为什么我得到错误java.lang.IllegalStateException：实例未初始化？
我得到错误
java.lang.IllegalStateException：实例未初始化
你可以在https://www.dropbox.com/s/gxeok1fyttsl54u/MyMirror.zip?dl=0
在operator fun getValue(thisRef: Any?, property: KProperty)... ，似乎代码operator fun getValue(thisRef: Any?, property: KProperty)...会导致错误。
但代码是来自示例代码，我几乎不会改变，你可以在https://github.com/antoniolg/Kotlin-for-Android-Developers/blob/master/app/src/main/看到源代码。 的Java / COM / antonioleiva / weatherapp / UI / App.kt
和
https://github.com/antoniolg/Kotlin-for-Android-Developers/blob/master/app/src/main/java/com/antonioleiva/weatherapp/extensions/DelegatesExtensions.kt
为什么？
java.lang.RuntimeException: Unable to start activity ComponentInfo{info.dodata.mirror/ui.UIMain}: java.lang.IllegalStateException: instance not initialized at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2107) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2132) at android.app.ActivityThread.access$700(ActivityThread.java:140) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1238) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:4918) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:994) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:761) at dalvik.system.NativeStart.main(Native Method) Caused by: java.lang.IllegalStateException: instance not initialized at ui.UIApp$NotNullSingleValueVar.getValue(UIApp.kt:23) at ui.UIApp$Companion.getInstance(UIApp.kt) at dal.DBSettingHelper.(DBSettingHelper.kt:9) at ui.UIMain.onCreate(UIMain.kt:14) at android.app.Activity.performCreate(Activity.java:5185) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2071) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2132)? at android.app.ActivityThread.access$700(ActivityThread.java:140)? at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1238)? at android.os.Handler.dispatchMessage(Handler.java:99)? at android.os.Looper.loop(Looper.java:137)? at android.app.ActivityThread.main(ActivityThread.java:4918)? at java.lang.reflect.Method.invokeNative(Native Method)? at java.lang.reflect.Method.invoke(Method.java:511)? at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:994)? at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:761)? at dalvik.system.NativeStart.main(Native Method)?
UIMain
package ui import android.os.Bundle import android.support.v7.app.AppCompatActivity import dal.DBSettingHelper import info.dodata.mirror.R class UIMain : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.layout_main) var ss= DBSettingHelper(); } }
DBSettingHelper
package dal import android.content.Context import android.database.sqlite.SQLiteDatabase import org.jetbrains.anko.db.* import ui.UIApp object DBSettingTable { val TableNAME = "SettingTable" val _ID = "_id" val Name = "name" val CreatedDate = "createdDate" val Description="description" } class DBSettingHelper(mContext: Context = UIApp.instance) : ManagedSQLiteOpenHelper( mContext, DB_NAME, null, DB_VERSION) { companion object { val DB_NAME = "setting.db" val DB_VERSION = 1 val instance by lazy { DBSettingHelper() } } override fun onCreate(db: SQLiteDatabase) { db.createTable( DBSettingTable.TableNAME , true, DBSettingTable._ID to INTEGER + PRIMARY_KEY, DBSettingTable.Name to TEXT, DBSettingTable.CreatedDate to INTEGER, DBSettingTable.Description to TEXT ) } override fun onUpgrade(db: SQLiteDatabase, oldVersion: Int, newVersion: Int) { db.dropTable(DBSettingTable.TableNAME, true) onCreate(db) } }
了UiApp
package ui import android.app.Application import kotlin.reflect.KProperty class UIApp : Application() { companion object { var instance: UIApp by NotNullSingleValueVar() } override fun onCreate() { super.onCreate() instance = this } class NotNullSingleValueVar { private var value: T? = null operator fun getValue(thisRef: Any?, property: KProperty): T = value ?: throw IllegalStateException("${property.name} not initialized") operator fun setValue(thisRef: Any?, property: KProperty, value: T) { this.value = if (this.value == null) value else throw IllegalStateException("${property.name} already initialized") } }
UIApp类中的onCreate函数永远不会被调用，因此UIApp的一个实例永远不会被初始化。 发生这种情况是因为您没有将UIApp类添加到AndroidManifest，并且因为您的应用程序没有意识到您在项目中具有您的自定义Application类。
android:name="ui.UIApp" android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round" android:supportsRtl="true" android:theme="@style/AppTheme">