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I'm developing an application which sends a message to a specific number in a specific period of time. The problem is that it continues sending that message after that period of time. How would I stop the timer after that specific time in order to stop sending that message?
CountDownTimer waitTimer;
waitTimer = new CountDownTimer(60000, 300) {
public void onTick(long millisUntilFinished) {
//called every 300 milliseconds, which could be used to
//send messages or some other action
}
public void onFinish() {
//After 60000 milliseconds (60 sec) finish current
//if you would like to execute something when time finishes
}
}.start();
to stop the timer early:
if(waitTimer != null) {
waitTimer.cancel();
waitTimer = null;
}
and.. we must call "waitTimer.purge()" for the GC. If you don't use Timer anymore, "purge()" !! "purge()" removes all canceled tasks from the task queue.
if(waitTimer != null) {
waitTimer.cancel();
waitTimer.purge();
waitTimer = null;
}
In java.util.timer one can use .cancel() to stop the timer and clear all pending tasks.
We can schedule the timer to do the work.After the end of the time we set the message won't send.
This is the code.
Timer timer=new Timer();
timer.scheduleAtFixedRate(new TimerTask() {
#Override
public void run() {
//here you can write the code for send the message
}
}, 10, 60000);
In here the method we are calling is,
public void scheduleAtFixedRate (TimerTask task, long delay, long period)
In here,
task : the task to schedule
delay: amount of time in milliseconds before first execution.
period: amount of time in milliseconds between subsequent executions.
For more information you can refer:
Android Developer
You can stop the timer by calling,
timer.cancel();
I had a similar problem: every time I push a particular button, I create a new Timer.
my_timer = new Timer("MY_TIMER");
my_timer.schedule(new TimerTask() {
...
}
Exiting from that activity I deleted the timer:
if(my_timer!=null){
my_timer.cancel();
my_timer = null;
}
But it was not enough because the cancel() method only canceled the latest Timer. The older ones were ignored an didn't stop running. The purge() method was not useful for me.
I solved the problem just checking the Timer instantiation:
if(my_timer == null){
my_timer = new Timer("MY_TIMER");
my_timer.schedule(new TimerTask() {
...
}
}
It says timer() is not available on android? You might find this article useful.
http://developer.android.com/resources/articles/timed-ui-updates.html
I was wrong. Timer() is available. It seems you either implement it the way it is one shot operation:
schedule(TimerTask task, Date when) // Schedule a task for single execution.
Or you cancel it after the first execution:
cancel() // Cancels the Timer and all scheduled tasks.
http://developer.android.com/reference/java/util/Timer.html
I had a similar problem and it was caused by the placement of the Timer initialisation.
It was placed in a method that was invoked oftener.
Try this:
Timer waitTimer;
void exampleMethod() {
if (waitTimer == null ) {
//initialize your Timer here
...
}
The "cancel()" method only canceled the latest Timer. The older ones were ignored an didn't stop running.
Related
I'd like to implement several timers (to create a multiple-stopwatches application), and CountDownTimer seems to be the obvious choice, however I'd like to provide the ability to pause one or all of the stopwatches.
From the documentation provided on CountDownTimer I don't see an obvious way to pause the countdown after it has begun, only to stop it or to increase/decrease it by a set amount.
Thanks!
I don't know much about using the CountDownTimer but I know that when I had to make a timer I used the built in Java Timer class with a TimerTask. If you were wanting to make several timers count down and pause them individually you could do something like this
task1 = new TimerTask() {
public void run() {
time1--;
}
};
task2 = new TimerTask() {
public void run() {
time2--;
}
};
Timer1 = new Timer();
Timer2 = new Timer();
Timer1.scheduleAtFixedRate(task1,0,1000);
Timer2.scheduleAtFixedRate(task2,0,1000);
#Override OnClickListener(stopButton1)
{
Timer.Cancel();
}
#Override OnClickListener(startButton1)
{
Timer1 = new Timer();
Timer1.scheduleAtFixedRate(task1,0,1000);
}
This isnt exact syntax but I think it relays the idea. Just a heads up but if you go this route you can't update the UI in that task normally, that would look like this.
Activity_name.this.runOnUiThread(new Runnable() {
public void run() {
text.setText("Level " + Integer.toString(level)+ " will start in " +Integer.toString(time) + " seceonds." );
}
});
which you would put in the "Run" part of the task. This doesn't really have to do with the exact question but I was stuck for days on updating the UI part until someone here helped me out.
I started out using CountDownTimer (but switched to Runnable and Handler.postDelayed).
On timer ticks I decremented a counter. To pause, I canceled the timer. To resume, I created a new timer using the saved counter value. It seemed a little kludgy, but it seemed the only option.
(I don't recall why I made the switch, unfortunately. IIRC at the time there was a reason, but I don't know if it was a limitation of CountDownTimer, or my particular needs.)
I'm calling my TimerTask (m_timer) upon a button click:
m_timer.schedule(m_progressUpdater, 0, 500);
Which kicks off my run method:
#Override
public void run() {
//do some stuff
progressBar.setProgress(currentProgress);
if (progress >= 100) {
handler.post(new Runnable() {
#Override
public void run() {
CompleteTask();
}
});
}
}
I can call this once and it works perfectly. When I call it again, my app stops responding. I'm thinking that I need to cancel the task in my CompleteTask() method, but I've tried cancelling both the TimerTask and the Timer, and it still crashes. Anyone know what the problem might be?
Have you tried creating new TimerTask instance for the second call? And by the way, don't cancel the timer otherwise it will cancel all of its task. And what did the log say?
When you reschedule a Timer, it throws:
java.lang.IllegalStateException: TimerTask is scheduled already
It seems that you can only use a timer for once.
In order to reschedule a Timer, you need to simply create a new instance of it, each time. like the following:
// if you have already started a TimerTask,
// you must(?) terminate the timer before rescheduling it again.
if(m_timer != null)
m_timer.cancel();
m_timer = new Timer();
m_progressUpdater = new myTimerTask();
m_timer.schedule(m_progressUpdater, 0, 500);
How can I reschedule a timer. I have tried to cancel the timer/timertask and and schedule it again using a method. But its showing an exception error:
Exception errorjava.lang.IllegalStateException: TimerTask is scheduled already
Code I have used it :
private Timer timer = new Timer("alertTimer",true);
public void reScheduleTimer(int duration) {
timer.cancel();
timer.schedule(timerTask, 1000L, duration * 1000L);
}
If you see the documentation on Timer.cancel() you'll see this:
"Cancels the Timer and all scheduled tasks. If there is a currently running task it is not affected. No more tasks may be scheduled on this Timer. Subsequent calls do nothing."
You'll need to initialize a new Timer when you are rescheduling:
EDIT:
public void reScheduleTimer(int duration) {
timer = new Timer("alertTimer",true);
timerTask = new MyTimerTask();
timer.schedule(timerTask, 1000L, duration * 1000L);
}
private class MyTimerTask extends TimerTask {
#Override
public void run() {
// Do stuff
}
}
In fact, if you look in the cancel method javadoc, you can see the following thing :
Does not interfere with a currently executing task (if it exists).
That tells the timer "ok, no more tasks now, but you can finish the one you're doing". I think you'll also need to cancel the TimerTask.
#Eric Nordvik answer is running fine.
One thing we can do is to cancel previous timer events execution
public void reScheduleTimer(int duration) {
// Cancel previous timer first
timer.cancel();
timer = new Timer("alertTimer",true);
timerTask = new MyTimerTask();
timer.schedule(timerTask, 1000L, duration * 1000L);
}
Actually you can use purge() so you don't have to initialize a new Timer.
public int purge ()
Added in API level 1
Removes all canceled tasks from the task queue. If there are no other references on the tasks, then after this call they are free to be garbage collected.
Returns the number of canceled tasks that were removed from the task queue.
Hello I am building an application that is going to execute a block of code at fixed periods of time (e.g. every 30 minutes). I would like that period to be strict,what I mean is that I would like to be guaranteed that the period will be 30 minutes and not 28 minutes or whenever the os whants to execute it.
I have a Timer object and use it as follows:
timer=new Timer();
timer.scheduleAtFixedRate(new GetLastLocation(), 0, this.getInterval());
where GetLastLocation is the handler class wich extends TimerTask.
This works fine,but I would like to be able to change the interval,what I am currently doing is using timer.scheduleAtFixedRate twice and changing the interval parameter to lets say a newInterval but I think that this is just having two timers execute every interval and new
Interval now, am I correct?
also I have tries cancelling the timer and then using the the method scheduleAtFixedRate() but this throws an exception as stated in the documentation.
what can I do to fix this?
regards maxsap
you can not schedule on a timer which was already cancelled or scheduled. You need to create a new timer for that.Timer timer;
synchronized void setupTimer(long duration){
if(timer != null) {
timer.cancel();
timer = null;
}
timer = new Timer();
timer.scheduleAtFixedRate(new GetLastLocation(), 0, duration);
}Now you can call setupTimer whenever you want to change the duration of the timer.PS: In fixed-rate execution, each execution is scheduled relative to the scheduled execution time of the initial execution. If an execution is delayed for any reason (such as garbage collection or other background activity), two or more executions will occur in rapid succession to "catch up." In the long run, the frequency of execution will be exactly the reciprocal of the specified period (assuming the system clock underlying Object.wait(long) is accurate).
Define your task inside a TimerTask (as you did) and schedule the timer.
public final void checkFunction(){
t = new Timer();
tt = new TimerTask() {
#Override
public void run() {
//Execute code...
}
};
t.schedule(tt, 10*1000); /* Run tt (your defined TimerTask)
again after 10 seconds. Change to your requested time. */
}
Just execute the function wherever you want, for example in onCreate or in onResume/onStart.
You can also use handler instead of timertask.
Handler mHandler = new Handler() {
public void handleMessage(Message msg) {
if(what.msg==1)
{
what.msg==2;
}
}
};
mHandler.sendEmptyMessageDelayed(1, 10* 1000);//10*1000 10 sec.specify your time
I am currently trying to set up a WiFi Scan in my Android application that scans for WiFi access points every 30 seconds.
I have used Timer and TimerTask to get the scan running correctly at the intervals which I require.
However I want to be able to stop and start the scanning when the user presses a button and I am currently having trouble stopping and then restarting the Timer and TimerTask.
Here is my code
TimerTask scanTask;
final Handler handler = new Handler();
Timer t = new Timer();
public void doWifiScan(){
scanTask = new TimerTask() {
public void run() {
handler.post(new Runnable() {
public void run() {
wifiManager.scan(context);
Log.d("TIMER", "Timer set off");
}
});
}};
t.schedule(scanTask, 300, 30000);
}
public void stopScan(){
if(scanTask!=null){
Log.d("TIMER", "timer canceled");
scanTask.cancel();
}
}
So the Timer and Task start fine and the scan happens every 30 seconds however I cant get it to stop, I can stop the Timer but the task still occurs and scanTask.cancel() doesn't seem to work either.
Is there a better way to do this? Or am I missing something in the Timer/TimerTask classes?
You might consider:
Examining the boolean result from calling cancel() on your task, as it should indicate if your request succeeds or fails
Try purge() or cancel() on the Timer instead of the TimerTask
If you do not necessarily need Timer and TimerTask, you can always use postDelayed() (available on Handler and on any View). This will schedule a Runnable to be executed on the UI thread after a delay. To have it recur, simply have it schedule itself again after doing your periodic bit of work. You can then monitor a boolean flag to indicate when this process should end. For example:
private Runnable onEverySecond=new Runnable() {
public void run() {
// do real work here
if (!isPaused) {
someLikelyWidget.postDelayed(onEverySecond, 1000);
}
}
};
using your code, instead of
scanTask.cancel();
the correct way is to cancel your timer (not timerTask):
t.cancel();
The Android documentation says that cancel() Cancels the Timer and all scheduled tasks. If there is a currently running task it is not affected. No more tasks may be scheduled on this Timer. Subsequent calls do nothing. Which explains the issue.