How to get the selected item from ListView in Kotlin? - kotlin

Question

Code Sample:
package tech.kapoor.listviewdemo
import android.content.Context
import android.graphics.Color
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.view.ViewGroup
import android.widget.BaseAdapter
import android.widget.ListView
import android.widget.TextView
import android.widget.AdapterView
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val listView = findViewById<ListView>(R.id.main_listview)
var redColor = Color.parseColor("#FF0000")
listView.setBackgroundColor(redColor)
listView.adapter = CustomAdapter(this)
}
private class CustomAdapter(context: Context): BaseAdapter() {
private val mContext: Context
init {
mContext = context
}
override fun getCount(): Int {
return 80
}
override fun getItemId(position: Int): Long {
return position.toLong()
}
override fun getItem(position: Int): Any {
return position
}
override fun getView(position: Int, view: View?, viewGroup: ViewGroup?): View {
val textView = TextView(mContext)
textView.text = "Here comes the !!"
return textView
}
}
}
I'm trying to understand list view instead of recycler view to understand basics first.
Anybody knows how we get the selected row id/index value on selection or onclick and also how to perform some action on selection of a specific row in kotlin?

Answer 1

To populate listview you must have dataset. Dataset may be any list of either datatypes like Strings or you can use list of model class. Something like this:
This is my simple list of dataset which I will use in ListView:
val data = ArrayList<TopicDTO>()
data.add(TopicDTO("1", "Info 1", true))
data.add(TopicDTO("2", "Info 2", false))
data.add(TopicDTO("3", "Info 3", true))
data.add(TopicDTO("4", "Info 4", false))
I have created one model class named TopicDTO which contains id,title and its status.
Now let's populate this into ListView:
list.adapter = ButtonListAdapter(baseContext, data)
Here is a simple adapter:
class ButtonListAdapter(//Class for rendering each ListItem
private val context: Context, private val rowItems: List<TopicDTO>) : BaseAdapter() {
override fun getCount(): Int {
return rowItems.size
}
override fun getItem(position: Int): Any {
return rowItems[position]
}
override fun getItemId(position: Int): Long {
return rowItems.indexOf(getItem(position)).toLong()
}
private inner class ViewHolder {
internal var main_text: TextView? = null //Display Name
internal var subtitle: TextView? = null //Display Description
internal var can_view_you_online: Button? = null //Button to set and display status of CanViewYouOnline flag of the class
}
override fun getView(position: Int, convertView: View?, parent: ViewGroup): View {
var convertView = convertView
var holder: ViewHolder? = null
val mInflater = context.getSystemService(Activity.LAYOUT_INFLATER_SERVICE) as LayoutInflater
holder = ViewHolder()
if (convertView == null) {
convertView = mInflater.inflate(R.layout.main_lp_view_item, null)
holder.main_text = convertView!!.findViewById(R.id.main_lp_text) as TextView
holder.subtitle = convertView.findViewById(R.id.main_lp_subtitle) as TextView
holder.can_view_you_online = convertView.findViewById(R.id.can_view_you_online) as Button
convertView.tag = holder
} else {
holder = convertView.tag as ViewHolder
}
val rowItem = rowItems[position]
val main_text: String
val subtitle: String
holder.main_text!!.text = rowItem.info
holder.subtitle!!.text = rowItem.info
if (rowItem.canViewYouOnline) {
holder.can_view_you_online!!.setBackgroundColor(context.resources.getColor(R.color.colorPrimary))
} else {
holder.can_view_you_online!!.setBackgroundColor(context.resources.getColor(R.color.colorAccent))
}
holder.can_view_you_online!!.setOnClickListener(object : View.OnClickListener {
internal var buttonClickFlag: Boolean = false
override fun onClick(v: View) { //The Onclick function allows one to click the button on the list item and set/reset the canViewYouOnline flag. It is working fine.
}
})
return convertView
}
}
Now you can get your selected item like this:
list.onItemClickListener = AdapterView.OnItemClickListener { parent, view, position, id ->
// This is your listview's selected item
val item = parent.getItemAtPosition(position) as TopicDTO
}
Hope you understands this.

Answer 2

You can use inside the getView() method something like:
view.setOnClickListener(object : View.OnClickListener {
override fun onClick(v: View?) {
//use getItem(position) to get the item
}
})
or using the lambda:
view.setOnClickListener({ v -> //use theItem(position) })
Just a tip:
I'm trying to understand list view instead of recycler view to understand basics first.
In my opinion in your projects you will use RecyclerView in 99% of the cases.

Answer 3

add OnItemClickListener in you oncreate()
listView.setOnItemClickListener{ parent, view, position, id ->
Toast.makeText(this, "You Clicked:"+" "+position,Toast.LENGTH_SHORT).show()
}
Add the array of Items in your CustomAdapter class.
class CustomAdptor(private val context: Activity): BaseAdapter() {
//Array of fruits names
var names = arrayOf("Apple", "Strawberry", "Pomegranates", "Oranges", "Watermelon", "Bananas", "Kiwi", "Tomato", "Grapes")
//Array of fruits desc
var desc = arrayOf("Malus Domestica", "Fragaria Ananassa ", "Punica Granatum", "Citrus Sinensis", "Citrullus Vulgaris", "Musa Acuminata", "Actinidia Deliciosa", "Solanum Lycopersicum", "Vitis vinifera")
//Array of fruits images
var image = intArrayOf(R.drawable.apple, R.drawable.strawberry, R.drawable.pomegranates, R.drawable.oranges, R.drawable.watermelon, R.drawable.banana, R.drawable.kiwi, R.drawable.tomato, R.drawable.grapes)
override fun getView(p0: Int, p1: View?, p2: ViewGroup?): View {
val inflater = context.layoutInflater
val view1 = inflater.inflate(R.layout.row_data,null)
val fimage = view1.findViewById(R.id.fimageView)
var fName = view1.findViewById(R.id.fName)
var fDesc = view1.findViewById(R.id.fDesc)
fimage.setImageResource(image[p0])
fName.setText(names[p0])
fDesc.setText(desc[p0])
return view1
}
override fun getItem(p0: Int): Any {
return image[p0]
}
override fun getItemId(p0: Int): Long {
return p0.toLong()
}
override fun getCount(): Int {
return image.size
}
}
You can find the whole tutorial at: listview with onItemClickListener using kotlin