无法获取此复选框来构建？

Question

我试图修复其他错误，所以它可能看起来有点不同，但这是我能做的最好的。

override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning()
    Box49.setImage(#imageLiteral(resourceName: "UnCheckBox"), for: .normal)
    Box49.setImage(#imageLiteral(resourceName: "CheckBox"), for: .selected)

    Box50.setImage(#imageLiteral(resourceName: "UnCheckBox"), for: .normal)
    Box50.setImage(#imageLiteral(resourceName: "CheckBox"), for: .selected)

    Box51.setImage(#imageLiteral(resourceName: "UnCheckBox"), for: .normal)
    Box51.setImage(#imageLiteral(resourceName: "CheckBox"), for: .selected)

}

@IBAction func Box49(_ sender: UIButton) {
    sender.isSelected = !(sender as AnyObject).isSelected
}


@IBAction func Box50(_ sender: UIButton) {
    sender.isSelected = !(sender as AnyObject).isSelected
}


@IBAction func Box51(_ sender: UIButton) {
    sender.isSelected = !(sender as AnyObject).isSelected
    }

Answer 1

首先，您需要创建3个按钮插座，因为您当前正在将图像设置为按钮操作，因此要么在界面构建器中设置选定图像和普通图像，要么创建3按钮插座，如下所示。

@IBOutlet var box49: UIButton!
@IBOutlet var box50: UIButton!
@IBOutlet var box51: UIButton!

现在将图像设置为viewDidLoad中的Button或viewDidAppear中不在didReceiveMemoryWarning中的按钮，也不需要将发件人转发到AnyObject以访问isSelected属性，因为发件人类型是UIButton，因此您可以直接访问isSelected属性。

var BoxOFF = #imageLiteral(resourceName: "UnCheckBox")
var BoxON = #imageLiteral(resourceName: "CheckBox") 
override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
     box49.setImage(BoxOFF, for: .normal)
     box49.setImage(BoxON, for: .selected)

     box50.setImage(BoxOFF, for: .normal)
     box50.setImage(BoxON, for: .selected)

     box51.setImage(BoxOFF, for: .normal)
     box51.setImage(BoxON, for: .selected)
} 

现在以这种方式设置你的按钮动作。

@IBAction func Box49(_ sender: Button) {
     sender.isSelected = !sender.isSelected
}

@IBAction func Box50(_ sender: Button) {
     sender.isSelected = !sender.isSelected
}

@IBAction func Box51(_ sender: Button) {
     sender.isSelected = !sender.isSelected
}

Answer 2

override func didReceiveMemoryWarning()
 {
    super.didReceiveMemoryWarning()
 }

当内存不足而需要释放任何资源时，会调用上述方法。

因此，您需要将上述方法中的代码添加到viewDidAppear或viewWillAppear。

所以替换如下代码：

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
     Box49.setImage(#imageLiteral(resourceName: "UnCheckBox"), for: .normal)
    Box49.setImage(#imageLiteral(resourceName: "CheckBox"), for: .selected)

    Box50.setImage(#imageLiteral(resourceName: "UnCheckBox"), for: .normal)
    Box50.setImage(#imageLiteral(resourceName: "CheckBox"), for: .selected)

    Box51.setImage(#imageLiteral(resourceName: "UnCheckBox"), for: .normal)
    Box51.setImage(#imageLiteral(resourceName: "CheckBox"), for: .selected)

} 

另一项改进是替换您的代码

sender.isSelected = !(sender as AnyObject).isSelected

带

sender.isSelected = !sender.isSelected