UILabel 的SDAutoLayout约束多行居中设置

[self addSubview:self.instructionLabeLabel];

self.instructionLabeLabel.textAlignment = NSTextAlignmentCenter;

self.instructionLabeLabel.sd_layout

.topSpaceToView(self.mailBox, 15)

.centerXEqualToView(self)

.widthIs(500)

.autoHeightRatio(0);

【widthIs(500)】这里的500设置成父视图的宽或者写成最大宽度