问题
I know how to create a simple countdown timer in Java. But I'd like to create this one in Kotlin.
package android.os;
new CountDownTimer(20000, 1000) {
public void onTick(long millisUntilFinished) {
mTextField.setText("seconds remaining: " + millisUntilFinished / 1000);
}
public void onFinish() {
mTextField.setText("Time's finished!");
}
}.start();
How can I do it using Kotlin?
回答1:
You can use Kotlin objects:
val timer = object: CountDownTimer(20000, 1000) {
override fun onTick(millisUntilFinished: Long) {...}
override fun onFinish() {...}
}
timer.start()
回答2:
Chronometer can be set to count down and it seems to me the easiest way.
Add the Chronometer view in your layout xml, example
<Chronometer
android:id="@+id/view_timer"
tools:targetApi="24"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
Then in your activity or fragment:
view_timer.isCountDown = true
view_timer.base = SystemClock.elapsedRealtime() + 20000
view_timer.start()
回答3:
Try to use objects, like this :
var countDownTimer = object : CountDownTimer(2000, 1000) {
// override object functions here, do it quicker by setting cursor on object, then type alt + enter ; implement members
}
Try this website : https://try.kotlinlang.org/#/Kotlin%20Koans/Introduction/Java%20to%20Kotlin%20conversion/Task.kt
You have a little button "Convert from Java" on the top right that could be useful to you.
EDIT:
Do not forget to start this object when you need it, by adding .start()
at the end of the declaration, or wherever in your activity / fragment :
countDownTimer.start()
回答4:
I've solved my problem with timer in Kotlin like this:
class Timer {
private val job = SupervisorJob()
private val scope = CoroutineScope(Dispatchers.Default + job)
private fun startCoroutineTimer(delayMillis: Long = 0, repeatMillis: Long = 0, action: () -> Unit) = scope.launch(Dispatchers.IO) {
delay(delayMillis)
if (repeatMillis > 0) {
while (true) {
action()
delay(repeatMillis)
}
} else {
action()
}
}
private val timer: Job = startCoroutineTimer(delayMillis = 0, repeatMillis = 20000) {
Log.d(TAG, "Background - tick")
doSomethingBackground()
scope.launch(Dispatchers.Main) {
Log.d(TAG, "Main thread - tick")
doSomethingMainThread()
}
}
fun startTimer() {
timer.start()
}
fun cancelTimer() {
timer.cancel()
}
//...
}
I've used Coroutines for a timer.
回答5:
If you want to show a countdown with days hours minutes and seconds
private lateinit var countDownTimer:CountDownTimer
.
.
.
fun printDifferenceDateForHours() {
val currentTime = Calendar.getInstance().time
val endDateDay = "03/02/2020 21:00:00"
val format1 = SimpleDateFormat("dd/MM/yyyy hh:mm:ss",Locale.getDefault())
val endDate = format1.parse(endDateDay)
//milliseconds
var different = endDate.time - currentTime.time
countDownTimer = object : CountDownTimer(different, 1000) {
override fun onTick(millisUntilFinished: Long) {
var diff = millisUntilFinished
val secondsInMilli: Long = 1000
val minutesInMilli = secondsInMilli * 60
val hoursInMilli = minutesInMilli * 60
val daysInMilli = hoursInMilli * 24
val elapsedDays = diff / daysInMilli
diff %= daysInMilli
val elapsedHours = diff / hoursInMilli
diff %= hoursInMilli
val elapsedMinutes = diff / minutesInMilli
diff %= minutesInMilli
val elapsedSeconds = diff / secondsInMilli
txt_timeleft.text = "$elapsedDays days $elapsedHours hs $elapsedMinutes min $elapsedSeconds sec"
}
override fun onFinish() {
txt_timeleft.text = "done!"
}
}.start()
}
If you are navigating to another activity/fragment, make sure to cancel the countdown
countDownTimer.cancel()
Code output
51 days 17 hs 56 min 5 sec
来源:https://stackoverflow.com/questions/54095875/how-to-create-a-simple-countdown-timer-in-kotlin