GreenDao的基本使用(android数据库)

在android中,在有些数据量相对较大或者处于安全考虑的情况下,会使用android自带的数据库—-sqlite:
但是使用sqlite需要考虑到以下几点:

    1.严格控制数据库资源的打开与关闭(db,cursor);    2.在遍历数据时候取到的是cursor要转化为list再使用    3.事务回滚,可以大大优化数据库的效率;

在android开发中我们会遇到一些数据库,内部框架做了封装使用起来比较方便:如 ormLite greenDao等

相比而言,greendao应该是最快,效率最高的数据库框架(greendao官网有介绍),ok直接代码详解greemdao.进入正题:

1.greenDao框架的初始化(准备工作与接入)

1.1

//首先实在project的build中配置:

buildscript {    repositories {        jcenter()    }    dependencies {        classpath 'com.android.tools.build:gradle:2.3.3'        //greenDao的配置        classpath 'org.greenrobot:greendao-gradle-plugin:3.2.2'    }}

1.2

//在moudle的build中配置

apply plugin: 'com.android.application'//greenDao依赖apply plugin: 'org.greenrobot.greendao'android {    ........    //在创建玩实体类之后make project 存放greenDao  DB 的包位置    greendao {        schemaVersion 1        daoPackage 'com.example.mysmall.greendao.greendao'//这个是生成代码保存的包名        targetGenDir 'src/main/java'//保存到java代码路径    }}dependencies {    compile fileTree(include: ['*.jar'], dir: 'libs')    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {        exclude group: 'com.android.support', module: 'support-annotations'    })    .....    //greenDao的配置    compile 'org.greenrobot:greendao:3.2.2'    compile 'org.greenrobot:greendao-generator:3.2.2'}

2.创建实体类 接着点击 Build -> Make Project

创建实体类: @Generated(hash = 664611791)中的hash参数 是build->Make Project之后生成的:

@Entitypublic class User {    /**定义主键*/    @Id(autoincrement = true)    private long id;    private String name;    private int age;    private String sex;    @Generated(hash = 664611791)    public User(long id, String name, int age, String sex) {        this.id = id;        this.name = name;        this.age = age;        this.sex = sex;    }    @Generated(hash = 586692638)    public User() {    }    public long getId() {        return id;    }    public void setId(long id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    public String getSex() {        return sex;    }    public void setSex(String sex) {        this.sex = sex;    }    @Override    public String toString() {        return "User{" +                "id=" + id +                ", name='" + name + '\'' +                ", age=" + age +                ", sex='" + sex + '\'' +                '}';    }}

需要注意一下 上面实体类通过注解会映射为数据库表(就不需要自己去写数据库创建的sal);
ok~下面来看注解:
@Entity表明该类是持久化的类(持久化含义，存入数据库文件中，作本地化处理)
@Id选择一个long或Long类型的属性作为该实体所对应数据库中数据表的主键(注意数据类型必须是long)
@Generated写在构造方法前

然后是关键性的一步build->Make Project然后自动生成数据库的操作类:

就是DaoMaster DaoSession UserDao;

3数据库操作类生成 开始用greenDao操作数据库:(用log来展示每次操作的数据变化):

3.1数据库的初始化
在 App(extends Application中实现代码):

public class App extends Application{    private UserDao userDao;    private static App mApp;    @Override    public void onCreate() {        super.onCreate();        /**初始化数据库*/        DaoMaster.DevOpenHelper mHelper = new DaoMaster.        DevOpenHelper(this, "user-db", null);        SQLiteDatabase db = mHelper.getWritableDatabase();        DaoMaster master = new DaoMaster(db);        DaoSession daoSession = master.newSession();        userDao = daoSession.getUserDao();    }    public static App getInstance(){        if (mApp == null){            synchronized (App.class){                mApp = new App();            }        }        return mApp;    }    public UserDao getDao(){        return userDao;    }}

核心代码:

 DaoMaster.DevOpenHelper mHelper = new DaoMaster.        DevOpenHelper(this, "user-db", null);        SQLiteDatabase db = mHelper.getWritableDatabase();        DaoMaster master = new DaoMaster(db);        DaoSession daoSession = master.newSession();        userDao = daoSession.getUserDao();

3.2数据库的增删改查:

    private void initDelete() {        //mDao.deleteByKey(Long.valueOf(1));        String trim = mPos.getText().toString().trim();        if (trim != null && !trim.equals("")) {            mDao.deleteByKey(Long.valueOf(trim));            QueryBuilder<User> qb = mDao.queryBuilder();            List<User> list = qb.where(UserDao.Properties.Id.eq(Long.valueOf(trim))).list();            if (list.size()<1){                Toast.makeText(this,"指定数据删除成功",Toast.LENGTH_SHORT).show();            }        }else {            mDao.deleteAll();        }    }    private void initUpdate() {        String trim = mPos.getText().toString().trim();        if (trim != null && !trim.equals("")) {            User user = mDao.load(Long.valueOf(trim));            user.setName("保尔柯察金");            mDao.update(user);        }    }    private void initInsert() {        for (int i = 0; i < 5; i++) {            mIndex ++;            if (isEcho(String.valueOf(mIndex))){                Toast.makeText(this,"主键重复",Toast.LENGTH_SHORT).show();            }else {                User user = new User(Long.valueOf(mIndex), "张三" + i, 18, "男");                mDao.insert(user);            }        }    }    private void initSelect() {        Query<User> query = mDao.queryBuilder().orderAsc(UserDao.Properties.Id).build();        List<User> list = query.list();        for (int i = 0; i < list.size(); i++) {            User user = list.get(i);            String s = user.toString();            Log.i("query",s);        }    }    /**判断主键是否重复*/    private boolean isEcho(String id){        QueryBuilder<User> qb = mDao.queryBuilder();        List<User> list = qb.where(UserDao.Properties.Id.eq(id)).list();        if (list.size() > 0){            return true;        }        return false;    }

ok~ 从上面代码中可以看到 没有依据sql的操作语句 而且 每次操作完成资源是自动开关,不需要你手动开关数据库/游标/事务

是不是很方便呢;

4完整代码展示 :

下面粘贴完整代码:

//app

package com.example.mysmall.greendao.global;import android.app.Application;import android.database.sqlite.SQLiteDatabase;import com.example.mysmall.greendao.greendao.DaoMaster;import com.example.mysmall.greendao.greendao.DaoSession;import com.example.mysmall.greendao.greendao.UserDao;/** * Created by houruixiang on 2017/10/31. */public class App extends Application{    private UserDao userDao;    private static App mApp;    @Override    public void onCreate() {        super.onCreate();        /**初始化数据库*/        DaoMaster.DevOpenHelper mHelper = new DaoMaster.DevOpenHelper(this, "user-db", null);        SQLiteDatabase db = mHelper.getWritableDatabase();        DaoMaster master = new DaoMaster(db);        DaoSession daoSession = master.newSession();        userDao = daoSession.getUserDao();    }    public static App getInstance(){        if (mApp == null){            synchronized (App.class){                mApp = new App();            }        }        return mApp;    }    public UserDao getDao(){        return userDao;    }}

//MainActivity

package com.example.mysmall.greendao;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import android.view.View;import android.widget.Button;import android.widget.EditText;import android.widget.Toast;import com.example.mysmall.greendao.global.App;import com.example.mysmall.greendao.greendao.UserDao;import com.example.mysmall.greendao.model.User;import org.greenrobot.greendao.query.Query;import org.greenrobot.greendao.query.QueryBuilder;import java.util.List;public class MainActivity extends AppCompatActivity implements View.OnClickListener {    private Button mSelect;    private Button mInsert;    private Button mUpdate;    private Button mDelete;    private int mIndex;    private UserDao mDao;    private EditText mPos;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        /**获取数据库操作对象*/        mDao = ((App) getApplication()).getDao();        initView();    }    private void initView() {        mSelect = (Button) findViewById(R.id.seclet);        mInsert = (Button) findViewById(R.id.insert);        mUpdate = (Button) findViewById(R.id.update);        mDelete = (Button) findViewById(R.id.delete);        mPos = (EditText) findViewById(R.id.tarPosition);        mSelect.setOnClickListener(this);        mInsert.setOnClickListener(this);        mUpdate.setOnClickListener(this);        mDelete.setOnClickListener(this);    }    @Override    public void onClick(View v) {        switch (v.getId()){            case R.id.seclet:                initSelect();                break;            case R.id.insert:                initInsert();                break;            case R.id.update:                initUpdate();                break;            case R.id.delete:                initDelete();                break;        }    }    private void initDelete() {        //mDao.deleteByKey(Long.valueOf(1));        String trim = mPos.getText().toString().trim();        if (trim != null && !trim.equals("")) {            mDao.deleteByKey(Long.valueOf(trim));            QueryBuilder<User> qb = mDao.queryBuilder();            List<User> list = qb.where(UserDao.Properties.Id.eq(Long.valueOf(trim))).list();            if (list.size()<1){                Toast.makeText(this,"指定数据删除成功",Toast.LENGTH_SHORT).show();            }        }else {            mDao.deleteAll();        }    }    private void initUpdate() {        String trim = mPos.getText().toString().trim();        if (trim != null && !trim.equals("")) {            User user = mDao.load(Long.valueOf(trim));            user.setName("保尔柯察金");            mDao.update(user);        }    }    private void initInsert() {        for (int i = 0; i < 5; i++) {            mIndex ++;            if (isEcho(String.valueOf(mIndex))){                Toast.makeText(this,"主键重复",Toast.LENGTH_SHORT).show();            }else {                User user = new User(Long.valueOf(mIndex), "张三" + i, 18, "男");                mDao.insert(user);            }        }    }    private void initSelect() {        Query<User> query = mDao.queryBuilder().orderAsc(UserDao.Properties.Id).build();        List<User> list = query.list();        for (int i = 0; i < list.size(); i++) {            User user = list.get(i);            String s = user.toString();            Log.i("query",s);        }    }    /**判断主键是否重复*/    private boolean isEcho(String id){        QueryBuilder<User> qb = mDao.queryBuilder();        List<User> list = qb.where(UserDao.Properties.Id.eq(id)).list();        if (list.size() > 0){            return true;        }        return false;    }}

总而言之 greendao的框架作为android的数据库框架会很大程度提高效率;有兴趣的可以探讨其内部实现原理机制~感谢阅读 天气转冷 小心感冒哦