当前，当选择文本字段并出现键盘时，会出现以下UIToolBar

let bar = UIToolbar()

let spacer = UIBarButtonItem(barButtonSystemItem: .flexibleSpace,target: nil,action: nil)

let reset = UIBarButtonItem(title: "Tool Bar Text",style: .plain,target: self,action: #selector(functionExample))
reset.tintColor = UIColor.white

bar.barTintColor = UIColor.red
bar.items = [spacer,reset,spacer]
bar.sizeToFit()
exampleTextField = bar

我想调整UIToolBar的高度以使其占据更多的屏幕，我尝试了以下操作，但似乎什么也没做。

bar.frame = CGRect(x: bar.frame.origin.x,y: bar.frame.origin.y,width: bar.frame.size.width,height: 150)
bar.frame = CGRect(x: 0,y: view.frame.size.height - 80,width: view.frame.size.width,height: 80)

我也尝试过： bar.frame = CGRect（x：myToolbar.frame.origin.x，y： bar.frame.origin.y，宽度：myToolbar.frame.size.width，高度：20）

这两种方法似乎根本不改变高度。

更新2：

所以这种方法似乎可行，但是我只希望它在键盘抬起时出现，而不是在视图控制器第一次打开时出现，

let toolBar = UIToolbar()
var items = [UIBarButtonItem]()

items.append(
    UIBarButtonItem(barButtonSystemItem: .flexibleSpace,action: nil)
)

items.append(
    UIBarButtonItem(title: "Tool Bar Text",action: #selector(confirmSignature))
)

items.append(
    UIBarButtonItem(barButtonSystemItem: .flexibleSpace,action: nil)
)

toolBar.setItems(items,animated: true)
toolBar.tintColor = .white
toolBar.barTintColor = UIColor.red



toolBar.translatesAutoresizingMaskintoConstraints = false


if #available(iOS 11.0,*) {
    let guide = self.view.safeAreaLayoutGuide
    toolBar.trailingAnchor.constraint(equalTo: guide.trailingAnchor).isactive = true
    toolBar.leadingAnchor.constraint(equalTo: guide.leadingAnchor).isactive = true
    toolBar.bottomAnchor.constraint(equalTo: guide.bottomAnchor).isactive = true
    toolBar.heightAnchor.constraint(equalToConstant: 80).isactive = true

}
else {
    NSLayoutConstraint(item: toolBar,attribute: .bottom,relatedBy: .equal,toItem: view,multiplier: 1.0,constant: 0).isactive = true
    NSLayoutConstraint(item: toolBar,attribute: .leading,attribute: .trailing,constant: 0).isactive = true

    toolBar.heightAnchor.constraint(equalToConstant: 44).isactive = true
}

exampleTextField.inputaccessoryView = toolBar
view.addSubview(toolBar)