iOS自定义动画-仿支付宝记账本

CALayer大部分属性都可以添加CAAnimation动画,动画添加到layer上之后就会自动开始执行,但这仅限于CALayer及其子类已有的属性,如果是自己添加的属性,是不会自动产生动画的,如果需要动画效果,就需要自定义动画了。

如何创建自定义动画?

大体来说有两种方法,一种是使用系统的绘制方法画出动画,一种是利用定时器自己绘制动画。

方法一

1、创建自定义Layer类继承自CAShapeLayer
2、给Layer添加需要执行动画的属性,在.m文件中使用@dynamic声明动画属性
3、重写几个系统方法:

// 告诉CALayer自定义属性需要进行重绘
+ (BOOL)needsDisplayForKey:(NSString *)key {
    if ([key isEqualToString:@"startAngle"]||[key isEqualToString:@"endAngle"]) {
        return YES;
    }
    return [super needsDisplayForKey:key];
}
// 如果自定义属性值改变,就生成动画,系统会自动调用display方法重绘
- (id<CAAction>)actionForKey:(NSString *)event {
    if ([event isEqualToString:@"startAngle"])
    {
        CABasicAnimation *anim = [CABasicAnimation animationWithKeyPath:event];
        anim.duration = 1;
        anim.fromValue = @([self.presentationLayer startAngle]);
        anim.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionDefault];
        return anim;
    } else if ([event isEqualToString:@"endAngle"]) {
        CABasicAnimation *anim = [CABasicAnimation animationWithKeyPath:event];
        anim.duration = 1;
        anim.fromValue = @([self.presentationLayer endAngle]);
        anim.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionDefault];
        return anim;
    }
    return [super actionForKey:event];
}

重写上面两个方法之后,在外部修改动画属性时就会触发界面重绘。系统会优先调用-display方法进行重绘,如果没有重写这个方法,系统会调用-drawInContext:进行重绘。要注意:

不在-drawInContext中绘图的时候,要在绘图代码前后加上:
UIGraphicsBeginImageContextWithOptions(self.bounds.size, NO, 0);
image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
在-drawInContext中绘制的时候不需要写。

绘制代码:
- (void)drawInContext:(CGContextRef)ctx {
CGPoint center = CGPointMake(self.bounds.size.width / 2, self.bounds.size.height / 2);
CGFloat presentStartAngle = [[self.presentationLayer valueForKey:@"startAngle"] doubleValue];
CGFloat presentEndAngle = [[self.presentationLayer valueForKey:@"endAngle"] doubleValue];
CGContextSetLineWidth(ctx, 40);
CGContextSetStrokeColorWithColor(ctx, [UIColor purpleColor].CGColor);
CGContextAddArc(ctx, center.x, center.y, 100, presentStartAngle, presentEndAngle, 0);
CGContextStrokePath(ctx);
}

- (void)display {
    CGPoint center = CGPointMake(self.bounds.size.width / 2, self.bounds.size.height / 2);
    CGFloat presentStartAngle = [[self.presentationLayer valueForKey:@"startAngle"] doubleValue];
    CGFloat presentEndAngle = [[self.presentationLayer valueForKey:@"endAngle"] doubleValue];

    UIGraphicsBeginImageContextWithOptions(self.bounds.size, NO, 0);
    CGContextRef ctx = UIGraphicsGetCurrentContext();

    CGContextSetLineWidth(ctx, 40);
    [self.color setStroke];
    CGContextAddArc(ctx, center.x, center.y, 100, presentStartAngle, presentEndAngle, 0);
    CGContextStrokePath(ctx);

    self.contents = (id)UIGraphicsGetImageFromCurrentImageContext().CGImage;
    UIGraphicsEndImageContext();
}

创建这个Layer对象的时候,需要给它设置frame,如果不设置frame,会出现绘制失败。所以最好用-initWithFrame:方法进行创建。

方法二

理论上讲重绘方法每秒会被调用60次,但真机实测发现只有50多次,并且调用次数会随着重绘代码的增多而减少,这会造成动画帧数下降,使动画看起来不够流畅。

第二种方法是创建定时器,每秒触发60次,每次触发都进行重绘,步骤:
1、创建Layer类继承自CAShapeLayer,重写-initWithLayer:方法
2、创建UIView类用来放置Layer,在view被添加到父视图之后给它上面的Layer创建动画
3、实现动画代理方法,动画开始时开启定时器,定时触发重绘
4、动画属性的值会随动画的执行不断变化,定时器触发时获取当前动画值,画出当前的位置

重写-initWithLayer:
- (instancetype)initWithLayer:(id)layer {
if (self = [super initWithLayer:layer]) {
if ([layer isKindOfClass:[CircleLayer class]]) {
self.startAngle = [(CircleLayer *)layer startAngle];
self.endAngle = [(CircleLayer *)layer endAngle];
}
}
return self;
}
CAAnimation生成关键帧是通过拷贝CALayer进行的,在拷贝时,只能拷贝原有的(系统的,非自定义的)属性,不能拷贝自定义的属性或持有的对象等等,因此需要重载initWithLayer来手动拷贝我们需要拷贝的东西。

创建动画:
- (void)createAnimationWithKeyPath:(NSString *)key fromValue:(NSNumber *)from toValue:(NSNumber *)to func:(NSString *)func layer:(CALayer *)layer {
CABasicAnimation *anim = [CABasicAnimation animationWithKeyPath:key];
NSNumber *currentAngle = [layer.presentationLayer valueForKey:key];
if (!currentAngle) {
currentAngle = from;
}
anim.fromValue = currentAngle;
anim.toValue = to;
anim.delegate = self;
anim.timingFunction = [CAMediaTimingFunction functionWithName:func];
[layer addAnimation:anim forKey:key];
// 设置结束值,这样动画结束之后就会停留在结束位置,而不会返回初始位置,一定要在添加动画之后设置
[layer setValue:to forKey:key];
}

给动画设置初始值和结束值,设置好动画执行方式,它就会在“暗地里”执行,执行期间可以通过layer.presentationLayer获取当前动画执行到的位置,获取之后就可以绘制layer了。这样每秒绘制60次就形成了流畅的动画效果。


支付宝的记账本里有一个非常酷炫的自定义控件,现在就模仿一下它的动画效果:

仿支付宝记账本.gif

代码如下:
- (instancetype)initWithFrame:(CGRect)frame {
if (self = [super initWithFrame:frame]) {
_animations = [[NSMutableArray alloc] init];
_pieCenter = CGPointMake(frame.size.width/2, frame.size.height/2);
_animationDuration = 3;
_startPieAngle = 0;
_pieLineWidth = 40;
_pieRadius = MIN(frame.size.width/2 - _pieLineWidth, frame.size.width/2 - _pieLineWidth);
_selectedIndex = -1;
_selectedOffsetRadius = 7.0;
}
return self;
}

- (void)reloadData {
    [CATransaction begin];
    [CATransaction setAnimationDuration:_animationDuration];

    CGFloat p = 2 * M_PI;
    NSArray *end = @[@(p/5),@(p/4),@(p/3),@(p/2),@(p/1)];
    NSArray *start = @[@(0),@(p/5),@(p/4),@(p/3),@(p/2)];

    for (int i = 0; i < 5; i ++) {
        CircleLayer *layer = [CircleLayer layer];
        [self.layer addSublayer:layer];
        CGFloat startAngle = [start[i] doubleValue];
        CGFloat endAngle = [end[i] doubleValue];
        layer.startAngle = startAngle;
        layer.endAngle = endAngle;
        layer.lineWidth = 30;
        layer.fillColor = [UIColor clearColor].CGColor;
        layer.strokeColor = [UIColor colorWithHue:((i/8)%20)/20.0+0.02 saturation:(i%8+3)/10.0 brightness:91/100.0 alpha:1].CGColor;
        [self createAnimationWithKeyPath:@"startAngle" fromValue:@0 toValue:@(startAngle) layer:layer];
        [self createAnimationWithKeyPath:@"endAngle" fromValue:@0 toValue:@(endAngle) layer:layer];
    }

    [CATransaction commit];
}

- (void)createAnimationWithKeyPath:(NSString *)key fromValue:(NSNumber *)from toValue:(NSNumber *)to layer:(CALayer *)layer {
    CABasicAnimation *anim = [CABasicAnimation animationWithKeyPath:key];
    NSNumber *currentAngle = [layer.presentationLayer valueForKey:key];
    if (!currentAngle) {
        currentAngle = from;
    }
    anim.fromValue = currentAngle;
    anim.toValue = to;
    anim.delegate = self;
    anim.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
    [layer addAnimation:anim forKey:key];
    [layer setValue:to forKey:key];
}

- (void)animationDidStart:(CAAnimation *)anim {
    if (!_animationTimer) {
        static float timeInterval = 1.0/60.0;
        _animationTimer= [NSTimer timerWithTimeInterval:timeInterval target:self selector:@selector(timerFired) userInfo:nil repeats:YES];
        [[NSRunLoop mainRunLoop] addTimer:_animationTimer forMode:NSRunLoopCommonModes];
    }
    [_animations addObject:anim];
}

- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag {
    [_animations removeObject:anim];
    if (_animations.count == 0) {
        [_animationTimer invalidate];
        _animationTimer = nil;
    }
}

- (void)timerFired {
    NSArray *sliceLayerArray = self.layer.sublayers;
    [sliceLayerArray enumerateObjectsUsingBlock:^(CircleLayer *layer, NSUInteger idx, BOOL *stop) {
        CGFloat currentStartAngle = [[layer.presentationLayer valueForKey:@"startAngle"] doubleValue];
        CGFloat currentEndAngle = [[layer.presentationLayer valueForKey:@"endAngle"] doubleValue];
    
        UIBezierPath *path = [UIBezierPath bezierPathWithArcCenter:_pieCenter radius:_pieRadius startAngle:currentStartAngle endAngle:currentEndAngle clockwise:1];
        layer.path = path.CGPath;
    }];
}

添加到ViewController上之后,调用reloadData就会开始动画。

仿写的支付宝记账本控件效果如下:

6.gif

完整demo请参考我的GitHub

推荐阅读更多精彩内容