自己画一个活动指示器

作者: 卡丁车手 | 来源:发表于2016-08-22 11:53 被阅读292次

自己画一个活动指示器
活动指示器UIActivityIndicatorView
[iOS学习]活动指示器和进度条
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iOS 9人机界面指南(四)：UI元素控件
活动指示器
iOS原生Loading效果
iOS交互设计基础之控件（二）

苹果的UI控件中有一个UIActivityIndicatorView，俗称菊花。→_→
现在我们仿照它来制作一个其它样式的指示器，如下：

ActivityView.png

自定义指示器

首先画一个白色的扇形。
创建一个MyLayer类继承自CALayer，重写它的绘图方法- (void)drawInContext:(CGContextRef)ctx：
- (void)drawInContext:(CGContextRef)ctx
{
CGContextSetRGBFillColor(ctx, 1, 1, 1, 1);
CGContextSetRGBStrokeColor(ctx, 1, 1, 1, 1);
CGContextMoveToPoint(ctx, CGRectGetMaxX(self.bounds)/2, CGRectGetMaxY(self.bounds));
// 顺时针从-70度画到-110度 (0度是3点钟方向)
CGContextAddArc(ctx, CGRectGetMaxX(self.bounds)/2, CGRectGetMaxY(self.bounds), 20, -70 * M_PI / 180, -110 * M_PI / 180, 1);
CGContextClosePath(ctx);
CGContextDrawPath(ctx, kCGPathFillStroke);
}
之后创建一个MyActiveView类继承自UIView，把上面创建的layer添加到MyActiveView上。

@implementation MyActiveView
{
    MyLayer *layer;
    CABasicAnimation *opacityAnim;
}
- (instancetype)initWithFrame:(CGRect)frame
{
    if (self = [super initWithFrame:frame]) {
        self.backgroundColor = [UIColor clearColor];
    
        CAReplicatorLayer *repLayer = [CAReplicatorLayer layer];
        repLayer.frame = self.bounds;
        [self.layer addSublayer:repLayer];
    
        // 画一个扇形的layer
        layer = [MyLayer layer];
        layer.frame = CGRectMake(0, 0, 22, 22);
        // 调用layer的drawInContext:进行绘图
        [layer setNeedsDisplay];
        // 设置2倍比率，防止边缘出现锯齿
        layer.contentsScale = 2;
        // 透明
        layer.opacity = 0;
        // 设置锚点
        layer.anchorPoint = CGPointMake(0.5, 0);
        // 设置第一个扇形layer的位置
        layer.position = CGPointMake(self.bounds.size.width/2, 0);
        [repLayer addSublayer:layer];
    
        // 设置透明度渐变的动画
        opacityAnim = [CABasicAnimation animationWithKeyPath:@"opacity"];
        // 透明度从1变为0
        opacityAnim.fromValue = [NSNumber numberWithFloat:1.0];
        opacityAnim.toValue = [NSNumber numberWithFloat:0];
        opacityAnim.removedOnCompletion = YES;
        opacityAnim.repeatCount = MAXFLOAT;
        CGFloat duration = 0.7;
        opacityAnim.duration = duration;
        [layer addAnimation:opacityAnim forKey:nil];
    
        int count = 8;
        CGFloat angle = M_PI * 2 / count;
        // 复制8个
        repLayer.instanceCount = count;
        // 绕z轴每隔angle角度复制一个
        repLayer.instanceTransform = CATransform3DMakeRotation(angle, 0, 0, 1);
        // 复制子层动画延迟时长
        repLayer.instanceDelay = duration / count;
    
        // 此视图绕z轴旋转22度
        CATransform3D transform = CATransform3DRotate(self.layer.transform, 22*M_PI/180, 0, 0, 1);
        self.layer.transform = transform;
    
        // 监听App进入前后台
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(stop) name:UIApplicationWillResignActiveNotification object:nil];
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(start) name:UIApplicationDidBecomeActiveNotification object:nil];
    }
    return self;
}
// 停止动画
- (void)stop
{
    [layer removeAllAnimations];
}
// 开始动画
- (void)start
{
    [layer addAnimation:opacityAnim forKey:nil];
}

接下来就可以创建使用了。记得把视图控制器view的白色改为其它颜色，否则你是看不到这个白色指示器的。

MyActiveView *activityView = [[MyActiveView alloc] initWithFrame:CGRectMake(self.view.bounds.size.width/2-25, self.view.bounds.size.height-200, 50, 50)];
[self.view addSubview:activityView];

OK搞定！旋转吧，小菊花！(ง •̀_•́)ง

ActiveView.gif

CAReplicatorLayer

使用CAReplicatorLayer可以创建出很多类似的重复动画效果，比如：

ActiveViews.gif

这些都是常见的指示器效果，它们的代码如下：

条形指示器

创建一个ActiveView1类，继承自UIView。
- (instancetype)initWithFrame:(CGRect)frame
{
if (self = [super initWithFrame:frame]) {
CAReplicatorLayer *repLayer = [CAReplicatorLayer layer];
repLayer.frame = self.bounds;
[self.layer addSublayer:repLayer];

        CALayer *layer = [CALayer layer];
        // 宽度5等分之后创建3个repLayer
        CGFloat width = frame.size.width/5;
        CGFloat height = frame.size.height;
        layer.bounds = CGRectMake(0, 0, width, height);
        // 第一个layer的位置
        layer.position = CGPointMake(width/2, height/2);
        layer.backgroundColor = [UIColor greenColor].CGColor;
        [repLayer addSublayer:layer];
    
        CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"transform.scale.y"];
        animation.fromValue = @1;
        animation.toValue = @0.3;
        animation.duration = 0.4;
        // 每次重复效果跟上次相反
        animation.autoreverses = YES;
        animation.repeatCount = CGFLOAT_MAX;
        [layer addAnimation:animation forKey:nil];
    
        repLayer.instanceCount = 3;
        repLayer.instanceDelay = 0.2;
        // x轴上每隔self.frame.size.width/5*2距离，放置一个repLayer
        repLayer.instanceTransform = CATransform3DMakeTranslation(frame.size.width/5*2, 0, 0);
    }
    return self;
}

在控制器中添加它即可：

ActiveView1 *view1 = [[ActiveView1 alloc] initWithFrame:CGRectMake(20, 200, 70, 50)];
[self.view addSubview:view1];

环形指示器

创建一个ActiveView2类，继承自UIView。
- (instancetype)initWithFrame:(CGRect)frame
{
if (self = [super initWithFrame:frame]) {
CAReplicatorLayer *repLayer = [CAReplicatorLayer layer];
repLayer.frame = self.bounds;
[self.layer addSublayer:repLayer];

        CALayer *layer = [CALayer layer];
        layer.bounds = CGRectMake(0, 0, 10, 10);
        layer.cornerRadius = 5;
        layer.masksToBounds = YES;
        layer.transform = CATransform3DMakeScale(0, 0, 0);
        // 第一个layer的位置
        layer.position = CGPointMake(frame.size.width/2, 5);
        layer.backgroundColor = [UIColor greenColor].CGColor;
        [repLayer addSublayer:layer];
    
        CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"transform.scale"];
        animation.fromValue = @1;
        animation.toValue = @0.2;
        CGFloat duration = 1.2;
        animation.duration = duration;
        animation.repeatCount = CGFLOAT_MAX;
        [layer addAnimation:animation forKey:nil];
    
        int count = 12;
        // 360度分成12份
        CGFloat angle = M_PI * 2 / count;
        // 设置子层总数
        repLayer.instanceCount = count;
        repLayer.instanceTransform = CATransform3DMakeRotation(angle, 0, 0, 1);
        repLayer.instanceDelay = duration / count;
    }
    return self;
}

在控制器中添加它：

ActiveView2 *view2 = [[ActiveView2 alloc] initWithFrame:CGRectMake(150, 200, 70, 70)];
[self.view addSubview:view2];

另外一种指示器

除了上面三种指示器，还有一种指示器比较常见，不过它的代码跟上面的不太一样，它不需要使用CAReplicatorLayer来创建，只需要用CAShapeLayer结合贝塞尔曲线画个圆就行。

Round.gif

代码如下：
- (instancetype)initWithFrame:(CGRect)frame
{
if (self = [super initWithFrame:frame]) {
// 设置直径为self宽/高的最小值
CGFloat diameter = MIN(frame.size.width, frame.size.height);

        CAShapeLayer *sLayer = [CAShapeLayer layer];
        sLayer.anchorPoint = CGPointMake(0.5, 0.5);
        sLayer.frame = CGRectMake(0, 0, diameter, diameter);
        sLayer.strokeColor = [UIColor greenColor].CGColor;
        sLayer.fillColor = [UIColor clearColor].CGColor;
        sLayer.lineWidth = 2;
    
        CGFloat raduis = diameter/2;
        UIBezierPath *roundPath = [UIBezierPath bezierPathWithArcCenter:CGPointMake(raduis, raduis)
                                                                 radius:raduis
                                                             startAngle:0
                                                               endAngle:(2*M_PI-M_PI_4)
                                                              clockwise:YES];
        sLayer.path = roundPath.CGPath;
        [self.layer addSublayer:sLayer];
    
        CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"transform.rotation"];
        animation.fromValue = @0;
        animation.toValue = @(2*M_PI);
        animation.duration = 1.f;
        animation.repeatCount = CGFLOAT_MAX;
        [sLayer addAnimation:animation forKey:nil];
    }
    return self;
}

先介绍以上几种指示器，如果有比较好看的新的指示器，我会继续更新。