我的Fragment
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-＆gt; Kotlin自动翻译器使用我以前的Java代码所做的事情（除了?在我找到PrefsFragment标签的行的末尾），所以它可能不完全是犹太人。我正在学习Kotlin。
现在，当我调用executePendingTransactions()时，我的应用程序崩溃抛出java.lang.IllegalArgumentException错误消息＆＃34;指定为非null的参数为null：方法kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull，参数savedInstanceState＆＃34;。现在，是的，savedInstanceState实际上是null，但它与显然抛出异常的调用有什么关系呢？我确保没有其他值/变量为空，所以我相信错误信息......但为什么呢？
编辑这是堆栈跟踪，以及让我做恶梦的源代码
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)
答案 0 :(得分：13)
该异常实际上并非来自该代码。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)
以下内容应允许savedInstanceState为null -
override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey : String)