Cancel a timer in BlackBerry - Java

Question

I am working with a BlackBerry App that has a number of timers in it to schedule sending reports to the server platform. It is all working fine until I changed the logic to prioritize reports. Therefore, now I am checking if, for instance, Report A is switched on and the user activates Report B as well, then only Report B should go through and Report A should halt UNTIL B is activated. Once B is deactivated (timer cancelled), Report A should resume. However, even when the code loops in the cancel timer task code, Report A continues to go through while B is still activated.

FieldChangeListener reportingListener = new FieldChangeListener() {   
        public void fieldChanged(Field field, int context) 
        {
            try {

            if (field == slider) {
                int i = slider.getValue();
                if(i==0) 
                    lblInterval.setText(1+" minute");
                if(i==1) 
                    lblInterval.setText(2+" minutes");
                if(i==2) 
                    lblInterval.setText(5+" minutes");
                if(i==3) 
                    lblInterval.setText(10+" minutes");
                if(i==4) 
                    lblInterval.setText(15+" minutes");
                if(i==5) 
                    lblInterval.setText(30+" minutes");
                if(i==6) 
                    lblInterval.setText(1+" hour");
                if(i==7) 
                    lblInterval.setText(2+" hours");
                if(i==8) 
                    lblInterval.setText(6+" hours");
                if(i==9) 
                    lblInterval.setText(12+" hours");
                if(i==10) 
                    lblInterval.setText(24+" hours");
                setSliderPosition(i);
                value=setLblIntervalValue(i);
                value2=setGpsTimerIntervalValue(i);
                gpsReportValue=lblInterval.getText();
                gpsIntervalValue1=setGpsTimerIntervalValue(i);
            }

            if (PersistentStoreHelper.persistentHashtable.containsKey("image")) 
                 {
            boolean trackONOFFImage = ((Boolean) PersistentStoreHelper.persistentHashtable.get("image")).booleanValue();
            if(trackONOFFImage==true)
            {
                if (PersistentStoreHelper.persistentHashtable.containsKey("panic"))
                 {
                     boolean panicImage = ((Boolean)PersistentStoreHelper.persistentHashtable.get("panic")).booleanValue();
                     if(panicImage==true)
                     {
                         MyScreen.currentlyReporting.setText("PANIC ALARM TRIGGERED");
                         if (PersistentStoreHelper.persistentHashtable.containsKey("tabTrackValid"))
                     {
                         boolean trackingTab = ((Boolean)PersistentStoreHelper.persistentHashtable.get("tabTrackValid")).booleanValue();
                         if(trackingTab==false)
                         {
                            trackSlider.cancel();
                         }
                        PersistentStoreHelper.persistentHashtable.put("tabTrackValid", Boolean.TRUE);
                     }

                     }
                     else
                     {
                        //int gpsIntervalValue1=setGpsTimerIntervalValue(i);
                    if (PersistentStoreHelper.persistentHashtable.containsKey("gpsTimerIntervalValue")) 
                     {
                        String intervalValue=((String)PersistentStoreHelper.persistentHashtable.get("gpsTimerIntervalValue"));
                        if(gpsIntervalValue1==Integer.parseInt(intervalValue))
                        {
                            //do nothing
                        }
                        else
                        {
                            trackSlider = new TimerTask() {
                                 public void run() {

                                    try {
                                        UiApplication.getUiApplication().invokeLater(new Runnable() 
                                        {
                                            public void run() {
                                               //Dialog.alert("Invalid login details");
                                            }
                                        });
                                        sendTrackingReport();
                                    } catch (Exception e) {
                                        Dialog.alert("Unable to track at the new interval set");
                                    }

                                 }
                              };
                              //trackSlider.run();
                              trackingTimerSlider.scheduleAtFixedRate(trackSlider , 0, gpsIntervalValue1);
                             PersistentStoreHelper.persistentHashtable.put("tabTrackValid", Boolean.FALSE);
                        }
                     }
                     }
                 }

            }//this
                }

        } catch (IllegalStateException e) {
            //Dialog.alert("CANCEL TRACK1");
            e.printStackTrace();
        } catch (NullPointerException e) {
            //Dialog.alert("CANCEL TRACK2");
            e.printStackTrace();
        }
        }   
     }; 

NOTE: Report A = Tracking. Report B = Panic. Panic has priority over Tracking. Slider is changing the timer interval value.

I debugged my code and while it goes into the loop and cancels the timer task of the requested report, I still see those reports going through. Am I not cancelling the timer correctly? Please advice.

Answer 1

From the TimerTask.cancel javadoc:

... If the task has been scheduled for repeated execution, it will never run again. (If the task is running when this call occurs, the task will run to completion, but will never run again.) ...

So to begin with, calling cancel from a thread does not immediatly stop the Timer thread as you can see.

Also you are creating a new Timer each time in your screen:

trackSlider = new TimerTask()

Thus it might be possible that if you create several instances of your screen during the app running, several timers of the same type will be created.