GreenDao的使用

如果你在添加GreenDao依赖的过程中出现了如下错误：

那么可以参考一下如下网址：

https://blog.csdn.net/u013472738/article/details/72895747

我并没有配置Project下的build.gradle，而是只配置了app下的build.gradle，代码如下所示：

apply plugin: 'com.android.application'
apply plugin: 'org.greenrobot.greendao'

android {
    compileSdkVersion 27
    buildToolsVersion "27.0.1"
    defaultConfig {
        applicationId "com.example.liang.renyibo"
        minSdkVersion 16
        targetSdkVersion 27
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    testCompile 'junit:junit:4.12'
    compile 'org.greenrobot:greendao:3.2.2'
}
buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'org.greenrobot:greendao-gradle-plugin:3.2.1'//注意这个greendao的插件得比greendao库的版本号小1才行了，我试了3.2.2版本的插件但是还是报错，3.2.1版本的插件不报错。
    }
}

示例代码如下：
在MyApplication文件中

public class MyApplication extends Application {
    private static DaoSession daoSession;
    @Override
    public void onCreate() {
        DaoMaster.DevOpenHelper devOpenHelper=new DaoMaster.DevOpenHelper(this,"mydatabase");
        SQLiteDatabase sqLiteDatabase=devOpenHelper.getWritableDatabase();
        DaoMaster daoMaster=new DaoMaster(sqLiteDatabase);
        daoSession=daoMaster.newSession();
    }

    public static DaoSession getDaoSession() {
        return daoSession;
    }
}

在MainActivity文件中

...
 @Override
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.save:
                Student student=new Student(2L,"laowang",24,"清徐");
                getDaoSession().insert(student);
                break;
            case R.id.select:
                List<Student>list=MyApplication.getDaoSession().loadAll(Student.class);
                for(Student student1:list){
                    Toast.makeText(this, student1.getName()+student1.getDiZhi(), Toast.LENGTH_SHORT).show();
                }
                break;
            case R.id.update:
                Student student1=new Student(2L,"laofu",24,"孝义");
                MyApplication.getDaoSession().update(student1);
                break;
            case R.id.delete:
                Student student2=new Student(2L,"laofu",24,"孝义");
                MyApplication.getDaoSession().delete(student2);//删除数据的时候是根据主键的值进行删除的，与其他值没有关系。
                break;
            default:
                break;
        }
...

在Student文件中

@Entity//标记该实体类为greendao的一个表
public class Student {
    @Id(autoincrement = true)//该字段为主键
    private Long id;
    @Unique//该字段的值不能重复
    private String name;
    @NotNull//该字段不能为空
    private int age;
    @Property(nameInDb = "address")//给该字段在表中起了一个列名
    private String diZhi;
    //**********************只需要给实体类设置好字段后，然后make project，即可生成以下代码***************************
    @Generated(hash = 814485105)
    public Student(Long id, String name, int age, String diZhi) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.diZhi = diZhi;
    }
    @Generated(hash = 1556870573)
    public Student() {
    }
    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;
    }
    public String getDiZhi() {
        return this.diZhi;
    }
    public void setDiZhi(String diZhi) {
        this.diZhi = diZhi;
    }
}

在写好实体类的字段后，然后build project，就会生成如下图所示的文件：

参考文章：

https://blog.csdn.net/qq_30379689/article/details/54410838
官方的github地址如下：
https://github.com/greenrobot/greenDAO
另外，这个人的博客写的文章都很好，可以看一看，网址如下：https://blog.csdn.net/qq_30379689/article/list/5