Develop Reference

All intent's extras are null while starting a new activity

This is an application with a list of dogs and information about the dog.
I'm trying to run a DetailActivity that contains information about a dog. It is launched after clicking the Show Details button, which has a setOnClickListener and runs the Intent, passing the name, age, hobby and other parameters of the dog to the running DetailActivity. But when I try to take those parameters in the DetailActivity code, they all equal null.
It's actually very simple and I've done the same thing in google course codelab before (now I decided to practice a bit) and I repeat everything as it's written there, but I don't understand what I'm doing wrong.
I'll insert the DetailActivity and DogCardAdapter code below. You can also see all the code at this link on GitHub: https://github.com/theMagusDev/DogglersApp
DetailActivity.kt:
import android.os.Bundle
import android.util.Log
import androidx.appcompat.app.AppCompatActivity
import com.example.dogglers.databinding.ActivityDetailBinding
class DetailActivity() : AppCompatActivity() {
private lateinit var binding: ActivityDetailBinding
private val TAG = "DetailActivity"
companion object {
const val DOG_IMAGE = "dogImage"
const val DOG_NAME = "dogName"
const val DOG_AGE = "dogAge"
const val DOG_HOBBIES = "dogHobbies"
const val DOG_SEX = "dogSex"
}
val dogImageResourceId = intent?.extras?.getString(DOG_IMAGE)
val dogName = intent?.extras?.getString(DOG_NAME)
val dogAge = intent?.extras?.getString(DOG_AGE)
val dogHobbies = intent?.extras?.getString(DOG_HOBBIES)
val dogSex = intent?.extras?.getString(DOG_SEX)
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
// Setup view binding
binding = ActivityDetailBinding.inflate(layoutInflater)
setContentView(binding.root)
val heOrShe: String = when(dogSex){
"male" -> "He"
else -> "She"
}
binding.dogName.text = dogName
Log.d(TAG, "${dogAge.toString()}, ${dogName.toString()}, $dogHobbies, $heOrShe, $dogImageResourceId")
binding.dogDescription.text = getString(R.string.dog_description, dogName, dogAge, dogSex, dogHobbies)
//binding.dogImage.setImageResource(dogImageResourceId!!.toInt())
binding.dogImage.setImageResource(R.drawable.bella)
Log.d(TAG, "dogDescription and dogImage were set")
title = getString(R.string.details_about, dogName)
}
Logcat:
2022-10-02 08:32:25.545 9660-9660/com.example.dogglers D/DetailActivity: null, null, null, She, null
2022-10-02 08:32:25.558 9660-9660/com.example.dogglers D/DetailActivity: dogDescription and dogImage were set
DogCardAdapter.kt:
import android.content.Context
import android.content.Intent
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Button
import android.widget.ImageView
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
import com.example.dogglers.DetailActivity
import com.example.dogglers.DetailActivity.Companion.DOG_AGE
import com.example.dogglers.DetailActivity.Companion.DOG_HOBBIES
import com.example.dogglers.DetailActivity.Companion.DOG_IMAGE
import com.example.dogglers.DetailActivity.Companion.DOG_NAME
import com.example.dogglers.DetailActivity.Companion.DOG_SEX
import com.example.dogglers.R
import com.example.dogglers.const.Layout.GRID
import com.example.dogglers.data.DataSource
/**
* Adapter to inflate the appropriate list item layout and populate the view with information
* from the appropriate data source
*/
class DogCardAdapter(
private val context: Context?,
private val layout: Int
): RecyclerView.Adapter<DogCardAdapter.DogCardViewHolder>() {
// Initialize the data using the List found in data/DataSource
val data = DataSource.dogs
/**
* Initialize view elements
*/
class DogCardViewHolder(view: View?): RecyclerView.ViewHolder(view!!) {
// Declare and initialize all of the list item UI components
val imageView: ImageView = view!!.findViewById(R.id.dog_image)
val dogName: TextView = view!!.findViewById(R.id.dog_name)
val dogAge: TextView = view!!.findViewById(R.id.dog_age)
val dogHobbies: TextView = view!!.findViewById(R.id.dog_hobbies)
var dogSex = "n/a"
val showDetailsButton: Button = view!!.findViewById(R.id.details_button)
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): DogCardViewHolder {
// Use a conditional to determine the layout type and set it accordingly.
// if the layout variable is Layout.GRID the grid list item should be used. Otherwise the
// the vertical/horizontal list item should be used.
val layoutType = when(layout) {
GRID -> R.layout.grid_list_item
else -> R.layout.vertical_horizontal_list_item
}
// Inflate the layout
val adapterLayout =LayoutInflater.from(parent.context)
.inflate(layoutType, parent, false)
// Null should not be passed into the view holder. This should be updated to reflect
// the inflated layout.
return DogCardViewHolder(adapterLayout)
}
override fun getItemCount(): Int = data.size
override fun onBindViewHolder(holder: DogCardViewHolder, position: Int) {
val resources = context?.resources
// Get the data at the current position
val item = data[position]
// Set the image resource for the current dog
holder.imageView.setImageResource(item.imageResourceId)
// Set the text for the current dog's name
holder.dogName.text = item.name
// Set the text for the current dog's age
holder.dogAge.text = resources?.getString(R.string.dog_age, item.age)
// Set the text for the current dog's hobbies by passing the hobbies to the
// R.string.dog_hobbies string constant.
holder.dogHobbies.text = resources?.getString(R.string.dog_hobbies, item.hobbies)
// Passing an argument to the string resource looks like:
// resources?.getString(R.string.dog_hobbies, dog.hobbies)
// Set the dog's sex variable
holder.dogSex = item.sex
// Declare context var
val context = holder.itemView.context
// Setting up OnClickListener
holder.showDetailsButton.setOnClickListener {
val intent = Intent(context, DetailActivity::class.java)
intent.putExtra(DOG_IMAGE, item.imageResourceId.toInt())
intent.putExtra(DOG_NAME, holder.dogName.toString())
intent.putExtra(DOG_AGE, holder.dogAge.toString())
intent.putExtra(DOG_HOBBIES, holder.dogHobbies.toString())
intent.putExtra(DOG_SEX, holder.dogSex.toString())
context.startActivity(intent)
}
}
}

Why does my app, written in Kotlin, stop when I press the 'balls' button?

My app has 2 screens and works correctly in development so far. It already has 2 buttons ('toss' and 'startGame'which work correctly. Now I have added a further button called 'balls', designed to change the background colours of 4 TextViews ('ball1' to 'ball4'). However, pressing it once does nothing, and pressing it again causes the app to stop, with the displayed message "GC Clicker has stopped" or "GC Clicker keeps stopping".
Here is the first section of my MainActivity.kt:
package com.example.golfclicker
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.widget.EditText
import android.widget.TextView
import android.graphics.Color
import android.widget.Button
import android.content.Intent
import android.media.AudioManager
import android.media.SoundPool
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val soundPool:SoundPool?
// Link variables to xml views
val player1Name = findViewById<EditText>(R.id.PersonName1)
val handicap1 = findViewById<EditText>(R.id.hpInput1)
val player2Name = findViewById<EditText>(R.id.PersonName2)
val handicap2 = findViewById<EditText>(R.id.hpInput2)
val startGame = findViewById<Button>(R.id.startGame)
val toss = findViewById<Button>(R.id.toss)
val bkgnd1 = findViewById<TextView>(R.id.Background1)
val bkgnd1a = findViewById<TextView>(R.id.Background1a)
val bkgnd1b = findViewById<TextView>(R.id.Background1b)
val bkgnd2 = findViewById<TextView>(R.id.Background2)
val bkgnd2a = findViewById<TextView>(R.id.Background2a)
val bkgnd2b = findViewById<TextView>(R.id.Background2b)
val balls = findViewById<Button>(R.id.balls)
val ball1 = findViewById<TextView>(R.id.ball1)
val ball2 = findViewById<TextView>(R.id.ball2)
val ball3 = findViewById<TextView>(R.id.ball3)
val ball4 = findViewById<TextView>(R.id.ball4)
var priSec = true // True:Primaries False:Secondaries
var tossedP1 = "" //String values to pass to Intent
var tossedHp1 =""
var tossedP2 = ""
var tossedHp2 =""
var tossed = false //has Toss button been used?
//Set up soundpool and load the sound file
soundPool = SoundPool(2,AudioManager.STREAM_MUSIC,0)
val sound1 = soundPool.load(baseContext,R.raw.computer_keyboard,1)
val sound2 = soundPool.load(baseContext,R.raw.coins,1)
//Handle balls button click
balls.setOnClickListener {
if(priSec==true) {
with(ball1) { setBackgroundColor(Color.parseColor("button_blue")) }
with(ball2) { setBackgroundColor(Color.parseColor("red")) }
with(ball3) { setBackgroundColor(Color.parseColor("black")) }
with(ball4) { setBackgroundColor(Color.parseColor("yellow")) }
} else {
with(ball1) { setBackgroundColor(Color.parseColor("green")) }
with(ball2) {setBackgroundColor(Color.parseColor("pink")) }
with(ball3) {setBackgroundColor(Color.parseColor("brown")) }
with(ball4) {setBackgroundColor(Color.parseColor("white")) }
}
priSec = !priSec //toggle primary/secondary
}
//Handle 'Toss' button click
toss.setOnClickListener {
var ran = (0..1).random() //Toss coin
// val ran = 1 //checking name-swapping
Any suggestions would be welcome.

Color.parseColor(...) works in different way than you think.
You can parse color like this:
Color.parseColor("#ff77bb")
In other words, you must pass hex code of color

this line is wrong .. because you didn't define the color
setBackgroundColor(Color.parseColor("button_blue")
try
setBackgroundColor(Color.parseColor("#39b8db")
or
context.getResources().getColor(android.R.color.white)

I finally found the following works to use colours defined in colors.xml.
I didn't want to include hex colours in my main code, as I may want to edit them at a later date.
ball1.setBackgroundColor(getResources().getColor(R.color.button_blue))
Thanks Niaj; this is similar to your last suggestion.

kotlin not working when i present letter condition

I try to learning kotlin.
I want a make a android app.
But im getting error.
i want to if i write "A" to edittext(#+id/tehlikesinifi), textview (uzmanucret) give me "40"
i write "B" to edittext(#+id/tehlikesinifi), textview (uzmanucret) give me "20"
i write "C" to edittext(#+id/tehlikesinifi), textview (uzmanucret)give me "10"
import abdullah.aydin.aykanosgb.databinding.ActivityFiyat2Binding
import android.annotation.SuppressLint
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
class fiyat2 : AppCompatActivity() {
private lateinit var binding: ActivityFiyat2Binding
#SuppressLint("SetTextI18n")
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding=ActivityFiyat2Binding.inflate(layoutInflater)
setContentView(binding.root)
var cs= binding.calisansayisi.text.toString()
var usaat=binding.usaatucret.text.toString()
var ts=binding.tehlikesinifi.text.toString()
var uzmanucret =binding.uzmanucret.text.toString()
binding.button.setOnClickListener {
if (ts.equals( "A")){
var uzmandk =40
}else if(ts.equals("B")){
var uzmandk =20
}else if(ts.equals("C")){
var uzmandk =10
}
var uzmandk: String=""
var sonuc: String
sonuc= uzmandk
var sonuc1 = sonuc
binding.uzmanucret.text= "$sonuc"
}
}
}

You have many redundant variables which make your code messy
ts is set only once in onCreate and never get updated. To get the latest value you typed in the EditText, you should get it within the onClickListener
Kotlin control flow expression can return a value. It is more suitable to use when in your case
You don't need to call equals to compare string in Kotlin.
binding.button.setOnClickListener {
binding.uzmanucret.text = when(binding.tehlikesinifi.text.toString()){
"A" -> "40"
"B" -> "20"
"C" -> "10"
else -> null
}
}

Can't change editText input from string to float

package com.example.tipcalculator
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.EditText
import android.widget.TextView
import kotlin.text.toFloat as kotlinTextToFloat
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
supportActionBar?.hide()
val tenPerTip: Button = findViewById(R.id.tenPerTipButton)
val fifteenPerTip: Button = findViewById(R.id.fifteenPerTipButton)
val twentyPerTip: Button = findViewById(R.id.twentyPerTipButton)
val customTip: Button = findViewById(R.id.customTipSubmit)
val sumRaw: EditText = findViewById(R.id.billEnter)
val tipOnlyResult: TextView = findViewById(R.id.tipOnlyResult)
val totalResult: TextView = findViewById(R.id.totalResult)
val sumString = sumRaw.toString()
val sumInput = sumString.toInt()
tenPerTip.setOnClickListener{
val sumTotal = sumInput * 1.1
val tipOnly = sumInput * 0.1
tipOnlyResult.text = tipOnly.toString()
totalResult.text = sumTotal.toString()
}
fifteenPerTip.setOnClickListener{
}
twentyPerTip.setOnClickListener{
}
customTip.setOnClickListener{
}
}
}
I was trying to switch the EditText input to a string and from there to a float so that I can do calculations on it. On the line with val sumInput = sumString.toInt() the code breaks. It will compile, but when I try to run an emulator it casts error codes about the toInt declaration. The code is using toInt in this because I was trying to see if the emulator would like that. Also whenever I declare that toInt it highlights in a light yellow italic font, which I haven't seen before.

I have Edited your code.
Changes to the code is explained with the comments below.
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
supportActionBar?.hide()
val tenPerTip: Button = findViewById(R.id.tenPerTipButton)
val fifteenPerTip: Button = findViewById(R.id.fifteenPerTipButton)
val twentyPerTip: Button = findViewById(R.id.twentyPerTipButton)
val customTip: Button = findViewById(R.id.customTipSubmit)
val sumRaw: EditText = findViewById(R.id.billEnter)
val tipOnlyResult: TextView = findViewById(R.id.tipOnlyResult)
val totalResult: TextView = findViewById(R.id.totalResult)
/** if you put sumString and sumInput here, what happens is when your app
* is created and the onCreate method is called sumString is initialized
* here without using .text, i.e., sumRaw.text command what happens is sumString
* will be initialized with sumRaw value (i guess maybe sumRaw id) and you will
* get error.
* Also, this is only called once when all the other variable are initialized.
* If you want to use it outside use a TextWatcher and change the variable as
* soon as it is updated in the EditText.
* A work-around would be initializing this value inside OnClickListener, what
* happens here is whenever you click tenPerTip Button sumString is Initialized
* with current values in sumRaw EditText.
*
* Do use .text else it will give errors.
*/
tenPerTip.setOnClickListener {
val sumString = sumRaw.text.toString()
// what happens here is sumString is converted to Double if it has valid pattern
// else it will return null
// And then the elvis operator will check for null. If its null, it will not
// not proceed further and will get out the listener.
val sumInput = sumString.toDoubleOrNull() ?: return#setOnClickListener
val sumTotal = sumInput * 1.1
val tipOnly = sumInput * 0.1
tipOnlyResult.text = tipOnly.toString()
totalResult.text = sumTotal.toString()
}
fifteenPerTip.setOnClickListener {
}
twentyPerTip.setOnClickListener {
}
customTip.setOnClickListener {
}
}
}

You seem to think the that when you write val sumString = sumRaw.toString(), it gives you the text entered in R.id.billEnter which is not correct. to get text from an EditText you have to use text property. As for your code it can be fixed as
tenPerTip.setOnClickListener{
val sumString = sumRaw.text.toString()
val sumInput = sumString.toInt()
val sumTotal = sumInput * 1.1
val tipOnly = sumInput * 0.1
tipOnlyResult.text = tipOnly.toString()
totalResult.text = sumTotal.toString()
}

Android with Kotlin recyclerView with checkboxes randomly checked after delete list item

apologies for my limited knowledge of programming and any sloppiness. I have a reyclerview with alarm objects that I can add and it creates them. When I add say 4 alarms, and delete three of them. The last alarms checkbox is checked by itself. I can not in anyway use the checkbox.setChecked() method for some reason. android studio is not recognizing it, if anyone could please let me know why that is. Also if you know of a solution to the auto check on the last alarm object please.
package com.example.alarmclock
import android.view.KeyEvent
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Button
import android.widget.Checkable
import android.widget.EditText
import android.widget.TextView
import androidx.core.widget.doAfterTextChanged
import androidx.core.widget.doBeforeTextChanged
import androidx.recyclerview.widget.RecyclerView
import java.security.Key
class AlarmAdapter (private val alarmList: MutableList<Alarm>) : RecyclerView.Adapter<AlarmAdapter.ViewHolder>() {
//start viewholder
inner class ViewHolder(alarm: View) : RecyclerView.ViewHolder(alarm) {
val alarmLabel = itemView.findViewById<EditText>(R.id.alarmLabel)
val editTextTime = itemView.findViewById<EditText>(R.id.editTextTime)
val textView1 = itemView.findViewById<TextView>(R.id.textView1)
val deleteCheckBox = itemView.findViewById<Button>(R.id.deleteAlarmCheckBox)
//val deleteButton = itemView.findViewById<Button>(R.id.deleteAlarmButton)
//val addButton = itemView.findViewById<Button>(R.id.addAlarmButton)
val mondayCheckBox = itemView.findViewById<Button>(R.id.mondayCheckBox)
val tuesdayCheckBox = itemView.findViewById<Button>(R.id.tuesdayCheckBox)
val wednesdayCheckBox = itemView.findViewById<Button>(R.id.wednesdayCheckBox)
val thursdayCheckBox = itemView.findViewById<Button>(R.id.thursdayCheckBox)
val fridayCheckBox = itemView.findViewById<Button>(R.id.fridayCheckBox)
val saturdayCheckBox = itemView.findViewById<Button>(R.id.saturdayCheckBox)
val sundayCheckBox = itemView.findViewById<Button>(R.id.sundayCheckBox)
val amCheckBox = itemView.findViewById<Button>(R.id.amCheckBox)
val pmCheckBox = itemView.findViewById<Button>(R.id.pmCheckBox)
}//end viewholder
fun addAlarm (alarm: Alarm) {
alarmList.add(alarm)
notifyItemInserted(alarmList.size - 1)
}
fun returnAlarmList (): MutableList<Alarm> {
return alarmList
}
fun removeAlarms() {
alarmList.removeAll {
alarm -> alarm.deleteCheck == true
}
//notifyDataSetChanged()
}
fun deleteAlarm (deletedAlarmList: List<Int> ) {
val deletedListIterator = deletedAlarmList.iterator()
val alarmListIterator = alarmList.iterator()
while (deletedListIterator.hasNext()){
while (alarmListIterator.hasNext()){
if (deletedListIterator.next() == alarmListIterator.next().alarmId){
alarmList.remove(alarmListIterator.next())
}
}
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val context = parent.context
val inflater = LayoutInflater.from(context)
val alarmView = inflater.inflate(R.layout.alarms, parent, false)
return ViewHolder(alarmView)
}
override fun getItemCount(): Int {
return alarmList.size
}
override fun onBindViewHolder(holder: AlarmAdapter.ViewHolder, position: Int) {
val alarm: Alarm = alarmList[position]
val alarmLabel = holder.alarmLabel
var textView1 = holder.textView1
var editTextTime = holder.editTextTime
var mondayCheckBox = holder.mondayCheckBox
var tuesdayCheckBox = holder.tuesdayCheckBox
var wednesdayCheckBox = holder.wednesdayCheckBox
var thursdayCheckBox = holder.thursdayCheckBox
var fridayCheckBox = holder.fridayCheckBox
var saturdayCheckBox = holder.saturdayCheckBox
var sundayCheckBox = holder.sundayCheckBox
var amCheckBox = holder.amCheckBox
var pmCheckBox = holder.pmCheckBox
var deleteAlarmCheckBox = holder.deleteCheckBox
var lastCharacter = ""
var secondLastCharacter = ""
deleteAlarmCheckBox.setOnClickListener {
alarm.deleteCheck = !alarm.deleteCheck
}
alarmLabel.doAfterTextChanged {
alarm.alarmLabel = alarmLabel.text.toString()
textView1.text = alarm.alarmLabel
}
editTextTime.doAfterTextChanged {
//lastCharacter = editTextTime.text.get(editTextTime.text.length-1).toString()
textView1.text = lastCharacter
if (editTextTime.text.length == 2 && secondLastCharacter != ":"){
//if (lastCharacter != ":") {
editTextTime.setText(editTextTime.text.toString().plus(":"))
editTextTime.setSelection(editTextTime.text.length)
//}
}
editTextTime.doBeforeTextChanged { _, _, _, _ ->
if (editTextTime.length() != 0) {
secondLastCharacter = editTextTime.text.get(editTextTime.text.length - 1).toString()
}
}
if (editTextTime.text.length == 5 ){
alarm.hour = editTextTime.text.get(0).toString().plus(editTextTime.text.get(1).toString())
if (alarm.hour.toInt() < 10) alarm.hour = "0".plus(alarm.hour)
///////
var inputedTimeList = editTextTime.text.toList()
val timeIterator = inputedTimeList.iterator()
}
}
mondayCheckBox.setOnClickListener {
alarm.monday = !alarm.monday
textView1.text = alarm.monday.toString()
}
tuesdayCheckBox.setOnClickListener {
alarm.tuesday = !alarm.tuesday
}
wednesdayCheckBox.setOnClickListener {
alarm.wednesday = !alarm.wednesday
}
thursdayCheckBox.setOnClickListener {
alarm.thursday = !alarm.thursday
}
fridayCheckBox.setOnClickListener {
alarm.friday = !alarm.friday
}
saturdayCheckBox.setOnClickListener {
alarm.saturday = !alarm.saturday
}
sundayCheckBox.setOnClickListener {
alarm.sunday = !alarm.sunday
}
amCheckBox.setOnClickListener {
alarm.amPm = !alarm.amPm
}
}
}

The answer is quite simple, RecyclerView items are reused, so be sure that you set the all the values onBindViewHolder, because after your item is deleted, the actual view is not, so previously set values might be preset although they are not correct according to your data.
The easiest way would be to have isChecked Boolean value store in the Alarm object, onBindViewHolder always set the isChecked param on the Checkbox according to the value returned from the Alarm and when you change the isChecked inside the Checkbox listener - make sure you also update the value inside the Alarm object.
Another solution would be calling notifyDatasetChanged() on the RecyclerView, but it's definitely not the best solution especially if you have dynamic row deletion (and possibly a neat animation).
P.S. consider using viewBinding in your project, it will save you time writing all that ugly findViewById code :)))