我正在 kotlin 中为我的数据库实现实现 Room 持久性库。
以下是我的 Entity
、Dao
和 Database
类:
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 $DATE = :date)")
fun getFood(date:Date):ArrayList<Food>
}
Converter.kt
class Converter {
companion object{
@TypeConverter
fun fromTimestamp(value: Long?): Date? {
return if (value == null) null else Date(value)
}
@TypeConverter
fun dateToTimestamp(date: Date): Long {
return date.time
}
}
}
FoodDatabase.kt
@Database(entities = arrayOf(Food::class, PersonalizedFood::class), version = 1)
@TypeConverters(Converter::class)
abstract class FoodDatabase : RoomDatabase(){
abstract fun foodDao():FoodDao
companion object{
private val databaseName = "diet"
var dbInstance:FoodDao? = null
fun getInstance(context:Context):FoodDao?{
if(dbInstance == null)
dbInstance = Room.inMemoryDatabaseBuilder(context, FoodDatabase::class.java).build().foodDao()
return dbInstance;
}
}
}
当我运行以下代码来创建数据库时:
FoodDatabase.getInstance(baseContext)?.getFood(Calendar.getInstance().time)
它给了我以下异常:
Caused by: java.lang.RuntimeException: cannot find implementation for com.chandilsachin.diettracker.database.FoodDatabase. FoodDatabase_Impl does not exist at android.arch.persistence.room.Room.getGeneratedImplementation(Room.java:90) at android.arch.persistence.room.RoomDatabase$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?
已编辑
此问题被标记为与 this 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,但在项目构建时导致了 gradle 错误。
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'.
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:
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?
最佳答案
在为这个问题转了一圈之后,我想到了解决方案。
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。
我必须对 gradle 插件和依赖项的所有组合进行多次测试和试验,因为我知道只有 gradle config 有问题。
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"
。
这是成功编译代码的gradle配置。
但是还有更多的事情需要检查。您必须初始化 @Entity class
的属性,这与 Room Persistence lib doc 中给出的 java 不同。 .虽然有getter setter,但没有提到创建一个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:
@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(伴生对象):
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)}"
}
}
我添加 build.gradle 文件也是为了更清楚:
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能够正常工作。
希望这对其他人也有帮助。
关于android - Kotlin 中的 Room Persistence lib 实现,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/44142964/