前言

个人愚见，Room数据库一般适合整套项目都用的项目。如果老项目没用，里面的一些注解使用API使用时间久了容易忘记，使用到在看！

1.实现细节

1.首先从编译后的包可以看到，里面使用了contentprovider来初始化：

public class ProcessLifecycleOwnerInitializer extends ContentProvider {
    @Override
    public boolean onCreate() {
        LifecycleDispatcher.init(getContext());
        ProcessLifecycleOwner.init(getContext());
        return true;
    }

2.大量使用注解定义字段相关的逻辑，编译后，在APT目录下，文件还是一些常规的数据库操作逻辑，生成如下文件

image.png

2.简单实用

1.创建database

@Database(entities = {Student.class,Address.class},version = 1,exportSchema = false)
public abstract class AppDatabase extends RoomDatabase {
    public abstract StudentDao userDao();
}

2.创建对象类

注解里面定义

@Entity(foreignKeys = @ForeignKey(entity = Address.class,parentColumns = "addressId",childColumns = "addressId"))
public class Student {
    @PrimaryKey(autoGenerate = true)
    private int uid;

    public int getUid() {
        return uid;
    }

    public void setUid(int uid) {
        this.uid = uid;
    }

    @ColumnInfo(name = "name")
    private String name;
    @ColumnInfo(name="pwd")
    private String password;
    @ColumnInfo(name="addressId")
    private int addressId;

    @Override
    public String toString() {
        return "Student{" +
                "id=" + uid +
                ", name='" + name + '\'' +
                ", password='" + password + '\'' +
                ", addressId=" + addressId +
                '}';
    }




    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public int getAddressId() {
        return addressId;
    }

    public void setAddressId(int addressId) {
        this.addressId = addressId;
    }

    public Student( String name, String password, int addressId) {
        this.name = name;
        this.password = password;
        this.addressId = addressId;
    }
}

3.创建Dao

@Dao
public interface StudentDao {
    @Insert
    void insert(Student... students);

    @Delete
    void delete(Student student);

    @Update
    void update(Student student);

    @Query("select * from Student")
    List<Student> getAll();

    //查询一条记录
    @Query("select * from Student where name like :name")
    Student findByName(String name);

    @Query("select * from Student where uid in(:userIds)")
    List<Student> getAllId(int[] userIds);

    @Query("select name,pwd from Student")
    public List<StudentTuple> getRecord();

//    @Query("select x,x,x from where student.x==address.x")

}

4. 测试代码

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //数据库的操作应该是在子线程
        DbTest t=new DbTest();
        t.start();
    }

    public class DbTest extends Thread{
        @Override
        public void run() {
            //数据库的操作都在这里进行
            AppDatabase jettDB= Room.databaseBuilder(getApplicationContext()
                            ,AppDatabase.class
                            ,"XXXDB").build();
            StudentDao dao=XXXDB.userDao();
            dao.insert(new Student("jett","123",1));
            dao.insert(new Student("jett1","123",2));
            dao.insert(new Student("jett2","123",3));
            dao.insert(new Student("jett3","123",4));

            List<Student> list=dao.getAll();
            Log.i("jett",list.toString());

            Student jett2=dao.findByName("jett3");
            Log.i("jett",jett2.toString());
            List<Student> allId=dao.getAllId(new int[]{2,3,4});
            Log.i("jett",allId.toString());

            List<StudentTuple> record=dao.getRecord();
            Log.i("jett",record.toString());
        }
    }

}

2.创建database

2.创建database

@Entity(foreignKeys = @ForeignKey(entity = Address.class,parentColumns = "addressId",childColumns = "addressId"))
public class Student {
    @PrimaryKey(autoGenerate = true)
    private int uid;

    public int getUid() {
        return uid;
    }

    public void setUid(int uid) {
        this.uid = uid;
    }

    @ColumnInfo(name = "name")
    private String name;
    @ColumnInfo(name="pwd")
    private String password;
    @ColumnInfo(name="addressId")
    private int addressId;

    @Override
    public String toString() {
        return "Student{" +
                "id=" + uid +
                ", name='" + name + '\'' +
                ", password='" + password + '\'' +
                ", addressId=" + addressId +
                '}';
    }




    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public int getAddressId() {
        return addressId;
    }

    public void setAddressId(int addressId) {
        this.addressId = addressId;
    }

    public Student( String name, String password, int addressId) {
        this.name = name;
        this.password = password;
        this.addressId = addressId;
    }
}