ios - Animation when drawing with CGContext -

my question how animate drawing process when drawing cgcontextref. possible? assuming is, how?

i have 2 code snippets animate. first 1 draws progress bar , second 1 draws simple line chart. drawing done inside subclass of uiview.

progress bar nice , easy. want sort of draw out left. pretty sure require using other uirectfill dont know how accomplish it.

- (void)drawprogressline {     [bgcolor set];     uirectfill(self.bounds);     [graphcolor set];     uirectfill(cgrectmake(0, 0, self.frame.size.width / 100 * [[items objectatindex:0] floatvalue], self.frame.size.height)); } 

the line chart bit more complex. really start drawing left line line completing towards right if how can fade in? code:

- (void)drawlinechart {     [bgcolor set];     uirectfill(self.bounds);     [graphcolor set];      if (items.count < 2) return;      cgrect bounds = cgrectmake(0, 50, self.bounds.size.width, self.bounds.size.height - 100);      float max = -1;     (graphitem *item in items)         if (item.value > max)             max = item.value;      float xstep = (self.frame.size.width) / (items.count - 1);      (int = 0; < items.count; i++)     {         if (i == items.count - 1) break;          float itemheight = bounds.origin.y + bounds.size.height - ((graphitem*)[items objectatindex:i]).value / max * bounds.size.height;         float nextitemheight = bounds.origin.y + bounds.size.height - ((graphitem*)[items objectatindex:i + 1]).value / max * bounds.size.height;         cgpoint start = cgpointmake(xstep * i, itemheight);         cgpoint stop = cgpointmake(xstep * (i + 1), nextitemheight);         [self drawlinefrompoint:start topoint:stop linewidth:1 color:graphcolor shadow:yes];     } } 

pretty simple guess. if important drawlinefrompoint..... implemented like:

- (void)drawlinefrompoint:(cgpoint)startpoint topoint:(cgpoint)endpoint linewidth:(cgfloat)width color:(uicolor *)color shadow:(bool)shadow {     if (shadow)     {         cgcolorspaceref colorspace = cgcolorspacecreatedevicergb();         cgfloat components[4] = {0.0, 0.0, 0.0, 1.0};         cgcolorref shadowcolor = cgcolorcreate(colorspace, components);         cgcontextsetshadowwithcolor(uigraphicsgetcurrentcontext(), cgsizemake(1,1), 2.0, shadowcolor);     }      cgcontextbeginpath(context);     cgcontextsetlinewidth(context, width);     cgcontextmovetopoint(context, startpoint.x, startpoint.y);     cgcontextaddlinetopoint(context, endpoint.x, endpoint.y);     cgcontextclosepath(context);     [color setstroke];     cgcontextstrokepath(context);     cgcontextsetshadowwithcolor(context, cgsizezero, 0, null); } 

i hope made myself clear cause 1 in country , post last thing stands between me , bed. cheers, jan.

it sounds don't understand uikit view drawing cycle. understand each time want change appearance of custom-drawn view, need send setneedsdisplay? , need redraw entirely in drawrect: method? drawing doesn't appear on screen until drawrect: returns, , after cannot draw more in view until receives drawrect: message. if want contents of view animated, need send setneedsdisplay view periodically (say, every 1/30th or 1/60th of second, using either nstimer or cadisplaylink).