iphone - Mixing NSThreads and NSTimer to update a view -

i want make app make appear , disappear circles on screen. circles enlarged on touchesbegan , smaller on touchesend. i'm able on 1 circle want everywhere user touch screen. know have work nsthreads, example don't work.

this piece of code:

- (void)touchesbegan:(nsset *)touches withevent:(uievent *)event {     uitouch *touch = [touches anyobject];     lastpoint = [touch locationinview:self.view];     zoomin = true;     rayoncercle = 25;      //creation d'un thread     timerthread = [[nsthread alloc] initwithtarget:self selector:@selector(cycle)         object:nil];     [timerthread start];      if ([touch tapcount] == 1) {             nslog(@"une touche");     }      if ([touch tapcount] == 2) {             drawimage.image = nil;             return;     } }      - (void) cycle {          nslog(@"cycle");          nsautoreleasepool* pool = [[nsautoreleasepool alloc] init];         nsrunloop* runloop = [nsrunloop currentrunloop];         time = [nstimer scheduledtimerwithtimeinterval: 0.1         target: self         selector: @selector(drawcircle:)         userinfo: nil         repeats: yes];      [runloop run];     [pool release]; }      - (void) drawcircle:(nstimer *)timer {              nslog(@"drawcircle");              uigraphicsbeginimagecontext(self.view.frame.size);             [drawimage.image drawinrect:cgrectmake(0, 0, self.view.frame.size.width,         self.view.frame.size.height)];               cggradientref mygradient;             cgcolorspaceref mycolorspace;             size_t locationcount = 3;             cgfloat locationlist[] = {0.0, 0.5, 1.0};             cgfloat colorlist[] = {             1.0, 0.0, 0.5, 1.0, //red, green, blue, alpha             1.0, 0.0, 1.0, 1.0,             0.3, 0.5, 1.0, 1.0             };             mycolorspace = cgcolorspacecreatedevicergb();             mygradient = cggradientcreatewithcolorcomponents(mycolorspace, colorlist,             locationlist, locationcount);              cgcontextdrawradialgradient(uigraphicsgetcurrentcontext(), mygradient, lastpoint, 0,                 lastpoint,rayoncercle, 0);                 drawimage.image = uigraphicsgetimagefromcurrentimagecontext();             uigraphicsendimagecontext();              if (rayoncercle < 200 && zoomin == true) {             _hue += 0.5;             _brightness += 0.005;             _saturation += 0.05;             rayoncercle += 15;             }             if (zoomin == false) {             if (rayoncercle < 0) {             [time invalidate];             [timerthread release];             } else {             _hue -= 0.5;             _brightness -= 0.005;             _saturation -= 0.05;             rayoncercle -= 1;             }     } }       - (void)touchesmoved:(nsset *)touches withevent:(uievent *)event {             uitouch *touch = [touches anyobject];                cgpoint currentpoint = [touch locationinview:self.view];             lastpoint = currentpoint;              _hue = 0.0;             _saturation = 0.0;             _brightness = 0.0;              rayoncercle = 25;             zoomin = true;     }      - (void)touchesended:(nsset *)touches withevent:(uievent *)event {              _hue = 0.0;             _saturation = 0.0;             _brightness = 0.0;              zoomin = false;              uitouch *touch = [touches anyobject];              if ([touch tapcount] == 2) {                     drawimage.image = nil;                     return;             }     } 

you don't need secondary thread update view. use delayed callback (nstimer, targeting main thread) invalidate areas must draw, , keep track of position of nearest touch know center drawing. rect invalidation callbacks coalesced using delayed callback, bonus.