ios - 如何在自定义的 UIBarButtonItem 上放置角标(Badge)

Question

我有一个带有两个按钮的导航栏，一个是后退按钮，另一个是聊天符号。

我这样写这段代码:

UIBarButtonItem *_btn=[[UIBarButtonItem alloc]initWithImage:[UIImage imageNamed:@"back.png"]
                                                      style:UIBarButtonItemStylePlain
                                                     target:self
                                                     action:@selector(goBackToPreviousView)];

self.navigationItem.leftBarButtonItem=_btn;
self.navigationItem.leftBarButtonItem.tintColor = [UIColor blackColor];


UIBarButtonItem *_btn2=[[UIBarButtonItem alloc]initWithImage:[UIImage imageNamed:@"chat.png"]
                                                      style:UIBarButtonItemStylePlain
                                                     target:self
                                                     action:@selector(startChat)];

self.navigationItem.rightBarButtonItem=_btn2;
self.navigationItem.rightBarButtonItem.tintColor = [Utility colorWithHexValue:CyanBlue];

我遇到的问题是，每当聊天中有一些我没有看到的新消息时，聊天按钮上应该有某种角标(Badge)或自定义标签，以指示您有多少条新消息有。

我该怎么做？

Answer 1

对于 Swift 3.0:

结果:

代码:

override func viewDidLoad() {
  super.viewDidLoad()

  // badge label
  let label = UILabel(frame: CGRect(x: 10, y: -10, width: 20, height: 20))
  label.layer.borderColor = UIColor.clear.cgColor
  label.layer.borderWidth = 2
  label.layer.cornerRadius = label.bounds.size.height / 2
  label.textAlignment = .center
  label.layer.masksToBounds = true
  label.font = UIFont(name: "SanFranciscoText-Light", size: 13)
  label.textColor = .white
  label.backgroundColor = .red
  label.text = "80"

  // button
  let rightButton = UIButton(frame: CGRect(x: 0, y: 0, width: 18, height: 16))
  rightButton.setBackgroundImage(UIImage(named: "inbox"), for: .normal)
  rightButton.addTarget(self, action: #selector(rightButtonTouched), for: .touchUpInside)
  rightButton.addSubview(label)

  // Bar button item
  let rightBarButtomItem = UIBarButtonItem(customView: rightButton)

  navigationItem.rightBarButtonItem = rightBarButtomItem
}

func rightButtonTouched() {
  print("right button touched")
}