Android Room 数据库忽略问题“尝试了以下构造函数，但未能匹配”

Question

我的实体类：

@Entity(tableName = "student")
data class Student(
    var name: String,  
    var age: Int,   
    var gpa: Double,
    var isSingle: Boolean,

    @PrimaryKey(autoGenerate = true)
    var id: Long = 0,    

    @Ignore                           //don't create column in database, just for run time use
    var isSelected: Boolean = false                     
)

然后我像这样插入（在 中测试androidTest）：

val student = Student("Sam", 27, 3.5, true)

studentDao.insert(student)

添加@Ignore注释后，它立即给了我这个错误：

C:\Android Project\RoomTest\app\build\tmp\kapt3\stubs\debug\com\example\roomtest\database\Student.java:7: ????: Entities and POJOs must have a usable public constructor. You can have an empty constructor or a constructor whose parameters match the fields (by name and type).
public final class Student {
         ^
  Tried the following constructors but they failed to match:
  Student(java.lang.String,int,double,boolean,boolean,long) -> [param:name -> 
matched field:name, param:age -> matched field:age, param:gpa -> matched 
field:gpa, param:isSingle -> matched field:isSingle, param:isSelected -> 
matched field:unmatched, param:id -> matched field:id][WARN] Incremental 
annotation processing requested, but support is disabled because the 
following processors are not incremental: androidx.room.RoomProcessor 
(DYNAMIC).

Answer 1

由于 Room 在编译期间仍然会生成 Java 类并且问题在于默认值参数，因此尝试使用@JvmOverloads作为构造函数：

@Entity(tableName = "student")
data class Student @JvmOverloads constructor(
    var name: String,
    .....  

更新

有趣的是，在文档中没有提到对这种情况的特殊处理。并且此问题已存在以修复此文档。

从这个问题至于问题本身的结论是：

使用@JvmOverloads 应该可以工作。在不久的将来有一天，我们可能会生成 Kotlin，这不会成为问题