如果将数据库反复导出会非常麻烦,下面可以使用命令进行查看数据库中的数据:

1)进行命令行模式,注意是在platform-tools目录下,而非tools目录

sdk/platform-tools$ ./adb shell

2)使用cd命令切换到test.db的目录

#cd /data/data/com.amos.android_database/databases/
# ls
test.db

3)使用sqlite3打开test.db

# sqlite3 test.db  
SQLite version 3.5.
Enter ".help" for instructions

sqlite> .database
seq  name             file
---  ---------------  ----------------------------------------------------------
    main             /data/data/com.amos.android_database/databases/test.db  

sqlite> .table
android_metadata  person     

查看其中的数据:

sqlite> select * from person;
|amsoli0|
|amsoli1|
|amsoli2|
|amsoli3|
|amsoli4|
|amsoli5|
|amsoli6|
|amsoli7|
|amsoli8|
.........

注:

i:关于Sqlite的教程可以参考:http://www.w3cschool.cc/sqlite/sqlite-tutorial.html

ii:关于本方源代码可以查看:https://github.com/amosli/android_basic/tree/database