Application Explanation of ListView and RecyclerView in Kotlin
- 2021-12-19 06:39:37
- OfStack
Write it down and read it later:
First, the layout file of item:
There is a picture and a text box inside
<?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:
Layout file:
<?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>
Adapter:
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
}
}
The rest is logical processing:
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:
Layout file:
<?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>
Adapter:
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)
}
}
Logic code:
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
}
}
The repeat function here is repeated three times, which means that there will be three ones to fifteen, which means that this recyclerView will have 45 item.
Now it slides vertically. If you want to change it to horizontal, comment out the ones in my code
//layoutManger.orientation = LinearLayoutManager.HORIZONTAL
You can realize horizontal sliding by canceling comments. If you don't dislike ugliness, you don't need to change the layout file.
Finally, there are entity classes:
class Fruit(val name : String,val image : Int) {
}
Defines 1 name to display the name and 1 image to display the picture.