becomeFirstResponder在iOS 8中不起作用 [英] becomeFirstResponder not working in iOS 8

问题描述

我正在使用UITextField的方法becomeFirstResponder来显示键盘。
这适用于iOS 7.但在iOS 8中，此方法不显示键盘。

I am using UITextField's method becomeFirstResponder to show the keyboard. This is working in iOS 7. But in iOS 8 this method doesn't show the keyboard.

 UITextField *txtAddNew = [[UITextField alloc] initWithFrame:CGRectMake(10,10,240, 21)];
 txtAddNew.font = [UIFont fontWithName:@"Helvetica" size:16];
 txtAddNew.clearButtonMode = UITextFieldViewModeWhileEditing;
 txtAddNew.returnKeyType = UIReturnKeyDone;
 txtAddNew.delegate = self;
 txtAddNew.autocorrectionType = UITextAutocorrectionTypeNo;
 txtAddNew.tag = 15;

 // Open keyboard
 [txtAddNew becomeFirstResponder];

在iOS 8中有什么办法吗？

Is there any way to do it in iOS 8?

推荐答案

尝试按下面的方式调用 becomeFirstResponder

Try calling becomeFirstResponder like below

[txtAddNew performSelector:@selector(becomeFirstResponder) withObject:nil afterDelay:0];

根据Apple，

如果当前
响应者可以辞退第一响应者状态（canResignFirstResponder）
并且新响应者可以成为第一响应者，则响应者对象仅成为第一响应者。

A responder object only becomes the first responder if the current responder can resign first-responder status (canResignFirstResponder) and the new responder can become first responder.

您可以调用此方法来创建响应者对象，例如查看
第一响应者。但是，如果
是视图层次结构的一部分，则只应在该视图上调用它。如果视图的window属性包含
UIWindow对象，则它已安装在视图层次结构中;如果
返回nil，则视图将从任何层次结构中分离。

You may call this method to make a responder object such as a view the first responder. However, you should only call it on that view if it is part of a view hierarchy. If the view’s window property holds a UIWindow object, it has been installed in a view hierarchy; if it returns nil, the view is detached from any hierarchy.

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