demo地址：https://github.com/xiaochaofeiyu/YSCAnimation
有用的話求個(gè)star杖剪，歡迎建議討論笆环。
1. CAGradientLayer實(shí)現(xiàn)漸變
CAGradientLayer是CALayer的一個(gè)特殊子類忍弛，用于生成顏色漸變的圖層癞揉，使用較為方便萧锉，下面介紹下它的相關(guān)屬性：
- colors 漸變的顏色
- locations 漸變顏色的分割點(diǎn)
- startPoint&endPoint 顏色漸變的方向践美，范圍在(0,0)與(1.0,1.0)之間，如(0,0)(1.0,0)代表水平方向漸變,(0,0)(0,1.0)代表豎直方向漸變
CAGradientLayer *gradientLayer = [CAGradientLayer layer];
gradientLayer.colors = @[(__bridge id)[UIColor redColor].CGColor, (__bridge id)[UIColor yellowColor].CGColor, (__bridge id)[UIColor blueColor].CGColor];
gradientLayer.locations = @[@0.3, @0.5, @1.0];
gradientLayer.startPoint = CGPointMake(0, 0);
gradientLayer.endPoint = CGPointMake(1.0, 0);
gradientLayer.frame = CGRectMake(0, 100, 300, 100);
[self.view.layer addSublayer:gradientLayer];
CAGradientLayer實(shí)現(xiàn)漸變標(biāo)間簡(jiǎn)單直觀寄猩，但存在一定的局限性嫉晶，比如無(wú)法自定義整個(gè)漸變區(qū)域的形狀，如環(huán)形、曲線形的漸變替废。
2. Core Graphics相關(guān)方法實(shí)現(xiàn)漸變
iOS Core Graphics中有兩個(gè)方法用于繪制漸變顏色箍铭，CGContextDrawLinearGradient可以用于生成線性漸變，CGContextDrawRadialGradient用于生成圓半徑方向顏色漸變椎镣。函數(shù)可以自定義path坡疼，無(wú)論是什么形狀都可以，原理都是用來(lái)做Clip衣陶，所以需要在CGContextClip函數(shù)前調(diào)用CGContextAddPath函數(shù)把CGPathRef加入到Context中。
另外一個(gè)需要注意的地方是漸變的方向闸氮，方向是由兩個(gè)點(diǎn)控制的剪况，點(diǎn)的單位就是坐標(biāo)。因此需要正確從CGPathRef中找到正確的點(diǎn)蒲跨，方法當(dāng)然有很多種看具體實(shí)現(xiàn)译断，本例中，我就是簡(jiǎn)單得通過(guò)調(diào)用CGPathGetBoundingBox函數(shù)或悲，返回CGPathRef的矩形區(qū)域孙咪，然后根據(jù)這個(gè)矩形取兩個(gè)點(diǎn)，讀者可以根據(jù)自行需求修改具體代碼巡语。
1-> 線性漸變
- (void)drawLinearGradient:(CGContextRef)context
path:(CGPathRef)path
startColor:(CGColorRef)startColor
endColor:(CGColorRef)endColor
{
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGFloat locations[] = { 0.0, 1.0 };
NSArray *colors = @[(__bridge id) startColor, (__bridge id) endColor];
CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef) colors, locations);
CGRect pathRect = CGPathGetBoundingBox(path);
//具體方向可根據(jù)需求修改
CGPoint startPoint = CGPointMake(CGRectGetMinX(pathRect), CGRectGetMidY(pathRect));
CGPoint endPoint = CGPointMake(CGRectGetMaxX(pathRect), CGRectGetMidY(pathRect));
CGContextSaveGState(context);
CGContextAddPath(context, path);
CGContextClip(context);
CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);
CGContextRestoreGState(context);
CGGradientRelease(gradient);
CGColorSpaceRelease(colorSpace);
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
//創(chuàng)建CGContextRef
UIGraphicsBeginImageContext(self.view.bounds.size);
CGContextRef gc = UIGraphicsGetCurrentContext();
//創(chuàng)建CGMutablePathRef
CGMutablePathRef path = CGPathCreateMutable();
//繪制Path
CGRect rect = CGRectMake(0, 100, 300, 200);
CGPathMoveToPoint(path, NULL, CGRectGetMinX(rect), CGRectGetMinY(rect));
CGPathAddLineToPoint(path, NULL, CGRectGetMidX(rect), CGRectGetMaxY(rect));
CGPathAddLineToPoint(path, NULL, CGRectGetWidth(rect), CGRectGetMaxY(rect));
CGPathCloseSubpath(path);
//繪制漸變
[self drawLinearGradient:gc path:path startColor:[UIColor greenColor].CGColor endColor:[UIColor redColor].CGColor];
//注意釋放CGMutablePathRef
CGPathRelease(path);
//從Context中獲取圖像翎蹈，并顯示在界面上
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageView *imgView = [[UIImageView alloc] initWithImage:img];
[self.view addSubview:imgView];
}
2-> 圓半徑方向漸變
- (void)drawRadialGradient:(CGContextRef)context
path:(CGPathRef)path
startColor:(CGColorRef)startColor
endColor:(CGColorRef)endColor
{
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGFloat locations[] = { 0.0, 1.0 };
NSArray *colors = @[(__bridge id) startColor, (__bridge id) endColor];
CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef) colors, locations);
CGRect pathRect = CGPathGetBoundingBox(path);
CGPoint center = CGPointMake(CGRectGetMidX(pathRect), CGRectGetMidY(pathRect));
CGFloat radius = MAX(pathRect.size.width / 2.0, pathRect.size.height / 2.0) * sqrt(2);
CGContextSaveGState(context);
CGContextAddPath(context, path);
CGContextEOClip(context);
CGContextDrawRadialGradient(context, gradient, center, 0, center, radius, 0);
CGContextRestoreGState(context);
CGGradientRelease(gradient);
CGColorSpaceRelease(colorSpace);
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
//創(chuàng)建CGContextRef
UIGraphicsBeginImageContext(self.view.bounds.size);
CGContextRef gc = UIGraphicsGetCurrentContext();
//創(chuàng)建CGMutablePathRef
CGMutablePathRef path = CGPathCreateMutable();
//繪制Path
CGRect rect = CGRectMake(0, 100, 300, 200);
CGPathMoveToPoint(path, NULL, CGRectGetMinX(rect), CGRectGetMinY(rect));
CGPathAddLineToPoint(path, NULL, CGRectGetMidX(rect), CGRectGetMaxY(rect));
CGPathAddLineToPoint(path, NULL, CGRectGetWidth(rect), CGRectGetMaxY(rect));
CGPathAddLineToPoint(path, NULL, CGRectGetWidth(rect), CGRectGetMinY(rect));
CGPathCloseSubpath(path);
//繪制漸變
[self drawRadialGradient:gc path:path startColor:[UIColor greenColor].CGColor endColor:[UIColor redColor].CGColor];
//注意釋放CGMutablePathRef
CGPathRelease(path);
//從Context中獲取圖像，并顯示在界面上
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageView *imgView = [[UIImageView alloc] initWithImage:img];
[self.view addSubview:imgView];
}
3. 以CAShapeLayer作為layer的mask屬性
CALayer的mask屬性可以作為遮罩讓layer顯示mask遮住(非透明)的部分男公；CAShapeLayer為CALayer的子類荤堪，通過(guò)path屬性可以生成不同的形狀，將CAShapeLayer對(duì)象用作layer的mask屬性的話枢赔，就可以生成不同形狀的圖層澄阳。故生成顏色漸變有以下幾個(gè)步驟：
- 生成一個(gè)imageView(也可以為layer)，image的屬性為顏色漸變的圖片
- 生成一個(gè)CAShapeLayer對(duì)象踏拜，根據(jù)path屬性指定所需的形狀
- 將CAShapeLayer對(duì)象賦值給imageView的mask屬性
- (void)viewDidLoad
{
[super viewDidLoad];
[self.view addSubview:self.firstCircle];
_firstCircle.frame = CGRectMake(0, 0, 200, 200);
_firstCircle.center = CGPointMake(CGRectGetWidth(self.view.bounds) / 2.0, CGRectGetHeight(self.view.bounds) / 2.0);
CGFloat firsCircleWidth = 5;
self.firstCircleShapeLayer = [self generateShapeLayerWithLineWidth:firsCircleWidth];
_firstCircleShapeLayer.path = [self generateBezierPathWithCenter:CGPointMake(100, 100) radius:100].CGPath;
_firstCircle.layer.mask = _firstCircleShapeLayer;
}
- (CAShapeLayer *)generateShapeLayerWithLineWidth:(CGFloat)lineWidth
{
CAShapeLayer *waveline = [CAShapeLayer layer];
waveline.lineCap = kCALineCapButt;
waveline.lineJoin = kCALineJoinRound;
waveline.strokeColor = [UIColor redColor].CGColor;
waveline.fillColor = [[UIColor clearColor] CGColor];
waveline.lineWidth = lineWidth;
waveline.backgroundColor = [UIColor clearColor].CGColor;
return waveline;
}
- (UIBezierPath *)generateBezierPathWithCenter:(CGPoint)center radius:(CGFloat)radius
{
UIBezierPath *circlePath = [UIBezierPath bezierPathWithArcCenter:center radius:radius startAngle:0 endAngle:2*M_PI clockwise:NO];
return circlePath;
}
- (UIImageView *)firstCircle
{
if (!_firstCircle) {
self.firstCircle = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"circleBackground"]];
_firstCircle.layer.masksToBounds = YES;
_firstCircle.alpha = 1.0;
}
return _firstCircle;
}
demo地址：https://github.com/xiaochaofeiyu/YSCAnimation
在YSCNewVoiceWaveView與YSCVoiceLoadingCircleView中
