我基本上有3个片段。活动加载时显示第一个。有一个活动和三个片段。单击第一个片段中的按钮时，将显示第二个片段。单击第二个片段中的按钮时，将加载第三个片段。 当我将第一个片段添加到后堆栈时，没有问题/错误。但是，当我调用第三个片段并将第二个片段添加到backstack时，它将引发以下错误：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.admin.unitconverter, PID: 9384
java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter view
at com.example.admin.unitconverter.SecondFragment$viewSolution$1.onItemSelected(SecondFragment.kt)
at android.widget.AdapterView.fireOnSelected(AdapterView.java:931)
at android.widget.AdapterView.dispatchOnItemSelected(AdapterView.java:920)
at android.widget.AdapterView.selectionChanged(AdapterView.java:914)
at android.widget.AdapterView.checkSelectionChanged(AdapterView.java:1092)
at android.widget.AdapterView.handleDataChanged(AdapterView.java:1068)
at android.widget.AbsSpinner.onMeasure(AbsSpinner.java:181)
at android.widget.Spinner.onMeasure(Spinner.java:592)
at android.support.v7.widget.AppCompatSpinner.onMeasure(AppCompatSpinner.java:426)
at android.view.View.measure(View.java:19857)
at android.support.constraint.ConstraintLayout.internalMeasureChildren(ConstraintLayout.java:1227)
at android.support.constraint.ConstraintLayout.onMeasure(ConstraintLayout.java:1572)
at android.view.View.measure(View.java:19857)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
at android.view.View.measure(View.java:19857)
at android.support.constraint.ConstraintLayout.internalMeasureChildren(ConstraintLayout.java:1227)
at android.support.constraint.ConstraintLayout.onMeasure(ConstraintLayout.java:1572)
at android.view.View.measure(View.java:19857)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083)
at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:714)
at android.support.design.widget.HeaderScrollingViewBehavior.onMeasureChild(HeaderScrollingViewBehavior.java:91)
at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onMeasureChild(AppBarLayout.java:1361)
at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:784)
at android.view.View.measure(View.java:19857)
at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:1060)
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)
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)
但是，如果我不将第二个片段添加到Backstack中，则不会引发任何错误，如果我随后运行该应用程序并单击片段3中的“后退”按钮，则该应用程序将省略片段2并跳转到片段1。
这是我的MainActivity
//val xv = "baseFragment"
when(fragment){
"secondfragment" -> {
toggle.isDrawerIndicatorEnabled = false
count = count + 1
//toggle.isDrawerIndicatorEnabled = false
//frameLayout.removeAllViews()
// fragmentManager.popBackStack("xv", FragmentManager.POP_BACK_STACK_INCLUSIVE);
val bundle = Bundle()
val fragment2 = SecondFragment()
bundle.putString("buttonClicked","Length")
fragment2.setArguments(bundle)
val fragmentManager = getFragmentManager()
// val ft = fragmentManager.beginTransaction()
val ft = supportFragmentManager.beginTransaction()
// Replace the contents of the container with the new fragment
//ft.remove(null)
ft.replace(R.id.fragment_container, fragment2)
ft.addToBackStack("xv")
ft.commit()
}
"searchfragment" -> {
toggle.isDrawerIndicatorEnabled = false
count = count + 1
//toggle.isDrawerIndicatorEnabled = false
// val bundle = Bundle()
//frameLayout.removeAllViews()
val searchFragment = SearchFragment()
// bundle.putString("buttonClicked","Length")
// searchFragment.setArguments(bundle);
val fragmentManager = getFragmentManager()
// val ft = fragmentManager.beginTransaction()
val ft = supportFragmentManager.beginTransaction()
//ft.remove(null)
// Replace the contents of the container with the new fragment
ft.replace(R.id.fragment_container, searchFragment)
ft.addToBackStack(null)
ft.commit()
}
}
if (toolbar != null) {
/* toggle = ActionBarDrawerToggle(
this, drawer_layout, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close)
toggle.syncState()
drawer_layout.setDrawerListener(toggle)*/
supportFragmentManager.addOnBackStackChangedListener(object : FragmentManager.OnBackStackChangedListener {
override fun onBackStackChanged() {
if (supportFragmentManager.backStackEntryCount > 0) {
supportActionBar?.setDisplayHomeAsUpEnabled(true) // show back button
toolbar.setNavigationOnClickListener(object : View.OnClickListener {
override fun onClick(v: View) {
Toast.makeText(getApplicationContext(),"Count Rock"+ count ,Toast.LENGTH_LONG).show()
onBackPressed()
}
})
} else {
//show hamburger
supportActionBar?.setDisplayHomeAsUpEnabled(false)
toggle.syncState()
toolbar.setNavigationOnClickListener(object : View.OnClickListener {
override fun onClick(v: View) {
drawer_layout.openDrawer(GravityCompat.START)
}
})
}
}
})
}
请问我到底在做错什么。任何帮助将不胜感激。谢谢
编辑：以下是@thehrlein要求的“ SecondFragment onItemSelected”
spinner1.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
override fun onItemSelected(adapterView: AdapterView<*>, view: View, i: Int, l: Long) {
//Toast.makeText(applicationContext, "This is " + adapterView.getItemAtPosition(i).toString(), Toast.LENGTH_LONG).show()
// Toast.makeText(applicationContext, "This is " + i, Toast.LENGTH_LONG).show()
var myAnswer = 0.0
try {
//Your task here
textView1.setText(spinner1.adapter.getItem(i).toString())
myAnswer = MathParser.eval(replaceOperators(myInput.text.toString()))
solution(myAnswer.toString())
spinnerIndex1 = spinner1.selectedItemPosition
spinnerIndex2 = spinner2.selectedItemPosition
val editor = sharedPreferences.edit()
editor.putInt("position1key", spinnerIndex1)
editor.putInt("position2key", spinnerIndex2)
//editor.putString("myInput", myInput.text.toString())
//editor.putString("myResult", result.text.toString())
editor.apply()
} catch (e: Exception) {
e.printStackTrace()
}
}
override fun onNothingSelected(adapterView: AdapterView<*>) {
}
}
spinner2.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
override fun onItemSelected(adapterView: AdapterView<*>, view: View, i: Int, l: Long) {
//Toast.makeText(applicationContext, "This is " + adapterView.getItemAtPosition(i).toString(), Toast.LENGTH_LONG).show()
// Toast.makeText(applicationContext, "This is " + i, Toast.LENGTH_LONG).show()
var myAnswer = 0.0
try {
//Your task here
textView2.setText(spinner2.adapter.getItem(i).toString())
myAnswer = MathParser.eval(replaceOperators(myInput.text.toString()))
solution(myAnswer.toString())
spinnerIndex1 = spinner1.selectedItemPosition
spinnerIndex2 = spinner2.selectedItemPosition
val editor = sharedPreferences.edit()
editor.putInt("position1key", spinnerIndex1)
editor.putInt("position2key", spinnerIndex2)
//editor.putString("myInput", myInput.text.toString())
//editor.putString("myResult", result.text.toString())
editor.apply()
} catch (e: Exception) {
e.printStackTrace()
}
}
override fun onNothingSelected(adapterView: AdapterView<*>) {
}
}
答案 0 :(得分：0)
首先，我建议您采用其他方法编写一些代码，以免重复做交易事务。
我不明白为什么“ firstfragment”代码为空，而在“ secondfragment”中，您首先从堆栈中弹出，然后替换某些内容？也许
activity?.onBackPressed()
您要搜索的是什么？
在您的日志中，您会收到有关SecondFragment onItemSelected的消息，从而导致问题。如果您还可以发布它的代码，将很有帮助;-）