Button.contentHorizontalAlignment = UIControlContentHorizontalAlignmentLeft;//左对齐(UIControlContentHorizontalAlignment、CenterUIControlContentHorizontalAlignmentFill、UIControlContentHorizontalAlignmentRight)
Button.contentVerticalAlignment = UIControlContentVerticalAlignmentBottom;//底部对其(UIControlContentVerticalAlignmentCenter、UIControlContentVerticalAlignmentFill、UIControlContentVerticalAlignmentTop)