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法律研究如何使用 Kotlin 创建可扩展的 ListView？
此示例演示了如何使用 Kotlin 创建可扩展的 ListView。
步骤 1 - 在 Android Studio 中创建一个新项目，转到文件？新建项目并填写所有必要信息以创建新项目。
步骤 2 - 将以下代码添加到 res/layout/activity_main.xml。
示例
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:padding="4dp" tools:context=".MainActivity"> <ExpandableListView android:id="@+id/expendableList" android:layout_width="match_parent" android:layout_height="match_parent" android:divider="@android:color/background_light" android:dividerHeight="0.5dp" /> </RelativeLayout>
步骤 3 - 创建一个新的 Kotlin 类 CustomExpandableListAdapter.kt 并添加以下代码 -
示例
import android.content.Context
import android.graphics.Typeface
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.BaseExpandableListAdapter
import android.widget.TextView
import java.util.HashMap
class CustomExpandableListAdapter internal constructor(
private val context: Context,
private val titleList: List<String>,
private val dataList: HashMap<String, List<String>>
) : BaseExpandableListAdapter() {
override fun getChild(listPosition: Int, expandedListPosition: Int): Any {
return this.dataList[this.titleList[listPosition]]!![expandedListPosition]
}
override fun getChildId(listPosition: Int, expandedListPosition: Int): Long {
return expandedListPosition.toLong()
}
override fun getChildView(
listPosition: Int,
expandedListPosition: Int,
isLastChild: Boolean,
convertView: View?,
parent: ViewGroup
): View {
var convertView = convertView
val expandedListText = getChild(listPosition, expandedListPosition) as String
if (convertView == null) {
val layoutInflater =
this.context.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
convertView = layoutInflater.inflate(R.layout.list_item, null)
}
val expandedListTextView = convertView!!.findViewById<TextView>(R.id.listView)
expandedListTextView.text = expandedListText
return convertView
}
override fun getChildrenCount(listPosition: Int): Int {
return this.dataList[this.titleList[listPosition]]!!.size
}
override fun getGroup(listPosition: Int): Any {
return this.titleList[listPosition]
}
override fun getGroupCount(): Int {
return this.titleList.size
}
override fun getGroupId(listPosition: Int): Long {
return listPosition.toLong()
}
override fun getGroupView(
listPosition: Int,
isExpanded: Boolean,
convertView: View?,
parent: ViewGroup
): View {
var convertView = convertView
val listTitle = getGroup(listPosition) as String
if (convertView == null) {
val layoutInflater =
this.context.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
convertView = layoutInflater.inflate(R.layout.list_item, null)
}
val listTitleTextView = convertView!!.findViewById<TextView>(R.id.listView)
istTitleTextView.setTypeface(null, Typeface.BOLD)
listTitleTextView.text = listTitle
return convertView
}
override fun hasStableIds(): Boolean {
return false
}
override fun isChildSelectable(listPosition: Int, expandedListPosition: Int): Boolean {
return true
}
}步骤 4 - 创建一个新的类 ExpandableListData.kt 并添加以下代码 -
示例
import java.util.*
internal object ExpandableListData {
val data: HashMap<String, List<String>>
get() {
val expandableListDetail =
HashMap<String, List<String>>()
val myFavCricketPlayers: MutableList<String> =
ArrayList()
myFavCricketPlayers.add("MS.Dhoni")
myFavCricketPlayers.add("Sehwag")
myFavCricketPlayers.add("Shane Watson")
myFavCricketPlayers.add("Ricky Ponting")
myFavCricketPlayers.add("Shahid Afridi")
val myFavFootballPlayers: MutableList<String> = ArrayList()
myFavFootballPlayers.add("Cristiano Ronaldo")
myFavFootballPlayers.add("Lionel Messi")
myFavFootballPlayers.add("Gareth Bale")
myFavFootballPlayers.add("Neymar JR")
myFavFootballPlayers.add("David de Gea")
val myFavTennisPlayers: MutableList<String> = ArrayList()
myFavTennisPlayers.add("Roger Federer")
myFavTennisPlayers.add("Rafael Nadal")
myFavTennisPlayers.add("Andy Murray")
myFavTennisPlayers.add("Novak Jokovic")
myFavTennisPlayers.add("Sania Mirza")
expandableListDetail["CRICKET PLAYERS"] = myFavCricketPlayers
expandableListDetail["FOOTBALL PLAYERS"] = myFavFootballPlayers
expandableListDetail["TENNIS PLAYERS"] = myFavTennisPlayers
return expandableListDetail
}
}步骤 5 - 将以下代码添加到 src/MainActivity.kt
示例
import android.os.Bundle
import android.widget.ExpandableListAdapter
import android.widget.ExpandableListView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import app.com.q14.ExpandableListData.data
class MainActivity : AppCompatActivity() {
private var expandableListView: ExpandableListView? = null
private var adapter: ExpandableListAdapter? = null
private var titleList: List<String>? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
title = "KotlinApp"
expandableListView = findViewById(R.id.expendableList)
if (expandableListView != null) {
val listData = data
titleList = ArrayList(listData.keys)
adapter = CustomExpandableListAdapter(this, titleList as ArrayList<String>, listData)
expandableListView!!.setAdapter(adapter)
expandableListView!!.setOnGroupExpandListener { groupPosition ->
Toast.makeText(
applicationContext,
(titleList as ArrayList<String>)[groupPosition] + " List Expanded.",
Toast.LENGTH_SHORT
).show()
}
expandableListView!!.setOnGroupCollapseListener { groupPosition ->
Toast.makeText(
applicationContext,
(titleList as ArrayList<String>)[groupPosition] + " List Collapsed.",
Toast.LENGTH_SHORT
).show()
}
expandableListView!!.setOnChildClickListener { _, _, groupPosition, childPosition, _ ->
Toast.makeText(
applicationContext,
"Clicked: " + (titleList as ArrayList<String>)[groupPosition] + " -> " + listData[(
titleList as
ArrayList<String>
)
[groupPosition]]!!.get(
childPosition
),
Toast.LENGTH_SHORT
).show()
false
}
}
}
}步骤 6 - 创建一个新的布局资源 (list_item.xml) 并添加以下代码。
示例
<?xml version="1.0" encoding="utf-8"?> <LinearLayout mlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <TextView android:id="@+id/listView" android:layout_width="match_parent" android:layout_height="wrap_content" android:paddingStart="?android:attr/expandableListPreferredItemPaddingLeft" android:paddingTop="10dp" android:paddingBottom="10dp" android:textColor="@android:color/black" /> </LinearLayout>
步骤 7 - 将以下代码添加到 androidManifest.xml
示例
<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.q13"> <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round" android:supportsRtl="true" android:theme="@style/AppTheme"> <activity android:name=".MainActivity"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest>
让我们尝试运行您的应用程序。我假设您已将您的实际 Android 移动设备连接到您的电脑。要从 Android Studio 运行应用程序，请打开您的一个项目活动文件，然后点击工具栏上的运行图标
。选择您的移动设备作为选项，然后检查您的移动设备，它将显示您的默认屏幕
更新于: 2020年5月23日
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