我UIButtonBarItem的不正確鋪陳與FlexibleSpace

Question

我以編程方式迅速建立一個UIToolBar及其項目：

var items = [UIBarButtonItem]() 
    let leftButton = UIBarButtonItem(image: UIImage(named: "left"), style: .Plain, target: self, action: Selector("doneClickedMaButton")) 
    let spacer  = UIBarButtonItem(barButtonSystemItem: .FlexibleSpace, target: nil, action: nil) 
    let rightButton = UIBarButtonItem(image: UIImage(named: "right"), style: .Plain, target: self, action: Selector("doneClickedRight")) 
    let searchButton = UIBarButtonItem(barButtonSystemItem: .Search, target: self, action: Selector("doneClickedSearch")) 
    items.append(leftButton) 
    items.append(spacer) 
    items.append(searchButton) 
    items.append(spacer)   
    items.append(rightButton) 

var toolBar   = UIToolbar() 
    toolBar.frame = CGRectMake(0, 0, self.view.frame.size.width, 50) 
    toolBar.translatesAutoresizingMaskIntoConstraints = false 
    toolBar.backgroundColor = UIColor.redColor() 
    toolBar.items = items 
    toolBar.sizeToFit() 
    view.addSubview(toolBar) 
    view.addConstraint(NSLayoutConstraint(item: toolBar, attribute: .Bottom, relatedBy: .Equal, toItem: view, attribute: .Bottom, multiplier: 1.0, constant: 0.0)) 

如果我不添加spacer項目，然後模擬器看起來像這樣的：

如果我有他們在，就像它是這麼說的這段代碼。我得到這個：

正如你所看到的，不僅是現在脫落朝左邊的屏幕上的圖像，但他們以正確的順序不再。

我想.FlexibleSpace只是增加了項目之間的動態間距。我在這裏錯過了什麼嗎？有人在各種帖子中提到，可以將寬度設置爲UIBarButtonItem中的UILabel，這可以讓.FlexibleSpace識別它。

Answer 1

問題是你沒有足夠的約束來滿足自動佈局引擎。您將工具欄固定在底部，但寬度縮小，因此只能容納按鈕，但您希望它是視圖的寬度。嘗試像這樣：

var items = [UIBarButtonItem]() 
    let leftButton = UIBarButtonItem(image: UIImage(named: "left"), style: .Plain, target: self, action: Selector("doneClickedMaButton")) 
    let spacer  = UIBarButtonItem(barButtonSystemItem: .FlexibleSpace, target: nil, action: nil) 
    let rightButton = UIBarButtonItem(image: UIImage(named: "right"), style: .Plain, target: self, action: Selector("doneClickedRight")) 
    let searchButton = UIBarButtonItem(barButtonSystemItem: .Search, target: self, action: Selector("doneClickedSearch")) 
    items.append(leftButton) 
    items.append(spacer) 
    items.append(searchButton) 
    items.append(spacer)   
    items.append(rightButton) 

var toolBar   = UIToolbar() 
    toolBar.frame = CGRectMake(0, 0, self.view.frame.size.width, 50) 
    toolBar.translatesAutoresizingMaskIntoConstraints = false 
    toolBar.backgroundColor = UIColor.redColor() 
    toolBar.items = items 
    toolBar.sizeToFit() 
    view.addSubview(toolBar) 
    toolBar.leadingAnchor.constraintEqualToAnchor(self.view.leadingAnchor).active = true 
    toolBar.trailingAnchor.constraintEqualToAnchor(self.view.trailingAnchor).active = true 
    toolBar.bottomAnchor.constraintEqualToAnchor(self.view.bottomAnchor).active = true