GreenDao的初次使用--号称Android最快的关系型数据库

一、准备工作

1、项目build.gradle文件下的dependencies中引入插件：

classpath 'org.greenrobot:greendao-gradle-plugin:3.2.1'

2、在module的build.gradle文件下顶部依赖插件：

apply plugin: 'org.greenrobot.greendao'

3、在module的build.gradle文件下的dependencies中引入依赖：

compile 'org.greenrobot:greendao:3.2.0'

二、greendao的注解

1、实体@entity注解：

  schema：告知greendao当前实体属于哪个schema

  active：标记一个实体处于活动状态，活动实体有更新、删除和刷新方法

  nameindb：在数据中使用的别名，默认使用的是实体的类名

  indexes：定义索引，可以跨越多个列

  createindb：标记创建数据库表

2、基础属性注解

  @id :主键 long型，可以通过@id(autoincrement = true)设置自增长

  @property：设置一个非默认关系映射所对应的列名，默认是的使用字段名 举例：@property (nameindb="name")

  @notnul：设置数据库表当前列不能为空

  @transient ：添加次标记之后不会生成数据库表的列

3、索引注解

  @index：使用@index作为一个属性来创建一个索引，通过name设置索引别名，也可以通过unique给索引添加约束

  @unique：向数据库列添加了一个唯一的约束

4、关系注解

  @toone：定义与另一个实体（一个实体对象）的关系

  @tomany：定义与多个实体对象的关系

三、简单使用----使用管理类dbmanager，操作名称为test_db的数据库，完成数据库中用户实体类user的增删改查等操作

1、创建实体用户类user，使用greendao进行注解，rebuild项目。

/**
 * <p>description:
 */
@entity
public class user {

    @id(autoincrement = true)
    private long id ;
    private string name ;
    private int age ;

    public user(string name,int age){
        this.name = name ;
        this.age = age ;
    }


    @generated(hash = 1309193360)
    public user(long id, string name, int age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }
    @generated(hash = 586692638)
    public user() {
    }
    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 int getage() {
        return this.age;
    }
    public void setage(int age) {
        this.age = age;
    }
}

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2、创建管理类dbmanager，完成对user的增删改查方法

public class dbmanager {

    private static dbmanager instance ;
    private final static string dbname = "test_db";

    private context mcontext ;

    private dbmanager(context context){
        this.mcontext = context ;
        openhelper = new daomaster.devopenhelper(context,dbname);
    }


    private daomaster.devopenhelper openhelper = null ;

    public static dbmanager getinstance(context context){
        if(instance == null){
            synchronized (dbmanager.class){
                if(instance == null){
                    instance = new dbmanager(context);
                }
            }
        }
        return instance ;
    }

    private sqlitedatabase getwriteabledatabase(){
        if(openhelper == null){
            openhelper = new daomaster.devopenhelper(mcontext,dbname);
        }
        return openhelper.getwritabledatabase();
    }
    private sqlitedatabase getredadabledatabase(){
        if(openhelper == null){
            openhelper = new daomaster.devopenhelper(mcontext,dbname);
        }
        return openhelper.getreadabledatabase() ;
    }


    public void saveuser(user user){
        daomaster daomaster = new daomaster(getwriteabledatabase());
        daosession daosession = daomaster.newsession();
        userdao userdao = daosession.getuserdao();
        //存入user对象
        userdao.save(user);

    }

    public void saveusers(list<user> users){
        daomaster daomaster = new daomaster(getwriteabledatabase());
        daosession daosession = daomaster.newsession();
        userdao userdao = daosession.getuserdao();
        userdao.saveintx(users);
    }

    public void delteuser(user user){
        daomaster daomaster = new daomaster(getwriteabledatabase());
        daosession daosession = daomaster.newsession();
        userdao userdao = daosession.getuserdao();
        userdao.delete(user);
    }

    public void updateuser(user user){
        daomaster daomaster = new daomaster(getwriteabledatabase());
        daosession daosession = daomaster.newsession();
        userdao userdao = daosession.getuserdao();
        userdao.update(user);
    }

    public list<user> queryuser(){
        daomaster daomaster = new daomaster(getredadabledatabase());
        daosession daosession = daomaster.newsession();
        userdao userdao = daosession.getuserdao();
        querybuilder<user> qb = userdao.querybuilder();
        list<user> list = qb.list();
        return list ;
    }

    public list<user> queryuser(int age){
        daomaster daomaster = new daomaster(getredadabledatabase());
        daosession daosession = daomaster.newsession();
        userdao userdao = daosession.getuserdao();
        querybuilder<user> qb = userdao.querybuilder();
        //添加查询条件
        qb.where(userdao.properties.age.eq(age));
        list<user> list = qb.list();
        return list ;
    }

}

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