直线的进度条并不能满足日常的开发需求，所以我们使用UIBezierPath和CAShapeLayer来自定义

一、需要用到的知识

1.UIBezierPath

贝塞尔曲线，可以画出我们想要的许多图形。

2.CAShapeLayer

CALayer的子类，配合贝塞尔曲线实现我们的自定义控件。

UIBezierPath和CAShapeLayer的详细介绍，网上有很多。

二、自定义进度视图

1.扇形进度

    _startAngle = - M_PI_2;
    _endAngle = _startAngle + _progress * M_PI * 2;
    
    UIBezierPath *fillPath = [UIBezierPath bezierPathWithArcCenter:_origin radius:_radius startAngle:_startAngle endAngle:_endAngle clockwise:YES];
    [fillPath addLineToPoint:_origin];
    _fillLayer.path = fillPath.CGPath;
    _fillLayer.fillColor = _fillColor.CGColor;
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2.球形进度

    _startAngle = M_PI_2 - _progress * M_PI;
    _endAngle = M_PI_2 + _progress * M_PI;
    
    UIBezierPath *fillPath = [UIBezierPath bezierPathWithArcCenter:_origin radius:_radius startAngle:_startAngle endAngle:_endAngle clockwise:YES];
    _fillLayer.path = fillPath.CGPath;
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3.圆弧进度

    _startAngle = - M_PI_2;
    _endAngle = _startAngle + _progress * M_PI * 2;
    
    UIBezierPath *topPath = [UIBezierPath bezierPathWithArcCenter:_origin radius:_radius - _topWidth startAngle:_startAngle endAngle:_endAngle clockwise:YES];
    _topLayer.path = topPath.CGPath;
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4.波浪进度

    CGFloat y = _waveY;
    UIBezierPath *path = [UIBezierPath bezierPath];
    [path moveToPoint:CGPointMake(0, y)];
    for (CGFloat x = 0.0; x <= _waveWidth; x++) {
        y = _waveA * sin(_waveP * x + _waveX + 0.5) + _waveY;
        [path addLineToPoint:CGPointMake(x, y)];
    }
    [path addLineToPoint:CGPointMake(_waveWidth, self.bounds.size.height)];
    [path addLineToPoint:CGPointMake(0, self.bounds.size.height)];
    [path closePath];
    _waveLayer.path = path.CGPath;
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5.渐变色进度

    //渐变层的创建
    CALayer *gradientLayer = [CALayer layer];
    
    CAGradientLayer *leftGradient = [CAGradientLayer layer];
    leftGradient.frame = CGRectMake(-layerWidth/2, -layerWidth/2, self.bounds.size.width / 2 + layerWidth/2, self.bounds.size.height + layerWidth);
    leftGradient.colors = @[(id)[UIColor yellowColor].CGColor,
                            (id)[UIColor redColor].CGColor];
    [leftGradient setLocations:@[@0.3, @0.9, @1]];

    CAGradientLayer *rightGradient = [CAGradientLayer layer];
    rightGradient.frame = CGRectMake(self.bounds.size.width / 2, -layerWidth/2, self.bounds.size.width / 2 + layerWidth/2, self.bounds.size.height + layerWidth);
    rightGradient.colors = @[(id)[UIColor yellowColor].CGColor,
                             (id)[UIColor greenColor].CGColor];
    [rightGradient setLocations:@[@0.3, @0.9, @1]];
    
    [gradientLayer addSublayer:leftGradient];
    [gradientLayer addSublayer:rightGradient];
    
    [gradientLayer setMask:_topLayer];
    [self.layer addSublayer:gradientLayer];
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github下载地址 ZXYProgressView