我为问答游戏中的计时器制作了动画。我想在动画中显示 UIImageView *cronometro 的背景，但我的动画显示了整个 UIImageView。
我想在动画中制作这个：
但我有这个：
这是我的代码：
//Chrono animation
-(void) startCronometro{
//Set timer
contoAllaRovescia = TIME;
[cronometro setImage:[UIImage imageNamed:@"cronoStart.png"]];
maskLayer = [CAShapeLayer layer];
CGFloat maskHeight = cronometro.frame.size.height;
CGFloat maskWidth = cronometro.frame.size.width;
CGPoint centerPoint;
centerPoint = CGPointMake(cronometro.frame.size.width/2, (cronometro.frame.size.height/2) + 3);//+3 because the image is not centered in UIImageView
//Make the radius of our arc large enough to reach into the corners of the image view.
CGFloat radius = sqrtf(maskWidth * maskWidth + maskHeight * maskHeight)/2;
//Don't fill the path, but stroke it in black.
maskLayer.fillColor = [[UIColor clearColor] CGColor];
maskLayer.strokeColor = [[UIColor blackColor] CGColor];
maskLayer.lineWidth = 30;
CGMutablePathRef arcPath = CGPathCreateMutable();
//Move to the starting point of the arc so there is no initial line connecting to the arc
CGPathMoveToPoint(arcPath, nil, centerPoint.x, centerPoint.y-radius/2);
//Create an arc at 1/2 our circle radius, with a line thickess of the full circle radius
CGPathAddArc(arcPath, nil, centerPoint.x, centerPoint.y, radius/2, 3*M_PI/2, -M_PI/2, NO);
maskLayer.path = arcPath;//[aPath CGPath];//arcPath;
//Start with an empty mask path (draw 0% of the arc)
maskLayer.strokeEnd = 0.1;
CFRelease(arcPath);
//Install the mask layer into out image view's layer.
cronometro.layer.mask = maskLayer;
//Set our mask layer's frame to the parent layer's bounds.
cronometro.layer.mask.frame = cronometro.layer.bounds;
//Create an animation that increases the stroke length to 1, then reverses it back to zero.
CABasicAnimation *swipe = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
swipe.duration = TIME;
swipe.delegate = self;
// [swipe setValue:@"string" forKey:@"key"];
swipe.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
swipe.fillMode = kCAFillModeForwards;
swipe.removedOnCompletion = NO;
swipe.toValue = [NSNumber numberWithFloat: 1.0];
[maskLayer addAnimation: swipe forKey: @"strokeEnd"];
//Aggiorno l'etichetta del conto alla rovescia ogni 0.1 millisecondi
timer = [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(whileCronometro) userInfo:nil repeats:YES];
}
谢谢你。