房间数据库构建器构建崩溃

Question

下面的代码行严重崩溃

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Room.databaseBuilder(\n        applicationContext,\n        MyDatabase::class.java, "MyDB")\n        .build()\n

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这是您可以轻松复制的最小完整可验证 (MCV) 应用程序

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在项目的 build.gradle 中，确保存在以下内容

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allprojects {\n    repositories {\n        google()\n        jcenter()\n    }\n}\n

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在应用程序的 build.gradle 中，确保存在以下内容

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dependencies {\n    def room_version = "1.1.1"\n\n    implementation "android.arch.persistence.room:runtime:$room_version"\n    kapt  "android.arch.persistence.room:compiler:$room_version" // because I\'m using Kotlin\n}\n

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所有设置说明均按照官方文档https://developer.android.com/topic/libraries/architecture/adding-components

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现在只需使用 Android Studio 并使用“空活动”模板创建一个项目。此 MCV 示例中仅需要 3 个新文件。

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创建第一个文件，名为MyThing.kt

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//MyThing.kt\nimport android.arch.persistence.room.ColumnInfo\nimport android.arch.persistence.room.Entity\n\n@Entity(tableName = "myThing")\ndata class MyThing(@ColumnInfo var myString: String)\n

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创建第二个文件，名为MyDao.kt

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import android.arch.persistence.room.Dao\nimport android.arch.persistence.room.Insert\nimport android.arch.persistence.room.OnConflictStrategy\n\n@Dao\ninterface MyDao {\n    @Insert(onConflict = OnConflictStrategy.REPLACE)\n    fun insert(myThing: MyThing)\n}\n

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创建第三个文件，名为MyDatabase.kt

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import android.arch.persistence.room.Database\nimport android.arch.persistence.room.RoomDatabase\n\n@Database(entities = arrayOf(MyThing::class), version = 1)\nabstract class MyDatabase : RoomDatabase() {\n    abstract fun myDao(): MyDao\n}\n

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现在修改MainActivity类

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class MainActivity : AppCompatActivity() {\n\n    private var myDB: MyDatabase? = null\n\n    override fun onCreate(savedInstanceState: Bundle?) {\n        super.onCreate(savedInstanceState)\n        setContentView(R.layout.activity_main)\n\n        myDB = Room.databaseBuilder(\n            applicationContext,\n            MyDatabase::class.java, "MyDB")\n            .build()\n    }\n}\n

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现在运行该应用程序将导致我上面提到的线路发生严重崩溃。我究竟做错了什么？

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更新：Logcat 输出

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--------- beginning of crash\n12-29 13:23:46.098 12801-12801/com.le.kevin.roommcv E/AndroidRuntime: FATAL EXCEPTION: main\n Process: com.le.kevin.roommcv, PID: 12801\n java.lang.RuntimeException: Unable to start activity ComponentInfo{com.le.kevin.roommcv/com.le.kevin.roommcv.MainActivity}: java.lang.RuntimeException: cannot find implementation for com.le.kevin.roommcv.MyDatabase. MyDatabase_Impl does not exist\n at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)\n at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)\n at android.app.ActivityThread.-wrap11(ActivityThread.java)\n at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)\n at android.os.Handler.dispatchMessage(Handler.java:102)\n at android.os.Looper.loop(Looper.java:148)\n at android.app.ActivityThread.main(ActivityThread.java:5417)\n at java.lang.reflect.Method.invoke(Native Method)\n at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)\n at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)\n Caused by: java.lang.RuntimeException: cannot find implementation for com.le.kevin.roommcv.MyDatabase. MyDatabase_Impl does not exist\n at android.arch.persistence.room.Room.getGeneratedImplementation(Room.java:93)\n at android.arch.persistence.room.RoomDatabase$Builder.build(RoomDatabase.java:630)\n at com.le.kevin.roommcv.MainActivity.onCreate(MainActivity.kt:19)\n at android.app.Activity.performCreate(Activity.java:6251)\n at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)\n at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)\n at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)\xc2\xa0\n at android.app.ActivityThread.-wrap11(ActivityThread.java)\xc2\xa0\n at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)\xc2\xa0\n at android.os.Handler.dispatchMessage(Handler.java:102)\xc2\xa0\n at android.os.Looper.loop(Looper.java:148)\xc2\xa0\n at android.app.ActivityThread.main(ActivityThread.java:5417)\xc2\xa0\n at java.lang.reflect.Method.invoke(Native Method)\xc2\xa0\n at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)\xc2\xa0\n at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)\xc2\xa0\n12-29 13:23:46.099 777-1936/? W/ActivityManager: Force finishing activity com.le.kevin.roommcv/.MainActivity\n

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实施？

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Answer 1

我通过添加让它工作

apply plugin: 'kotlin-kapt'

在应用程序的 build.gradle 中

通过查看上面评论建议的 logcat，我找到了答案，然后通过答案Room + 找不到实现 DB + DB_Impl 不存在

官方文档https://developer.android.com/topic/libraries/architecture/adding-components不完整