I want to be able to call the following method after a specified delay.
In objective c there was something like:
[self performSelector:#selector(DoSomething) withObject:nil afterDelay:5];
Is there an equivalent of this method in android with java?
For example I need to be able to call a method after 5 seconds.
public void DoSomething()
{
//do something here
}
Kotlin
Handler(Looper.getMainLooper()).postDelayed({
//Do something after 100ms
}, 100)
Java
final Handler handler = new Handler(Looper.getMainLooper());
handler.postDelayed(new Runnable() {
#Override
public void run() {
//Do something after 100ms
}
}, 100);
The class to import is android.os.handler.
I couldn't use any of the other answers in my case.
I used the native java Timer instead.
new Timer().schedule(new TimerTask() {
#Override
public void run() {
// this code will be executed after 2 seconds
}
}, 2000);
Note: This answer was given when the question didn't specify Android as the context. For an answer specific to the Android UI thread look here.
It looks like the Mac OS API lets the current thread continue, and schedules the task to run asynchronously. In the Java, the equivalent function is provided by the java.util.concurrent package. I'm not sure what limitations Android might impose.
private static final ScheduledExecutorService worker =
Executors.newSingleThreadScheduledExecutor();
void someMethod() {
⋮
Runnable task = new Runnable() {
public void run() {
/* Do something… */
}
};
worker.schedule(task, 5, TimeUnit.SECONDS);
⋮
}
For executing something in the UI Thread after 5 seconds:
new Handler(Looper.getMainLooper()).postDelayed(new Runnable() {
#Override
public void run() {
//Do something here
}
}, 5000);
Kotlin & Java Many Ways
1. Using Handler
Handler().postDelayed({
TODO("Do something")
}, 2000)
2. Using TimerTask
Timer().schedule(object : TimerTask() {
override fun run() {
TODO("Do something")
}
}, 2000)
Or even shorter
Timer().schedule(timerTask {
TODO("Do something")
}, 2000)
Or shortest would be
Timer().schedule(2000) {
TODO("Do something")
}
3. Using Executors
Executors.newSingleThreadScheduledExecutor().schedule({
TODO("Do something")
}, 2, TimeUnit.SECONDS)
In Java
1. Using Handler
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
//Do something
}
}, 2000);
2. Using Timer
new Timer().schedule(new TimerTask() {
#Override
public void run() {
// Do something
}
}, 2000);
3. Using ScheduledExecutorService
private static final ScheduledExecutorService worker = Executors.newSingleThreadScheduledExecutor();
Runnable runnable = new Runnable() {
public void run() {
// Do something
}
};
worker.schedule(runnable, 2, TimeUnit.SECONDS);
you can use Handler inside UIThread:
runOnUiThread(new Runnable() {
#Override
public void run() {
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
//add your code here
}
}, 1000);
}
});
Thanks for all the great answers, I found a solution that best suits my needs.
Handler myHandler = new DoSomething();
Message m = new Message();
m.obj = c;//passing a parameter here
myHandler.sendMessageDelayed(m, 1000);
class DoSomething extends Handler {
#Override
public void handleMessage(Message msg) {
MyObject o = (MyObject) msg.obj;
//do something here
}
}
See this demo:
import java.util.Timer;
import java.util.TimerTask;
class Test {
public static void main( String [] args ) {
int delay = 5000;// in ms
Timer timer = new Timer();
timer.schedule( new TimerTask(){
public void run() {
System.out.println("Wait, what..:");
}
}, delay);
System.out.println("Would it run?");
}
}
More Safety - With Kotlin Coroutine
Most of the answers use Handler but I give a different solution to delay in activity, fragment, view model with Android Lifecycle ext. This way will auto cancel when the lifecycle begins destroyed - avoid leaking the memory or crashed app
In Activity or Fragment:
lifecycleScope.launch {
delay(DELAY_MS)
doSomething()
}
In ViewModel:
viewModelScope.lanch {
delay(DELAY_MS)
doSomething()
}
In suspend function: (Kotlin Coroutine)
suspend fun doSomethingAfter(){
delay(DELAY_MS)
doSomething()
}
If you get an error with the lifecycleScope not found! - import this dependency to the app gradle file:
implementation "androidx.lifecycle:lifecycle-runtime-ktx:2.4.0"
If you have to use the Handler, but you are into another thread, you can use runonuithread to run the handler in UI thread. This will save you from Exceptions thrown asking to call Looper.Prepare()
runOnUiThread(new Runnable() {
#Override
public void run() {
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
//Do something after 1 second
}
}, 1000);
}
});
Looks quite messy, but this is one of the way.
I prefer to use View.postDelayed() method, simple code below:
mView.postDelayed(new Runnable() {
#Override
public void run() {
// Do something after 1000 ms
}
}, 1000);
Here is my shortest solution:
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
//Do something after 100ms
}
}, 100);
If you are using Android Studio 3.0 and above you can use lambda expressions. The method callMyMethod() is called after 2 seconds:
new Handler().postDelayed(() -> callMyMethod(), 2000);
In case you need to cancel the delayed runnable use this:
Handler handler = new Handler();
handler.postDelayed(() -> callMyMethod(), 2000);
// When you need to cancel all your posted runnables just use:
handler.removeCallbacksAndMessages(null);
final Handler handler = new Handler();
Timer t = new Timer();
t.schedule(new TimerTask() {
public void run() {
handler.post(new Runnable() {
public void run() {
//DO SOME ACTIONS HERE , THIS ACTIONS WILL WILL EXECUTE AFTER 5 SECONDS...
}
});
}
}, 5000);
I suggest the Timer, it allows you to schedule a method to be called on a very specific interval. This will not block your UI, and keep your app resonsive while the method is being executed.
The other option, is the wait(); method, this will block the current thread for the specified length of time. This will cause your UI to stop responding if you do this on the UI thread.
So there are a few things to consider here as there are so many ways to skin this cat. Although answers have all already been given selected and chosen. I think it's important that this gets revisited with proper coding guidelines to avoid anyone going the wrong direction just because of "majority selected simple answer".
So first let's discuss the simple Post Delayed answer that is the winner selected answer overall in this thread.
A couple of things to consider. After the post delay, you can encounter memory leaks, dead objects, life cycles that have gone away, and more. So handling it properly is important as well. You can do this in a couple of ways.
For sake of modern development, I'll supply in KOTLIN
Here is a simple example of using the UI thread on a callback and confirming that your activity is still alive and well when you hit your callback.
Handler(Looper.getMainLooper()).postDelayed({
if(activity != null && activity?.isFinishing == false){
txtNewInfo.visibility = View.GONE
}
}, NEW_INFO_SHOW_TIMEOUT_MS)
However, this is still not perfect as there is no reason to hit your callback if the activity has gone away. so a better way would be to keep a reference to it and remove it's callbacks like this.
private fun showFacebookStylePlus1NewsFeedOnPushReceived(){
A35Log.v(TAG, "showFacebookStylePlus1NewsFeedOnPushReceived")
if(activity != null && activity?.isFinishing == false){
txtNewInfo.visibility = View.VISIBLE
mHandler.postDelayed({
if(activity != null && activity?.isFinishing == false){
txtNewInfo.visibility = View.GONE
}
}, NEW_INFO_SHOW_TIMEOUT_MS)
}
}
and of course handle cleanup on the onPause so it doesn't hit the callback.
override fun onPause() {
super.onPause()
mHandler.removeCallbacks(null)
}
Now that we have talked through the obvious, let's talk about a cleaner option with modern day coroutines and kotlin :). If you aren't using these yet, you are really missing out.
fun doActionAfterDelay()
launch(UI) {
delay(MS_TO_DELAY)
actionToTake()
}
}
or if you want to always do a UI launch on that method you can simply do:
fun doActionAfterDelay() = launch(UI){
delay(MS_TO_DELAY)
actionToTake()
}
Of course just like the PostDelayed you have to make sure you handle canceling so you can either do the activity checks after the delay call or you can cancel it in the onPause just like the other route.
var mDelayedJob: Job? = null
fun doActionAfterDelay()
mDelayedJob = launch(UI) {
try {
delay(MS_TO_DELAY)
actionToTake()
}catch(ex: JobCancellationException){
showFancyToast("Delayed Job canceled", true, FancyToast.ERROR, "Delayed Job canceled: ${ex.message}")
}
}
}
}
//handle cleanup
override fun onPause() {
super.onPause()
if(mDelayedJob != null && mDelayedJob!!.isActive) {
A35Log.v(mClassTag, "canceling delayed job")
mDelayedJob?.cancel() //this should throw CancelationException in coroutine, you can catch and handle appropriately
}
}
If you put the launch(UI) into the method signature the job can be assigned in the calling line of code.
so moral of the story is to be safe with your delayed actions, make sure you remove your callbacks, or cancel your jobs and of course confirm you have the right life cycle to touch items on your delay callback complete. The Coroutines also offers cancelable actions.
Also worth noting that you should typically handle the various exceptions that can come with coroutines. For example, a cancelation, an exception, a timeout, whatever you decide to use. Here is a more advanced example if you decide to really start utilizing coroutines.
mLoadJob = launch(UI){
try {
//Applies timeout
withTimeout(4000) {
//Moves to background thread
withContext(DefaultDispatcher) {
mDeviceModelList.addArrayList(SSDBHelper.getAllDevices())
}
}
//Continues after async with context above
showFancyToast("Loading complete", true, FancyToast.SUCCESS)
}catch(ex: JobCancellationException){
showFancyToast("Save canceled", true, FancyToast.ERROR, "Save canceled: ${ex.message}")
}catch (ex: TimeoutCancellationException) {
showFancyToast("Timed out saving, please try again or press back", true, FancyToast.ERROR, "Timed out saving to database: ${ex.message}")
}catch(ex: Exception){
showFancyToast("Error saving to database, please try again or press back", true, FancyToast.ERROR, "Error saving to database: ${ex.message}")
}
}
For a Simple line Handle Post delay, you can do as following :
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
// Do someting
}
}, 3000);
I hope this helps
You can use this for Simplest Solution:
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
//Write your code here
}
}, 5000); //Timer is in ms here.
Else, Below can be another clean useful solution:
new Handler().postDelayed(() ->
{/*Do something here*/},
5000); //time in ms
You can make it much cleaner by using the newly introduced lambda expressions:
new Handler().postDelayed(() -> {/*your code here*/}, time);
Using Kotlin, we can achieve by doing the following
Handler().postDelayed({
// do something after 1000ms
}, 1000)
If you use RxAndroid then thread and error handling becomes much easier. Following code executes after a delay
Observable.timer(delay, TimeUnit.SECONDS)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(aLong -> {
// Execute code here
}, Throwable::printStackTrace);
I created simpler method to call this.
public static void CallWithDelay(long miliseconds, final Activity activity, final String methodName)
{
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
try {
Method method = activity.getClass().getMethod(methodName);
method.invoke(activity);
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
}, miliseconds);
}
To use it, just call : .CallWithDelay(5000, this, "DoSomething");
Below one works when you get,
java.lang.RuntimeException: Can't create handler inside thread that
has not called Looper.prepare()
final Handler handler = new Handler(Looper.getMainLooper());
handler.postDelayed(new Runnable() {
#Override
public void run() {
//Do something after 100ms
}
}, 100);
It's very easy using the CountDownTimer.
For more details https://developer.android.com/reference/android/os/CountDownTimer.html
import android.os.CountDownTimer;
// calls onTick every second, finishes after 3 seconds
new CountDownTimer(3000, 1000) {
public void onTick(long millisUntilFinished) {
Log.d("log", millisUntilFinished / 1000);
}
public void onFinish() {
// called after count down is finished
}
}.start();
I like things cleaner:
Here is my implementation, inline code to use inside your method
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
//Do something after 100ms
}
}, 100);
everybody seems to forget to clean the Handler before posting a new runnable or message on it. Otherway they could potentially accumulate and cause bad behaviour.
handler.removeMessages(int what);
// Remove any pending posts of messages with code 'what' that are in the message queue.
handler.removeCallbacks(Runnable r)
// Remove any pending posts of Runnable r that are in the message queue.
Here is another tricky way: it won't throw exception when the runnable change UI elements.
public class SimpleDelayAnimation extends Animation implements Animation.AnimationListener {
Runnable callBack;
public SimpleDelayAnimation(Runnable runnable, int delayTimeMilli) {
setDuration(delayTimeMilli);
callBack = runnable;
setAnimationListener(this);
}
#Override
public void onAnimationStart(Animation animation) {
}
#Override
public void onAnimationEnd(Animation animation) {
callBack.run();
}
#Override
public void onAnimationRepeat(Animation animation) {
}
}
You can call the animation like this:
view.startAnimation(new SimpleDelayAnimation(delayRunnable, 500));
Animation can attach to any view.
Here is the answer in Kotlin you lazy, lazy people:
Handler().postDelayed({
//doSomethingHere()
}, 1000)
Kotlin
runOnUiThread from a Fragment
Timer
example:
Timer().schedule(500) {
activity?.runOnUiThread {
// code
}
}
A suitable solution in android:
private static long SLEEP_TIME = 2 // for 2 second
.
.
MyLauncher launcher = new MyLauncher();
launcher.start();
.
.
private class MyLauncher extends Thread {
#Override
/**
* Sleep for 2 seconds as you can also change SLEEP_TIME 2 to any.
*/
public void run() {
try {
// Sleeping
Thread.sleep(SLEEP_TIME * 1000);
} catch (Exception e) {
Log.e(TAG, e.getMessage());
}
//do something you want to do
//And your code will be executed after 2 second
}
}
I'm trying to make a countdown timer in android for use in a small android app. The app will countdown from some number of seconds to 0, upon which it will do some action. I'm using the coundowntimer supplied by android.os.countdowntimer. Here is my code:
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.quizlayout);
new CountDownTimer(30000, 1000) {
TextView tx = (TextView) findViewById(R.id.textView2);
public void onTick(long millisUntilFinished) {
tx.setText("seconds remaining: " + millisUntilFinished / 1000);
}
public void onFinish() {
tx.setText("done!");
}
}.start();
}
However, this countdown timer is really slow. It takes like 3 real-time seconds for the timer to countdown by one second. I wonder what's going on? The code I have above is more or less copied straight from google (CountDownTimer)
Can anyone help me as per why my timer is so slow, and offer a way to speed it up a bit?
(EDIT): I am running this on an emulator, the intel atom x86. I am emulating an android 2.3.3 environment.
According to Android documentation for countdown timer
The calls to onTick(long) are synchronized to this object so that one call to onTick(long) won't ever occur before the previous callback is complete. This is only relevant when the implementation of onTick(long) takes an amount of time to execute that is significant compared to the countdown interval.
Take a look at this example for countdown timer
Countdown timer example
Alternately you can spawn a new thread and just get that thread to sleep for the interval you want and take actions when it wakes or vice versa.
You can also timertask
use a handler that will post the same runnable . this will remove the need for extra threads :
Handler handler=new Handler();
handler.postRunnable(... , 1000) ;
in the runnable , call the postRunnable again for the same handler (and add a condition for when to stop) .
CountDownTimer is not efficient regardless to ui updating performances. For a flawless ui update, it is better to create a custom countdown. I did my own so here it is. It is flawless on my app.
public abstract class CountDown {
int totalTime = 0;
int tickTime = 0;
Thread thread;
boolean canceled = false;
public CountDown(int totalTime,int tickTime){
this.totalTime = totalTime;
this.tickTime = tickTime;
}
public abstract void onTick();
public abstract void onFinish();
public void start(){
thread = new Thread(new Runnable() {
#Override
public void run() {
// Do in thread
canceled = false;
for (int elapsedTime = 0; elapsedTime < totalTime; elapsedTime += tickTime) {
if(!canceled){
onTick();
try {
thread.sleep(tickTime);
} catch (InterruptedException e) {
e.printStackTrace();
}
}else{
break;
}
}
if(!canceled){
onFinish();
}
}
});
thread.start();
}
public void cancel(){
canceled = true;
}
}
Remember that every time you have to update your ui, call a runOnUiThread, or else you will have an exception, you are not in a handler and not on ui thread.
Here is how to use it in your code, it is identical to CountDownTimer, so you could just rename lines in your code :
CountDown cDown = new CountDown(10000, 20) {
public void onTick() {
// Do something
}
public void onFinish() {
runOnUiThread(new Runnable() {
#Override
public void run() {
myButton.setImageDrawable(drawable);
}
});
}
};
I'm developing a Service for Android, that must run in background, executing a function each 100 seconds. That's the source code (example)
package com.example
import ....
public class Servizio extends Service {
public IBinder onBind(Intent intent) {
}
public void onCreate() {
}
public void onDestroy() {
//here put the code that stop the timer cycle
}
public void onStart(Intent intent, int startid) {
//i want to begin here the timercycle that each 100 s call myCycle()
}
public void myCycle() {
//code that i can't move on other class!!!
}
}
How I can do that? Now the service execute myCycle() just one time, beacause I put a calling in onStart().
Use a Timer with a TimerTask. To execute your method every 100 seconds, you can use the following in your onStart method. Be aware that this method creates a new thread.
new Timer().schedule(new TimerTask() {
#Override
public void run() {
myCycle();
}
}, 0, 100000);
Alternatively, use an android.os.Handler as described in this article: Updating the UI from a Timer. It is better than a Timer because it runs in the main thread, avoiding the overhead of a second thread.
private Handler handler = new Handler();
Runnable task = new Runnable() {
#Override
public void run() {
myCycle();
handler.postDelayed(this, 100000);
}
};
handler.removeCallbacks(task);
handler.post(task);
I usually do this, if I understood correctly you wanted the myCycle to execute every 100 secs.
Timer myTimer = new Timer();
myTimer.schedule(new TimerTask() {
#Override
public void run() {
myCycle();
}
}, 0,100000);
When I had this issue, where I call out to a webservice on a periodic basis this was my solution:
public class MyService extends Service {
private Handler mHandler = new Handler();
public static final int ONE_MINUTE = 60000;
private Runnable periodicTask = new Runnable() {
public void run() {
mHandler.postDelayed(periodicTask, 100 * ONE_MINUTE);
token = retrieveToken();
callWebService(token);
}
};
I call the postDelayed early so that the delay from the webservice call doesn't cause the timing to shift.
The two functions are actually in the MyService class.
UPDATE:
You can pass a Runnable to postDelayed as shown here:
http://developer.android.com/reference/android/os/Handler.html#postDelayed(java.lang.Runnable, long)
public final boolean postDelayed (Runnable r, long delayMillis)
Since: API Level 1 Causes the Runnable r to be added to the message
queue, to be run after the specified amount of time elapses. The
runnable will be run on the thread to which this handler is attached.
Also, my code won't compile due to missing functions, this is shown as an example of what the OP can do.