Android Room Persistences库和Kotlin

Question

我正在尝试使用Kotlin和Room Persistance Library编写一个简单的应用程序.我按照Android Persistance codelab中的教程进行操作.

这是我AppDatabase在Kotlin的课程:

@Database(entities = arrayOf(User::class), version = 1)
abstract class AppDatabase : RoomDatabase() {
    abstract fun userModel(): UserDao

    companion object {
        private var INSTANCE: AppDatabase? = null
        @JvmStatic fun getInMemoryDatabase(context: Context): AppDatabase {
            if (INSTANCE == null) {
                INSTANCE = Room.inMemoryDatabaseBuilder(context.applicationContext, AppDatabase::class.java).allowMainThreadQueries().build()
            }
            return INSTANCE!!
        }

        @JvmStatic fun destroyInstance() {
            INSTANCE = null
        }
    }
}

但是当我试图运行应用程序时,它会立即崩溃.这是崩溃日志:

Caused by: java.lang.RuntimeException: cannot find implementation for com.ttp.kotlin.kotlinsample.room.AppDatabase. AppDatabase_Impl does not exist
    at android.arch.persistence.room.Room.getGeneratedImplementation(Room.java:90)
    at android.arch.persistence.room.RoomDatabase$Builder.build(RoomDatabase.java:340)
    at com.ttp.kotlin.kotlinsample.room.AppDatabase$Companion.getInMemoryDatabase(AppDatabase.kt:19)
    at com.ttp.kotlin.kotlinsample.MainKotlinActivity.onCreate(MainKotlinActivity.kt:28)
    at android.app.Activity.performCreate(Activity.java:6272)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2387)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2494) 
    at android.app.ActivityThread.access$900(ActivityThread.java:157) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1356)

看起来AppDatabase_Impl类没有自动生成.我检查了从codelab下载的原始java应用程序,发现AppDatabase_Impl是自动生成的.

Kotlin版本:1.1.2-3房间版本:1.0.0-alpha1

有没有人经历过这个？

编辑: 使用kapt解决了我的问题.在我的情况下,我必须用kapt替换annotationProcessor.

Answer 1

通常在项目中build.gradle我定义依赖项版本:

ext {
    buildToolsVersion = '25.0.2'
    supportLibVersion = '25.3.1'
    espressoVersion = '2.2.2'
    archRoomVersion = '1.0.0-alpha1'
}

所以在应用程序build.gradle中依赖项看起来像:

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"

    compile "com.android.support:appcompat-v7:${rootProject.supportLibVersion}"

    compile "android.arch.persistence.room:runtime:${rootProject.archRoomVersion}"
    annotationProcessor "android.arch.persistence.room:compiler:${rootProject.archRoomVersion}"
    kapt "android.arch.persistence.room:compiler:${rootProject.archRoomVersion}"

    androidTestCompile("com.android.support.test.espresso:espresso-core:${rootProject.espressoVersion}", {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    testCompile 'junit:junit:4.12'
}

现在,您可以在Kotlin中定义实体Daos和数据库.

数据库:

@Database(entities = arrayOf(User::class), version = 1)
abstract class Database : RoomDatabase() {
    abstract fun userDao(): UserDao
}

实体:

@Entity(tableName = "user")
class User {
    @PrimaryKey(autoGenerate = true)
    var id: Int = 0
    var name: String = ""
}

道:

@Dao
interface UserDao {
    @Query("SELECT * FROM user")
    fun getAll(): List<User>

    @Insert
    fun insertAll(vararg users: User)

    @Delete
    fun delete(user: User)
}

注意:使用参数查询. Kotlin重命名params,因此通过userId检索属于用户的所有电子邮件的SQL查询是:

@Query("SELECT * FROM email "
            + "INNER JOIN user ON user.id = email.userId "
            + "WHERE user.id = :arg0")
    fun getEmailsForUser(userId: Int): List<Email>

Answer 2

在我的情况下,在build.gradle中,当你有"annotationProcessor"时,你需要复制"kapt"并且它有效.

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

Answer 3

尝试这些步骤

步骤1.room_version在project.gradle文件中设置

buildscript {
    ext.kotlin_version = '1.1.51'
    ext.room_version = '1.0.0-alpha9-1'
...

步骤2.kotlin-kapt在app.gradle文件中应用插件,这解决了我的问题.

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

android {
    compileSdkVersion 26
    buildToolsVersion "26.0.1"
...

步骤3.kapt在app.gradle文件中添加依赖项

dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation "android.arch.persistence.room:runtime:$room_version"
    annotationProcessor "android.arch.persistence.room:compiler:$room_version"
    kapt "android.arch.persistence.room:compiler:$room_version"
...
}