Android(安卓)GreenDao数据库—基础详解

1.GreenDao数据库简介

greenDAO是一个对象关系映射（ORM）的框架，能够提供一个接口通过操作对象的方式去操作关系型数据库，它能够让你操作数据库时更简单、更方便。如下图所示：

官网地址：http://greenrobot.org/greendao

github：https://github.com/greenrobot/greenDAO

2.GreenDao 优点

2.1.性能高，号称Android最快的关系型数据库。

2.2.内存占用小库文件比较小，小于100K，编译时间低，而且可以避免65K方法限制。

2.3.支持数据库加密 greendao支持SQLCipher进行数据库加密。

2.4.简洁易用的API。

3.代码讲解

3.1.配置Gradle

根目录gradle

// Top-level build file where you can add configuration options common to all sub-projects/modules.buildscript {    repositories {        google()        jcenter()    }    dependencies {        classpath 'com.android.tools.build:gradle:3.3.2'        classpath 'org.greenrobot:greendao-gradle-plugin:3.2.2' // add plugin        // NOTE: Do not place your application dependencies here; they belong        // in the individual module build.gradle files    }}allprojects {    repositories {        google()        jcenter()    }}task clean(type: Delete) {    delete rootProject.buildDir}

app gradle

apply plugin: 'com.android.application'apply plugin: 'org.greenrobot.greendao' // apply pluginandroid {    compileSdkVersion 28    defaultConfig {        applicationId "com.wjn.androiddbdemo"        minSdkVersion 15        targetSdkVersion 26        versionCode 1        versionName "1.0"        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"    }    greendao {        // 版本号        schemaVersion 1        //greendao输出dao的数据库操作实体类文件夹        daoPackage 'com.wjn.androiddbdemo.greendao'        //greenDao实体类包文件夹        targetGenDir 'src/main/java'    }    buildTypes {        release {            minifyEnabled false            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'        }    }}dependencies {    implementation fileTree(dir: 'libs', include: ['*.jar'])    implementation 'com.android.support:appcompat-v7:28.0.0'    testImplementation 'junit:junit:4.12'    androidTestImplementation 'com.android.support.test:runner:1.0.2'    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'    implementation 'com.readystatesoftware.systembartint:systembartint:1.0.3'    implementation 'org.greenrobot:greendao:3.2.2' // add library}

3.2.创建实体类

步骤

3.2.1.创建类名为People的普通类并创建所需要的属性

public class People {    private Long id;    private String name;    private String height;    private String weight;}

id 必须为Long

3.2.2.类名上@Entity

3.2.3.Make Project

稍等片刻后实体类变成如下

@Entitypublic class People {    @Id(autoincrement = true)    private Long id;    private String name;    private String height;    private String weight;    @Generated(hash = 516943684)    public People(Long id, String name, String height, String weight) {        this.id = id;        this.name = name;        this.height = height;        this.weight = weight;    }    @Generated(hash = 1406030881)    public People() {    }    public Long getId() {        return this.id;    }    public void setId(Long id) {        this.id = id;    }    public String getName() {        return this.name;    }    public void setName(String name) {        this.name = name;    }    public String getHeight() {        return this.height;    }    public void setHeight(String height) {        this.height = height;    }    public String getWeight() {        return this.weight;    }    public void setWeight(String weight) {        this.weight = weight;    }}

注意：主键要添加autoincrement 自增

否则会报 does not have a single-column primary key 错误

设置的文件夹中会生成以下类

3.3.在Application中获取 DaoSession

public class MyApplication extends Application {    private static DaoSession daoSession;    @Override    public void onCreate() {        super.onCreate();        setupDatabase();    }    /**     * 配置数据库     */    private void setupDatabase() {        //创建数据库shop.db 创建SQLite数据库的SQLiteOpenHelper的具体实现        DaoMaster.DevOpenHelper helper = new DaoMaster.DevOpenHelper(this, "greendaodemo.db", null);        //获取SQLiteDatabase对象        SQLiteDatabase db = helper.getReadableDatabase();        //获取数据库对象        DaoMaster daoMaster = new DaoMaster(db);        //获取dao对象管理者        daoSession = daoMaster.newSession();    }    /**     * 获取 DaoSession 外部调用     * */    public static DaoSession getDaoInstant() {        return daoSession;    }}

3.4.Activity代码

public class GreenDaoActivity extends AppCompatActivity implements View.OnClickListener {    private TextView textView1;    private TextView textView2;    private TextView textView3;    private TextView textView4;    private TextView textView;    private String string="123456";    private Long id;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_greendao);        initView();    }    /**     * 初始化各种View     */    private void initView() {        //根据状态栏颜色来决定 状态栏背景 用黑色还是白色 true:是否修改状态栏字体颜色        StatusBarUtil.setStatusBarMode(this, false, false, R.color.colorPrimary);        textView1 = findViewById(R.id.activity_greendao_textview1);        textView2 = findViewById(R.id.activity_greendao_textview2);        textView3 = findViewById(R.id.activity_greendao_textview3);        textView4 = findViewById(R.id.activity_greendao_textview4);        textView = findViewById(R.id.activity_greendao_textview);        textView1.setOnClickListener(this);        textView2.setOnClickListener(this);        textView3.setOnClickListener(this);        textView4.setOnClickListener(this);        id=Long.parseLong(string);    }    /**     * 各种点击事件的方法     */    @Override    public void onClick(View v) {        switch (v.getId()) {            case R.id.activity_greendao_textview1://增                insertUser();                break;            case R.id.activity_greendao_textview2://删                deleteUser();                break;            case R.id.activity_greendao_textview3://改                updateUser();                break;            case R.id.activity_greendao_textview4://查                List list=queryUserList();                StringBuilder sbBuilder = new StringBuilder();                for(int i=0;i queryUserList() {        UserInfoDao userInfoDao= MyApplication.getDaoInstant().getUserInfoDao();        QueryBuilder qb = userInfoDao.queryBuilder();        List list = qb.list();        return list;    }}

3.5.结果

3.5.1.增——>查

3.5.2.删——>查

3.5.3.改——>查

3.6.注意

主键设置了自增后插入是就可以不用设置id

3.6.1.插入数据

/**     * 插入一条记录     */    public void insertUser() {        UserInfo userInfo=new UserInfo();        userInfo.setName("张三");        userInfo.setAge("29");        UserInfo userInfo1=new UserInfo();        userInfo1.setName("李四");        userInfo1.setAge("39");        UserInfo userInfo2=new UserInfo();        userInfo2.setName("旺旺");        userInfo2.setAge("19");        UserInfo userInfo3=new UserInfo();        userInfo3.setName("王伟");        userInfo3.setAge("59");        List list=new ArrayList<>();        list.add(userInfo);        list.add(userInfo1);        list.add(userInfo2);        list.add(userInfo3);        UserInfoDao userInfoDao= MyApplication.getDaoInstant().getUserInfoDao();        userInfoDao.insertInTx(list);    }

3.6.2.结果

代码链接：https://github.com/wujianning/AndroidDBDemo

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