Hi I am working on TCP socket.
I can read data for every 1 sec. to achieve it I used TimerTask as shown in below code.
Handler handler = new Handler();
Timer timer = new Timer();
TimerTask doAsynchronousTask = new TimerTask() {
#Override
public void run() {
finalizer = new Runnable() {
public void run() {
try {
if (navBool) {
runOnUiThread(new Runnable() {
public void run() {
new RetriveStock().execute(); // AsyncTask.
}
});
}
} catch (Exception e) {
}
}
};
handler.post(finalizer);
}
};
timer.schedule(doAsynchronousTask, 0, 1000);
For canceling this timer I used code as
timer.cancel();
timer = null;
handler.removeCallbacks(finalizer);
But it is not cancelling the timer. I do not know why.
Instead of calling timer.cancel(), you should be canceling the task that is assigned to that timer (doAsynchronousTask in your case). Since multiple TimerTasks can be assigned to one timer, calling timer.cancel() will not interfere with a currently running task.
From the Timer JavaDoc:
public void cancel()
Terminates this timer, discarding any currently scheduled tasks. Does
not interfere with a currently executing task (if it exists). Once a
timer has been terminated, its execution thread terminates gracefully,
and no more tasks may be scheduled on it.
Related
I am new to programming and I am doing one android application on which I have one requirement where I need to monitor some logs for the 30s. I am using a timer task but what is happening, if the 30s are over and the run method executed once it is terminated the timer task not repeating.
Here is my code:
connectivityTimerTask = new ConnectivityTimerTask();
timer = new Timer(true);
//timer = new Timer(); // tried with this but it is not working
timer.schedule(connectivityTimerTask,30 * 1000);
TimerTask:
public class ConnectivityTimerTask extends TimerTask {
#Override
public void run() {
Log.error("----- ACK NotReceived -----" + System.currentTimeMillis());
//resetMonitor(); using this method I am setting the timer again
}
}
I want to know what's the best practice for scheduling repeating time.
Am I using the correct way? Can I use the resetMonitor() method?
Instead of of schedule(), You can use Timer task that can be scheduled at fixed rate with scheduleAtFixedRate,
int THIRTY_SECONDS = 30 * 1000;
Timer mTimer = new Timer();
mTimer.scheduleAtFixedRate(new TimerTask() {
#Override
public void run() {
// do whatever you want every 30s
Log.e("TAG", "----- ACK NotReceived -----" + System.currentTimeMillis());
}
}, 0, THIRTY_SECONDS);
Whenever you want to stop the timer call timer.cancel()
The line
timer.schedule(connectivityTimerTask,30 * 1000)
runs your task after a 30s delay and once the task completes, the timer's job is done.
If you want to keep running your task at periodic intervals, you have to also specify an interval period
schedule (TimerTask task, long delay, long period) // "period" specifies how often you want to run the task
Read the documentation here.
To repeatedly run some code after a set period of time, use a Runnable with a Handler like so
Handler handler = new Handler();
Runnable runnable = new Runnable() {
#Override
public void run() {
// do your logging
handler.postDelayed(this, 30000);
}
};
handler.post(runnable); // or handler.postDelayed(runnable, 30000) if you want it to wait 30s before starting initially
To cancel
handler.removeCallbacks(runnable);
In a run method of a TimerTask object, How can I submit the timerTask itself to another Timer.
When the timerTask is running, I should do a judge and decide whether it can do some work. If it not meet the condition, I should cancel it and put it to another Timer.
Code of my TimerTask is like this:
#Override
public void run() {
try {
if (flag) {
// do something
} else {
new Timer().schedule(this, 1000 * 60)；
}
} catch (Exception e) {
e.printStackTrace();
}
Will it work?
You should only use one Timer and then monitor the condition from external, for example from a Thread, a Runnable or another Timer. Then stop, cancel, re-assign, start the timer as necessary from your external monitor.
Here's a TimerTask:
public class OurTask extends TimerTask {
#Override
public void run() {
// Do something
}
}
And here's the monitor:
public Monitor implements Runnable() {
private Timer mTimerToMonitor;
public Monitor(Timer timerToMonitor) {
this.mTimerToMonitor = timerToMonitor;
}
#Override
public void run() {
while (true) {
if (!flag) {
// Cancel the timer and start a new
this.mTimerToMonitor.cancel();
this.mTimerToMonitor = new Timer();
this.mTimerToMonitor.schedule(...);
}
// Wait a second
Thread.sleep(1000);
}
}
}
Note that in practice your Monitor should also be able to get canceled from outside, currently it runs infinitely.
And this is how you could call it:
Timer timer = new Timer();
timer.schedule(new OurTask(), ...);
Thread monitorThread = new Thread(new Monitor(timer));
monitorThread.start();
Also note that instead of using Runnable, Timer and Thread it could be worth taking a look into the new Java 8 stuff, especially the interface Future and classes implementing it.
I have two AsyncTasks doing network operations. I want to call them periodically (like after one min.). How do I do that? I dont think I can do it on the UI thread. Do i need to create a new thread? Is it possible to implemet this without AlarmManager/Service?
Basically I want to exectue these two statements periodically after one min.
new UploadAsyncTask().execute();
new DownloadAsyncTask().execute();
Thank you
Just use a timer.
final Handler handler = new Handler();
Timer timer = new Timer();
TimerTask task = new TimerTask() {
#Override
public void run() {
handler.post(new Runnable() {
public void run() {
new UploadAsyncTask().execute();
new DownloadAsyncTask().execute();
}
});
}
};
timer.schedule(task, 0, 1000); //it executes this every 1000ms
In my method, I want to call another method that will run 1 second later. This is what I have.
final Timer timer = new Timer();
timer.schedule(new TimerTask() {
public void run() {
MyMethod();
Log.w("General", "This has been called one second later");
timer.cancel();
}
}, 1000);
Is this how it's supposed to be done?
Are there other ways to do it since I'm on Android?
Can it be repeated without any problems?
There are several alternatives. But here is Android specific one.
If you thread is using Looper (and Normally all Activity's, BroadcastRecevier's and Service's methods onCreate, onReceive, onDestroy, etc. are called from such a thread), then you can use Handler. Here is an example:
Handler handler = new Handler();
handler.postDelayed(new Runnable()
{
#Override
public void run()
{
myMethod();
}
}, 1000);
Note that you do not have to cancel anything here. This will be run only once on the same thread your Handler was created.
Instead of a Timer, I'd recommend using a ScheduledExecutorService
final ScheduledExecutorService exec = Executors.newScheduledThreadPool(1);
exec.schedule(new Runnable(){
#Override
public void run(){
MyMethod();
}
}, 1, TimeUnit.SECONDS);
If you are not in UI thread, consider adding a very simple:
try
{
Thread.sleep( 1000 );
}//try
catch( Exception ex)
{ ex.printStackTrace(); }//catch
//call your method
ScheduledExecutorService or AsyncTask for UI related.
Note that if you are to update UI, that code should be posted to UI thread. as in Processes and Threads Guide
final Bitmap bitmap = loadImageFromNetwork("http://example.com/image.png");
mImageView.post(new Runnable() {
public void run() {
mImageView.setImageBitmap(bitmap);
}
});
There is also nice postDelayed method in View
mImageView.postDelayed(new Runnable(){
#Override
public void run() {
mImageView.setImageResource(R.drawable.ic_inactive);
}
}, 1000);
that will update UI after 1 sec.
I am using java.util.Timer class and I am using its schedule method to perform some task, but after executing it for 6 times I have to stop its task.
How should I do that?
Keep a reference to the timer somewhere, and use:
timer.cancel();
timer.purge();
to stop whatever it's doing. You could put this code inside the task you're performing with a static int to count the number of times you've gone around, e.g.
private static int count = 0;
public static void run() {
count++;
if (count >= 6) {
timer.cancel();
timer.purge();
return;
}
... perform task here ....
}
Either call cancel() on the Timer if that's all it's doing, or cancel() on the TimerTask if the timer itself has other tasks which you wish to continue.
You should stop the task that you have scheduled on the timer:
Your timer:
Timer t = new Timer();
TimerTask tt = new TimerTask() {
#Override
public void run() {
//do something
};
};
t.schedule(tt,1000,1000);
In order to stop:
tt.cancel();
t.cancel(); //In order to gracefully terminate the timer thread
Notice that just cancelling the timer will not terminate ongoing timertasks.
Terminate the Timer once after awake at a specific time in milliseconds.
Timer t = new Timer();
t.schedule(new TimerTask() {
#Override
public void run() {
System.out.println(" Run spcific task at given time.");
t.cancel();
}
}, 10000);