Kotlin RecyclerView how select first list item after activity load? tried (code below) failed :( - kotlin

Question

I can select 1st item in RecyclerView (working code below, click on "email" FAB button - boom! 1st selected)
However I cannot get 1st RecyclerView click in code when app starts,
I looked for override fun onViewCreated() but nothing like it for activity,
where can I call selectFirstOnList() after activity & recyclerview fully rendered?
what event fires on activity fully rendered/loaded?
or is my noob kotlin way of thinking flawed? its 99.9% working :(
Thanks in advance for any help :)
SOLUTIUON (code edited to bottom of this post will replace code in ItemListActivity.kt)
postdelay select first (you can see from original code I'd already tried something like this!) PHEW! hope this helps someone :)
ItemListActivity.kt
package ie.dpsystems.asm.list
import android.content.Context
import android.content.Intent
import android.content.res.Configuration
import android.graphics.Color
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.recyclerview.widget.RecyclerView
import com.google.android.material.snackbar.Snackbar
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import android.widget.Toast
import ie.dpsystems.asm.R
import ie.dpsystems.asm.data.Orientation
import ie.dpsystems.asm.data.State
import ie.dpsystems.asm.data.State.Companion.trackLog
import ie.dpsystems.asm.detail.ItemDetailActivity
import ie.dpsystems.asm.detail.ItemDetailFragment
import kotlinx.android.synthetic.main.activity_item_list.*
import kotlinx.android.synthetic.main.item_list_content.view.*
import kotlinx.android.synthetic.main.item_list.*
import android.os.Handler
class ItemListActivity : AppCompatActivity() {
private var twoPane: Boolean = false
private var showToastEvents: Boolean = true
private fun uiIsTwoPane():Boolean{
try{
if (item_detail_container != null) {
// The detail container view will be present only in the
// large-screen layouts (res/values-w900dp).
// If this view is present, then the
// activity should be in two-pane mode.
return true
}
}catch(e:Exception)
{
Toast.makeText(this,"E: ${e.toString()}",Toast.LENGTH_SHORT).show()
}
return false
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
trackLog(this,"onCreate()")
setContentView(R.layout.activity_item_list)
twoPane = uiIsTwoPane()
setSupportActionBar(toolbar)
toolbar.title = title
fab.setOnClickListener { view -> onListFabClick(view) }
setupRecyclerView(recycleview_list)
refreshUI()
}
private fun setupRecyclerView(recyclerView: RecyclerView) {
trackLog(this,"setupRecyclerView()")
State.dataRows = ListContent.ITEMS
recyclerView.adapter = SimpleItemRecyclerViewAdapter(
this,
twoPane,
this
)
var recycleViewUI = recycleview_list
postAndNotifyAdapter(Handler(), recycleViewUI)
}
override fun onConfigurationChanged(newConfig: Configuration?) {
super.onConfigurationChanged(newConfig)
trackLog(this,"onConfigurationChanged()")
}
override fun onStart() {
super.onStart()
trackLog(this,"onStart()")
}
override fun onResume() {
super.onResume()
trackLog(this,"onResume() A")
checkOrientationChange()
refreshUI()
trackLog(this,"onResume() B")
}
private fun checkOrientationChange() {
trackLog(this,"checkOrientationChange()")
if (State.lastOrientation != null) {
val thisOrientation = if (twoPane) Orientation.landscape else Orientation.portrate
if (thisOrientation != State.lastOrientation) {
putDetailFragmentOnDetailFragmentHolder()
}
}
}
private fun putDetailFragmentOnDetailFragmentHolder() {
trackLog(this,"putDetailFragmentOnDetailFragmentHolder()")
if(item_detail_container!=null){
val fragment = ItemDetailFragment() //val fragment = ItemDetailFragment().apply {arguments = Bundle().apply {putInt("SOME UNIQUE TAG", selectedItemUniqueID)}}
val container = item_detail_container
container.removeAllViewsInLayout()
supportFragmentManager.beginTransaction().replace(R.id.item_detail_container, fragment).commit()
}
}
override fun onPause() {
super.onPause()
trackLog(this,"onPause()")
}
override fun onStop() {
super.onStop()
trackLog(this,"onStop()")
}
class SimpleItemRecyclerViewAdapter( private val parentActivity: ItemListActivity
,private val twoPane: Boolean
,private val context: Context //private val context = parentActivity.applicationContext
) : RecyclerView.Adapter<SimpleItemRecyclerViewAdapter.ViewHolder>() {
override fun getItemCount(): Int {
return State.dataRows.size
}
override fun onBindViewHolder(recyclerViewRow: ViewHolder, position: Int) {
trackLog(context, "onBindViewHolder()")
val dataThisRow = State.dataRows[position]
dataThisRow.listRowIndex = position
setDataToRecyclerRow(recyclerViewRow, dataThisRow)
recyclerViewRow.itemView.setOnClickListener {
onListItemClick(dataThisRow.uniqueID)
}
if (dataThisRow.uniqueID == State.selectedListItemUniqueId) {
recyclerViewRow.idRow.setBackgroundColor(Color.parseColor("#009688"))
} else {
recyclerViewRow.idRow.setBackgroundColor(Color.WHITE)
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
trackLog(context, "onCreateViewHolder()")
val view = LayoutInflater.from(parent.context)
.inflate(R.layout.item_list_content, parent, false)
return ViewHolder(view, 1)
}
override fun onViewAttachedToWindow(holder: ViewHolder) {
super.onViewAttachedToWindow(holder)
trackLog(context, "onViewAttachedToWindow()")
}
inner class ViewHolder(itemView: View, position: Int) : RecyclerView.ViewHolder(itemView) {
val idView: TextView = itemView.id_text
val contentView: TextView = itemView.content
val idRow = itemView.id_row_linear_layout
}
private fun setDataToRecyclerRow(recyclerViewRow: ViewHolder, data: ListContent.ListItem) {
trackLog(context, "setDataToRecyclerRow(id: ${data.id})")
recyclerViewRow.idView.text = data.id
recyclerViewRow.contentView.text = data.itemTitle
recyclerViewRow.itemView.tag = data
}
private fun onListItemClick(selectedItemUniqueID: Int) {
trackLog(context, "onListItemClick($selectedItemUniqueID)")
State.selectedListItemUniqueId = selectedItemUniqueID
if (twoPane) {
State.lastOrientation = Orientation.landscape
putDetailFragmentOnDetailActivity()
} else {
State.lastOrientation = Orientation.portrate
launchDetailActivity()
}
notifyDataSetChanged()
}
private fun launchDetailActivity() {
trackLog(context, "launchDetailActivity()")
val intent = Intent(
context,
ItemDetailActivity::class.java
) //val intent = Intent(context, ItemDetailActivity::class.java).apply {putExtra(ItemDetailFragment.ARG_ITEM_ID, selectedItemUniqueID)}
context.startActivity(intent)
}
private fun putDetailFragmentOnDetailActivity() {
trackLog(context, "putDetailFragmentOnDetailFragmentHolder()")
val fragment =
ItemDetailFragment() //val fragment = ItemDetailFragment().apply {arguments = Bundle().apply {putInt("SOME UNIQUE TAG", selectedItemUniqueID)}}
val container = parentActivity.item_detail_container
container.removeAllViewsInLayout()
parentActivity.supportFragmentManager.beginTransaction()
.replace(R.id.item_detail_container, fragment).commit()
}
}
private fun onListFabClick(view: View) {
trackLog(this, "onListFabClick()")
selectFirstOnList()
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show()
}
private fun refreshUI() {
trackLog(this, "refreshUI()")
var recycleViewUI = recycleview_list
if (State.selectedListItemUniqueId == null) {
selectFirstOnList()
} else {
val selectedListItem: ListContent.ListItem? =
State.findDataRowByUniqueId(State.selectedListItemUniqueId)
if (selectedListItem == null) {
selectFirstOnList()
recycleViewUI.findViewHolderForAdapterPosition(0)?.itemView?.performClick()
} else {
recycleViewUI.getLayoutManager()
?.scrollToPosition(selectedListItem.listRowIndex)
}
}
}
private fun selectFirstOnList() {
trackLog(this, "selectFirstOnList()")
if (twoPane) {
var recycleViewUI = recycleview_list
//recycleViewUI.getLayoutManager()?.scrollToPosition(0)
recycleViewUI.findViewHolderForAdapterPosition(0)?.itemView?.performClick()
}
}
protected fun postAndNotifyAdapter(handler: Handler, recyclerView: RecyclerView) {
trackLog(this, "postAndNotifyAdapter()")
/*
handler.post(Runnable {
if (!recyclerView.isComputingLayout) {
// This will call first item by calling "performClick()" of view.
(recyclerView.findViewHolderForLayoutPosition(0) as RecyclerView.ViewHolder).itemView.performClick()
} else {
postAndNotifyAdapter(handler, recyclerView) //, adapter
}
})
*/
}
}
class State (hold selected on screen rotation/activity changes)
import android.content.Context
import android.util.Log
import android.widget.Toast
import ie.dpsystems.asm.list.ListContent
import java.util.ArrayList
enum class Orientation { portrate, landscape }
class State {
companion object {
public var selectedListItemUniqueId:Int? = null
public var dataRows: MutableList<ListContent.ListItem> = ArrayList()
public var lastOrientation:Orientation? = null
public fun findDataRowByUniqueId(uniqueID:Int?):ListContent.ListItem?{
if(uniqueID==null) return null
return State.dataRows.find { it.uniqueID == uniqueID}
}
public fun trackLog(context: Context, text:String){
//Toast.makeText(context,text, Toast.LENGTH_LONG).show()
Log.d("track",text)
}
}
}
src/main/res/layout-w900dp/item_list.xml (2 pane for tablet)
<?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"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="16dp"
android:layout_marginRight="16dp"
android:baselineAligned="false"
android:divider="?android:attr/dividerHorizontal"
android:orientation="horizontal"
android:showDividers="middle"
tools:context=".list.ItemListActivity">
<!--
This layout is a two-pane layout for list / detail
-->
<androidx.recyclerview.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/recycleview_list"
android:name="ie.dpsystems.asm.ItemListFragment"
android:layout_width="#dimen/item_width"
android:layout_height="match_parent"
android:layout_marginLeft="16dp"
android:layout_marginRight="16dp"
app:layoutManager="LinearLayoutManager"
tools:context="ie.dpsystems.asm.list.ItemListActivity"
tools:listitem="#layout/item_list_content" />
<FrameLayout
android:id="#+id/item_detail_container"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="3" />
</LinearLayout>
item_list_content.xml (RecyclerView per row layout)
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/id_row_linear_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<TextView
android:id="#+id/id_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="#dimen/text_margin"
android:textAppearance="?attr/textAppearanceListItem" />
<TextView
android:id="#+id/content"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="#dimen/text_margin"
android:textAppearance="?attr/textAppearanceListItem" />
</LinearLayout>
object ListContent (to put fake data into list during development)
import java.util.ArrayList
import java.util.HashMap
/**
* Helper class for providing sample itemTitle for user interfaces created by
* Android template wizards.
*
* TODO: Replace all uses of this class before publishing your app.
*/
object ListContent {
/**
* An array of sample (dummy) items.
*/
val ITEMS: MutableList<ListItem> = ArrayList()
/**
* A map of sample (dummy) items, by ID.
*/
val ITEM_MAP: MutableMap<String, ListItem> = HashMap()
private val COUNT = 25
init {
// Add some sample items.
for (i in 1..COUNT) {
addItem(fakeGetRecordFromSqlite(i))
}
}
private fun addItem(item: ListItem) {
ITEMS.add(item)
ITEM_MAP.put(item.id, item)
}
private fun fakeGetRecordFromSqlite(position: Int): ListItem {
return ListItem(position, -1, position.toString(), "Item " + position, fakeGetRecordCollectionFromSqlite(position))
}
private fun fakeGetRecordCollectionFromSqlite(position: Int): String {
val builder = StringBuilder()
builder.append("Details about Item: ").append(position)
for (i in 0..position - 1) {
builder.append("\nMore details information here.")
}
return builder.toString()
}
/**
* A dummy item representing a piece of itemTitle.
*/
data class ListItem(val uniqueID:Int, var listRowIndex:Int, val id: String, val itemTitle: String, val details: String) {
override fun toString(): String = itemTitle
}
}
class ItemDetailFragment (display details in detail fragment)
import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import ie.dpsystems.asm.R
import ie.dpsystems.asm.data.State
import ie.dpsystems.asm.list.ListContent
import kotlinx.android.synthetic.main.activity_item_detail.*
import kotlinx.android.synthetic.main.item_detail.view.*
/**
* A fragment representing a single Item detail screen.
* This fragment is either contained in a [ItemListActivity]
* in two-pane mode (on tablets) or a [ItemDetailActivity]
* on handsets.
*/
class ItemDetailFragment : Fragment() {
/**
* The dummy itemTitle this fragment is presenting.
*/
private var item: ListContent.ListItem? = null
private var selectedItemUniqueID:Int? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
//arguments?.let { if (it.containsKey(ARG_ITEM_ID)) {val uniqueID = it.getInt(ARG_ITEM_ID)}}
item = State.findDataRowByUniqueId(State.selectedListItemUniqueId)
activity?.toolbar_layout?.title = item?.itemTitle
}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,savedInstanceState: Bundle?): View? {
val rootView = inflater.inflate(R.layout.item_detail, container, false)
item?.let {rootView.item_detail.text = it.details}
return rootView
}
}
class ItemDetailActivity (for single pane screen size devices)
import android.content.Intent
import android.os.Bundle
import com.google.android.material.snackbar.Snackbar
import androidx.appcompat.app.AppCompatActivity
import androidx.core.app.NavUtils
import android.view.MenuItem
import android.view.View
import ie.dpsystems.asm.list.ItemListActivity
import ie.dpsystems.asm.R
import kotlinx.android.synthetic.main.activity_item_detail.*
import kotlinx.android.synthetic.main.activity_item_detail.fab
/**
* An activity representing a single Item detail screen. This
* activity is only used on narrow width devices. On tablet-size devices,
* item details are presented side-by-side with a list of items
* in a [ItemListActivity].
*/
class ItemDetailActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_item_detail)
setSupportActionBar(detail_toolbar)
fab.setOnClickListener { view -> onListFabClick(view) }
supportActionBar?.setDisplayHomeAsUpEnabled(true) // Show the Up button in the action bar.
putDetailFragmentOnDetailActivity(savedInstanceState)
}
private fun putDetailFragmentOnDetailActivity(savedInstanceState: Bundle?){ // Create the detail fragment and add it to the activity using a fragment transaction.
// savedInstanceState is non-null when there is fragment state
// saved from previous configurations of this activity
// (e.g. when rotating the screen from portrait to landscape).
// In this case, the fragment will automatically be re-added
// to its container so we don't need to manually add it.
// For more information, see the Fragments API guide at:
// http://developer.android.com/guide/components/fragments.html
if (savedInstanceState == null) {
val fragment = ItemDetailFragment() //val fragment = ItemDetailFragment().apply {arguments = Bundle().apply {putString("SOME UNIQUE TAG",intent.getStringExtra("SOME UNIQUE TAG"))}}
supportFragmentManager.beginTransaction().add(R.id.item_detail_container, fragment).commit()
}
}
private fun onListFabClick(view: View?) {
if(view!=null) Snackbar.make(view, "Replace with your own detail action", Snackbar.LENGTH_LONG).setAction("Action", null).show()
}
override fun onOptionsItemSelected(item: MenuItem) =
when (item.itemId) {
android.R.id.home -> {
// This ID represents the Home or Up button. In the case of this
// activity, the Up button is shown. Use NavUtils to allow users
// to navigate up one level in the application structure. For
// more details, see the Navigation pattern on Android Design:
//
// http://developer.android.com/design/patterns/navigation.html#up-vs-back
NavUtils.navigateUpTo(this, Intent(this, ItemListActivity::class.java))
true
}
else -> super.onOptionsItemSelected(item)
}
}
SOLUTIUON
postdelay select first (you can see from original code I'd already tried something like this!) PHEW! hope this helps someone :)
protected fun postAndNotifyAdapter(handler: Handler, recyclerView: RecyclerView) {
trackLog(this, "postAndNotifyAdapter() ${State.selectedListItemUniqueId}")
if (twoPane && State.selectedListItemUniqueId==null) {
Handler().postDelayed({
if (!recyclerView.isComputingLayout) {
trackLog(this, "postAndNotifyAdapter() !recyclerView.isComputingLayout ${State.selectedListItemUniqueId}")
selectFirstOnList()
} else {
postAndNotifyAdapter(handler, recyclerView) //, adapter
}
}, 1000)
}
}

Answer 1

I've edited my original post above to be complete with answer!

Answer 2

I recommend you use an interface to notify when recyclerview is done rendering it's items.
How to know when the RecyclerView has finished laying down the items?