自定义一个继承于UISlider的类  重写touchesBegan方法:

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{

    CGRect t = [self trackRectForBounds: [self bounds]];

    float v = [self minimumValue] + ([[touches anyObject] locationInView: self].x - t.origin.x - 4.0) * (([self maximumValue]-[self minimumValue]) / (t.size.width - 8.0));

    [self setValue: v];

    [super touchesBegan: touches withEvent: event];

}