objective c - What's the easiest way to animate a line? -

i creating app involves animating lines within workspace on time. current approach use code in drawrect:

cgcontextsetstrokecolor(context, black); cgcontextbeginpath(context); cgcontextmovetopoint(context, startpoint.x, startpoint.y); cgcontextaddlinetopoint(context, finalpoint.x, finalpoint.y); cgcontextstrokepath(context); 

...and setting timer run every 0.05 seconds update finalpoint , call setneedsdisplay.

i'm finding approach (when there's 5ish lines moving @ once) slows down app terribly, , such high refresh frequency, still appears jerky.

there must better way perform simple line drawing in animated line - i.e. saying want line start @ x1, y1 , stretching x2, y2 on given length of time. options this? need make perform faster , love rid of clunky timer.

thanks!

use cashapelayers, , combination of catransactions , cabasicanimation.

you can add given path shapelayer , let rendering.

a cashapelayer object has 2 properties called strokestart , strokeend, defines along path end of line should render. defaults 0.0 strokestart, , 1.0 strokeend.

if set path strokeend starts @ 0.0, see no line.

you can animate, 0.0 1.0, strokeend property , see line lengthen.

to change cashapelayer's implicit 0.25s default animation timing, can add function class, so:

-(void)animatestrokeend:(cgfloat)_strokeend {     [catransaction begin];     cabasicanimation *animation = [cabasicanimation animationwithkeypath:keypath];     animation.duration = 2.0f; //or long want happen     animation.fromvalue = [nsnumber numberwithfloat:self.strokeend]; // current strokeend value     animation.tovalue = [nsnumber numberwithfloat:_strokeend]; //to end of path     [catransaction setcompletionblock:^{ self.strokeend = _strokeend }];     [self addanimation:animation forkey:@"animatestrokeend"];     [catransaction commit]; } 

you can pass value 0.0f 1.0f value of _strokeend.

the setcompletionblock: ensures value passing explicitly set after animation completes.