使用贝塞尔曲线绘制水波纹

示例：

示例.gif

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思路：

使用贝塞尔曲线绘制正弦曲线；使用CAShapeLayer绘制形状；使用CADisplayLink做刷屏；
CADisplayLink是一个能让我们以和屏幕刷新率相同的频率将内容画到屏幕上的定时器。一但 CADisplayLink以特定的模式注册到runloop之后，每当屏幕需要刷新的时候，runloop就会调用CADisplayLink绑定的target上的selector；iOS设备的刷新频率事60HZ也就是每秒60次。那么每一次刷新的时间就是1/60秒 大概16.7毫秒；下面直接上代码：
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一. 创建THWave类，继承于UIView

/** 浪宽： 一个完整的浪的宽度 */
@property (nonatomic, assign) CGFloat waveWidth;

/** 浪高： 波峰到波谷的距离 */
@property (nonatomic, assign) CGFloat waveHeight;

/** 浪速： 浪线的移动速度 */
@property (nonatomic, assign) CGFloat waveSpeed;

/** 浪速： 浪的内填充颜色 */
@property (nonatomic, strong) UIColor *waveColor;

/** 返回浪的Y点 */
@property (nonatomic, copy) WaveYBlock waveY;


/** 开始波动 */
- (void)startWaveAnimation;
/** 结束波动 */
- (void)endWaveAnimation;

二. 创建CAShapeLayer

#pragma mark - initUI
- (void)initUI{
    // 设置底色
    self.backgroundColor = [UIColor whiteColor];
    
    // 创建layer
    _waveLayer = [CAShapeLayer layer];
    [self.layer addSublayer:_waveLayer];
}

#pragma mark - 设置浪高
- (void)setWaveHeight:(CGFloat)waveHeight{
    _waveHeight = waveHeight;
    
    CGRect frame = self.bounds;
    frame.origin.y = frame.size.height - self.waveHeight;
    frame.size.height = self.waveHeight;
    _waveLayer.frame = frame;
    
}
#pragma mark - 设置浪色
- (void)setWaveColor:(UIColor *)waveColor{
    _waveColor = waveColor;
    _waveLayer.fillColor = waveColor.CGColor;
}

三. 创建刷屏器

#pragma mark - 开始和结束动画
- (void)startWaveAnimation{
    self.timer = [CADisplayLink displayLinkWithTarget:self selector:@selector(wave)];
    [self.timer addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
}
- (void)endWaveAnimation{
    [self.timer invalidate];
    self.timer = nil;
}

四. 绘制

// 动画实现
- (void)wave{
    
    // 1. 随机
    int speed = [@(self.waveSpeed) intValue];
    int num = arc4random() % speed;
    self.offset += num;
    
    CGFloat width = self.bounds.size.width;
    CGFloat height = self.waveHeight;
    CGFloat y = 0.f;
    // 2. 绘线
    UIBezierPath *path = [UIBezierPath bezierPath];
    [path moveToPoint:CGPointMake(0, height)];
    for (CGFloat x = 0.f; x <= width; x++) {
        y = height * sinf(2*M_PI/self.waveWidth *x - self.offset * 0.0045);
        [path addLineToPoint:CGPointMake(x, y)];
    }
    
    // 3. 返回x等于中心点时的Y值
    CGFloat centerX = self.bounds.size.width / 2.0;
    CGFloat centerY = height * sinf(2*M_PI/self.waveWidth * centerX - self.offset * 0.0045);
    if (self.waveY) {
        self.waveY(centerY);
    }
    
    // 4. 闭合曲线
    [path addLineToPoint:CGPointMake(width, height)];
    [path addLineToPoint:CGPointMake(0, height)];
    [path closePath];
    self.waveLayer.path = path.CGPath;
}

五. 外部引用,顺便加条小船

#pragma mark - creatWave
-(void)creatWave{
    // 1. view 增加浪
    [self.view addSubview: ({
        THWave *wave = [[THWave alloc] initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, 300)];
        wave.waveHeight = 18;
        wave.waveSpeed = 15;
        wave.waveWidth = 300;
        wave.waveColor = [UIColor colorWithRed:48/255.0 green:204/255.0 blue:249/255.0 alpha:1];
        
        // 2. 浪增加船
        UIImageView *boat;
        [wave addSubview:({
            boat = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"boat"]];
            boat.bounds = CGRectMake(0, 0, 123.3, 106.6);
            boat.contentMode = UIViewContentModeScaleToFill;
            boat;
        })];
       
        // 3. 弱化，调整船的位置
        __weak typeof(self)weakSelf = self;
        __weak typeof(wave)weakWave = wave;
        wave.waveY = ^(CGFloat waveY){
            CGRect frame = boat.bounds;
            frame.origin.x = CGRectGetWidth(weakSelf.view.frame)/2.0 - CGRectGetWidth(frame)/2.0;
            frame.origin.y = weakWave.bounds.size.height - boat.bounds.size.height - weakWave.waveHeight + waveY;
            boat.frame = frame;
        };
        [wave startWaveAnimation];
        wave;
    })];
}

大功告成！！！
介绍一个强大的进度展示地址
https://github.com/ninjaprox/NVActivityIndicatorView
你也可以从这里看详细的demo示例；