为什么UITextField成为firstResponder在我的子viewcontroller中不显示键盘？

Question

In my first ViewController, I make one UITextField to becomeFirstResponder, and the focus stay that TextField and keyboard appear automatically. It just works fine. But then I present another child ViewController which has 3 UITextFields (A,B,C) in this ViewController, I set the first UITextField (say A) to becomeFirstResponder in this child ViewController, the focus stay the A but the keyboard doesn't appear. I searched all the answers the whole day, but nothing found.

Here is the code.

in parent VC, I set:

TestVC *testVC= [[TestVC alloc] init];
testVC.modalPresentationStyle=UIModalPresentationFormSheet;
[detailvc presentViewController:testVC animated:NO completion:nil];

in child VC TestVC, I set:

UITextField *v_matcode=[MyViewUtil addTextField:@"" x:10 y:10 width:100 height:40];
[self.view addSubview:v_matcode];
[v_matcode becomeFirstResponder];

and this is the addTextField():

+(UITextField *) addTextField:(NSString *)text x:(int)_x y:(int)_y width:(int)_width height:(int)_height {
  UITextField *v_txt = [[UITextField alloc] init];
  v_txt.frame= CGRectMake(_x, _y, _width, _height);
  v_txt.borderStyle = UITextBorderStyleRoundedRect;
  return v_txt;}

The v_matcode has the focus, but the keyboard doesn't appear. But if I don't set this textfield becomeFirstResponder and let user tap it,the keyboard appear correctly. Why is that?

Answer 1

try setting animated to YES

[detailvc presentViewController:testVC animated:YES completion:nil];