Android房间数据库忽略问题"Tried the following constructors but they failed to match"

Question

我的实体class:

@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androidTest中测试）：

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

studentDao.insert(student)

在我添加 @Ignore 注释后立即出现此错误：

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 在编译期间仍会生成 Java-classes，问题出在 default-valued 参数上，请尝试对构造函数使用 @JvmOverloads：

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

更新

有趣的是 here in documentation there is no mentioning of special treatment to this case. And this issue 已经存在以修复此文档。

来自this issue至于问题本身的结论是：

Using @JvmOverloads should work. One day in the not-so-distant future we might generate Kotlin and this won't be an issue

Android房间数据库忽略问题"Tried the following constructors but they failed to match"

Android Room Database Ignore Problem "Tried the following constructors but they failed to match"

android

android-database

android-room

android-jetpack