Kotlin中ListView与RecyclerView的应用讲解
写下来自己以后看：
先是item的布局文件：
里边放了一个图片和一个文本框
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/linearLayout"
>
<ImageView
android:id="@+id/imageView"
android:layout_width="40dp"
android:layout_height="40dp"
android:layout_gravity="center_vertical"
/>
<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_vertical"
/>
</LinearLayout>
ListView：
布局文件：
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".ListViewActivity">
<ListView
android:id="@+id/listView"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
适配器：
class FruitAdapter(private val context: Context, private val list : List<Fruit>) : BaseAdapter() {
override fun getCount(): Int = list.size
override fun getItem(position: Int): Any = list[position]
override fun getItemId(position: Int): Long = position.toLong()
override fun getView(position: Int, convertView: View?, parent: ViewGroup?): View? {
var convertView = convertView
var holder : ViewHolder? = null
if (convertView == null){
holder = ViewHolder()
convertView = View.inflate(context,R.layout.item_list_view,null)
holder.textView = convertView.findViewById<View>(R.id.textView) as TextView
holder.imageView = convertView.findViewById<View>(R.id.imageView) as ImageView
holder.linearLayout = convertView.findViewById<View>(R.id.linearLayout) as LinearLayout
convertView.tag = holder
}else{
holder = convertView.tag as ViewHolder
}
holder.textView!!.text = list[position].name
holder.imageView!!.setImageResource(list[position].image)
holder.linearLayout!!.setOnClickListener {
Toast.makeText(context,list[position].name,Toast.LENGTH_SHORT).show()
}
return convertView
}
internal class ViewHolder{
var textView : TextView? = null
var imageView : ImageView? = null
var linearLayout : LinearLayout? = null
}
}
剩下的就是逻辑处理：
class ListViewActivity : AppCompatActivity() {
private val bean = ArrayList<Fruit>()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_list_view)
for (i in 1..100){
bean.add(Fruit(i.toString(),R.drawable.ic_launcher_foreground))
}
val adapter = FruitAdapter(this,bean)
listView.adapter = adapter
}
}
RecyclerView：
布局文件：
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".RecyclerViewActivity">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</androidx.constraintlayout.widget.ConstraintLayout>
适配器：
class FruitRecyclerViewAdapter(private val context: Context,private val list: List<Fruit>) : RecyclerView.Adapter<FruitRecyclerViewAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view : View = LayoutInflater.from(context).inflate(R.layout.item_list_view,null)
return ViewHolder(view)
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.itemView.textView.text = list[position].name
holder.itemView.imageView.setImageResource(list[position].image)
holder.itemView.linearLayout.setOnClickListener {
Toast.makeText(context,list[position].name,Toast.LENGTH_SHORT).show()
}
}
override fun getItemCount(): Int = list.size
class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
private val textView : TextView = itemView.findViewById(R.id.textView)
private val imageView : ImageView = itemView.findViewById(R.id.imageView)
private val linearLayout : LinearLayout = itemView.findViewById(R.id.linearLayout)
}
}
逻辑代码：
class RecyclerViewActivity : AppCompatActivity() {
private val bean = ArrayList<Fruit>()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_recycler_view)
repeat(3){
for (i in 1..15){
bean.add(Fruit(i.toString(),R.drawable.ic_launcher_foreground))
}
}
val layoutManger = LinearLayoutManager(this)
//layoutManger.orientation = LinearLayoutManager.HORIZONTAL
recyclerView.layoutManager = layoutManger
val adapter = FruitRecyclerViewAdapter(this,bean)
recyclerView.adapter = adapter
}
}
这里的repeat函数是重复三次，意思就是会有三个1到15，也就是此recyclerView会有45个item.
现在的是纵向滑动的，如果要改成横向的，就把我代码中的注释掉的
//layoutManger.orientation = LinearLayoutManager.HORIZONTAL
取消注释就可以实现横向滑动了，如果不嫌弃难看，布局文件就不用改。
最后是实体类：
class Fruit(val name : String,val image : Int) {
}
定义了一个name用来显示名字，定义了一个image，用来显示图片。
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