FragmentManager在Kotlin中抛出IllegalArgumentException
我在我的Fragment有以下方法
override fun onActivityCreated(savedInstanceState: Bundle?) { super.onActivityCreated(savedInstanceState) val fm = childFragmentManager var prefsFragment: PrefsFragment? = fm.findFragmentByTag(tableName) as PrefsFragment? if (prefsFragment == null) { prefsFragment = PrefsFragment() val ft = fm.beginTransaction() ft.add(R.id.parameters_fragment_container, prefsFragment, tableName) ft.commit() fm.executePendingTransactions() } }
我不得不说这是Java-> Kotlin automagic翻译器对我以前的Java代码所做的事情（除了在我找到PrefsFragment标签的行尾之外），所以它可能不完全是犹太教。 我正在学习Kotlin。
现在，当我调用executePendingTransactions() ，我的应用程序崩溃抛出java.lang.IllegalArgumentException异常错误消息“参数指定为非null为空：方法kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull，参数savedInstanceState”。 现在，是的，savedInstanceState实际上是空的，但是它与显然抛出异常的调用有什么关系呢？ 我确信没有其他值/变量是空的，所以我相信错误信息…但是为什么？
编辑这里是堆栈跟踪，和给我做恶梦的源代码
https://gist.github.com/Morpheu5/8ec7e2064f53679405769b43c64f2cb7
E/AndroidRuntime: FATAL EXCEPTION: main Process: net.morpheu5.bleedingscorecalculator, PID: 2685 java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter savedInstanceState at net.morpheu5.bleedingscorecalculator.CalculatorScreen$PrefsFragment.onCreatePreferences(CalculatorScreen.kt:0) at android.support.v7.preference.PreferenceFragmentCompat.onCreate(PreferenceFragmentCompat.java:223) at android.support.v4.app.Fragment.performCreate(Fragment.java:2075) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1060) at android.support.v4.app.BackStackRecord.setLastIn(BackStackRecord.java:838) at android.support.v4.app.BackStackRecord.calculateFragments(BackStackRecord.java:861) at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:719) at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1682) at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:594) at net.morpheu5.bleedingscorecalculator.CalculatorScreen.onActivityCreated(CalculatorScreen.kt:34) at android.support.v4.app.Fragment.performActivityCreated(Fragment.java:2096) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1138) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1295) at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:801) at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:1643) at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:679) at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:143) at android.support.v4.view.ViewPager.populate(ViewPager.java:1272) at android.support.v4.view.ViewPager.populate(ViewPager.java:1120) at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1646) at android.view.View.measure(View.java:19857) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083) at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:703) at android.support.design.widget.HeaderScrollingViewBehavior.onMeasureChild(HeaderScrollingViewBehavior.java:90) at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onMeasureChild(AppBarLayout.java:1367) at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:768) at android.view.View.measure(View.java:19857) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083) at android.widget.FrameLayout.onMeasure(FrameLayout.java:185) at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:139) at android.view.View.measure(View.java:19857) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1464) at android.widget.LinearLayout.measureVertical(LinearLayout.java:758) at android.widget.LinearLayout.onMeasure(LinearLayout.java:640) at android.view.View.measure(View.java:19857) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083) at android.widget.FrameLayout.onMeasure(FrameLayout.java:185) at android.view.View.measure(View.java:19857) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1464) at android.widget.LinearLayout.measureVertical(LinearLayout.java:758) at android.widget.LinearLayout.onMeasure(LinearLayout.java:640) at android.view.View.measure(View.java:19857) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083) at android.widget.FrameLayout.onMeasure(FrameLayout.java:185) at com.android.internal.policy.DecorView.onMeasure(DecorView.java:689) at android.view.View.measure(View.java:19857) at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2275) E/AndroidRuntime: at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1366) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1619) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1254) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6337) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:874) at android.view.Choreographer.doCallbacks(Choreographer.java:686) at android.view.Choreographer.doFrame(Choreographer.java:621) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:860) at android.os.Handler.handleCallback(Handler.java:751) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6119) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
该例外实际上不是来自该代码。 它来自您的CalculatorScreen.PrefsFragment.onCreatePreferences()方法。 如果你看那里，它看起来像 –
override fun onCreatePreferences(savedInstanceState: Bundle, rootKey : String)
它应该是以下允许savedInstanceState为null –
override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey : String)