I want the text view to be updated every second or less in a dynamic random way and at the end of the loop the text view show the last random number.
I tried to add a sleep method but it did not work every time I click the button the text view show the last random number directly.
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val rollButton: Button = findViewById(R.id.button1)
var result: TextView = findViewById(R.id.textView)
rollButton.setOnClickListener {
for (i in 1..10){
result.text = "${(1..6).random()}"
}
Toast.makeText(this, "Dice Rolled!", Toast.LENGTH_SHORT).show()
}
}
}
Coroutine delay is a way to do that, which is suggested in ltp's answer,
Another way is Runnable and Handler, an example function:
fun animateTextView(handler: Handler, textView: TextView, animate: Boolean = true) {
val runnable: Runnable = object : Runnable {
var randomNumber = 0
override fun run() {
randomNumber = (1..100).random()
textView.text = "$randomNumber"
handler.postDelayed(this, 500L)
}
}
// animate == false -> end text updates
if (animate) handler.postDelayed(runnable, 500L)
else handler.removeCallbacks(runnable)
}
Example use of the function:
private val textAnimaterHandler = Handler(Looper.getMainLooper())
animateTextView(textAnimaterHandler, binding.textView)
// Stop updates:
animateTextView(textAnimaterHandler, binding.textView, animate = false)
You can use Coroutine delay
rollButton.setOnClickListener {
CoroutineScope(Dispatchers.Main).launch {
//Disable button temporarily to prevent multiple clicks
it.isEnabled = false
for (i in 1..10) {
binding.textviewFirst.text = "${(1..6).random()}"
//One second delay before the next
delay(1000)
//If you want random delay - say 100ms to 1s
//delay((100L..1000L).random())
}
it.isEnabled = true
Toast.makeText(this#MainActivity, "Dice Rolled!", Toast.LENGTH_SHORT).show()
}
}
Related
I am new to Android Development... Sorry for asking something so trivial. I don't know how to google this problem.
So let me explain:
I am doing the Android Development Course from Google and in the exercise you have a TextView that is repeatedly changed by an easy mathematical function 4 times after setContentViewis called. Between the changes Thread.sleep(1000) is called to delay the changes.
Expected behavior:
The Main Activity starts and you can see the TextView changing 4 times.
What actually happens:
The App start is delayed for as long as the calculations are set and then afterwards it will display the Main Activity with only the very last calculated result. In this case I would wait 4 seconds (with Thread.sleep(1000) being called 4 times) until the App is completely up and then you only see the result 60 because of 60 / 1.
This is the code:
private const val TAG = "MainActivity"
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
division()
}
private fun division() {
val numerator = 60
var denominator = 4
repeat(4) {
Thread.sleep(1000)
Log.v(TAG, "${numerator / denominator}")
val view: TextView = findViewById(R.id.division_textview)
view.setText("${numerator / denominator}")
denominator--
}
}
Thanks in advance. I hope someone knows why Google is suggesting this code, but it does not work on my machine.
You need to make a delay by Timer instead of Thread.sleep()
For training you can try something like this.
private val timerHandler = Handler(Looper.getMainLooper())
private val timerRunnable = Runnable {
denominator--
if(demominator != 0) {
//UI changes here
decrementTimer()
}
}
private fun decrementTimer() {
timerHandler.postDelayed(timerRunnable, DELAY_TIME)
}
If you need to start first run immediately use timerRunnable.run() in other case call decrementTimer().
Also would be helpful to control handler with removeCallbacks function when activity goes to background
You can wait in another thread so you don't block the main thread,
try this code it should work correctly, the code inside the lifecycleScope.launch will be moved to another thread so it will not block the UI:
private const val TAG = "MainActivity"
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
division()
}
private fun division() {
val numerator = 60
var denominator = 4
lifecycleScope.launch {
repeat(4) {
delay(1000)
Log.v(TAG, "${numerator / denominator}")
val view: TextView = findViewById(R.id.division_textview)
view.setText("${numerator / denominator}")
denominator--
}
}
}
Note: You need to be sure that you add the lifecycle dependency in you app gradle
dependencies {
...
implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.4.1'
...
}
Thanks for your answers everyone. Each of them helped me searching for the right topics. I liked the Handler Class the most and after some further searching, I came up with this solution:
private fun division() {
val numerator = 60
var denominator = 4
val handler = Handler(Looper.getMainLooper())
val divRunnable = object: Runnable {
override fun run() {
if (denominator != 0) {
Log.v(TAG, "${numerator / denominator}")
val view: TextView = findViewById(R.id.division_textview)
view.text = "${numerator / denominator}"
denominator--
handler.postDelayed(this, 1000)
}
}
}
handler.post(divRunnable)
}
This is working exactly as I wanted it to work.
My goal:
in the view of the fragment I have a button that, when pressed once, launches a method in the viewModel which cyclically calls a suspend function to be repeated every few seconds from its conclusion. Pressing the button again stops this cycle.
My approach:
inside the fragment I set the onclicklistener of the button
binding.demoButton.setOnClickListener {
viewModel.toggleDemo()
}
in the viewModel:
private var startDemo : Boolean = false //I need to know whether to start the loop or stop it
private var isBusy : Boolean = false //I need to know if my task is running or finished
fun toggleDemo(){
val oldValue : Boolean = startDemo
val newValue = !oldValue
startDemo = newValue
if(startDemo){
saveLogLine("** start demo **") //method that passes some log strings to the fragment
startDemo()
}else{
saveLogLine("NO start demo!!")
}
}
private fun startDemo(){
GlobalScope.launch(Dispatchers.IO) {
saveLogLineAsync("before while loop")
while(startDemo){
if(!isBusy){
isBusy = true
Handler(Looper.getMainLooper()).postDelayed({
runBlocking(Dispatchers.IO) {
saveLogLineAsync("inside runBlocking")
initDemo()
}
isBusy = false
saveLogLineAsync("inside handler")
}, 5000)
}
}
saveLogLineAsync("after while loop")
}
}
private suspend fun initDemo(){ //my task
}
Is there a more elegant way to do this?
I would have liked to use a Service () or a BroadcastReceiver () but in both cases I would not know how to make them communicate with the fragment or with the viewModel (more precisely, they should be able to use the 2 methods 'saveLogLineAsync' and 'intDemo')
You can simplify your code with this:
private var demoRunning = false
private var demoJob: Job? = null
fun toggleDemo() {
if (!demoRunning) {
startDemo()
} else {
demoJob?.cancel()
}
demoRunning = !demoRunning
}
private fun startDemo() {
demoJob = viewModelScope.launch(Dispatchers.IO) {
while (true) {
initDemo()
delay(5000)
}
}
}
private suspend fun initDemo() { //my task
Log.e("INIT DEMO", "initDemo Ran")
}
Trying to display multiple Toast messages one after another, but only the last toast message gets displayed. I tried using Thread.sleep, and handlers to buffer the messages, but neither worked. Any other tips? Here's my code:
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_add_cow)
// updates the variables with these values
Submit.setOnClickListener {
cowName = Cow_Name.text.toString()
cowWeight = Cow_Weight.text.toString().toIntOrNull()
cowSex = Cow_Sex.text.toString()
cowAge = Cow_Age.text.toString()
showToast(cowName.toString())
showToast(cowWeight.toString())
showToast(cowSex.toString())
showToast(cowAge.toString())
}
}
private fun showToast(text: String)
{
Toast.makeText(this, text, Toast.LENGTH_SHORT).show()
handler.postDelayed ({
// Do nothing
}, 2000)
}
At minimum you should add a "delay" variable to "showToast" and move the Toast call to inside the posted Runnable:
private fun showToast(text: String, delayInMilliseconds: Int) {
val context = this
handler.postDelayed (
{ Toast.makeText(context, text, Toast.LENGTH_SHORT).show() },
delayInMilliseconds
)
}
Then you'd call it like
showToast(cowName.toString(), 0)
showToast(cowWeight.toString(), 1000)
showToast(cowSex.toString(), 2000)
showToast(cowAge.toString(), 3000)
Or whatever delay values were required to make that work.
I want to create a simple countdown for my game, when the game starts I want this function to be called every second:
fun minusOneSecond(){
if secondsLeft > 0{
secondsLeft -= 1
seconds_thegame.text = secondsLeft.toString()
}
}
I tried this:
var secondsLeft = 15
timer.scheduleAtFixedRate(
object : TimerTask() {
override fun run() {
minusOneSecond()
}
},0, 1000
) // 1000 Millisecond = 1 second
But the app unfortunately stops, the 2nd time the run function is called
I just started with android development and Kotlin 3 weeks ago and so far I understand the most out of it.
With swift in Xcode I use this line and I thought something similar would work with Kotlin
setTimer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(minusOneSecond), userInfo: nil, repeats: true)
Problem: Timer class uses a background thread with a queue to queue and execute all tasks sequentially. From your code, because you update UI (changing TextView content in minusOneSecond function). That why the app throws the following exception and make your app crash.
android.view.ViewRootImpl$CalledFromWrongThreadException: Only the
original thread that created a view hierarchy can touch its views.
Solution: There are many ways to achieve your task, but I prefer using post() and postDelayed() method from Handler class. Because it's simple and easy to understand.
val mainHandler = Handler(Looper.getMainLooper())
mainHandler.post(object : Runnable {
override fun run() {
minusOneSecond()
mainHandler.postDelayed(this, 1000)
}
})
Update: From author's comment about how to pause/resume the task from Handler. Here is an example.
class MainActivityKt : AppCompatActivity() {
lateinit var mainHandler: Handler
private val updateTextTask = object : Runnable {
override fun run() {
minusOneSecond()
mainHandler.postDelayed(this, 1000)
}
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
// Your logic code
...
mainHandler = Handler(Looper.getMainLooper())
}
override fun onPause() {
super.onPause()
mainHandler.removeCallbacks(updateTextTask)
}
override fun onResume() {
super.onResume()
mainHandler.post(updateTextTask)
}
fun minusOneSecond() {
if secondsLeft > 0 {
secondsLeft -= 1
seconds_thegame.text = secondsLeft.toString()
}
}
}
I am using this code to update a clock every minute
fixedRateTimer("timer", false, 0L, 60 * 1000) {
this#FullscreenActivity.runOnUiThread {
tvTime.text = SimpleDateFormat("dd MMM - HH:mm", Locale.US).format(Date())
}
}
so you have to run it with paratemer 1000 instead of 60*1000
val timer = object: CountDownTimer(10000, 1000) {
override fun onTick(millisUntilFinished: Long) {
// do something
}
override fun onFinish() {
// do something
}
}
timer.start()
You can also use CountDownTimer for this purpose. As this takes two parameters (the total time and the interval time)
Plus it also provides an on finish method to perform any task when the total time is finished.
please use
inline fun Timer.schedule(
time: Date,
period: Long,
crossinline action: TimerTask.() -> Unit
): TimerTask
reference: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.concurrent/java.util.-timer/schedule.html
I am calling my function every second like this
val handler = Handler()
handler.postDelayed(object : Runnable {
override fun run() {
//Call your function here
handler.postDelayed(this, 1000)//1 sec delay
}
}, 0)
My solution
viewModelScope.launch(Dispatchers.IO) {
while(isActive) {
when(val response = repository.getApi()) {
is NetworkState.Success -> {
getAllData.postValue(response.data)
}
is NetworkState.Error -> this#MainViewModel.isActive = false
}
delay(API_CALL_DELAY)
}
}
if you use any background task or background service try this code
val timer = Executors.newSingleThreadScheduledExecutor().scheduleAtFixedRate({
Log.d("RUNNING ","Thread")
},0,10,TimeUnit.SECONDS)
if you work with UI thers like update UI layout try this code
val timer = Executors.newSingleThreadScheduledExecutor().scheduleAtFixedRate({
Log.d("RUNNING ","BACKGROUN Thread")
runOnUiThread {
Log.d("RUNNING ","Update UI Thread")
btnUpdate.setText(System.currentTimeMillis().toString())
}
},0,1,TimeUnit.SECONDS)
I'm using recursion with Coroutine its very simple
private fun loop() {
CoroutineScope(IO).launch {
delay(5000)
CoroutineScope(Main).launch {
ManagerToWorker()
loop()
}
}
}
var isActionAchieved = false
var secondsPassed = 0
fun cDTimer(){
if (!isActionAchieved && secondsPassed < 10){ // repeat check if Action NOT Achieved for max of 10 seconds
Handler(Looper.getMainLooper()).postDelayed({
repeatThisFunction()
repeater()
secondsPassed++
}, 1000) //one second till next execution
}
}
fun repeater(){
cDTimer()
}
in the timer I use how to add a time when a button is pressed? for example, I want millisUntilFinished to increase by 5 seconds when I press a button. I tried with the global variable but it didn't.
object :CountDownTimer(10000,1000){
override fun onFinish() {
timeText.text = "Left : 0"
handler.removeCallbacks(runnable)
for (image in imageArray){
image.visibility = View.INVISIBLE
}
for (add in timeAdd){
add.visibility = View.INVISIBLE
}
button.visibility = View.VISIBLE
}
override fun onTick(millisUntilFinished: Long) {
timeText.text = "Left : "+millisUntilFinished/1000
}
}.start()
Here is a count down timer we use
fun message(msg:String){
object : CountDownTimer(4000, 1000) {
override fun onTick(millisUntilFinished: Long) {
tvMsg.visibility = View.VISIBLE
tvMsg.text = msg
}
override fun onFinish() {
tvMsg.visibility = View.INVISIBLE
tvMsg.text = ""
}
}.start()
}
And our use of a plain timer
if (result) {
etItemData.setText("")
message("Record Removed")
Timer().schedule(1000){
thisACTIVITY()
}
Kotlin complains about this not sure why
addition to Vector's answer I made an button that display countdown timer every 1 second. I put Vector's answer into a function then call it when my button is pressed. Hope this help someone. With this example it counts down from 4 seconds.
private fun countdown(){
object : CountDownTimer(4000, 1000) {
override fun onTick(millisUntilFinished: Long) {
otp_resend.text = (millisUntilFinished / 1000).toString()
}
override fun onFinish() {
// do something after countdown is done ie. enable button, change color
etc.
otp_resend.text = "done!"
}
}.start()
}
You can't change the remaining time on an already-created CountDownTimer.
Looking at the source, both millisInFuture and countDownInterval are assigned to final variables; you can't change them.
Now, the mStopTimeInFuture variable, the one the timer actually uses to stop, isn't final, and can be changed. But it's a private variable, meaning you'd need to use reflection, and it might not work properly.
If you want a mutable CountDownTimer, you'll need to roll your own (easiest way would probably be to copy the CountDownTimer source and make the mStopTimeInFuture variable public and add milliseconds to it when needed).
As #TheWanderer answered you can not update the millisUntilFinished as there is no such method available in CountDownTimer class.
To update the Timer you need to stop the current timer and start the new timer with updated millisInFuture value. Here is the sample code which will help you to achieve what you want.
var timer: Timer?=null
//Call this method to start timer on activity start
private fun startTimer(){
timer = Timer(10000);
timer?.start()
}
//Call this method to update the timer
private fun updateTimer(){
if(timer!=null) {
val miliis = timer?.millisUntilFinished + TimeUnit.SECONDS.toMillis(5)
//Here you need to maintain single instance for previous
timer?.cancel()
timer = Timer(miliis);
timer?.start()
}else{
startTimer()
}
}
inner class Timer(miliis:Long) : CountDownTimer(miliis,1000){
var millisUntilFinished:Long = 0
override fun onFinish() {
timeText.text = "Left : 0"
handler.removeCallbacks(runnable)
for (image in imageArray){
image.visibility = View.INVISIBLE
}
for (add in timeAdd){
add.visibility = View.INVISIBLE
}
button.visibility = View.VISIBLE
}
override fun onTick(millisUntilFinished: Long) {
this.millisUntilFinished = millisUntilFinished
timeText.text = "Left : "+millisUntilFinished/1000
}
}