小编And*_*cha的帖子

您好，我有2个应用程序仅通过将数据库文件复制到sdcard中和从中复制数据库文件来依赖于制作和恢复数据库的备份，并且在弄清楚如何在关闭数据库以使其成为数据库后如何重新打开Room Database单例方面遇到了困难份。

建立数据库：

@Database(version = 15, exportSchema = true, entities = [list of entities])
abstract class AppDatabase : RoomDatabase() {

//list of DAOs

companion object {

    @Volatile private var INSTANCE: AppDatabase? = null

    fun getInstance(context: Context): AppDatabase =
            INSTANCE ?: synchronized(this) {
                INSTANCE ?: buildDatabase(context).also {
                    INSTANCE = it
                }
            }

    private fun buildDatabase(context: Context) =

            Room.databaseBuilder(
                    context.applicationContext,
                    AppDatabase::class.java,
                    "Fazendao.sqlitedb"
            )
            .addMigrations(Migration1315)
            .build()

    }
}

关闭数据库：

fun closeDatabase() {
    if(db.isOpen) {
        db.openHelper.close()
    }
}

复制数据库文件（在ViewModel内部）：

fun exportaBkpObservable(nome: String, auto: String, …

升级到kotlin 1.2.40后,我在构建时遇到以下错误:

e: [kapt] An exception occurred: java.lang.NoClassDefFoundError: org/jetbrains/kotlin/serialization/jvm/JvmProtoBufUtil
at me.eugeniomarletti.kotlin.metadata.KotlinClassMetadata$data$2.invoke(KotlinMetadata.kt:51)
at me.eugeniomarletti.kotlin.metadata.KotlinClassMetadata$data$2.invoke(KotlinMetadata.kt:50)
at kotlin.SynchronizedLazyImpl.getValue(Lazy.kt:131)
at me.eugeniomarletti.kotlin.metadata.KotlinClassMetadata.getData(KotlinMetadata.kt)
at android.arch.persistence.room.ext.KotlinMetadataProcessor$DefaultImpls.getParameterNames(KotlinMetadataProcessor.kt:33)
at android.arch.persistence.room.processor.PojoProcessor.getParameterNames(PojoProcessor.kt:73)
at android.arch.persistence.room.processor.PojoProcessor.getParamNames(PojoProcessor.kt:245)
at android.arch.persistence.room.processor.PojoProcessor.chooseConstructor(PojoProcessor.kt:263)
at android.arch.persistence.room.processor.PojoProcessor.doProcess(PojoProcessor.kt:207)
at android.arch.persistence.room.processor.PojoProcessor.access$doProcess(PojoProcessor.kt:73)
at android.arch.persistence.room.processor.PojoProcessor$process$1.invoke(PojoProcessor.kt:104)
at android.arch.persistence.room.processor.PojoProcessor$process$1.invoke(PojoProcessor.kt:73)
at android.arch.persistence.room.processor.cache.Cache$Bucket.get(Cache.kt:46)
at android.arch.persistence.room.processor.PojoProcessor.process(PojoProcessor.kt:101)
at android.arch.persistence.room.processor.EntityProcessor.doProcess(EntityProcessor.kt:68)
at android.arch.persistence.room.processor.EntityProcessor.access$doProcess(EntityProcessor.kt:50)
at android.arch.persistence.room.processor.EntityProcessor$process$1.invoke(EntityProcessor.kt:57)
at android.arch.persistence.room.processor.EntityProcessor$process$1.invoke(EntityProcessor.kt:50)
at android.arch.persistence.room.processor.cache.Cache$Bucket.get(Cache.kt:46)
at android.arch.persistence.room.processor.EntityProcessor.process(EntityProcessor.kt:56)
at android.arch.persistence.room.processor.DatabaseProcessor.processEntities(DatabaseProcessor.kt:248)
at android.arch.persistence.room.processor.DatabaseProcessor.doProcess(DatabaseProcessor.kt:63)
at android.arch.persistence.room.processor.DatabaseProcessor.process(DatabaseProcessor.kt:53)
at android.arch.persistence.room.RoomProcessor$DatabaseProcessingStep.process(RoomProcessor.kt:57)
at com.google.auto.common.BasicAnnotationProcessor.process(BasicAnnotationProcessor.java:318)
at com.google.auto.common.BasicAnnotationProcessor.process(BasicAnnotationProcessor.java:171)
at org.jetbrains.kotlin.kapt3.ProcessorWrapper.process(annotationProcessing.kt:131)
at com.sun.tools.javac.processing.JavacProcessingEnvironment.callProcessor(JavacProcessingEnvironment.java:794)
at com.sun.tools.javac.processing.JavacProcessingEnvironment.discoverAndRunProcs(JavacProcessingEnvironment.java:705)
at com.sun.tools.javac.processing.JavacProcessingEnvironment.access$1800(JavacProcessingEnvironment.java:91)
at com.sun.tools.javac.processing.JavacProcessingEnvironment$Round.run(JavacProcessingEnvironment.java:1039)
at com.sun.tools.javac.processing.JavacProcessingEnvironment.doProcessing(JavacProcessingEnvironment.java:1180)
at com.sun.tools.javac.main.JavaCompiler.processAnnotations(JavaCompiler.java:1170)
at com.sun.tools.javac.main.JavaCompiler.processAnnotations(JavaCompiler.java:1068)
at org.jetbrains.kotlin.kapt3.AnnotationProcessingKt.doAnnotationProcessing(annotationProcessing.kt:87)
at …