In my Android app, I want to schedule a task to run in 10 seconds, unless the user presses a specific button.
What is the best way to do this? Should I use a java.util.Timer, java.util.concurrent.ScheduledThreadPoolExecutor or something else?
Thank you in advance.
A handler is fit for this if you are accessing the UI from your task :
Runnable runnable = new Runnable() {
public void run () {
// Do your stuff here
}
}
Handler handler = new Handler();
handler.postDelayed(runnable, 10000);
in your button action :
handler.removeCallbacks(runnable);
Otherwise, a Timer is fine.
and Handler and its postDelayed method
private Runnable requester = new Runnable() {
#Override
public void run() {
// cpde to execute here
}
};
public void onClick(View v) {
new Handler().postDelayed(requester, 10000);
}
You able to use TimerTask and Handler.
Related
I would like to run a function periodically every 5 seconds in a foreground service. I use android.os.Handler.postDelayed for that, like this:
private Handler handler = new Handler();
private Runnable updater = new Runnable() {
#Override
public void run() {
// Do some work
scheduleTask();
}
};
private void scheduleTask() {
handler.postDelayed(updater, 5000);
}
#Override
public void onCreate() {
super.onCreate();
scheduleTask();
}
#Override
public void onDestroy() {
super.onDestroy();
handler.removeCallbacks(updater);
}
Is it possible for the handler.postDelayed to fail? Can the OS just cancel the delayed request? How to catch that?
I need this to run stable for days.
If the app is in the foreground then there is no chance that the handler gets cancelled. It only gets cancelled when the app is running in background for some time or the Main thread has been destroyed.
For reference you can read the android developers documentation
https://developer.android.com/reference/android/os/Handler
I need a thread to start after 3 seconds of a button being idle, is there a simple way of doing it?
I'm building a counter app, the button triggers two counters, the total counter and the "tapping counter", the tapping counter helps keep track of the actual change of values, showing how many taps the user did, I need it to vanish after some seconds so the user can tap again.
for stuffs like that I usually use a Handler with a Runnable in order to do stuff after X milliseconds the user isn't doing a specific action.
First, create a runnable and a handler
final android.os.Handler handler = new android.os.Handler();
private Runnable runnable;
private final long DELAY = 3000; // how many milliseconds you want to wait
Then add the onClickListener:
myButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
}
});
Then, inside onClick event, remove callbacks and istantiate the handler again as follows:
if(runnable != null) {
// in this case the user already clicked once at least
handler.removeCallbacks(runnable);
}
runnable = new Runnable() {
#Override
public void run() {
//this code will run when user isn't clicking for the time you set before.
}
};
handler.postDelayed(runnable, DELAY);
Final result:
final android.os.Handler handler = new android.os.Handler();
private Runnable runnable;
private final long DELAY = 3000; // how many milliseconds you want to wait
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// all your previous stuffs
myButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if(runnable != null) {
// in this case the user already clicked once at least
handler.removeCallbacks(runnable);
}
runnable = new Runnable() {
#Override
public void run() {
//this code will run when user isn't clicking for the time you set before.
}
};
handler.postDelayed(runnable, DELAY);
}
});
}
I hope this helps, for any question feel free to ask
Handler may work in this scenario, with a 3000 milisecond delay.
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
// do action
}
}, 3000);
At first, you create a Timer with a TimerTask(with your Thread) and schedule it to run after 3 seconds.
Every time the button is pressed, you reset the timer.
public class MyClass{
private Timer timer=new Timer()
private TimerTask task=new TimerTask(){
public void run(){
//your action
}
};
public void init(){
timer.schedule(task,3000);
}
public void onButtonClick(){
task.cancel();
timer.schedule(task,3000);
}
}
I've got game based on CountDownTimer, which is continuously repeating countdowns. This countDown is counting time for user to react on some action related to number, if user reacts onFinish() is called by some clickListener or by itself if the time was up. Depending of succesCondition(), method success or fail is called and those methods are defining if game is still running.
OnCreate
loop = gameLoop(time).start();
MainActivity
public CountDownTimer gameLoop(int time){
return new CountDownTimer(time, time+100) {
#Override
public void onTick(long millisUntilFinished) {
}
#Override
public void onFinish() {
if (!Conditions.succesCondition(number)) {
success();
} else {
fail();
}
}
};
}
public void success() {
loop.cancel();
scoreCount++;
animation.start();
}
public void fail(){
loop.cancel();
}
However this timer runs on Main thread and that provides well known issue skipped xx frames, your app might be doing too much work on its main thread and I found that this is common issue for CountDownTimer and replacing it with Handler is a solution.
I can't put this timer in AsyncTask because it performs mainly UI related tasks (TextViews, TextSwitcher, some progressBar etc. in success() method. I didn't put that in code in those methods for more clean view of the main problem. I'm trying to reconstruct CountDownTimer- like concept with handler and runnable to replace my Timer, but I'm actually stuck with nothing. As you can see I'm using only onFinish method, onTick is not necessary.
I suggest using a combination of java.util.Timer, java.util.TimerTask and Activity.runOnUiThread(). First create a Timer and call one of its schedule...()methods. Any action that needs to be done on the main (ui) thread can be wrapped in runOnUiThread(() -> { ...}). Be sure to call cancel() on TimerTask and Timer if those objects are no longer needed. Cancelling the Timer cancels the TimerTask as well.
Here is how this may look like:
public class TimerTaskActivity extends Activity {
Timer timer;
TimerTask timerTask;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.timertask);
...
}
#Override
protected void onStart() {
super.onStart();
timer = new Timer();
timerTask = new TimerTask() {
#Override
public void run() {
runOnUiThread(() -> {
....
});
}
};
timer.scheduleAtFixedRate(timerTask, 2000, 2000);
}
#Override
protected void onPause() {
super.onPause();
timer.cancel();
}
}
You may handle this situation using AsyncTask as well overriding the onProgressUpdate method.
Here's an example about how you can achieve the behaviour to interact with your main thread from AsyncTask. The example shows the update of a download which can be easily transformed to your specific problem of timer.
Update
In my case almost all code would be in onProgressUpdate, would it
still make any sense?
No, your code will not be in onProgressUpdate. The onProgressUpdate method will only be updating your timer in your UI. As far as I could understand, the success and the fail will be triggered based on user action as well. Then those actions are triggered, you can stop the AsyncTask to update your timer as well. You just need to AsyncTask to update the timer value time to time.
You will get a callback in your Activity when the AsyncTask finishes. See the mNotificationHelper.completed(); function in the above example. When you are notified in your Activity when the timer finishes, you might then execute the following task there.
public void completed() {
if (!Conditions.succesCondition(number)) {
success();
} else {
fail();
}
}
OK. I finally figured out how to handle it with handler (hehe):
public void startGameAction() {
//My game actions
handler = new Handler();
runnable = () -> {
if (!Conditions.succesCondition(number)) {
success();
} else {
fail();
}
};
handler.postDelayed(runnable,time);
}
public void success(){
handler.removeCallbacks(runnable);
handler = null;
scoreCount++;
//other stuff
startGameAction();
}
private void fail() {
handler.removeCallbacks(runnable);
//other stuff
}
onCreate only startGame call, handler and runnable defined as class fields
startGameAction();
I'm creating a button to stop a light sensor after grabbing two equal light values for a duration of 2 seconds using the handler's delay function. It works fine at first but when I press the button again, the delay seems to get shorter and shorter, and eventually doesn't happen at all.
stateLx.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
onResume();
stateLx.setEnabled(false);
doub2x.setText(Double.toString(0));
doub1x.setText(Double.toString(0));
//Stabilization Handlers
m_handler = new Handler();
m_handlerTask = new Runnable() {
public void run() {
doub1 = movingValue[0];
doub1x.setText(Double.toString(doub1));
m_handler.postDelayed(this, 1000);
}
};
m2_handler = new Handler();
m2_handlerTask = new Runnable() {
public void run() {
doub2 = movingValue[0];
doub2x.setText(Double.toString(doub2));
m2_handler.postDelayed(this, 2000);
if (doub1 != doub2) {
instructions.setText("unequal");
} else {
instructions.setText("equal");
getInitialLightValue();
reCalculateInitial();
beerLambert(volValues, lxValuesNew);
}
}
};
//Handlers for stabilizer
m_handler.postDelayed(m_handlerTask, 1000);
m2_handler.postDelayed(m2_handlerTask, 3000);
lame.setText(Double.toString(absorbValues[0]));
stateLx.setEnabled(true);
}
});
I've tried putting the handlers both in and out of the onclick function, as well as including the onResume() function at the beginning of the button press, but I'm having no luck. Is there something wrong with my code?
You keep recreating your Handlers and Runnables. This is part of the problem, you should check to see if you are already polling before starting again.
Also, this is a side note -- but it's odd to call lifecycle methods, like onResume() yourself, since it calls up to the super.
I have an AsyncTask class that I execute that downloads a big list of data from a website.
In the case that the end user has a very slow or spotty data connection at the time of use, I'd like to make the AsyncTask timeout after a period of time. My first approach to this is like so:
MyDownloader downloader = new MyDownloader();
downloader.execute();
Handler handler = new Handler();
handler.postDelayed(new Runnable()
{
#Override
public void run() {
if ( downloader.getStatus() == AsyncTask.Status.RUNNING )
downloader.cancel(true);
}
}, 30000 );
After starting the AsyncTask, a new handler is started that will cancel the AsyncTask after 30 seconds if it's still running.
Is this a good approach? Or is there something built into AsyncTask that is better suited for this purpose?
Yes, there is AsyncTask.get()
myDownloader.get(30000, TimeUnit.MILLISECONDS);
Note that by calling this in main thread (AKA. UI thread) will block execution, You probably need call it in a separate thread.
Use CountDownTimer Class in side the extended class for AsyncTask in the onPreExecute() method:
Main advantage, the Async monitoring done internally in the class.
public class YouExtendedClass extends AsyncTask<String,Integer,String> {
...
public YouExtendedClass asyncObject; // as CountDownTimer has similar method -> to prevent shadowing
...
#Override
protected void onPreExecute() {
asyncObject = this;
new CountDownTimer(7000, 7000) {
public void onTick(long millisUntilFinished) {
// You can monitor the progress here as well by changing the onTick() time
}
public void onFinish() {
// stop async task if not in progress
if (asyncObject.getStatus() == AsyncTask.Status.RUNNING) {
asyncObject.cancel(false);
// Add any specific task you wish to do as your extended class variable works here as well.
}
}
}.start();
...
change CountDownTimer(7000, 7000) -> CountDownTimer(7000, 1000) for example and it will call onTick() 6 times before calling onFinish(). This is good if you want to add some monitoring.
Thanks for all the good advice I got in this page :-)
In the case, your downloader is based upon an for an URL connection, you have a number of parameters that could help you to define a timeout without complex code:
HttpURLConnection urlc = (HttpURLConnection) url.openConnection();
urlc.setConnectTimeout(15000);
urlc.setReadTimeout(15000);
If you just bring this code into your async task, it is ok.
'Read Timeout' is to test a bad network all along the transfer.
'Connection Timeout' is only called at the beginning to test if the server is up or not.
I don't think there's anything like that built into AsyncTask. Your approach seems to be a good one. Just be sure to periodically check the value of isCancelled() in your AsyncTask's doInBackground method to end this method once the UI thread cancels it.
If you want to avoid using the handler for some reason, you could check System.currentTimeMillis periodically within your AsyncTask and exit on timeout, although I like your solution better since it can actually interrupt the thread.
Context mContext;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mContext = this;
//async task
final RunTask tsk = new RunTask ();
tsk.execute();
//setting timeout thread for async task
Thread thread1 = new Thread(){
public void run(){
try {
tsk.get(30000, TimeUnit.MILLISECONDS); //set time in milisecond(in this timeout is 30 seconds
} catch (Exception e) {
tsk.cancel(true);
((Activity) mContext).runOnUiThread(new Runnable()
{
#SuppressLint("ShowToast")
public void run()
{
Toast.makeText(mContext, "Time Out.", Toast.LENGTH_LONG).show();
finish(); //will close the current activity comment if you don't want to close current activity.
}
});
}
}
};
thread1.start();
}
You can put one more condition to make cancellation more robust. e.g.,
if (downloader.getStatus() == AsyncTask.Status.RUNNING || downloader.getStatus() == AsyncTask.Status.PENDING)
downloader.cancel(true);
Inspiring from question I have written a method which do some background task via AsyncTask and if processing takes more then LOADING_TIMEOUT then an alert dialogue to retry will appear.
public void loadData()
{
final Load loadUserList=new Load();
loadUserList.execute();
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
if (loadUserList.getStatus() == AsyncTask.Status.RUNNING) {
loadUserList.cancel(true);
pDialog.cancel();
new AlertDialog.Builder(UserList.this)
.setTitle("Error..!")
.setMessage("Sorry you dont have proper net connectivity..!\nCheck your internet settings or retry.")
.setCancelable(false)
.setPositiveButton("Retry", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialogInterface, int i) {
loadData();
}
})
.setNegativeButton("Exit", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialogInterface, int i) {
System.exit(0);
}
})
.show();
}
}
}, LOADING_TIMEOUT);
return;
}