乾貨系列之手把手教你使用Core animation 做動畫

發表於2016-03-25

動畫

原始碼下載：原始碼

最近在技術群裡，有人發了一張帶有動畫效果的圖片。覺得很有意思，便動手實現了一下。在這篇文章中你將會學到Core Animation顯式動畫中的關鍵幀動畫、組合動畫、CABasicAnimation動畫。先上一張原圖的動畫效果。

點選此檢視原圖動畫效果。

本文要實現的效果圖如下：

實現的效果圖.gif

把原動畫gif動畫在mac上使用圖片瀏覽模式開啟，我們可以看到動畫每一幀的顯示。從每一幀上的展示過程，可以把整體的動畫進行拆分成兩大部分。

第一部分（Part1）從初始狀態變成取消狀態（圖片上是由橫實線變成上線橫線交叉的圓）。
第二部分（Part2）從取消狀態變回初始狀態。

下面我們先詳細分析Part1是怎麼實現的。根據動畫圖，把Part1再細分成三步。

Step1 : 中間橫實線的由右向左的運動效果。這其實是一個組合動畫。是先向左偏移的同時橫線變短。先看一下實現的動態效果。

step1 Animation.gif

■ 向左偏移—使用基本動畫中animationWithKeyPath鍵值對的方式來改變動畫的值。我們這裡使用position.x,同樣可以使用transform.translation.x來平移。

■ 改變橫線的大小—使用經典的strokeStart和strokeEnd。其實上橫線長度的變化的由strokeStart到strokeEnd之間的值來共同來決定。改變strokeEnd的值由1.0到0.4，不改變strokeStart的值。橫線的長度會從右側方向由1.0倍長度減少到0.4倍長度。參見示意圖的紅色區域。

stroke示意圖.png

-(void) animationStep1{

    //最終changedLayer的狀態
    _changedLayer.strokeEnd = 0.4;
    //基本動畫，長度有1.0減少到0.4
    CABasicAnimation *strokeAnimation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
    strokeAnimation.fromValue = [NSNumber numberWithFloat:1.0f];
    strokeAnimation.toValue = [NSNumber numberWithFloat:0.4f];
    //基本動畫，向左偏移10個畫素
    CABasicAnimation *pathAnimation = [CABasicAnimation animationWithKeyPath:@"position.x"];
    pathAnimation.fromValue = [NSNumber numberWithFloat:0.0];
    pathAnimation.toValue = [NSNumber numberWithFloat:-10];
    //組合動畫，平移和長度減少同時進行
    CAAnimationGroup *animationGroup = [CAAnimationGroup animation];
    animationGroup.animations = [NSArray arrayWithObjects:strokeAnimation,pathAnimation, nil];
    animationGroup.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn];
    animationGroup.duration = kStep1Duration;
    //設定代理
    animationGroup.delegate = self;
    animationGroup.removedOnCompletion = YES;
    //監聽動畫
    [animationGroup setValue:@"animationStep1" forKey:@"animationName"];
    //動畫加入到changedLayer上
    [_changedLayer addAnimation:animationGroup forKey:nil];
}

-(void) animationStep1{

//最終changedLayer的狀態

_changedLayer.strokeEnd = 0.4;

//基本動畫，長度有1.0減少到0.4

CABasicAnimation *strokeAnimation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];

strokeAnimation.fromValue = [NSNumber numberWithFloat:1.0f];

strokeAnimation.toValue = [NSNumber numberWithFloat:0.4f];

//基本動畫，向左偏移10個畫素

CABasicAnimation *pathAnimation = [CABasicAnimation animationWithKeyPath:@"position.x"];

pathAnimation.fromValue = [NSNumber numberWithFloat:0.0];

pathAnimation.toValue = [NSNumber numberWithFloat:-10];

//組合動畫，平移和長度減少同時進行

CAAnimationGroup *animationGroup = [CAAnimationGroup animation];

animationGroup.animations = [NSArray arrayWithObjects:strokeAnimation,pathAnimation, nil];

animationGroup.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn];

animationGroup.duration = kStep1Duration;

//設定代理

animationGroup.delegate = self;

animationGroup.removedOnCompletion = YES;

//監聽動畫

[animationGroup setValue:@"animationStep1" forKey:@"animationName"];

//動畫加入到changedLayer上

[_changedLayer addAnimation:animationGroup forKey:nil];

}

Step2 : 由左向右的動畫–向右偏移同時橫線長度變長。看一下Step2要實現的動畫效果。其思路和Step1是一樣的。

step2 Animation.gif

-(void)animationStep2
{
    CABasicAnimation *translationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.translation.x"];
    translationAnimation.fromValue = [NSNumber numberWithFloat:-10];
    //strokeEnd:0.8 剩餘的距離toValue = lineWidth * (1 - 0.8);

    translationAnimation.toValue = [NSNumber numberWithFloat:0.2 * lineWidth ];

    _changedLayer.strokeEnd = 0.8;
    CABasicAnimation *strokeAnimation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
    strokeAnimation.fromValue = [NSNumber numberWithFloat:0.4f];
    strokeAnimation.toValue = [NSNumber numberWithFloat:0.8f];

    CAAnimationGroup *animationGroup = [CAAnimationGroup animation];
    animationGroup.animations = [NSArray arrayWithObjects:strokeAnimation,translationAnimation, nil];
    animationGroup.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
    animationGroup.duration = kStep2Duration;
    //設定代理
    animationGroup.delegate = self;
    animationGroup.removedOnCompletion = YES;
    [animationGroup setValue:@"animationStep2" forKey:@"animationName"];
    [_changedLayer addAnimation:animationGroup forKey:nil];
}

-(void)animationStep2

{

CABasicAnimation *translationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.translation.x"];

translationAnimation.fromValue = [NSNumber numberWithFloat:-10];

//strokeEnd:0.8 剩餘的距離toValue = lineWidth * (1 - 0.8);

translationAnimation.toValue = [NSNumber numberWithFloat:0.2 * lineWidth ];

_changedLayer.strokeEnd = 0.8;

CABasicAnimation *strokeAnimation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];

strokeAnimation.fromValue = [NSNumber numberWithFloat:0.4f];

strokeAnimation.toValue = [NSNumber numberWithFloat:0.8f];

CAAnimationGroup *animationGroup = [CAAnimationGroup animation];

animationGroup.animations = [NSArray arrayWithObjects:strokeAnimation,translationAnimation, nil];

animationGroup.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];

animationGroup.duration = kStep2Duration;

//設定代理

animationGroup.delegate = self;

animationGroup.removedOnCompletion = YES;

[animationGroup setValue:@"animationStep2" forKey:@"animationName"];

[_changedLayer addAnimation:animationGroup forKey:nil];

}

Step3: 圓弧的動畫效果和上下兩個橫實線的動畫效果。

畫圓弧，首先想到是使用UIBezierPath。畫個示意圖來分析動畫路徑。示意圖如下：

step3 示意圖.jpg

整個path路徑是由三部分組成，ABC曲線、CD圓弧、DD′圓。
使用UIBezierPath的方法

- (void)appendPath:(UIBezierPath *)bezierPath;

1	- (void)appendPath:(UIBezierPath *)bezierPath;

把三部分路徑關聯起來。詳細講解思路。

• ABC曲線就是貝塞爾曲線，可以根據A、B、C三點的位置使用方法

//endPoint 終點座標 controlPoint1 起點座標
//controlPoint2 起點和終點在曲線上的切點延伸相交的交點座標
- (void)addCurveToPoint:(CGPoint)endPoint 
          controlPoint1:(CGPoint)controlPoint1 
          controlPoint2:(CGPoint)controlPoint2;

//endPoint 終點座標 controlPoint1 起點座標

//controlPoint2 起點和終點在曲線上的切點延伸相交的交點座標

- (void)addCurveToPoint:(CGPoint)endPoint

controlPoint1:(CGPoint)controlPoint1

controlPoint2:(CGPoint)controlPoint2;

二次貝塞爾曲線示意圖如下：

二次貝塞爾曲線.png

其中control point 點是從曲線上取 start point和end point 切點相交匯的所得到的交點。如下圖：

control point .png

首先C點取圓上的一點，-30°。那麼，

CGFloat angle = Radians(30);

1	CGFloat angle = Radians(30);

C點座標為：

    //C點
    CGFloat endPointX = self.center.x + Raduis * cos(angle);
    CGFloat endPointY = kCenterY - Raduis * sin(angle);

//C點

CGFloat endPointX = self.center.x + Raduis * cos(angle);

CGFloat endPointY = kCenterY - Raduis * sin(angle);

A點座標為：

    //A點 取橫線最右邊的點
    CGFloat startPointX = self.center.x + lineWidth/2.0 ;
    CGFloat startPointY = controlPointY;

//A點取橫線最右邊的點

CGFloat startPointX = self.center.x + lineWidth/2.0 ;

CGFloat startPointY = controlPointY;

control point 為E點：

    //E點 半徑*反餘弦(30°)
    CGFloat startPointX = self.center.x + Raduis *acos(angle);
    CGFloat startPointY = controlPointY;

//E點半徑*反餘弦(30°)

CGFloat startPointX = self.center.x + Raduis *acos(angle);

CGFloat startPointY = controlPointY;

• CD圓弧的路徑使用此方法確定

+ (instancetype)bezierPathWithArcCenter:(CGPoint)center radius:(CGFloat)radius startAngle:(CGFloat)startAngle endAngle:(CGFloat)endAngle clockwise:(BOOL)clockwise;

1	+ (instancetype)bezierPathWithArcCenter:(CGPoint)center radius:(CGFloat)radius startAngle:(CGFloat)startAngle endAngle:(CGFloat)endAngle clockwise:(BOOL)clockwise;

關於弧度問題，UIBezierPath的官方文件中的這張圖：

弧度.jpg

StartAngle 弧度即C點弧度，EndAngel弧度即D點弧度。

CGFloat StartAngle = 2 * M_PI - angle;
CGFloat EndAngle = M_PI + angle;

1 2	CGFloat StartAngle = 2 * M_PI - angle; CGFloat EndAngle = M_PI + angle;

• DD′圓的路徑和上面2一樣的方法確定。

StartAngle 弧度即D點弧度，EndAngel弧度即D′點弧度。

CGFloat StartAngle = M_PI *3/2 - (M_PI_2 -angle);
CGFloat EndAngle = -M_PI_2 - (M_PI_2 -angle);

1 2	CGFloat StartAngle = M_PI *3/2 - (M_PI_2 -angle); CGFloat EndAngle = -M_PI_2 - (M_PI_2 -angle);

下面部分程式碼是所有path路徑。

    UIBezierPath *path = [UIBezierPath bezierPath];

    // 畫貝塞爾曲線 圓弧
    [path moveToPoint:CGPointMake(self.center.x +  lineWidth/2.0 , kCenterY)];

     CGFloat angle = Radians(30);
    //C點
    CGFloat endPointX = self.center.x + Raduis * cos(angle);
    CGFloat endPointY = kCenterY - Raduis * sin(angle);
    //A點
    CGFloat startPointX = self.center.x + lineWidth/2.0;
    CGFloat startPointY = kCenterY;
    //E點 半徑*反餘弦(30°)
    CGFloat controlPointX = self.center.x + Raduis *acos(angle);
    CGFloat controlPointY = kCenterY;

    //貝塞爾曲線 ABC曲線
    [path addCurveToPoint:CGPointMake(endPointX, endPointY)
            controlPoint1:CGPointMake(startPointX , startPointY)
            controlPoint2:CGPointMake(controlPointX , controlPointY)];

    // （360°- 30°） ->（180°+30°） 逆時針的圓弧 CD圓弧
    UIBezierPath *path1 = [UIBezierPath bezierPathWithArcCenter:CGPointMake(self.center.x,kCenterY)
                                                         radius:Raduis
                                                     startAngle:2 * M_PI - angle
                                                       endAngle:M_PI + angle
                                                      clockwise:NO];
    [path appendPath:path1];
     // （3/2π- 60°） ->（-1/2π -60°） 逆時針的圓 DD′圓
    UIBezierPath *path2 = [UIBezierPath bezierPathWithArcCenter:CGPointMake(self.center.x,kCenterY)
                                                        radius:Raduis
                                                    startAngle:M_PI *3/2 - (M_PI_2 -angle)
                                                      endAngle:-M_PI_2 - (M_PI_2 -angle)
                                                     clockwise:NO];

    [path appendPath:path2];

    _changedLayer.path = path.CGPath;

UIBezierPath *path = [UIBezierPath bezierPath];

// 畫貝塞爾曲線圓弧

[path moveToPoint:CGPointMake(self.center.x + lineWidth/2.0 , kCenterY)];

CGFloat angle = Radians(30);

//C點

CGFloat endPointX = self.center.x + Raduis * cos(angle);

CGFloat endPointY = kCenterY - Raduis * sin(angle);

//A點

CGFloat startPointX = self.center.x + lineWidth/2.0;

CGFloat startPointY = kCenterY;

//E點半徑*反餘弦(30°)

CGFloat controlPointX = self.center.x + Raduis *acos(angle);

CGFloat controlPointY = kCenterY;

//貝塞爾曲線 ABC曲線

[path addCurveToPoint:CGPointMake(endPointX, endPointY)

controlPoint1:CGPointMake(startPointX , startPointY)

controlPoint2:CGPointMake(controlPointX , controlPointY)];

// （360°- 30°） ->（180°+30°）逆時針的圓弧 CD圓弧

UIBezierPath *path1 = [UIBezierPath bezierPathWithArcCenter:CGPointMake(self.center.x,kCenterY)

radius:Raduis

startAngle:2 * M_PI - angle

endAngle:M_PI + angle

clockwise:NO];

[path appendPath:path1];

// （3/2π- 60°） ->（-1/2π -60°）逆時針的圓 DD′圓

UIBezierPath *path2 = [UIBezierPath bezierPathWithArcCenter:CGPointMake(self.center.x,kCenterY)

radius:Raduis

startAngle:M_PI *3/2 - (M_PI_2 -angle)

endAngle:-M_PI_2 - (M_PI_2 -angle)

clockwise:NO];

[path appendPath:path2];

_changedLayer.path = path.CGPath;

Path路徑有了，接著實現動畫效果。
圓弧的長度逐漸變長。我們還是使用經典的strokeStart和strokeEnd。但是圓弧是如何變長的呢？

(1) 初始圓弧有一段長度。
(2) 在原始長度的基礎上逐漸變長，逐漸遠離A點，同時要在D點停止。
(3) 長度逐漸變長，最終要在D與D′點交匯。

我們分別解決這個三個問題。

第一個問題，strokeEnd - strokeStart > 0這樣能保證有一段圓弧。

第二個問題，逐漸變長,意味著strokeEnd值不斷變大。遠離A點意味著strokeStart的值不斷變大。在D點停止，說明了strokeStart有上限值。

第三個問題，意味著strokeEnd值不斷變大，最終值為1.0。

這三個問題說明了一個問題，strokeEnd和strokeStart是一組變化的資料。

那麼core animation 中可以控制一組值的動畫是關鍵幀動畫（CAKeyframeAnimation）。

為了更準確的給出strokeEnd和strokeStart值，我們使用長度比來確定。

假設我們初始的長度就是曲線ABC的長度。但是貝塞爾曲線長度怎麼計算？使用下面方法:

//求貝塞爾曲線長度
-(CGFloat) bezierCurveLengthFromStartPoint:(CGPoint)start toEndPoint:(CGPoint) end withControlPoint:(CGPoint) control
{
    const int kSubdivisions = 50;
    const float step = 1.0f/(float)kSubdivisions;

    float totalLength = 0.0f;
    CGPoint prevPoint = start;

    // starting from i = 1, since for i = 0 calulated point is equal to start point
    for (int i = 1; i <= kSubdivisions; i++)
    {
        float t = i*step;

        float x = (1.0 - t)*(1.0 - t)*start.x + 2.0*(1.0 - t)*t*control.x + t*t*end.x;
        float y = (1.0 - t)*(1.0 - t)*start.y + 2.0*(1.0 - t)*t*control.y + t*t*end.y;

        CGPoint diff = CGPointMake(x - prevPoint.x, y - prevPoint.y);

        totalLength += sqrtf(diff.x*diff.x + diff.y*diff.y); // Pythagorean

        prevPoint = CGPointMake(x, y);
    }

    return totalLength;
}

//求貝塞爾曲線長度

-(CGFloat) bezierCurveLengthFromStartPoint:(CGPoint)start toEndPoint:(CGPoint) end withControlPoint:(CGPoint) control

{

const int kSubdivisions = 50;

const float step = 1.0f/(float)kSubdivisions;

float totalLength = 0.0f;

CGPoint prevPoint = start;

// starting from i = 1, since for i = 0 calulated point is equal to start point

for (int i = 1; i <= kSubdivisions; i++)

{

float t = i*step;

float x = (1.0 - t)*(1.0 - t)*start.x + 2.0*(1.0 - t)*t*control.x + t*t*end.x;

float y = (1.0 - t)*(1.0 - t)*start.y + 2.0*(1.0 - t)*t*control.y + t*t*end.y;

CGPoint diff = CGPointMake(x - prevPoint.x, y - prevPoint.y);

totalLength += sqrtf(diff.x*diff.x + diff.y*diff.y); // Pythagorean

prevPoint = CGPointMake(x, y);

}

return totalLength;

}

計算貝塞爾曲線所在的比例為：

CGFloat orignPercent = [self calculateCurveLength]/[self calculateTotalLength];

1	CGFloat orignPercent = [self calculateCurveLength]/[self calculateTotalLength];

初始的strokeStart = 0、strokeEnd = orignPercent。
最終的stokeStart = ？

//結果就是貝塞爾曲線長度加上120°圓弧的長度與總長度相比得到的結果。
CGFloat endPercent =([self calculateCurveLength] + Radians(120) *Raduis ) / [self calculateTotalLength];

1 2	//結果就是貝塞爾曲線長度加上120°圓弧的長度與總長度相比得到的結果。 CGFloat endPercent =([self calculateCurveLength] + Radians(120) *Raduis ) / [self calculateTotalLength];

實現動畫的程式碼為

    CGFloat orignPercent = [self calculateCurveLength] / [self calculateTotalLength];
    CGFloat endPercent =([self calculateCurveLength] + Radians(120) *Raduis ) / [self calculateTotalLength];

    _changedLayer.strokeStart = endPercent;

    //方案1
    CAKeyframeAnimation *startAnimation = [CAKeyframeAnimation animationWithKeyPath:@"strokeStart"];
    startAnimation.values = @[@0.0,@(endPercent)];

    CAKeyframeAnimation *EndAnimation = [CAKeyframeAnimation animationWithKeyPath:@"strokeEnd"];
    EndAnimation.values = @[@(orignPercent),@1.0];

    CAAnimationGroup *animationGroup = [CAAnimationGroup animation];
    animationGroup.animations = [NSArray arrayWithObjects:startAnimation,EndAnimation, nil];
    animationGroup.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
    animationGroup.duration = kStep3Duration;
    animationGroup.delegate = self;
    animationGroup.removedOnCompletion = YES;
    [animationGroup setValue:@"animationStep3" forKey:@"animationName"];
    [_changedLayer addAnimation:animationGroup forKey:nil];

CGFloat orignPercent = [self calculateCurveLength] / [self calculateTotalLength];

CGFloat endPercent =([self calculateCurveLength] + Radians(120) *Raduis ) / [self calculateTotalLength];

_changedLayer.strokeStart = endPercent;

//方案1

CAKeyframeAnimation *startAnimation = [CAKeyframeAnimation animationWithKeyPath:@"strokeStart"];

startAnimation.values = @[@0.0,@(endPercent)];

CAKeyframeAnimation *EndAnimation = [CAKeyframeAnimation animationWithKeyPath:@"strokeEnd"];

EndAnimation.values = @[@(orignPercent),@1.0];

CAAnimationGroup *animationGroup = [CAAnimationGroup animation];

animationGroup.animations = [NSArray arrayWithObjects:startAnimation,EndAnimation, nil];

animationGroup.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];

animationGroup.duration = kStep3Duration;

animationGroup.delegate = self;

animationGroup.removedOnCompletion = YES;

[animationGroup setValue:@"animationStep3" forKey:@"animationName"];

[_changedLayer addAnimation:animationGroup forKey:nil];

效果圖為：

step3-1 Animation.gif

2.上下橫線的動畫效果。

此動畫效果，需要使用transform.rotation.z轉動角度。

上橫線轉動的角度順序為 0 -> 10° -> (-55°) -> (-45°)
這是一組資料，使用關鍵幀處理動畫。

    CAKeyframeAnimation *rotationAnimation1 = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"];
    rotationAnimation1.values = @[[NSNumber numberWithFloat:0],
                                 [NSNumber numberWithFloat:Radians(10) ],
                                 [NSNumber numberWithFloat:Radians(-10) - M_PI_4 ],
                                 [NSNumber numberWithFloat:- M_PI_4 ]
                                 ];

CAKeyframeAnimation *rotationAnimation1 = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"];

rotationAnimation1.values = @[[NSNumber numberWithFloat:0],

[NSNumber numberWithFloat:Radians(10) ],

[NSNumber numberWithFloat:Radians(-10) - M_PI_4 ],

[NSNumber numberWithFloat:- M_PI_4 ]

];

下橫線轉動的角度順序為0 -> (-10°) -> (55°) -> (45°)

    CAKeyframeAnimation *rotationAnimation2 = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"];
    rotationAnimation2.values = @[[NSNumber numberWithFloat:0],
                                 [NSNumber numberWithFloat:Radians(-10) ],
                                 [NSNumber numberWithFloat:Radians(10)  + M_PI_4 ],
                                 [NSNumber numberWithFloat: M_PI_4 ]
                                 ];

CAKeyframeAnimation *rotationAnimation2 = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"];

rotationAnimation2.values = @[[NSNumber numberWithFloat:0],

[NSNumber numberWithFloat:Radians(-10) ],

[NSNumber numberWithFloat:Radians(10) + M_PI_4 ],

[NSNumber numberWithFloat: M_PI_4 ]

];

你認為這麼就結束了? 最終結束的動畫如下：

step3-2 finished Animation.jpg

發現相交的直線沒有居中，而是靠左顯示。

向左平移，使用transform.translation.x

    //平移量
    CGFloat toValue = lineWidth *(1- cos(M_PI_4)) /2.0;

1 2	//平移量 CGFloat toValue = lineWidth *(1- cos(M_PI_4)) /2.0;

即旋轉角度又發生偏移量，使用組合動畫。

上橫線組合動畫

     //平移x
    CABasicAnimation *translationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.translation.x"];
    translationAnimation.fromValue = [NSNumber numberWithFloat:0];
    translationAnimation.toValue = [NSNumber numberWithFloat:-toValue];

    //角度關鍵幀 上橫線的關鍵幀 0 - 10° - (-55°) - (-45°)
    CAKeyframeAnimation *rotationAnimation1 = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"];
    rotationAnimation1.values = @[[NSNumber numberWithFloat:0],
                                 [NSNumber numberWithFloat:Radians(10) ],
                                 [NSNumber numberWithFloat:Radians(-10) - M_PI_4 ],
                                 [NSNumber numberWithFloat:- M_PI_4 ]
                                 ];

    CAAnimationGroup *transformGroup1 = [CAAnimationGroup animation];
    transformGroup1.animations = [NSArray arrayWithObjects:rotationAnimation1,translationAnimation, nil];
    transformGroup1.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
    transformGroup1.duration = kStep3Duration;
    transformGroup1.removedOnCompletion = YES;
    [_topLineLayer addAnimation:transformGroup1 forKey:nil];

//平移x

CABasicAnimation *translationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.translation.x"];

translationAnimation.fromValue = [NSNumber numberWithFloat:0];

translationAnimation.toValue = [NSNumber numberWithFloat:-toValue];

//角度關鍵幀上橫線的關鍵幀 0 - 10° - (-55°) - (-45°)

CAKeyframeAnimation *rotationAnimation1 = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"];

rotationAnimation1.values = @[[NSNumber numberWithFloat:0],

[NSNumber numberWithFloat:Radians(10) ],

[NSNumber numberWithFloat:Radians(-10) - M_PI_4 ],

[NSNumber numberWithFloat:- M_PI_4 ]

];

CAAnimationGroup *transformGroup1 = [CAAnimationGroup animation];

transformGroup1.animations = [NSArray arrayWithObjects:rotationAnimation1,translationAnimation, nil];

transformGroup1.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];

transformGroup1.duration = kStep3Duration;

transformGroup1.removedOnCompletion = YES;

[_topLineLayer addAnimation:transformGroup1 forKey:nil];

下橫線組合動畫

    //角度關鍵幀 下橫線的關鍵幀 0 - （-10°） - (55°) - (45°)
    CAKeyframeAnimation *rotationAnimation2 = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"];
    rotationAnimation2.values = @[[NSNumber numberWithFloat:0],
                                 [NSNumber numberWithFloat:Radians(-10) ],
                                 [NSNumber numberWithFloat:Radians(10) + M_PI_4 ],
                                 [NSNumber numberWithFloat: M_PI_4 ]
                                 ];

    CAAnimationGroup *transformGroup2 = [CAAnimationGroup animation];
    transformGroup2.animations = [NSArray arrayWithObjects:rotationAnimation2,translationAnimation, nil];
    transformGroup2.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
    transformGroup2.duration = kStep3Duration ;
    transformGroup2.delegate = self;
    transformGroup2.removedOnCompletion = YES;
    [_bottomLineLayer addAnimation:transformGroup2 forKey:nil];

//角度關鍵幀下橫線的關鍵幀 0 - （-10°） - (55°) - (45°)

CAKeyframeAnimation *rotationAnimation2 = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"];

rotationAnimation2.values = @[[NSNumber numberWithFloat:0],

[NSNumber numberWithFloat:Radians(-10) ],

[NSNumber numberWithFloat:Radians(10) + M_PI_4 ],

[NSNumber numberWithFloat: M_PI_4 ]

];

CAAnimationGroup *transformGroup2 = [CAAnimationGroup animation];

transformGroup2.animations = [NSArray arrayWithObjects:rotationAnimation2,translationAnimation, nil];

transformGroup2.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];

transformGroup2.duration = kStep3Duration ;

transformGroup2.delegate = self;

transformGroup2.removedOnCompletion = YES;

[_bottomLineLayer addAnimation:transformGroup2 forKey:nil];

Part1到此結束。最終效果圖

Part1 animation.gif

Part2的思路和Part1思路是一樣的。你可以參考程式碼自己思考一下。核心程式碼

-(void)cancelAnimation
{
    //最關鍵是path路徑

    UIBezierPath *path = [UIBezierPath bezierPath];
    //30度,經過反覆測試，效果最好
    CGFloat angle = Radians(30);

    CGFloat startPointX = self.center.x + Raduis * cos(angle);
    CGFloat startPointY = kCenterY - Raduis * sin(angle);

    CGFloat controlPointX = self.center.x + Raduis *acos(angle);
    CGFloat controlPointY = kCenterY;

    CGFloat endPointX = self.center.x + lineWidth /2;
    CGFloat endPointY = kCenterY;

    //組合path 路徑 起點 -150° 順時針的圓
    path = [UIBezierPath bezierPathWithArcCenter:CGPointMake(self.center.x,kCenterY)
                                                         radius:Raduis
                                                     startAngle:-M_PI + angle
                                                       endAngle:M_PI + angle
                                                      clockwise:YES];

    //起點為 180°-> (360°-30°)
    UIBezierPath *path1 = [UIBezierPath bezierPathWithArcCenter:CGPointMake(self.center.x,kCenterY)
                                                         radius:Raduis
                                                     startAngle:M_PI + angle
                                                       endAngle:2 * M_PI - angle
                                                      clockwise:YES];
    [path appendPath:path1];

    //三點曲線
    UIBezierPath *path2 = [UIBezierPath bezierPath];

    [path2 moveToPoint:CGPointMake(startPointX, startPointY)];

    [path2 addCurveToPoint:CGPointMake(endPointX,endPointY)
             controlPoint1:CGPointMake(startPointX, startPointY)
             controlPoint2:CGPointMake(controlPointX, controlPointY)];

    [path appendPath:path2];

    //比原始狀態向左偏移5個畫素
    UIBezierPath *path3 = [UIBezierPath bezierPath];
    [path3 moveToPoint:CGPointMake(endPointX,endPointY)];
    [path3 addLineToPoint:CGPointMake(self.center.x - lineWidth/2 -5,endPointY)];
    [path appendPath:path3];

    _changedLayer.path = path.CGPath;

    //平移量
    CGFloat toValue = lineWidth *(1- cos(M_PI_4)) /2.0;
    //finished 最終狀態
    CGAffineTransform transform1 = CGAffineTransformMakeRotation(0);
    CGAffineTransform transform2 = CGAffineTransformMakeTranslation(0, 0);
    CGAffineTransform transform3 = CGAffineTransformMakeRotation(0);

    CGAffineTransform transform = CGAffineTransformConcat(transform1, transform2);
    _topLineLayer.affineTransform = transform;
    transform = CGAffineTransformConcat(transform3, transform2);
    _bottomLineLayer.affineTransform = transform;

    //一個圓的長度比
    CGFloat endPercent = 2* M_PI *Raduis / ([self calculateTotalLength] + lineWidth);

    //橫線佔總path的百分比
    CGFloat percent = lineWidth / ([self calculateTotalLength] + lineWidth);

    _changedLayer.strokeStart = 1.0 -percent;

    CAKeyframeAnimation *startAnimation = [CAKeyframeAnimation animationWithKeyPath:@"strokeStart"];
    startAnimation.values = @[@0.0,@0.3,@(1.0 -percent)];

    //在π+ angle
    CAKeyframeAnimation *EndAnimation = [CAKeyframeAnimation animationWithKeyPath:@"strokeEnd"];
    EndAnimation.values = @[@(endPercent),@(endPercent),@1.0];

    CAAnimationGroup *animationGroup = [CAAnimationGroup animation];
    animationGroup.animations = [NSArray arrayWithObjects:startAnimation,EndAnimation, nil];
    animationGroup.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    animationGroup.duration = kStep4Duration;
    animationGroup.delegate = self;
    animationGroup.removedOnCompletion = YES;
    [animationGroup setValue:@"animationStep4" forKey:@"animationName"];
    [_changedLayer addAnimation:animationGroup forKey:nil];

    //平移x
    CABasicAnimation *translationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.translation.x"];
    translationAnimation.fromValue = [NSNumber numberWithFloat:-toValue];
    translationAnimation.toValue = [NSNumber numberWithFloat:0];

    //角度關鍵幀 上橫線的關鍵幀  (-45°) -> (-55°)-> 10° -> 0
    CAKeyframeAnimation *rotationAnimation1 = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"];
    rotationAnimation1.values = @[[NSNumber numberWithFloat:- M_PI_4 ],
                                  [NSNumber numberWithFloat:- Radians(10) - M_PI_4 ],
                                  [NSNumber numberWithFloat:Radians(10) ],
                                  [NSNumber numberWithFloat:0]
                                  ];

    CAAnimationGroup *transformGroup1 = [CAAnimationGroup animation];
    transformGroup1.animations = [NSArray arrayWithObjects:rotationAnimation1,translationAnimation, nil];
    transformGroup1.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
    transformGroup1.duration = kStep4Duration;
    transformGroup1.removedOnCompletion = YES;
    [_topLineLayer addAnimation:transformGroup1 forKey:nil];

    //角度關鍵幀 下橫線的關鍵幀  (45°)-> (55°)- >（-10°）-> 0
    CAKeyframeAnimation *rotationAnimation2 = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"];
    rotationAnimation2.values = @[[NSNumber numberWithFloat: M_PI_4 ],
                                  [NSNumber numberWithFloat:Radians(10) + M_PI_4 ],
                                  [NSNumber numberWithFloat:-Radians(10) ],
                                  [NSNumber numberWithFloat:0]
                                  ];

    CAAnimationGroup *transformGroup2 = [CAAnimationGroup animation];
    transformGroup2.animations = [NSArray arrayWithObjects:rotationAnimation2,translationAnimation, nil];
    transformGroup2.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
    transformGroup2.duration = kStep4Duration;
    transformGroup2.delegate = self;
    transformGroup2.removedOnCompletion = YES;
    [_bottomLineLayer addAnimation:transformGroup2 forKey:nil];

}

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-(void)cancelAnimation

{

//最關鍵是path路徑

UIBezierPath *path = [UIBezierPath bezierPath];

//30度,經過反覆測試，效果最好

CGFloat angle = Radians(30);

CGFloat startPointX = self.center.x + Raduis * cos(angle);

CGFloat startPointY = kCenterY - Raduis * sin(angle);

CGFloat controlPointX = self.center.x + Raduis *acos(angle);

CGFloat controlPointY = kCenterY;

CGFloat endPointX = self.center.x + lineWidth /2;

CGFloat endPointY = kCenterY;

//組合path 路徑起點 -150° 順時針的圓

path = [UIBezierPath bezierPathWithArcCenter:CGPointMake(self.center.x,kCenterY)

radius:Raduis

startAngle:-M_PI + angle

endAngle:M_PI + angle

clockwise:YES];

//起點為 180°-> (360°-30°)

UIBezierPath *path1 = [UIBezierPath bezierPathWithArcCenter:CGPointMake(self.center.x,kCenterY)

radius:Raduis

startAngle:M_PI + angle

endAngle:2 * M_PI - angle

clockwise:YES];

[path appendPath:path1];

//三點曲線

UIBezierPath *path2 = [UIBezierPath bezierPath];

[path2 moveToPoint:CGPointMake(startPointX, startPointY)];

[path2 addCurveToPoint:CGPointMake(endPointX,endPointY)

controlPoint1:CGPointMake(startPointX, startPointY)

controlPoint2:CGPointMake(controlPointX, controlPointY)];

[path appendPath:path2];

//比原始狀態向左偏移5個畫素

UIBezierPath *path3 = [UIBezierPath bezierPath];

[path3 moveToPoint:CGPointMake(endPointX,endPointY)];

[path3 addLineToPoint:CGPointMake(self.center.x - lineWidth/2 -5,endPointY)];

[path appendPath:path3];

_changedLayer.path = path.CGPath;

//平移量

CGFloat toValue = lineWidth *(1- cos(M_PI_4)) /2.0;

//finished 最終狀態

CGAffineTransform transform1 = CGAffineTransformMakeRotation(0);

CGAffineTransform transform2 = CGAffineTransformMakeTranslation(0, 0);

CGAffineTransform transform3 = CGAffineTransformMakeRotation(0);

CGAffineTransform transform = CGAffineTransformConcat(transform1, transform2);

_topLineLayer.affineTransform = transform;

transform = CGAffineTransformConcat(transform3, transform2);

_bottomLineLayer.affineTransform = transform;

//一個圓的長度比

CGFloat endPercent = 2* M_PI *Raduis / ([self calculateTotalLength] + lineWidth);

//橫線佔總path的百分比

CGFloat percent = lineWidth / ([self calculateTotalLength] + lineWidth);

_changedLayer.strokeStart = 1.0 -percent;

CAKeyframeAnimation *startAnimation = [CAKeyframeAnimation animationWithKeyPath:@"strokeStart"];

startAnimation.values = @[@0.0,@0.3,@(1.0 -percent)];

//在π+ angle

CAKeyframeAnimation *EndAnimation = [CAKeyframeAnimation animationWithKeyPath:@"strokeEnd"];

EndAnimation.values = @[@(endPercent),@(endPercent),@1.0];

CAAnimationGroup *animationGroup = [CAAnimationGroup animation];

animationGroup.animations = [NSArray arrayWithObjects:startAnimation,EndAnimation, nil];

animationGroup.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];

animationGroup.duration = kStep4Duration;

animationGroup.delegate = self;

animationGroup.removedOnCompletion = YES;

[animationGroup setValue:@"animationStep4" forKey:@"animationName"];

[_changedLayer addAnimation:animationGroup forKey:nil];

//平移x

CABasicAnimation *translationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.translation.x"];

translationAnimation.fromValue = [NSNumber numberWithFloat:-toValue];

translationAnimation.toValue = [NSNumber numberWithFloat:0];

//角度關鍵幀上橫線的關鍵幀 (-45°) -> (-55°)-> 10° -> 0

CAKeyframeAnimation *rotationAnimation1 = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"];

rotationAnimation1.values = @[[NSNumber numberWithFloat:- M_PI_4 ],

[NSNumber numberWithFloat:- Radians(10) - M_PI_4 ],

[NSNumber numberWithFloat:Radians(10) ],

[NSNumber numberWithFloat:0]

];

CAAnimationGroup *transformGroup1 = [CAAnimationGroup animation];

transformGroup1.animations = [NSArray arrayWithObjects:rotationAnimation1,translationAnimation, nil];

transformGroup1.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];

transformGroup1.duration = kStep4Duration;

transformGroup1.removedOnCompletion = YES;

[_topLineLayer addAnimation:transformGroup1 forKey:nil];

//角度關鍵幀下橫線的關鍵幀 (45°)-> (55°)- >（-10°）-> 0

CAKeyframeAnimation *rotationAnimation2 = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"];

rotationAnimation2.values = @[[NSNumber numberWithFloat: M_PI_4 ],

[NSNumber numberWithFloat:Radians(10) + M_PI_4 ],

[NSNumber numberWithFloat:-Radians(10) ],

[NSNumber numberWithFloat:0]

];

CAAnimationGroup *transformGroup2 = [CAAnimationGroup animation];

transformGroup2.animations = [NSArray arrayWithObjects:rotationAnimation2,translationAnimation, nil];

transformGroup2.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];

transformGroup2.duration = kStep4Duration;

transformGroup2.delegate = self;

transformGroup2.removedOnCompletion = YES;

[_bottomLineLayer addAnimation:transformGroup2 forKey:nil];

}

最終效果圖：

finished animation.gif

本篇文章講解結束！

程式碼點此連結下載：https://github.com/WZF-Fei/ZFChangeAnimation

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