我尝试建立房间时会引用空对象 [英] Null object reference when I try to build room

问题描述

我想使用函数getDatabase(context)在Kotlin中建立空间，并且出现此错误:

I want to build room in Kotlin using my function getDatabase(context) and I have this error :

W/System.err: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Package.getName()' on a null object reference
W/System.err:     at android.arch.persistence.room.Room.getGeneratedImplementation(Room.java:77)

这很奇怪，因为这是我第一次遇到此错误(我在其他项目中使用Room，但没有此错误). 该应用程序不会崩溃，但数据库无法正常工作.

This is very strange because it's the first time I have this error (I use Room in other project and I don't have this bug). The app don't crash but the database is not working.

我尝试在Internet上查找，但对此错误没有看到任何信息(仅此日本家伙: https: //teratail.com/questions/118177 ，但我不懂日语).

I try looking in internet but I don't see nothing about this bug (only this japanese guy : https://teratail.com/questions/118177 but I don't understand japanese).

AppDatabase:

@Database(entities = [(Wallet::class), (Historique::class)], version = 1)
abstract class AppDatabase : RoomDatabase() {
    abstract fun walletDao(): WalletDao
    abstract fun historiqueDao(): HistoriqueDao
}

private var INSTANCE: AppDatabase? = null

fun getDatabase(context: Context?): AppDatabase {
    if (INSTANCE == null)
        INSTANCE = context?.let { Room.databaseBuilder(context, AppDatabase::class.java, DATABASE_NAME).build() }
    return INSTANCE as AppDatabase
}

这是我的Gradle:

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

android {
    compileSdkVersion 27
    defaultConfig {
        applicationId "my.app"
        minSdkVersion 19
        targetSdkVersion 27
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
    implementation 'com.android.support:appcompat-v7:27.1.1'
    implementation 'com.android.support.constraint:constraint-layout:1.1.0'
    implementation 'com.android.support:support-v4:27.1.1'

    implementation "android.arch.persistence.room:runtime:1.0.0"
    annotationProcessor "android.arch.persistence.room:compiler:1.0.0"
    kapt "android.arch.persistence.room:compiler:1.0.0"

    implementation "org.jetbrains.anko:anko-commons:0.10.4"
    implementation "org.jetbrains.anko:anko-design:0.10.4"
    implementation "com.chibatching.kotpref:kotpref:2.5.0"
    implementation "com.chibatching.kotpref:initializer:2.5.0"
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.1'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
}

推荐答案

问题出在某些导入中(通过处理其他项目中的类).

The problem was from some imports (by coping the class from an other project).

这篇关于我尝试建立房间时会引用空对象的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！