完全自定义动画

- (void)createArcAnimationForKey:(NSString *)key fromValue:(NSNumber *)from toValue:(NSNumber *)to Delegate:(id)delegate

{

    CABasicAnimation *arcAnimation = [CABasicAnimation animationWithKeyPath:key];

    NSNumber *currentAngle = [[self presentationLayer] valueForKey:key];

    if(!currentAngle) currentAngle = from;

    [arcAnimation setFromValue:currentAngle];

    [arcAnimation setToValue:to];         

    [arcAnimation setDelegate:delegate];

    [arcAnimation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionDefault]];

    [self addAnimation:arcAnimation forKey:key];

    [self setValue:to forKey:key];

}

- (void)updateTimerFired:(NSTimer *)timer;

{   

    CALayer *parentLayer = [_pieView layer];

    NSArray *pieLayers = [parentLayer sublayers];

    [pieLayers enumerateObjectsUsingBlock:^(CAShapeLayer * obj, NSUInteger idx, BOOL *stop) {

        

        NSNumber *presentationLayerStartAngle = [[obj presentationLayer] valueForKey:@"startAngle"];

        CGFloat interpolatedStartAngle = [presentationLayerStartAngle doubleValue];

        

        NSNumber *presentationLayerEndAngle = [[obj presentationLayer] valueForKey:@"endAngle"];

        CGFloat interpolatedEndAngle = [presentationLayerEndAngle doubleValue];

        CGPathRef path = CGPathCreateArc(_pieCenter, _pieRadius, interpolatedStartAngle, interpolatedEndAngle);

        [obj setPath:path];

        CFRelease(path);

        

        {

            CALayer *labelLayer = [[obj sublayers] objectAtIndex:0];

            CGFloat interpolatedMidAngle = (interpolatedEndAngle + interpolatedStartAngle) / 2;        

            [CATransaction setDisableActions:YES];

            [labelLayer setPosition:CGPointMake(_pieCenter.x + (_labelRadius * cos(interpolatedMidAngle)), _pieCenter.y + (_labelRadius * sin(interpolatedMidAngle)))];

            [CATransaction setDisableActions:NO];

        }

    }];

}

- (void)animationDidStart:(CAAnimation *)anim

{

    if (_animationTimer == nil) {

        static float timeInterval = 1.0/60.0;

        // Run the animation timer on the main thread.

        // We want to allow the user to interact with the UI while this timer is running.

        // If we run it on this thread, the timer will be halted while the user is touching the screen (that's why the chart was disappearing in our collection view).

        _animationTimer= [NSTimer timerWithTimeInterval:timeInterval target:self selector:@selector(updateTimerFired:) userInfo:nil repeats:YES];

        [[NSRunLoop mainRunLoop] addTimer:_animationTimer forMode:NSRunLoopCommonModes];

    }

    

    [_animations addObject:anim];

}