Kotlin 中的 Room Persistence lib 实现 [英] Room Persistence lib implementation in Kotlin

问题描述

我正在 kotlin 中为我的数据库实现实现 Room 持久性库.

I am implementing Room persistence lib in kotlin for my database implementation.

以下是我的Entity、Dao 和Database 类:

Following are my Entity, Dao and Database classes:

Food.kt

@Entity
class Food(@ColumnInfo(name = "food_name") var foodName: String,
           @ColumnInfo(name = "food_desc") var foodDesc: String,
           @ColumnInfo(name = "protein") var protein: Double,
           @ColumnInfo(name = "carbs") var carbs: Double,
           @ColumnInfo(name = "fat") var fat: Double)
{
    @ColumnInfo(name = "id")
    @PrimaryKey(autoGenerate = true)
    var id: Long = 0
    @ColumnInfo(name = "calories")
    var calories: Double = 0.toDouble()
}

PersonalizedFood.kt

@Entity(primaryKeys = arrayOf("food_id","date"))
class PersonalizedFood(@ColumnInfo(name = "quantity") var quantity: Int,
                       @ColumnInfo(name = "unit") var unit: String,
                       @ColumnInfo(name = "date") var date: Date){

    @ColumnInfo(name = "food_id")
    var foodId:Long = 0
}

FoodDao.kt

@Dao
interface FoodDao {

    companion object{
        const val ID = "id"
        const val NAME = "name"
        const val PROTEIN = "protein"
        const val DESC = "desc"
        const val CARBS = "carbs"
        const val FAT = "fat"

        const val DATE = "date"
        const val FOOD_ID = "food_id"

        const val ALL_FOOD_LIST = "food"
        const val PERSONALISED_FOOD_LIST = "personalised_food"
    }

    /**
     * Returns food details of a food given by food_id
     */
    @Query("SELECT * FROM $ALL_FOOD_LIST WHERE $ID=:food_id")
    fun getFoodDetails(food_id:Long):Food

    /**
     * Inserts food items in all_food_list
     */
    @Insert
    fun addFoodList(list:ArrayList<Food>)

    @Insert(onConflict = REPLACE)
    fun saveFood(food:PersonalizedFood)

    @Query("SELECT * FROM $PERSONALISED_FOOD_LIST WHERE $FOOD_ID=:foodId and $DATE=:date")
    fun getFood(foodId:Int, data:Date):PersonalizedFood

    @Query("SELECT * FROM $ALL_FOOD_LIST where $ID in (select $FOOD_ID from $PERSONALISED_FOOD_LIST where $DATE = :date)")
    fun getFood(date:Date):ArrayList<Food>
}

Converter.kt

class Converter {

    companion object{
        @TypeConverter
        fun fromTimestamp(value: Long?): Date? {
            return if (value == null) null else Date(value)
        }

        @TypeConverter
        fun dateToTimestamp(date: Date): Long {
            return date.time
        }
    }
}

FoodDatabase.kt

@Database(entities = arrayOf(Food::class, PersonalizedFood::class), version = 1)
@TypeConverters(Converter::class)
abstract class FoodDatabase : RoomDatabase(){
    abstract fun foodDao():FoodDao

    companion object{
        private val databaseName = "diet"

        var dbInstance:FoodDao? = null
        fun getInstance(context:Context):FoodDao?{
            if(dbInstance == null)
                dbInstance = Room.inMemoryDatabaseBuilder(context, FoodDatabase::class.java).build().foodDao()
            return dbInstance;
        }
    }
}

当我运行以下代码来创建数据库时:

And when i run following code to create database:

FoodDatabase.getInstance(baseContext)?.getFood(Calendar.getInstance().time)

它给了我以下异常:

Caused by: java.lang.RuntimeException: cannot find implementation forcom.chandilsachin.diettracker.database.FoodDatabase.FoodDatabase_Impl不存在在android.arch.persistence.room.Room.getGeneratedImplementation(Room.java:90)在android.arch.persistence.room.RoomDatabase$Builder.build(RoomDatabase.java:340)在com.chandilsachin.diettracker.database.FoodDatabase$Companion.getInstance(FoodDatabase.kt:21)在com.chandilsachin.diettracker.MainActivity$SetUpFoodDatabase.doInBackground(MainActivity.kt:95)在com.chandilsachin.diettracker.MainActivity$SetUpFoodDatabase.doInBackground(MainActivity.kt:77)在 android.os.AsyncTask$2.call(AsyncTask.java:295)在 java.util.concurrent.FutureTask.run(FutureTask.java:237)在 android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)在java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)在java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)在 java.lang.Thread.run(Thread.java:818)

Caused by: java.lang.RuntimeException: cannot find implementation for com.chandilsachin.diettracker.database.FoodDatabase. FoodDatabase_Impl does not exist at android.arch.persistence.room.Room.getGeneratedImplementation(Room.java:90) at android.arch.persistence.room.RoomDatabase$Builder.build(RoomDatabase.java:340) at com.chandilsachin.diettracker.database.FoodDatabase$Companion.getInstance(FoodDatabase.kt:21) at com.chandilsachin.diettracker.MainActivity$SetUpFoodDatabase.doInBackground(MainActivity.kt:95) at com.chandilsachin.diettracker.MainActivity$SetUpFoodDatabase.doInBackground(MainActivity.kt:77) at android.os.AsyncTask$2.call(AsyncTask.java:295) at java.util.concurrent.FutureTask.run(FutureTask.java:237) at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)  at java.lang.Thread.run(Thread.java:818)

有人在 kotlin 中实现了房间持久化吗?

Has anyone implemented room persistence in kotlin?

已编辑这个问题被标记为与这个重复.虽然问题陈述相同，但给出的解决方案并不能解决我的问题.解决方案说我必须将替换 annotationProcessor 添加到 kapt "android.arch.persistence.room:compiler:1.0.0-alpha1" 依赖项.我进行了这些更改，结果在项目构建时出现了 gradle 错误.

Edited This question was marked duplicate of this. Though problem statement is same but solution given does not solve my problem. Solution says i have to add replace annotationProcessor to kapt "android.arch.persistence.room:compiler:1.0.0-alpha1" dependency. I made those changes and it resulted in gradle error while project build.

信息:Gradle 任务 [:app:assembleDebug] 警告:警告:来自注释处理器的支持的源版本RELEASE_7"'android.arch.persistence.room.RoomProcessor' 小于 -source '1.8'警告:警告:以下选项未被任何人识别处理器:'[kapt.kotlin.generated]'/Users/BBI-M1025/Documents/BBI/Workspace_fun/Android/diet-tracker/app/src/main/java/com/chandilsachin/diettracker/database/Food.kt错误:(1, 1) 处理注释时出现一些错误.请参阅上面的错误消息.错误:任务:app:kaptDebugKotlin"的执行失败.

Information:Gradle tasks [:app:assembleDebug] Warning:warning: Supported source version 'RELEASE_7' from annotation processor 'android.arch.persistence.room.RoomProcessor' less than -source '1.8' Warning:warning: The following options were not recognized by any processor: '[kapt.kotlin.generated]' /Users/BBI-M1025/Documents/BBI/Workspace_fun/Android/diet-tracker/app/src/main/java/com/chandilsachin/diettracker/database/Food.kt Error:(1, 1) Some error(s) occurred while processing annotations. Please see the error messages above. Error:Execution failed for task ':app:kaptDebugKotlin'.

编译错误.查看日志了解更多详情信息:BUILD 在 10 秒内失败信息:2个错误信息:2 条警告信息:在控制台查看完整输出

Compilation error. See log for more details Information:BUILD FAILED in 10s Information:2 errors Information:2 warnings Information:See complete output in console

我还附上了我的 gradle 文件:

I am attaching my gradle file also:

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

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.2"
    defaultConfig {
        applicationId "com.chandilsachin.diettracker"
        minSdkVersion 16
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
    compile 'com.android.support:appcompat-v7:25.0.1'
    compile 'com.android.support.constraint:constraint-layout:1.0.0-alpha8'
    compile 'com.android.support:cardview-v7:25.0.1'
    compile 'com.android.support:recyclerview-v7:25.0.1'
    compile 'com.github.ne1c:rainbowmvp:1.2.1'
    compile "org.jetbrains.anko:anko-commons:0.10.0"

    /*annotationProcessor "android.arch.persistence.room:compiler:1.0.0-alpha1"
    compile "android.arch.lifecycle:extensions:1.0.0-alpha1"
    annotationProcessor "android.arch.lifecycle:compiler:1.0.0-alpha1"*/

    compile "android.arch.persistence.room:runtime:1.0.0-alpha1"
    annotationProcessor "android.arch.persistence.room:compiler:1.0.0-alpha1"
    kapt "android.arch.persistence.room:compiler:1.0.0-alpha1"

    testCompile 'junit:junit:4.12'
}
repositories {
    mavenCentral()
}

有人遇到过这个问题吗?

Has anyone come across this issue?

推荐答案

在我对这个问题绞尽脑汁想了一会儿之后，我找到了解决方案.

After spinning my head around for a while with this problem, I came across to the solution.

这真的很难，因为目前还没有官方教程、博客等来帮助解决这个问题.

It was really hard as there is no official tutorial, blog etc out there to help with this problem as of now.

我不得不对 gradle 插件和依赖项的所有组合进行多次尝试和试验，因为我知道只有 gradle 配置有问题.

I had to do several hit and trial for all the combination of gradle plugins and dependencies as i knew that something is wrong with gradle config only.

让我们来解决:

我不得不从 build.gradle(:module) 文件中删除 apply plugin: 'kotlin-kapt'并将 annotationProcessor "android.arch.persistence.room:compiler:1.0.0-alpha1" 替换为 kapt "android.arch.persistence.room:compiler:1.0.0-alpha1";.

I had to remove apply plugin: 'kotlin-kapt' from build.gradle(:module) file and replace annotationProcessor "android.arch.persistence.room:compiler:1.0.0-alpha1" to kapt "android.arch.persistence.room:compiler:1.0.0-alpha1".

这是成功编译代码的gradle配置.

This is the gradle configuration to successfully compile code.

但是还有更多的事情需要检查.您必须初始化 @Entity 类 的属性，这与 房间持久性库文档.虽然有 getter setter，但没有提到创建带有初始化的构造函数.所以我不得不用这个来改变我的 @Entity 类:

But there more things to check. You have to initialise properties of your @Entity class unlike java given in Room Persistence lib doc. Though there are getter setter but it is not mentioned to create a constructor with initialisation. So I had to change my @Entity class with this:

@Entity(tableName = "all_food_list")
class Food (@ColumnInfo(name = "food_name") var foodName: String = "",
            @ColumnInfo(name = "food_desc") var foodDesc: String = "",
            @ColumnInfo(name = "protein") var protein: Double = 0.0,
            @ColumnInfo(name = "carbs") var carbs: Double = 0.0,
            @ColumnInfo(name = "fat") var fat: Double = 0.0,
            @ColumnInfo(name = "calories") var calories: Double = 0.0)
{
    @ColumnInfo(name = "id")
    @PrimaryKey(autoGenerate = true)
    var id: Long = 0
}

现在对于TypeConverts，与java不同，您需要创建普通函数而不是静态函数(伴随对象):

Now for TypeConverts, Unlike java, you need to create normal function not static functions(companion object):

class Converters{

        @TypeConverter
        fun fromTimestamp(value: String): Calendar {
            val arr = value.split("-")
            val cal = Calendar.getInstance()
            cal.set(arr[0].toInt(), arr[1].toInt(), arr[2].toInt())
            return cal
        }

        @TypeConverter
        fun dateToTimestamp(date: Calendar): String {
            return "${date.get(Calendar.DATE)}-${date.get(Calendar.MONTH)+1}-${date.get(Calendar.YEAR)}"
        }

}

我还添加了 build.gradle 文件以使其更加清晰:

I am adding build.gradle file also to make it more clear:

build.gradle(:project)

buildscript {
    ext.kotlin_version = '1.1.2-4'
    ext.gradle_version_stable = '2.3.2'
    ext.gradle_version_preview = '3.0.0-alpha1'
    ext.anko_version = '0.10.0'
    repositories {
        maven { url 'https://maven.google.com' }
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.0.0-alpha1'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        maven { url 'https://maven.google.com' }
        jcenter()
        maven { url "https://jitpack.io" }
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

build.gradle(:module)

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

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.2"
    defaultConfig {
        applicationId "com.chandilsachin.diettracker"
        minSdkVersion 16
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}


dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
    ...
    ...
    // room persistence dependency 
    compile "android.arch.persistence.room:runtime:1.0.0-alpha1"
    kapt "android.arch.persistence.room:compiler:1.0.0-alpha1"

    testCompile 'junit:junit:4.12'
}
repositories {
    mavenCentral()
}

我想这就是全部，我这样做是为了让我的代码工作起来.

I think this is all, I did to make my code woking.

希望这对其他人也有帮助.

Hope this helps someone else also.

这篇关于Kotlin 中的 Room Persistence lib 实现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！