java - Why does my simple timer app keep getting faster each time I pause? -

ok, thought problem each time press stop , start, new runnable created, have multiple runnable running @ same time, updating timer quicker , quicker each time. doesn't seems problem: changed code adding boolean "running" pressing start/stop changes boolean variable. in way, think 1 runnable running. still gets faster click start/stop several times in row. can tell me problem is?

package com.example.timernew;  import android.app.activity; import android.os.bundle; import android.os.handler; import android.view.menu; import android.view.menuitem; import android.view.view; import android.view.view.onclicklistener; import android.widget.button; import android.widget.textview;  public class mainactivity extends activity {     handler h=new handler();     textview t;     button start, stop,reset;     boolean running;     runnable run=new runnable() {              @override public void run() { updatetime(); } };;      @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_main);         t = (textview) findviewbyid(r.id.textarea);          start = (button) findviewbyid(r.id.start_button);          stop=(button) findviewbyid(r.id.stop_button);         running=false;         h.post(run);              start.setonclicklistener(new onclicklistener(){             @override             public void onclick(view v){                 if(running==false){                 running=true;                 }             }         });         stop.setonclicklistener(new onclicklistener(){             @override             public void onclick(view v){                 if(running==true){                 running=false;                 }             }         });      }      public void updatetime() {         if(running==true){         t.settext("" + (integer.parseint(t.gettext().tostring()) +1));          h.postdelayed(run, 1000);}     }  } 

i added call updatetime() in start button onclicklistenter , have had no problems count continuing after hitting stop. after waiting 10+ seconds, hitting start again starts continues left off.

i did notice value increase twice in quick succession if hit start within 1 second of hitting stop. because hitting start calls updatetime() , posted runnable's delay has not finished, when does, increments time.

a better bet use asynctask:

    package com.example.timernew;  import android.app.activity; import android.os.asynctask; import android.os.bundle; import android.os.handler; import android.util.log; import android.view.view; import android.view.view.onclicklistener; import android.widget.button; import android.widget.textview;  public class mainactivity extends activity {     handler h=new handler();     textview t;     button start, stop,reset;     volatile boolean running;     updatetimetask mupdatetimetask;     int counter = 0;      @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_main);         t = (textview) findviewbyid(r.id.textarea);          start = (button) findviewbyid(r.id.start_button);          stop=(button) findviewbyid(r.id.stop_button);         running=false;          start.setonclicklistener(new onclicklistener(){             @override             public void onclick(view v){                 if (null == mupdatetimetask) {                     mupdatetimetask = new updatetimetask();                     mupdatetimetask.execute();                 }             }         });          stop.setonclicklistener(new onclicklistener(){             @override             public void onclick(view v){                 if(null != mupdatetimetask) {                     mupdatetimetask.cancel(true);                     mupdatetimetask = null;                 }             }         });      }       public class updatetimetask extends asynctask<void, void, void> {           protected void doinbackground(void... params) {              while (true) {                 try {                     thread.sleep(1000);                 } catch (interruptedexception ie) {                     log.e("timer app", "a problem occurred while sleeping or task cancelled", ie);                     return null;                 }                 counter++;                 publishprogress();             }         }          @override         protected void onprogressupdate(void... values) {             super.onprogressupdate(values);             t.settext(string.valueof(counter));         }     } } 

to answer question changing boolean value , calling updatetime():

in original code, updatetime() called during oncreate() @ line:

h.post(run); 

and since have boolean set false, nothing , finishes running.

now, suppose add call updatetime() inside start_button click listener , hit start, stop, start in quick succession. here's what's happening (assuming each happen @ 100ms intervals):

0ms
click start sets boolean true, calls updatetime()

10ms
updatetime() called, boolean true, changes text , posts runnable run in 1000ms

100ms click stop sets boolean false

200ms click start sets boolean true, calls updatetime()

210ms updatetime() called, boolean true, changes text , posts runnable run in 1000ms

1010ms first posted runnable runs, sees boolean true, changes text , posts runnable run in 1000ms

1210ms second posted runnable runs, sees boolean true, changes text, , posts runnable

at point less 1.3 seconds in , count @ 3 seconds. now, text changed approximately every n + .1 , n + .2 seconds now.