Android學習---數據庫的增刪改查(sqlite CRUD)

時間 2019-11-06

標籤 android 學習數據庫增刪 sqlite crud 欄目 Android 简体版

原文原文鏈接

上一篇文章介紹了sqlite數據庫的建立,以及數據的訪問,本文將主要介紹數據庫的增刪改查.html

下面直接看代碼:java

MyDBHelper.java(建立數據庫,添加一列phone)android

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{
    /**
     * 建立數據庫的構造方法
     * @param context 應用程序上下文
     * name 數據庫的名字
     * factory 查詢數據庫的遊標工廠通常狀況下用sdk默認的
     * version 數據庫的版本通常大於0
     */
    public MyDBHelper(Context context) {
        super(context, "test.db", null, 4);
    }
    private String tag = "MyDBHelper.class";
    /**
     * 在數據庫第一次建立時會執行
     * @param db
     */
    @Override
    public void onCreate(SQLiteDatabase db) {
        Log.d(tag, "onCreate.....");
        //建立一個數據庫
        db.execSQL("create table person (personid integer primary key autoincrement ,name varchar(30) )");

    }

    /**
     * 更新數據的時候調用的方法
     * @param db
     * @param oldVersion
     * @param newVersion
     */
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        Log.d(tag,"onUpgrade*******");
        //增長一列
        db.execSQL("alter table person add phone varchar(13) null");

    }


}

PersonDao.java(增刪查改都在這了)git

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出來的時候就實現myDBHelper初始化
    public PersonDao(Context context) {
        myDBHelper = new MyDBHelper(context);
    }

    //增長
    public void addPerson(String name, String phone) {
        SQLiteDatabase database = myDBHelper.getWritableDatabase();
        //先判斷數據庫是否可用
        if (database.isOpen()) { //執行插入操做
            //database.execSQL("insert into person (name,phone) values('"+name+"','"+phone+"')");

            //推薦以下寫法
            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()) {//遊標是否移動到下一行,若是是,那說明有數據返回
                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;
    }

    //刪除一條數據
    public void deletePerson(String phone) {
        SQLiteDatabase database = myDBHelper.getWritableDatabase();
        if (database.isOpen()) {
            database.execSQL("delete from person where phone=?", new Object[]{phone});
        }
        database.close();
    }

    //更新一條數據
    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();
    }

    //查找全部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:github

１.由上面的方法能夠看到,查找數據主要調用的是rawQuery方法,而增刪改都是經過execSQL執行數據的sql

２.必定要注意,使用database前必定要判斷是否可用,使用database.isOpen();shell

3.使用完database必定要注意關閉數據庫,database.close();否則會報異常!數據庫

AndroidManifest.xml(配置測試環境,看加粗部分)app

<?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>

測試類PersonDaoTest.javadom

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,"添加一些新用戶");
        }
        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());
            }
        }
}

因爲要反覆測試,因此若是將數據庫反覆導出會很是麻煩,下面能夠使用命令進行查看數據庫中的數據:

1)進行命令行模式,注意是在platform-tools目錄下,而非tools目錄

sdk/platform-tools$ ./adb shell

2)使用cd命令切換到test.db的目錄

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

3)使用sqlite3打開test.db

# sqlite3 test.db   
SQLite version 3.5.9
Enter ".help" for instructions

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

sqlite> .table
android_metadata  person

查看其中的數據:

sqlite> select * from person;
1|amsoli0|1318888700
2|amsoli1|1318888701
3|amsoli2|1318888702
4|amsoli3|1318888703
5|amsoli4|1318888704
6|amsoli5|1318888705
7|amsoli6|1318888706
8|amsoli7|1318888707
9|amsoli8|1318888708
.........