Using a counter inside a java.util.Timer in Android Activity causes app to crash -

i'd accomplish think simple, turning out hassle.

i have loading screen picture, , i'd fade in , out application loading. decided accomplish changing it's opacity relative sine value of counter. code follows:

imageview   loadingraven;   //loading raven @ start of app timer       timer;          //timer we're gonna have use int         elapsed = 0;    //elapsed time far  /*  * following in oncreate() method after contentview has been set  */  loadingraven = (imageview)findviewbyid(r.id.imageview1);   //fade raven in , out timertask task = new timertask() {     public void run()     {         elapsed++;          //this line causes app fail         loadingraven.setalpha((float)(math.sin(elapsed)+1)/2);     } }; timer = new timer(); timer.scheduleatfixedrate(task, 0, 50); 

what problem that's causing program fail? correctly using timer , timertask? or there perhaps better way update opacity of image eases in , out smoothly?

thanks

timertask runs on different thread. update ui on main ui thread. use runonuithread

      timertask task = new timertask()       {         public void run()          {           elapsed++;               runonuithread(new runnable() //run on ui thread                  {                   public void run()                    {                         loadingraven.setalpha((float)(math.sin(elapsed)+1)/2)                  }                  });       }   }; 

timertask runs on different thread. can use handler , postdelayed suggested pskink