Question

我在第一次创建会议室数据库时一直遇到这个异常

  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
        }
    }

}

以及gradle代码：

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"

在建立项目时也会出现此错误：

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

可能是什么原因？我在这里看到了类似的问题，但没有任何线索。请帮忙！

更新！在我的刀中，我得到了这个错误

所以如何让@Query理解我给它一个Java字符串而不是Kotlin字符串

另请参阅堆栈跟踪：

/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

看到类似的问题：

using Room with kotlin, get exception when build the database

Null object reference when I try to build room

Answer 1

您收到Android Room模式目录错误

/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 {

未将架构导出目录提供给注释处理器

您需要将架构目录添加到应用的gradle.build 中，如下所示，

android {

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

}

这将告诉您的房间注释处理器生成数据库架构，并将其放在"room.schemaLocation"下提到的目录下

如何在Kotlin中首次建立Room数据库时解决异常问题

1 个答案: