在kotlin首次建立房间数据库时如何修复异常

Question

在第一次创建房间数据库时，我不断遇到这种异常

  java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Package.getName()' on a null object reference

这是我的房间数据库代码：

@Database(entities = [Channel::class], version = 1)
abstract class ChannelRoomDatabase : RoomDatabase() {

    abstract fun channelDao(): ChannelDao

    companion object {
        private var INSTANCE: ChannelRoomDatabase? = null

        fun getInstance(application: Application): ChannelRoomDatabase? {
            if (INSTANCE == null) {

                    INSTANCE = Room.databaseBuilder(application,
                            ChannelRoomDatabase::class.java,
                            "channels")
                            .build()
            }

            return INSTANCE
        }
    }

}

还有格雷德尔密码：

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
apply plugin: 'kotlin-kapt'

    def room_version = "1.1.1"

    implementation "android.arch.persistence.room:runtime:$room_version"
    kapt "android.arch.persistence.room:compiler:$room_version"

在构建项目时，我也会遇到这样的错误：

Execution failed for task ':app:kaptGenerateStubsDebugKotlin'.

Folder /home/Desktop/MySendBird/app/build/generated/source/kaptKotlin/debug


Folder /home/Desktop/MySendBird/app/build/generated/source/kaptKotlin/release


3rd-party Gradle plug-ins may be the cause

原因可能是什么？我在这里看到过类似的问题，但没有任何线索。请帮忙！

使现代化在我的刀中，我得到了这个错误

那么，如何让@Query理解它，我给它一个java字符串，而不是Kotlin字符串

另请参阅stackTrack：

/home/Desktop/MySendBird/app/build/tmp/kapt3/stubs/debug/ChannelRoomDatabase.java:6: warning: Schema export directory is not provided to the annotation processor so we cannot export the schema. You can either provide `room.schemaLocation` annotation processor argument OR set exportSchema to false.
public abstract class ChannelRoomDatabase extends android.arch.persistence.room.RoomDatabase {
                ^
:app:compileDebugKotlin
w: /home/Desktop/MySendBird/app/src/main/java/com/example/anna/mysendbird/repository/ChannelRepository.kt: (16, 13): Variable 'db' is never used
w: /home/Desktop/MySendBird/app/src/main/java/com/example/anna/mysendbird/repository/ChannelRepository.kt: (47, 23): Parameter 'channel' is never used
w: /home/Desktop/MySendBird/app/src/main/java/com/example/anna/mysendbird/view/MainActivity.kt: (179, 29): Parameter 'userId' is never used

查看类似的问题：

使用Room with kotlin，在构建数据库时会出现异常

当我试图构建房间时，空对象引用

Answer 1

您收到Android房间架构目录错误

/home/Desktop/MySendBird/app/build/tmp/kapt3/stubs/debug/ChannelRoomDatabase.java:6: warning: Schema export directory is not provided to the annotation processor so we cannot export the schema. You can either provide `room.schemaLocation` annotation processor argument OR set exportSchema to false.
public abstract class ChannelRoomDatabase extends android.arch.persistence.room.RoomDatabase {

架构导出目录未提供给批注处理器

您需要将模式目录添加到应用程序的gradle中。构建如下所示，

android {

    defaultConfig {
        javaCompileOptions {
            annotationProcessorOptions {
                arguments = ["room.schemaLocation": "$projectDir/schemas".toString()]
            }
        }
    }

}

这将告诉房间注释处理器生成数据库模式，并将其放在“Room.schemaLocation”