因此，在完成无数教程之后，我以“正确”的方式实现了ExpandableList：Adapter然后在主活动上调用它。
我不断遇到null和non-null问题。当我尝试添加或删除它们时，有些问题说我需要/不需要空值。
许多安全通话和!!都在那里，因为Android Studio'对此大声喊叫。
这是我的适配器
class ExpandableListAdapter(
val context: Context,
val listDataHeader: List<String>,
val listHashMap: HashMap<String, List<String>>
) : BaseExpandableListAdapter() {
override fun getChild(groupPosition: Int, childPosition: Int): Any {
return listHashMap.get(listDataHeader.get(groupPosition))!!.get(childPosition); // i = Group Item , i1 = ChildIte
}
override fun getChildId(groupPosition: Int, childPosition: Int): Long {
return childPosition.toLong()
}
override fun getChildView(groupPosition: Int, childPosition: Int, isLastChild: Boolean, view: View, parent: ViewGroup?): View {
val childText = getChild(groupPosition, childPosition) as String
if (view == null) {
val inflater = this.context.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
inflater.inflate(R.layout.list_item, null)
}
val txtListChild = view.findViewById(R.id.lblListItem) as TextView
txtListChild.text = childText
return view }
override fun getChildrenCount(groupPosition: Int): Int {
return listHashMap[listDataHeader[groupPosition]]!!.size
}
override fun getGroup(groupPosition: Int): Any {
return listDataHeader[groupPosition]
}
override fun getGroupCount(): Int {
return listDataHeader.size
}
override fun getGroupId(groupPosition: Int): Long {
return groupPosition.toLong()
}
override fun getGroupView(groupPosition: Int, isExpanded: Boolean, view: View?, parent: ViewGroup?): View? {
var headerTitle = getGroup(groupPosition!!) as String
if (view == null) {
var inflater = this.context.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
inflater.inflate(R.layout.list_group, null)
}
val lblListHeader = view?.findViewById(R.id.lblListHeader) as TextView?
lblListHeader?.setTypeface(null, Typeface.BOLD)
lblListHeader?.text = headerTitle
return view
}
override fun hasStableIds(): Boolean {
return false
}
override fun isChildSelectable(groupPosition: Int, childPosition: Int): Boolean {
return true
}
}
这是我的主要活动
class GirlsActivity : AppCompatActivity() {
private var db = FirebaseFirestore.getInstance()
lateinit var listView: ExpandableListView
lateinit var listAdapter: ExpandableListAdapter
lateinit var listDataHeader: MutableList<String>
lateinit var listHash: HashMap<String, List<String>>
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_girls)
listView = girlsWodsList
initData()
listAdapter = ExpandableListAdapter(this, listDataHeader, listHash)
listView?.setAdapter(listAdapter)
}
private fun initData() {
listDataHeader = ArrayList()
listHash = HashMap()
listDataHeader?.add("EDMTDev")
listDataHeader?.add("Android")
listDataHeader?.add("Xamarin")
listDataHeader?.add("UWP")
val edmtDev = ArrayList<String>()
edmtDev.add("This is Expandable ListView")
val androidStudio = ArrayList<String>()
androidStudio.add("Expandable ListView")
androidStudio.add("Google Map")
androidStudio.add("Chat Application")
androidStudio.add("Firebase ")
val xamarin = ArrayList<String>()
xamarin.add("Xamarin Expandable ListView")
xamarin.add("Xamarin Google Map")
xamarin.add("Xamarin Chat Application")
xamarin.add("Xamarin Firebase ")
val uwp = ArrayList<String>()
uwp.add("UWP Expandable ListView")
uwp.add("UWP Google Map")
uwp.add("UWP Chat Application")
uwp.add("UWP Firebase ")
listHash!![listDataHeader!!.get(0)] = edmtDev
listHash!![listDataHeader!!.get(1)] = androidStudio
listHash!![listDataHeader!!.get(2)] = xamarin
listHash!![listDataHeader!!.get(3)] = uwp
}
}
有什么想法吗？
由于
logcat的
E/AndroidRuntime: FATAL EXCEPTION: main Process: com.reecreate.woderator2, PID: 9201 java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.View.getImportantForAccessibility()' on a null object reference
at android.widget.AbsListView.obtainView(AbsListView.java:2380)
at android.widget.ListView.measureHeightOfChildren(ListView.java:1326)
at android.widget.ListView.onMeasure(ListView.java:1233)
at android.view.View.measure(View.java:19857)
at android.support.constraint.ConstraintLayout.internalMeasureChildren(ConstraintLayout.java:1054)
at android.support.constraint.ConstraintLayout.onMeasure(ConstraintLayout.java:1111)
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.support.v7.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:400)
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)
答案 0 :(得分：0)
我不知道ExpandableListAdapter有什么问题，但我知道，使用Epoxy会更好 - https://github.com/airbnb/epoxy