ios - 正在显示 View 但打印宽度显示为 0

Question

我正在使用这段代码以编程方式创建我的 View :

      let statusfilterui = UIView(frame: CGRectMake(0, 300, 0, 0))
    var height : CGFloat = 0
    var width : CGFloat = 0
    self.cancelledByAdmin.frame = CGRectMake(0,0,0,0)
    if width == 0{
        width = self.cancelledByAdmin.frame.width
        height = self.cancelledByAdmin.frame.height
    }
    let cancelledByAdminlabel = UILabel(frame: CGRectMake(0, 0, 0, 0))
    cancelledByAdminlabel.text = "لغو شده توسط پذیرش"
    cancelledByAdminlabel.sizeToFit()
    self.cancelledByAdmin.frame = CGRectMake(cancelledByAdminlabel.frame.width+10, 0, 0, 0)
    let cancelledLabel = UILabel(frame: CGRectMake(0, height+10, 0, 0))
    cancelledLabel.text = "لغو شده توسط کاربر"
    cancelledLabel.sizeToFit()
    self.cancelled.frame = CGRectMake(cancelledLabel.frame.width+10, height + 10, 0, 0)
    let reservedLabel = UILabel(frame: CGRectMake(0, 2*(height + 10), 0, 0))
    reservedLabel.text = "لغو شده توسط پذیرش"
    reservedLabel.sizeToFit()
    self.reserved.frame = CGRectMake(reservedLabel.frame.width+10, 2*(height + 10), 0, 0)
    let deprecatedLabel = UILabel(frame: CGRectMake(0, 3*(height + 10), 0, 0))
    deprecatedLabel.text = "منقضی شده"
    deprecatedLabel.sizeToFit()
    self.deprecated.frame = CGRectMake(deprecatedLabel.frame.width+10, 3*(height + 10), 0, 0)
    statusfilterui.addSubview(self.cancelledByAdmin)
    statusfilterui.addSubview(cancelledByAdminlabel)
    statusfilterui.addSubview(self.cancelled)
    statusfilterui.addSubview(cancelledLabel)
    statusfilterui.addSubview(self.reserved)
    statusfilterui.addSubview(reservedLabel)
    statusfilterui.addSubview(self.deprecated)
    statusfilterui.addSubview(deprecatedLabel)
    print(statusfilterui.frame.width)
    statusfilterui.sizeToFit()
    print(statusfilterui.frame.width)
    self.filterview.addSubview(statusfilterui)
    print(statusfilterui.frame.width)

我想通过获取 View 宽度使我的 statusfilterui 居中，但问题是我正在打印 statusfilterui.f​​rame.width 3 次并且每次在控制台中打印 0.0。怎么了？

Answer 1

首先将 statusfilterui 添加到父级。然后调用 statusfilterui.sizeToFit()。然后它应该可以工作。

parentView.addSubview(statusfilterui)
statusfilterui.sizeToFit()

Apple doc on sizeToFit()