我正在开发一个可扩展的列表视图，在我创建一个奖励广告后，我希望在用户观看奖励广告后添加一个可展开的列表视图，但该应用程序会因Android监视器错误而崩溃。这是代码......
class MainActivity : Activity(),RewardedVideoAdListener {
override fun onRewardedVideoAdClosed() = Unit
override fun onRewardedVideoAdLeftApplication() = Unit
override fun onRewardedVideoAdLoaded() = Unit
override fun onRewardedVideoAdOpened() = Unit
override fun onRewarded(rewardedLiterature: RewardItem?) {
rewardedLiterature.apply {
ParentList.add("New Articles")
ParentList.reverse()
}
}
override fun onRewardedVideoStarted() = Unit
override fun onRewardedVideoAdFailedToLoad(p0: Int) {
Toast.makeText(this,"Please try again",Toast.LENGTH_SHORT).show()
}
private lateinit var childlist: MutableList<String>
private lateinit var ParentListItems: MutableMap<String, List<String>>
private lateinit var expandabilityView: ExpandableListView
private var ParentList: MutableList<String> = ArrayList()
)
private var poems = arrayOf("Five","Six","Seven")
private var LoveName = arrayOf("Eight","Nine","Ten","Eleven")
private var moreLiterature = arrayOf("ZOne","zTwo","ZThree")
private var ByDefaultMessage = arrayOf("Items Loading")
private lateinit var mRewardedVideoAd : RewardedVideoAd
init {
ParentList.add("Letters")
ParentList.add("Poems")
ParentList.add("Let's Chill!")
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
mRewardedVideoAd = MobileAds.getRewardedVideoAdInstance(this)
mRewardedVideoAd.rewardedVideoAdListener = this
loadRewardedVideoAd()
val moreContentButton = findViewById<FloatingActionButton>(R.id.moreContents)
moreContentButton.setOnClickListener{
if (mRewardedVideoAd.isLoaded) {
mRewardedVideoAd.show()
}
}
ParentListItems = LinkedHashMap()
for (HoldItem in ParentList) {
when (HoldItem) {
"Letters" -> loadChild(funnyLiterature)
"Poems" -> loadChild(poems)
"Let's Chill!" -> loadChild(LoveName)
"New Articles" -> loadChild(moreLiterature)
else -> loadChild(ByDefaultMessage)
}
ParentListItems.put(HoldItem, childlist)
}
expandabilityView = findViewById(R.id.expandableListView1)
val expListAdapter = ListAdapter(
this, ParentList, ParentListItems)
expandabilityView.setAdapter(expListAdapter)
expListAdapter.notifyDataSetChanged()
expandabilityView.setOnChildClickListener {_, _, groupPosition, childPosition, _ ->
val selected = expListAdapter.getChild(
groupPosition, childPosition) as String
val intent = Intent(this@MainActivity, DetailActivity::class.java)
when (selected) {
"ማትስ ተማሪ ለፍቅረኛዋ የፃፈችዉ ደብዳቤ" -> titleOfContent = detailContents[0]
"የህግ ተመራቂ ለፍቅረኛዉ የፃፈዉ መልእክት" -> titleOfContent = detailContents[1]
"የ‹ለምን አንተን ወደድኩህ?›ፍልስፍና" -> titleOfContent = detailContents[2]
"አጭር መልእክት" -> titleOfContent = detailContents[3]
}
private fun loadRewardedVideoAd() =
mRewardedVideoAd.loadAd("ca-app-pub-xxxxxxx", AdRequest.Builder().build())
private fun loadChild(ParentElementsName: Array<String>) {
childlist = ArrayList()
for (model in ParentElementsName)
childlist.add(model)
}
companion object {
internal var titleOfContent: String ?= null
private var detailContents = arrayOf("This","Is","a","Test")
这是适配器类 ...
class ListAdapter(private val context: Activity, private val Items: List<String>,
private val ParentListItems: Map<String, List<String>>) : BaseExpandableListAdapter() {
override fun getChild(groupPosition: Int, childPosition: Int): Any =
ParentListItems[Items[groupPosition]]!![childPosition]
override fun getChildId(groupPosition: Int, childPosition: Int): Long = childPosition.toLong()
override fun getChildView(groupPosition: Int, childPosition: Int,
isLastChild: Boolean, ListView: View?, parent: ViewGroup): View {
var myListView = ListView
val contentPosition = getChild(groupPosition, childPosition) as String
val inflater = context.layoutInflater
if (myListView == null) myListView = inflater.inflate(R.layout.child_list_item, null)
val item = myListView!!.findViewById<TextView>(R.id.textView1)
item.text = contentPosition
return myListView
}
override fun getChildrenCount(groupPosition: Int): Int =
ParentListItems[Items[groupPosition]]!!.size
override fun getGroup(groupPosition: Int): Any = Items[groupPosition]
override fun getGroupCount(): Int = Items.size
override fun getGroupId(groupPosition: Int): Long = groupPosition.toLong()
override fun getGroupView(groupPosition: Int, isExpanded: Boolean,
ListView: View?, parent: ViewGroup): View {
var myListView= ListView
val allContents = getGroup(groupPosition) as String
if (myListView == null) {
val textInflater = context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
myListView = textInflater.inflate(R.layout.parent_list_item, null)
}
val item = myListView!!.findViewById<TextView>(R.id.textView1)
item.text = allContents
return myListView
}
override fun hasStableIds(): Boolean = true
override fun isChildSelectable(groupPosition: Int, childPosition: Int): Boolean = true
}
Android Monitor表示在 getChildrenCount函数的Adapter类中找到了Kotlin NullPoint Exception。