再次说明本系列文章是我在通拦学习iOS开发中回顾时觉得有必要再加深印象的地方，如有不准确欢迎批评指正，如果帮到读者理解学习就更好了。
CALayer
UIView VS CALayer
相对于UIView CALayer在更下面一层布局，view持有layer 所以都有view.layer 来对view设置其layer 关于layer有哪些属性及方法不再多说
CALayer旋转tranform是3D的，UIview是2D的
CALayer可以做显示（阴影、圆角、边框、遮罩、变换...) 动画
//CALayer展示
CALayer* layer1=[[CALayeralloc]init];
layer1.backgroundColor=[UIColor grayColor].CGColor;
layer1.frame=CGRectMake(100,100,150,150);
//layer的坐标系也是在左上角原点
//设置layer的边框
layer1.borderColor=[UIColor blackColor].CGColor;
layer1.borderWidth=2;
// 设置layer的圆角
layer1.cornerRadius=20;
//contents可以用来设置图片
layer1.contents=(id)[UIImage ImageNamed:@"..."]；
//不让子layer超出父layer的范围
layer1.masksToBounds=YES;
属性介绍position 与 anchorPoint
position相当于view的center ，但当anchorPoint改变时就不是center了而是锚点的坐标，anchorPoint相当于一张纸被一个图钉定住只可以绕着图钉转，这个图钉的位置就是anchorPoint这张纸就是layer,anchorPonit是CGPoint类型的取值范围是（0-1，0-1）
默认情况下锚点是（0.5，0.5）
如上述代码将layer1的锚点设置为（0，0），position的坐标就变成的（175，175） frame是（175，175，150，150）；
公式position.x=anchorPonit.x*frame.size.width+frame.origin.x y值一样，把x换y
Mask Layer
UIImageView* image=[[UIImageView alloc]initWithImage:[UIImage imageNamed:@"1.jpg"]];
image.frame=CGRectMake(50,150,200,250);
image.contentMode=UIViewContentModeScaleAspectFill;
[self.viewaddSubview:image];
UIImageView*imageMask=[[UIImageViewalloc]init];
imageMask.image=[[UIImage imageNamed:@"imageMask.png"]stretchableImageWithLeftCapWidth:14 topCapHeight:28];
imageMask.frame=image.bounds;
image.layer.mask=imageMask.layer;
GAGrandient Layer
//渐变颜色
CAGradientLayer*layer=[[CAGradientLayer alloc]init];
layer.frame=CGRectMake(100,100,150,150);
[layersetColors:@[
(id)[UIColoryellowColor].CGColor,
(id)[UIColorgreenColor].CGColor,
(id)[UIColorblueColor].CGColor
]];
//默认为从上至下
//使用渐变分割线
[layersetLocations:@[@0.25,@0.5,@0.75]];
//渐变方向 startpoint endpoint （0-1，0-1）;
[layersetStartPoint:CGPointMake(0, 0)];
[layersetEndPoint:CGPointMake(1, 0)];
[self.view.layeraddSublayer:layer];
//作为mask
UIImageView *imageView=[[UIImageView alloc]init];
imageView.image=[UIImage imageNamed:@"nature.jpg"];
imageView.contentMode=UIViewContentModeScaleAspectFill;
imageView.frame=CGRectMake(100, 260,150,100);
[self.view addSubview:imageView];
//镜像效果
UIImageView* mirrorImgView=[[UIImageView alloc]init];
mirrorImgView.image=imageView.image;
mirrorImgView.contentMode=UIViewContentModeScaleAspectFill;
//翻转
mirrorImgView.transform=CGAffineTransformMakeScale(1, -1);
mirrorImgView.frame=CGRectMake(0, 0, 150, 100);
mirrorImgView.center=CGPointMake(imageView.center.x, imageView.center.y+imageView.bounds.size.height);
[self.view addSubview:mirrorImgView];
CAGradientLayer* GDlayer=[CAGradientLayer layer];
GDlayer.frame=CGRectMake(0, 0, 150, 100);
[GDlayer setColors:@[(id)[UIColor clearColor].CGColor, (id)[UIColor colorWithWhite:0 alpha:0.5].CGColor ]];
[GDlayer setStartPoint:CGPointMake(0, 0.7)];
[GDlayer setEndPoint:CGPointMake(0, 1)];
mirrorImgView.layer.mask=GDlayer;
CAShaperLayer
用以绘制形状、CGPath
CAShapeLayer *shapeLayer=[CAShapeLayer layer];
shapeLayer.strokeColor=[UIColor redColor].CGColor;
shapeLayer.fillColor=[UIColor clearColor].CGColor;
[self.view.layeraddSublayer:shapeLayer];
CGMutablePathRef path=CGPathCreateMutable();
CGPathMoveToPoint(path,nil,50,200);
CGPathAddCurveToPoint(path,nil,100,100,250,300,300,200);
shapeLayer.path=path;
CGPathRelease(path);
beizer曲线
CAShapeLayer* slayer=[CAShapeLayer layer];
CGPointstartPoint=CGPointMake(50,200);
CGPointendPoint=CGPointMake(300,200);
CGPointcontrolPoint1=CGPointMake(100,100);
CGPointcontrolPoint2=CGPointMake(250,300);
UIBezierPath* path=[UIBezierPath bezierPath];
[pathmoveToPoint:startPoint];
[pathaddCurveToPoint:endPointcontrolPoint1:controlPoint1controlPoint2:controlPoint2];
slayer.path=path.CGPath;
slayer.strokeColor=[UIColor redColor].CGColor;
slayer.fillColor=[UIColor clearColor].CGColor;
//矩形
UIBezierPath* path2=[UIBezierPath bezierPathWithRect:CGRectMake(100, 100, 200, 200)];
slayer.path=path2.CGPath;
//[self.view.layer addSublayer:slayer];
//带圆角的矩形 还有圆形等其他图形
UIBezierPath* path3=[UIBezierPath bezierPathWithRoundedRect:CGRectMake(100, 100, 200, 200) cornerRadius:100];
slayer.path=path3.CGPath;
[self.view.layeraddSublayer:slayer];
//画图 ponit点我是随便写的主要想说明方法
UIBezierPath *bezierPath=[UIBezierPath bezierPath];
[bezierPath moveToPoint:CGPointMake(0, 0)];
[bezierPath addLineToPoint:CGPointMake(10,20)];
[bezierPath addCurveToPoint:CGPointMake(100, 200) controlPoint1:CGPointMake(50, 50) controlPoint2:CGPointMake(70, 120)];
[bezierPath closePath];
自定义Layer
调用时要将opaque置为0 当用法二时还要调用一下 setNeedDisplay ，法二的优先级高
//方法1
- (void)drawRect:(CGRect)rect {
CGContextRef ctx=UIGraphicsGetCurrentContext();
CGContextAddRect(ctx, CGRectMake(50, 50, 100, 100));
CGContextSetRGBFillColor(ctx, 0, 0, 1, 1);
CGContextFillPath(ctx);
}
//方法二
-(void)drawLayer:(CALayer*)layer inContext:(CGContextRef)ctx{
CGContextAddRect(ctx, CGRectMake(50, 50, 100, 100));
CGContextSetRGBFillColor(ctx, 1, 0, 0, 1);
CGContextFillPath(ctx);
}