Question

我正在尝试在我的应用中实现ExpandableListView，但它没有显示。

我仔细检查过：

正确命名和引用我的所有三种XML布局（对于ExpandableListView，列表标题和列表项），
调试以查看我的列表是否已填入prepareListdata()方法（它们是）。

我认为问题在我的ExpandableListAdapterClass中类参数listDataHeader : ArrayList<String>, listDataChild : HashMap<String, ArrayList<String>>正在变色粗糙的灰色线未使用。

如何正确地告诉我的应用程序那些等于我的活动成员变量？还是有一些我不知道的东西？

这是我的代码：

适配器

 class ExpandableListAdapter (context: Context, listDataHeader : ArrayList<String>, listDataChild : HashMap<String, ArrayList<String>>) : BaseExpandableListAdapter() {


        var listDataHeader = arrayListOf<String>() //list sub-headers

        var listDataChild = HashMap<String, List<String>>() //list sub-points

        private val inflater: LayoutInflater = LayoutInflater.from(context)

        override fun getGroup(groupPosition: Int): Any {
            return this.listDataHeader[groupPosition]
        }

        override fun isChildSelectable(p0: Int, p1: Int): Boolean {
            return true
        }

        override fun hasStableIds(): Boolean {
            return false
        }

        override fun getGroupView(groupPosition: Int, isExpanded: Boolean, convertView: View?, parent: ViewGroup?): View? {
            val headerTitle: Int = getGroup(groupPosition) as Int
            if (convertView == null) {
                inflater.inflate(R.layout.main_list_group_header, parent, false)
            }

            val listHeader = convertView?.findViewById<TextView>(R.id.list_header)
            listHeader?.setTypeface(null, Typeface.BOLD)
            listHeader?.setText(headerTitle)

            return convertView
        }

        override fun getChildrenCount(groupPosition: Int): Int {
            return this.listDataChild[this.listDataHeader[groupPosition]]!!.size
        }

        override fun getChild(groupPosition: Int, childPosition: Int): Any {
            return this.listDataChild[this.listDataHeader[groupPosition]]!![childPosition]
        }

        override fun getGroupId(groupPosition: Int): Long {
            return groupPosition.toLong()
        }

        override fun getChildView(groupPosition: Int, childPosition: Int, isLastChild: Boolean, convertView: View?, parent: ViewGroup?): View? {
            val childText: Int = getChild(groupPosition, childPosition) as Int
            if (convertView == null) {
                inflater.inflate(R.layout.main_list_item, parent, false)
            }

            val textListChild = convertView?.findViewById<TextView>(R.id.list_item)
            textListChild?.setText(childText)
            return convertView
        }

        override fun getChildId(groupPosition: Int, childPosition: Int): Long {
            return childPosition.toLong()
        }

        override fun getGroupCount(): Int {
            return this.listDataHeader.size
        }
    }

MainActivity和prepareListData（）函数的其余部分

class MainListActivity : AppCompatActivity() {

    lateinit var adapter : ExpandableListAdapter
    val listDataHeader = arrayListOf<String>()
    val listDataChild = HashMap<String, ArrayList<String>>()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_mainlistactivity)
        prepareListData()
        adapter = ExpandableListAdapter(this, listDataHeader, listDataChild)
        expandable_list.setAdapter(adapter)
    }

    private fun prepareListData() {

        listDataHeader.add("Gathering data")
        listDataHeader.add("Simulate")

        val gatheringDataChildList = arrayListOf<String>()
        gatheringDataChildList.add("Record data: video + accelerometer")

        val simulateChildList = arrayListOf<String>()
        simulateChildList.add("Driving simulator")

        listDataChild.put(listDataHeader[0], gatheringDataChildList)
        listDataChild.put(listDataHeader[1], simulateChildList)
    }

这是我想要实现的截图：

Answer 1

你们非常接近解决问题：）

 class ExpandableListAdapter (context: Context, listDataHeader : ArrayList<String>, listDataChild : HashMap<String, ArrayList<String>>) : BaseExpandableListAdapter() {


        var listDataHeader = arrayListOf<String>() //list sub-headers

        var listDataChild = HashMap<String, List<String>>() //list sub-points
        //...
}

在第一行指定构造函数参数，但根本不使用它们。（var listDataHeader是类'属性，意味着它与构造函数参数listDataHeader不同。）

你可能想要这样的东西：

 class ExpandableListAdapter (context: Context, private val listDataHeader : ArrayList<String>, private val listDataChild : HashMap<String, ArrayList<String>>) : BaseExpandableListAdapter() {
//no declaration of another fields

//rest of adapter code here...
}

请在构造函数参数之前注意private val。这些是在构造函数中直接声明的类属性。您可以在此处详细了解：https://kotlinlang.org/docs/reference/classes.html

ExpandableListView未显示在我的Activity中

1 个答案: