ios - becomeFirstResponder not showing from viewDidLoad -

here have simple example. im calling firstresponder in viewdidload. accessory view shows after tapping screen. why isn't showing start?

class testviewcontroller: mainpageviewcontroller {      private let accessoryview = uiview() //textinputview() // messageinputaccessoryview()      override var inputaccessoryview: uiview {         return accessoryview     }      override var canbecomefirstresponder: bool { return true }        override func viewdidload() {         super.viewdidload()          accessoryview.backgroundcolor = .red         accessoryview.frame = cgrect(x: 0, y: 0, width: 300, height: 50)         self.becomefirstresponder()          // additional setup after loading view.          let tap = uitapgesturerecognizer(target: self, action: #selector(tappo))         self.view.isuserinteractionenabled = true         self.view.addgesturerecognizer(tap)          tappo()     }       func tappo() {         self.becomefirstresponder()     }   } 

viewwillappear better place put becomesfirstresponder. try that.