我想在按下按钮后添加图像，然后在再次按下按钮后将其删除，然后添加具有不同大小和位置的同一图像。我尝试使用
imageView.image =无
但这没有用，因为什么都不会显示！
@IBAction func btnCalc(sender: AnyObject) {
let Lead1 = txtLead1.text
let LeadI: Float = (Lead1! as NSString).floatValue
let Lead2 = txtLead2.text
let LeadII: Float = (Lead2! as NSString).floatValue
let Lead3 = txtLead3.text
let LeadIII: Float = (Lead3! as NSString).floatValue
let a = 0.5*(LeadII + LeadIII)
let b = 0.5*(LeadI - LeadIII)
let c = (-0.5*(LeadI + LeadII))
let d :Float = 2/1.7320508075688772935274463415058723669428052538103806280558
let e = LeadIII/LeadI
let y :Float = Float (atan(d*(e+0.5)))
let z = (y*180)/3.141592654
let z1 = z + 180
let zz = LeadI/(cos((z*3.141592654)/180))
let zzz = -zz
let Z1 = CGFloat((z1*3.141592654)/180)
let Z = CGFloat((z*3.141592654)/180)
let imageName = "Arrow.png"
let image = UIImage(named: imageName)
let imageView = UIImageView(image: image!)
if LeadI == 0 && LeadII == 0 && LeadIII == 0 {
lblaVF.text = "aVF = 0"
lblaVL.text = "aVL = 0"
lblaVR.text = "aVR = 0"
lblmEA.text = "Mean Electrical Axis = 0"
lblA.text = "A = 0"
//Remove old image from view
} else if LeadII == LeadIII + LeadI && zz<0 {
lblaVF.text = "aVF = \(a)"
lblaVL.text = "aVL = \(b)"
lblaVR.text = "aVR = \(c)"
lblmEA.text = "Mean Electrical Axis = \(z1)"
lblA.text = "A = \(zzz)"
imageView.frame = CGRect(x: 107, y: 340, width: 160, height: 24)
view.addSubview(imageView)
imageView.transform = CGAffineTransformMakeRotation(Z1)
} else if LeadII == LeadIII + LeadI {
lblaVF.text = "aVF = \(a)"
lblaVL.text = "aVL = \(b)"
lblaVR.text = "aVR = \(c)"
lblmEA.text = "Mean Electrical Axis = \(z)"
lblA.text = "A = \(zz)"
imageView.frame = CGRect(x: 107, y: 340, width: 160, height: 24)
view.addSubview(imageView)
imageView.transform = CGAffineTransformMakeRotation(Z)
} else {
//Remove old image from view
lblaVF.text = "aVF ="
lblaVL.text = "aVL ="
lblaVR.text = "aVR ="
lblmEA.text = "Mean Electrical Axis ="
lblA.text = "A ="
let alert = UIAlertController(title:"Houston, we've got a problem!", message:"Rememer that Lead II = Lead I + Lead III", preferredStyle:UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title:"OK",style: UIAlertActionStyle.Default, handler:nil))
self.presentViewController(alert, animated:true, completion:nil)
}
}
最佳答案
通过查看您的示例，所有这些都是在IBAction中发生的，并且每次您创建新的UIImageView时都会发生。因此，如果您将image设置为新创建的UIImageView的nil，则您将看不到任何效果，因为尚未将其添加到视图中。
看来您将在UIImageView的视图控制器上需要一个实例变量。在viewDidLoad中添加一次imageView，然后在IBAction中对其进行修改，而不是每次都创建一个新视图。
这里还有其他需要考虑的事项可以帮助您进行调试：
也许您应该考虑将其分解为较小的方法，以便在视图控制器上使用实例变量来保持某种状态。
变量名应该有意义，而不是（a，b，c，d等）
为清楚起见，变量名应以小写字母开头，而类应以大写字母开头。
尽可能避免使用幻数，尤其是在有其他可用替代方法时。 M_PI而不是3.14 ....
关于ios - 如何快速删除具有不同特征的图像然后读取？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/34041048/