上次介紹了 UIview的block動畫 ，
這次說一下 view的layer層的關鍵幀動畫
layer層的動畫相對於 view層的動畫 會更輕量。
直接看程式碼 每一個屬性的詳細說明 見程式碼下面的表格

     //先建立一個view用於執行動畫
    UIView * myview = [[UIView alloc]initWithFrame:CGRectMake(0, 0, 100, 100)];
    myview.layer.contents = (id)[UIImage imageNamed:@"123"].CGImage;
    myview.center = CGPointMake(CGRectGetWidth(self.view
 
.frame)/2, CGRectGetHeight(self.view.frame)/2);
    /*
    //可以設定 動畫的錨點。用於控制動畫縮放，放大，移動的中心點
    //左上角
    myview.layer.anchorPoint = CGPointMake(0, 0);
    //中心
    myview.layer.anchorPoint = CGPointMake(0.5,0.5);
    //右下角
    myview.layer.anchorPoint = CGPointMake(1, 1);
    */
    [self.view addSubview:myview];

    //關鍵幀  單一動畫
    CAKeyframeAnimation *keyAnima1=[CAKeyframeAnimation animationWithKeyPath:@"transform.rotation"
 
];
    keyAnima1.duration =1;
    keyAnima1.values = @[@(0),@(M_PI/4),@(M_PI/2)];
    keyAnima1.keyTimes = @[@0.0,@0.1,@1.0];
    keyAnima1.fillMode=kCAFillModeForwards;
    keyAnima1.removedOnCompletion = NO;
    keyAnima1.repeatCount = 1;//或    keyAnima1.repeatDuration = 100;
    keyAnima1.beginTime = CACurrentMediaTime() + 1
 
;
    keyAnima1.timingFunction =[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    keyAnima1.delegate = self;
    [myview.layer addAnimation:keyAnima1 forKey:@"brushTransformAnimation"];

    //關鍵幀  組合動畫
    //旋轉動畫
    CAKeyframeAnimation *keyAnima_group1=[CAKeyframeAnimation animationWithKeyPath:@"transform.rotation"];
    keyAnima_group1.values = @[@(M_PI/2),@(M_PI),@(M_PI * 2)];;
    //位置移動動畫
    CAKeyframeAnimation *keyAnima_group2=[CAKeyframeAnimation animationWithKeyPath:@"position"];
    NSValue *value1=[NSValue valueWithCGPoint:CGPointMake(myview.center.x,myview.center.y)];
    NSValue *value2=[NSValue valueWithCGPoint:CGPointMake(200, 200)];
    NSValue *value3=[NSValue valueWithCGPoint:CGPointMake(150, 150)];
    keyAnima_group2.values= @[value1,value2,value3];
    //組合兩個動畫
    CAAnimationGroup * g = [CAAnimationGroup animation];
    g.animations = @[keyAnima_group1,keyAnima_group2];
    g.duration = 3;
    g.fillMode=kCAFillModeForwards;
    g.removedOnCompletion = NO;
    //再上一個動畫執行完 在執行
    g.beginTime = CACurrentMediaTime() + 2;
    [myview.layer addAnimation:g forKey:@"g"];

    //關鍵幀 單一動畫。設定關鍵幀的 path 而不是 value
    CAKeyframeAnimation * keyAnima2 = [CAKeyframeAnimation animationWithKeyPath:@"position"];
    keyAnima2.calculationMode = kCAAnimationPaced;
    keyAnima2.fillMode = kCAFillModeForwards;
    keyAnima2.removedOnCompletion = NO;
    keyAnima2.duration = 2;
    keyAnima2.timingFunction =[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    keyAnima2.beginTime = CACurrentMediaTime() + 5;
    CGMutablePathRef curvedPath_3 = CGPathCreateMutable();
    CGPathMoveToPoint(curvedPath_3, NULL, 150, 150);
    CGPathAddArc(curvedPath_3, NULL,  100, 150, 50, 0 , M_PI*2 , NO);
    keyAnima2.path = curvedPath_3;
    CGPathRelease(curvedPath_3);
    [myview.layer addAnimation:keyAnima2 forKey:@"moveTheSquare"];

基本屬性的說明

表1
KeyPath屬性的設定詳解：

備註：keyPath 對應的 “values” 陣列內大多數存的是 NSNumber 物件 。position ，frame 等 存的是 NSValue *value2=[NSValue valueWithCGPoint:CGPointMake(200, 200)]; 這樣的物件。

表2
fillMode屬性的設定詳解：

表3
速度控制函式(CAMediaTimingFunction)設定詳解：

動畫的代理方法

CALayer上動畫的暫停和恢復

#pragma mark 暫停CALayer的動畫
-(void)pauseLayer:(CALayer*)layer
{
    CFTimeInterval pausedTime = [layer convertTime:CACurrentMediaTime() fromLayer:nil];

    // 讓CALayer的時間停止走動
      layer.speed = 0.0;
    // 讓CALayer的時間停留在pausedTime這個時刻
    layer.timeOffset = pausedTime;
}

#pragma mark 恢復CALayer的動畫
-(void)resumeLayer:(CALayer*)layer
{
    CFTimeInterval pausedTime = layer.timeOffset;
    // 1. 讓CALayer的時間繼續行走
      layer.speed = 1.0;
    // 2. 取消上次記錄的停留時刻
      layer.timeOffset = 0.0;
    // 3. 取消上次設定的時間
      layer.beginTime = 0.0;
    // 4. 計算暫停的時間(這裡也可以用CACurrentMediaTime()-pausedTime)
    CFTimeInterval timeSincePause = [layer convertTime:CACurrentMediaTime() fromLayer:nil] - pausedTime;
    // 5. 設定相對於父座標系的開始時間(往後退timeSincePause)
      layer.beginTime = timeSincePause;
}