1.CADisplayLink

//自行定義的函式，用來設定使用CADisplayLink的相關參數-(void)initializeTimer {     //theTimer是CADisplayLink型態的指標，用來存放當前的設定狀態    theTimer = [CADisplayLink displayLinkWithTarget:self selector:@selector(countTotalFrames)];     //CADisplayLink內定值就是每秒60張（參數=1），參數=2就是每秒30張，以此類推    double fps = 60 / theTimer.frameInterval;    fpsLabel.text = [NSString stringWithFormat:@"%0.1f" , fps];     //設定執行狀態並啟動theTimer    [theTimer addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];}如同 Timer / 計時器一樣，selector 是設定每次觸發時所需要呼叫的函式，其寫法如下。-(void)countTotalFrames {    frameCount ++;    framesLabel.text = [NSString stringWithFormat:@"%d", frameCount];}

3.CATextLayer可以直接支持NSAttributedString！

CATextLayer代码：CATextLayer *lary = [CATextLayer layer];    lary.string = @"dasfasa";    lary.bounds = CGRectMake(0, 0, 320, 20);       lary.font = @"HiraKakuProN-W3"; //字体的名字 不是 UIFont    lary.fontSize = 12.f; //字体的大小       lary.alignmentMode = kCAAlignmentCenter;//字体的对齐方式    lary.position = CGPointMake(160, 410);       lary.foregroundColor = [UIColor redColor].CGColor;//字体的颜色    [self.view.layer addSublayer:lary];

demon：http://www.cocoachina.com/bbs/read.php?tid=31132

levelsOfDetail是指，从UIScrollView的1倍zoomScale开始，能够支持细节刷新的缩小级数。每一级是上一级的1/2，所以假设levelsOfDetail = n，levelsOfDetailBias不指定的话，CATiledLayer将会在UIScrollView的zoomScale为以下数字时重新drawLayer
2^-1 -> 2^-2 -> ... -> 2^-n
也就是
1/2, 1/4, 1/8, 1/16, ... , 1/2^n

在levelsOfDetailBias不指定的情况下，zoomScale大于0.5后就不会再drawLayer，所以若继续放大UIScrollView的话，画面将越来越模糊。

这个时候levelsOfDetailBias就有用了。
levelsOfDetailBias = m表示，将原来的1/2，移到2^m倍的位置。
假设levelsOfDetail = n，levelsOfDetailBias = m的话，会有如下队列：
2^m * 2^-1 -> 2^m * 2^-2 -> ... -> 2^m * 2^-n
简化一下即
2^(m - 1) -> 2^(m - 2) -> 2^(m - 3) ->... -> 2^(m - n)

举例，levelsOfDetail = 3，levelsOfDetailBias = 3，则你的UIScrollView将会在以下zoomScale时drawLayer
2^(3 - 1) -> 2^(3 - 2) -> 2^(3 - 3)
即4 -> 2 -> 1

特例是，levelsOfDetailBias > levelsOfDetail时，则每相差2倍就会drawLayer一下。

可以简单理解成：
levelsOfDetail表示一共有多少个drawLayer的位置
levelsOfDetailBias表示比1大的位置里有多少个drawLayer的位置（包括1）

CAShapeLayer

利用CAShapeLayer可以制作出任意的几何图形，其一是把它作为UIImageView的遮罩，达到把图片做成圆形效果。

 //创建个人主页头部的用户头像        self.userHead = [[UIImageView alloc]initWithFrame:CGRectMake(10, 35, 80, 80)];        self.userHead.image = [UIImage imageNamed:@"start.jpg"];                //创建圆形遮罩，把用户头像变成圆形        UIBezierPath* path = [UIBezierPath bezierPathWithArcCenter:CGPointMake(40, 40) radius:40 startAngle:0 endAngle:2*M_PI clockwise:YES];        CAShapeLayer* shape = [CAShapeLayer layer];        shape.path = path.CGPath;        self.userHead.layer.mask = shape;        [self addSubview:self.userHead];

使用CAReplicatorLayer重建动态的倒影

它自己能够重建包括自己在内的n个copies，这些copies是原layer中的所有sublayers，并且任何对原layer的sublayers设置的transform是可以积累的(accumulative). 基本上这样的一个关系：我们首先会重建一个CAReplicatorLayer实例，作为我们的sourceLayer, 这个sourceLayer我们需要一份copy，那包括自己在内就是2; 所以我们设置了它的instantCount = 2;这个是包括自己在内总共为2. 然后我们将SourceLayer的宽度设置为image的宽度，但是将其高度设置为image.size.height * 1.5； 并且在sourcelayer上加上masksToBounds为true的属性，这样一来我们可以保证超出的倒影部分会cut调一半，加上sourceLayer上正常的image，刚刚好组成了我们的完整的倒影。我们sourceLayer的sublayer就是_imageLayer,。但是我们只是单纯设置instantCount = 2的话， 那个_imageReplicatorLayer(这个就指代的是copy过来的第一个变量）是会继承sourceLayers中_imagelayer的Geometry,所以它两是重合的。那么我们必须做出transform, CARepliatorLayer有一个属性叫做instantTransform，这个属性指定了除了原来copy之外所有replication layer的trasnform规则，重要的是它是递增的。比如我们这里需要将imageReplicatorLayer应该往下移动image的高度，这一样来可以保证它是刚刚好在原来imagelayer的正下方，就跟倒影一样。 但是不一样的地方是：这个复制的imageReplicatorLayer它不是正常的，它是需要倒过来的，所以我们在transform上使用了 transform = CATransform3DScale(transform, 1.0, -1.0, 1.0); 这一个的意思是大小不变，但是y轴倒过来，这个应用到imageReplicatorLayer的坐标系是y轴朝上。 这样以来你就不能单纯是向原来一样移动image.height了， 因为y轴反了过来，所以你应该是 -2 * image.size.height 这样以来就搞定了。 最后我们给它加了一个渐变层，让它看起来更接近倒影的感觉。

- (void)viewDidLoad{    [super viewDidLoad];    UIView *view = [self view];    //    // Yes, this is a very long method. I find it easier to explain what is happening by     // keeping the code in a single location (instead of breaking it up over multiple methods).    //     // Load the image to "reflect"    UIImage *image = [UIImage imageNamed:@"american-flag"];    // The replicator layer is where all of the magic happens    CAReplicatorLayer *replicatorLayer = [CAReplicatorLayer layer];    [replicatorLayer setContentsScale:[[UIScreen mainScreen] scale]];    // The replicator layer‘s height is 1.5 times the size of the image. This means that     // we will effectively clip/ fade out our "reflection".    //    // ********    <- any y-flipping is performed along this plane    // *  %%  *    // *      *    image height    // *  ^^  *    // ********    // ========    // =  ^^  =  + half height (mask to bounds effectively clips the reflected image)    // =      =    //     //           = total height of layer    [replicatorLayer setBounds:CGRectMake(0.0, 0.0, [image size].width, [image size].height * 1.5)];    // This ensures that the replicated image is clipped to the replicator‘s height    [replicatorLayer setMasksToBounds:YES];    // Position the replicator layer at the top of the view    // - use the x center point to make the math easy (place in center of view)    // - use the y upper point to position the layer 10 points below the top of the view (just a little bit of padding)    [replicatorLayer setAnchorPoint:CGPointMake(0.5, 0.0)];    [replicatorLayer setPosition:CGPointMake(view.frame.size.width / 2.0, 80.0)];    // We need two instances:     //   1) the main image layer     //   2) a replicated layer for the reflection    [replicatorLayer setInstanceCount:2];    // Create a transform used by the replicator layer to "flip" and position our reflected layer below the original image    //    // I will see if I can explain this.    // For clarity... we start with an identity    CATransform3D transform = CATransform3DIdentity;    //     // @*******    <- this is the top of the replicator layer (the X,Y origin is at the @, with Y going down)    // *  %%  *    // *      *        // *  ^^  *    // ********        //    //    // Apply a negative scale to y (effectively flips)    //    // For example, hold your right hand in front of your face (knuckles facing you, thumb down). Now flip your     // hand up keeping your pinky finger in place (i.e. your pinky is a hinge).     //    // ========    <- will draw a flipped version up here    // =  ^^  =    // =      =    // =  %%  =    // ========    // ********    <- the "flip" is performed along here    // *  %%  *    // *      *    image height    // *  ^^  *    // ********        transform = CATransform3DScale(transform, 1.0, -1.0, 1.0);    // translate down by 2x height to position the "flipped" layer below the main layer    // - 2x moves the flipped image under the main image giving us the "reflection"    //    // ********    <- y plane (any flipping is performed along this plane)    // *  %%  *    // *      *    image height    // *  ^^  *    // ********        // ========          // =  ^^  =    // =      =    <-- Remember: only half of the "relection" layer renders because the replicator layer clips to bounds.    // =  %%  =    // ========      transform = CATransform3DTranslate(transform, 0.0, -[image size].height * 2, 1.0);    [replicatorLayer setInstanceTransform:transform];    // Next we create a layer that displays the American flag image.    _imageLayer = [CALayer layer];    [_imageLayer setContentsScale:[[UIScreen mainScreen] scale]];    [_imageLayer setContents:(__bridge id)[image CGImage]];    [_imageLayer setBounds:CGRectMake(0.0, 0.0, [image size].width, [image size].height)];    [_imageLayer setAnchorPoint:CGPointMake(0.0, 0.0)];    [replicatorLayer addSublayer:_imageLayer];    // Finally overlay a gradient layer on top of the "reflection" layer.     CAGradientLayer *gradientLayer = [CAGradientLayer layer];    [gradientLayer setContentsScale:[[UIScreen mainScreen] scale]];    [gradientLayer setColors:@[        (__bridge id)[[[UIColor whiteColor] colorWithAlphaComponent:0.25] CGColor],        (__bridge id)[[UIColor whiteColor] CGColor]    ]];    // Remember that the reflected layer is half the size, which is why the height of the gradient layer is cut in half.    [gradientLayer setBounds:CGRectMake(0.0, 0.0, replicatorLayer.frame.size.width, [image size].height * 0.5 + 1.0)];    [gradientLayer setAnchorPoint:CGPointMake(0.5, 0.0)];    [gradientLayer setPosition:CGPointMake(view.frame.size.width / 2, [image size].height + 80.0)];    [gradientLayer setZPosition:1]; // make sure the gradient is placed on top of the reflection.    [[view layer] addSublayer:replicatorLayer];    [[view layer] addSublayer:gradientLayer];    // One final (and fun step):     //   Create a text layer that is a sublayer of the image layer.    //   Core Animation will animate the text in all replicated layers. VERY COOL!!    CATextLayer *textLayer = [CATextLayer layer];    [textLayer setContentsScale:[[UIScreen mainScreen] scale]];    [textLayer setString:@"U.S.A."];    [textLayer setAlignmentMode:kCAAlignmentCenter];    CGFloat height = [(UIFont *)[textLayer font] lineHeight];    [textLayer setBounds:CGRectMake(0.0, 0.0, [_imageLayer frame].size.width, height)];    [textLayer setPosition:CGPointMake([_imageLayer frame].size.width / 2.0, [_imageLayer frame].size.height - 25.0)];    [textLayer setAnchorPoint:CGPointMake(0.5, 0.5)];    [_imageLayer addSublayer:textLayer];    // When the user taps, start _animating the image‘s text layer up and down.    [view setUserInteractionEnabled:YES];    [view setMultipleTouchEnabled:YES];    [view addGestureRecognizer:[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(animateTextLayer:)]];}- (void)animateTextLayer:(UIGestureRecognizer *)recognizer{    CALayer *textLayer = (CALayer *)[[_imageLayer sublayers] objectAtIndex:0];    CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"position.y"];    CGFloat halfBoxHeight = [textLayer frame].size.height / 2.0;    [animation setFromValue:@([textLayer frame].origin.y + halfBoxHeight)];    [animation setToValue:@(halfBoxHeight)];    [animation setDuration:3.0];    [animation setRepeatCount:MAXFLOAT];    [animation setAutoreverses:YES];    [textLayer addAnimation:animation forKey:nil];}

7.区分隐式动画和隐式事务：隐式动画通过隐式事务实现动画 。

区分显式动画和显式事务：显式动画有多种实现方式，显式事务是一种实现显式动画的方式。

->隐式事务
除显式事务外,任何对于CALayer属性的修改,都是隐式事务.这样的事务会在run-loop中被提交.

- (void)viewDidLoad {    //初始化一个layer,添加到主视图    layer=[CALayer layer];    layer.bounds = CGRectMake(0, 0, 200, 200);    layer.position = CGPointMake(160, 250);    layer.backgroundColor = [UIColor redColor].CGColor;    layer.borderColor = [UIColor blackColor].CGColor;    layer.opacity = 1.0f;    [self.view.layer addSublayer:layer];        [super viewDidLoad];}-(IBAction)changeLayerProperty{    //设置变化动画过程是否显示，默认为YES不显示    [CATransaction setDisableActions:NO];    //设置圆角    layer.cornerRadius = (layer.cornerRadius == 0.0f) ? 30.0f : 0.0f;    //设置透明度    layer.opacity = (layer.opacity == 1.0f) ? 0.5f : 1.0f;}  

->显式事务

通过明确的调用begin,commit来提交动画

修改执行时间 [CATransaction begin];//显式事务默认开启动画效果,kCFBooleanTrue关闭[CATransaction setValue:(id)kCFBooleanFalseforKey:kCATransactionDisableActions];//动画执行时间[CATransaction setValue:[NSNumber numberWithFloat:5.0f] forKey:kCATransactionAnimationDuration];    //[CATransaction setAnimationDuration:[NSNumber numberWithFloat:5.0f]];anotherLayer.cornerRadius = (anotherLayer.cornerRadius == 0.0f) ? 30.0f : 0.0f;layer.opacity = (layer.opacity == 1.0f) ? 0.5f : 1.0f;[CATransaction commit];

事务嵌套        [CATransaction begin];     [CATransaction begin];    [CATransaction setDisableActions:YES];     layer.cornerRadius = (layer.cornerRadius == 0.0f) ? 30.0f : 0.0f;    [CATransaction commit];    //上面的动画并不会立即执行，需要等最外层的commit    [NSThread sleepForTimeInterval:10];    //显式事务默认开启动画效果,kCFBooleanTrue关闭    [CATransaction setValue:(id)kCFBooleanFalse                     forKey:kCATransactionDisableActions];    //动画执行时间    [CATransaction setValue:[NSNumber numberWithFloat:10.0f] forKey:kCATransactionAnimationDuration];    //[CATransaction setAnimationDuration:[NSNumber numberWithFloat:5.0f]];    anotherLayer.cornerRadius = (anotherLayer.cornerRadius == 0.0f) ? 30.0f : 0.0f;        [CATransaction commit];

1. ;
2. CGFloat m41（x平移）, m42（y平移）, m43（z平移）, m44（）;