蒙版

@property(nullable, strong) CALayer *mask;

A layer whose alpha channel is used as a mask to select between the layer's background and the result of compositing the layer's contents with its filtered background. Defaults to nil. When used as a mask the layer's compositing Filter and backgroundFilters properties are ignored. When setting the mask to a new layer, the new layer must have a nil superlayer, otherwise the behavior is undefined. Nested masks (mask layers with their own masks) are unsupported.

效果图

PJProgressBar.gif

核心代码

进度条的构建

- (void)setupProgressBar {
    
    CALayer *backgroundLayer = [CALayer layer];
    backgroundLayer.frame = self.bounds;
    backgroundLayer.backgroundColor = [UIColor grayColor].CGColor;
    backgroundLayer.masksToBounds = YES;
    backgroundLayer.cornerRadius = self.height / 2;
    [self.layer addSublayer:backgroundLayer];
    
    _maskLayer = [CALayer layer];
    _maskLayer.frame = CGRectMake(0, 0, 0, self.height);
    _maskLayer.cornerRadius = self.height / 2;
    _maskLayer.borderWidth = self.bounds.size.height / 2;
    
    CAGradientLayer *gradientLayer = [CAGradientLayer layer];
    gradientLayer.frame = self.bounds;
    gradientLayer.masksToBounds = YES;
    gradientLayer.cornerRadius = self.height / 2;
    gradientLayer.colors = @[(id)[[self p_colorWithHex:0xFF6347] CGColor],
                             (id)[[self p_colorWithHex:0xFFEC8B] CGColor],
                             (id)[[self p_colorWithHex:0x98FB98] CGColor],
                             (id)[[self p_colorWithHex:0x00B2EE] CGColor],
                             (id)[[self p_colorWithHex:0x9400D3] CGColor]];
    gradientLayer.locations = @[@0.1, @0.3, @0.5, @0.7, @1];
    gradientLayer.startPoint = CGPointMake(0, 0);
    gradientLayer.endPoint = CGPointMake(1, 0);
    gradientLayer.mask = _maskLayer;
    [self.layer addSublayer:gradientLayer];
}

1、创建背景Layer。
2、创建maskLayer，用于对gradientLayer的遮盖。
3、创建gradientLayer。(CAGradientLayer：颜色渐变的Layer)

设置进度

- (void)setProgressBarPercent:(CGFloat)percent {
    
    if (percent > 100.0f) {
        percent = 100.0f;
    }
    
    if (percent < 0.0f) {
        percent = 0.0f;
    }
    
    [_maskLayer setFrame:CGRectMake(0, 0, self.width * percent / 100.0f, self.height)];
}

Demo地址

https://github.com/codelyw/iOSDemo

参考

http://www.cnblogs.com/gardenLee/archive/2016/04/09/5371377.html