当在kotlin表达不按预期工作
问题描述:
我不知道有人能帮我解决这个问题代表When Expression
特定的代码块?当在kotlin表达不按预期工作
我有2个活动之间连接:
第一个活动是MainActivity.kt
和第二活性Main2Activity.kt
,在第二活动我得到问题用于施加当与特定的代码块的表达内Main2Activity class
因为我想通过专用适配器内Main2Activity class
在MainActivity class
图像点击喜欢传球ADAPTER_TYPE_2
当点击图像b
中的第一个活动类,以及它的主要问题始终是应用的一个代码块内Main2Activity class
注:第一次活动中使用GridView
和第二届活动中使用ListView
和我有内部Main2Activity.kt
2个适配器和我使用enum
包括在第二活动
这里每个适配器的是MainActivity.kt
class MainActivity : AppCompatActivity() {
var adapter:FoodAdapter?=null
var listOfFoods =ArrayList<Food>()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(layout.activity_main)
// load foods
listOfFoods.add(Food("Coffee"," Coffee preparation is", a))
listOfFoods.add(Food("Coffee"," Coffee preparation is", b))
listOfFoods.add(Food("Coffee"," Coffee preparation is", c))
listOfFoods.add(Food("Coffee"," Coffee preparation is", d))
adapter= FoodAdapter(this,listOfFoods)
gvListFood.adapter =adapter
}
class FoodAdapter: BaseAdapter {
var listOfFood= ArrayList<Food>()
var context: Context?=null
constructor(context:Context,listOfFood:ArrayList<Food>):super(){
this.context=context
this.listOfFood=listOfFood
}
override fun getView(p0: Int, p1: View?, p2: ViewGroup?): View? {
val food = this.listOfFood[p0]
var inflator = context!!.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
var foodView= inflator.inflate(layout.food_ticket,null)
foodView.ivFoodImage.setImageResource(food.image!!)
foodView.ivFoodImage.setOnClickListener {
val intent = Intent(context, Main2Activity::class.java)
when (foodView) {
foodView.ivFoodImage.also { a } ->
intent.putExtra(Main2Activity.EXTRA_ADAPTER_MODE, AdapterType.ADAPTER_TYPE_1.ordinal) {
intent.putExtra("name", food.name!!)
intent.putExtra("des", food.des!!)
intent.putExtra("image", food.image!!)
context!!.startActivity(intent)
}
foodView.ivFoodImage.also { b } ->
intent.putExtra(Main2Activity.EXTRA_ADAPTER_MODE, AdapterType.ADAPTER_TYPE_2.ordinal) {
intent.putExtra("name", food.name!!)
intent.putExtra("des", food.des!!)
intent.putExtra("image", food.image!!)
context!!.startActivity(intent)
}
}
}
return foodView
}
override fun getItem(p0: Int): Any {
return listOfFood[p0]
}
override fun getItemId(p0: Int): Long {
return p0.toLong()
}
override fun getCount(): Int {
return listOfFood.size
}
}
}
这里是第一个活动food_ticket.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="63pt"
android:layout_height="wrap_content"
android:background="@color/gray"
android:orientation="vertical"
android:padding="3pt">
<LinearLayout
android:gravity="center"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/background"
android:orientation="vertical">
<ImageView
android:id="@+id/ivFoodImage"
android:layout_width="50pt"
android:layout_height="50pt"
app:srcCompat="@drawable/c" />
<TextView
android:id="@+id/tvName"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:text="Coffe"
android:textSize="20sp" />
</LinearLayout>
</LinearLayout>
这里是一个Main2Activity.kt
class Main2Activity : AppCompatActivity() {
companion object {
val EXTRA_ADAPTER_MODE = "extra_adapter_mode"
}
var adapter1: FoodAdapter1?= null
var adapter2: FoodAdapter2? = null
var listOfFoods2 = ArrayList<Food>()
var listOfFoods3 = ArrayList<Food>()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(activity_main2)
val bundle = intent.extras
val adapterTypeOrdinal = intent.getIntExtra(EXTRA_ADAPTER_MODE, 0) // 0 is the default value
val type = AdapterType.fromOrdinal(ordinal = adapterTypeOrdinal)
val name = bundle.getString("name")
val des = bundle.getString("des")
val image = bundle.getInt("image")
ivFoodImage2?.let {
it.setImageResource(image)
}
tvName2?.let {
it.text = name
}
tvDes2?.let {
it.text = des
}
// load foods2
listOfFoods2.add(Food("Coffee", " Coffee1 preparation is", R.drawable.a))
listOfFoods2.add(Food("Coffee", " Coffee2 preparation is", R.drawable.b))
// load foods3
listOfFoods3.add(Food("Coffee", " Coffee3 preparation is", R.drawable.c))
listOfFoods3.add(Food("Coffee", " Coffee4 preparation is", R.drawable.d))
//var ADAPTER_TYPE_1 = adapter1
//var ADAPTER_TYPE_2 = adapter2
lvFoods2.adapter = when (type) {
AdapterType.ADAPTER_TYPE_1-> FoodAdapter1(listOfFoods2, this)
AdapterType.ADAPTER_TYPE_2-> FoodAdapter2(listOfFoods3, this)
else -> lvFoods2.adapter
}
}
class FoodAdapter1 : BaseAdapter{
var context: Context? = null
var listOfFoodsLocal2 = ArrayList<Food>()
constructor(listOfFoods2: ArrayList<Food>, context: Context) : super() {
this.listOfFoodsLocal2 = listOfFoods2
this.context = context
}
override fun getView(p0: Int, foodView: View?, p2: ViewGroup?): View {
val food = this.listOfFoodsLocal2[p0]
var inflator = context!!.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
val foodView = inflator.inflate(food_ticket2, null)
foodView.ivFoodImage2?.let {
it.setImageResource(food.image!!)
}
foodView.tvName2?.let {
it.text = food.name!!
}
foodView.tvDes2?.let {
it.text = food.des!!
}
foodView.ivFoodImage2.setOnClickListener {
//move to next
val intent = Intent(context, FoodDetails::class.java)
intent.putExtra("name", food.name!!)
intent.putExtra("des", food.des!!)
intent.putExtra("image", food.image!!)
context!!.startActivity(intent)
}
return foodView
}
override fun getItem(p0: Int): Any {
return listOfFoodsLocal2[p0]
}
override fun getItemId(p0: Int): Long {
return p0.toLong()
}
override fun getCount(): Int {
return listOfFoodsLocal2.size
}
}
class FoodAdapter2 : BaseAdapter {
var context: Context? = null
var listOfFoodsLocal3 = ArrayList<Food>()
constructor(listOfFoods3: ArrayList<Food>, context: Context) : super() {
this.listOfFoodsLocal3 = listOfFoods3
this.context = context
}
override fun getView(p0: Int, p1: View?, p2: ViewGroup?): View {
val food = this.listOfFoodsLocal3[p0]
var inflator = context!!.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
val foodView = inflator.inflate(food_ticket2, null)
foodView.ivFoodImage2?.let {
it.setImageResource(food.image!!)
}
foodView.tvName2?.let {
it.text = food.name!!
}
foodView.tvDes2?.let {
it.text = food.des!!
}
foodView.ivFoodImage2.setOnClickListener {
//move to next
val intent = Intent(context, FoodDetails::class.java)
intent.putExtra("name", food.name!!)
intent.putExtra("des", food.des!!)
intent.putExtra("image", food.image!!)
context!!.startActivity(intent)
}
return foodView
}
override fun getItem(p0: Int): Any {
return listOfFoodsLocal3[p0]
}
override fun getItemId(p0: Int): Long {
return p0.toLong()
}
override fun getCount(): Int {
return listOfFoodsLocal3.size
}
}
}
activity_main2.xml对于第二活动
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:background="@color/gray"
android:orientation="vertical"
tools:context="com.marzadmz.startup.Main2Activity">
<ListView
android:id="@+id/lvFoods2"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/gray" />
</LinearLayout>
AdapterType.kt用于枚举类
enum class AdapterType {
ADAPTER_TYPE_1,
ADAPTER_TYPE_2;
companion object {
fun fromOrdinal(ordinal: Int): AdapterType? {
return AdapterType.values().firstOrNull { it.ordinal == ordinal }
}
}
}
答
实现是关闭
var ADAPTER_TYPE_1 = adapter1
var ADAPTER_TYPE_2 = adapter2
lvFoods2.adapter = when (lvFoods2.adapter) {
ADAPTER_TYPE_1 -> FoodAdapter1(listOfFoods2, this).also { ADAPTER_TYPE_1 = it }
ADAPTER_TYPE_2 -> FoodAdapter2(listOfFoods3, this).also { ADAPTER_TYPE_2 = it }
else -> lvFoods2.adapter
}
adapter1
的变量为空以及lvFoods2.adapter
。从我如何理解你的代码,它应该看起来像:
lvFoods2.adapter = when (type) {
ADAPTER_TYPE_1 -> FoodAdapter1(listOfFoods2, this)
ADAPTER_TYPE_2 -> FoodAdapter2(listOfFoods3, this)
else -> lvFoods2.adapter
}
非常感谢你对@tynn回答,其实我没有,但它显示我此消息 '不相容类型:??Main2Activity.FoodAdapter1和适配器类型'和我的问题是通过添加图像更新'null错误'你可以检查它 – andios
你也必须删除'var ADAPTER_TYPE_x'。 – tynn
我的问题是更新的,我做了,但它仍然是相同的,请你可以检查我的第二张图片@tynn – andios