显示隐藏按钮

Question

请耐心等待，因为我仍在学习目标c的绳索。

我目前有一个按钮，当按下隐藏iOS键盘。我想知道如何才能做到与此相反。当选择文本字段时，键盘自动出现 - 同时，我希望此按钮也出现在屏幕上。

谢谢！

-(IBAction)done:(id)sender{ 
//... 
//... 
[Screen resignFirstResponder]; 
done.hidden = YES; 
}; 

Answer 1

您将不得不使用NSNotification。实施addObserver在viewWillAppear中和removeObserver在viewWillDisappear

-(void)viewWillAppear:(BOOL)animated{ 
    [super viewWillAppear:animated]; 
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil]; 
} 

-(void)viewWillDisappear:(BOOL)animated{ 
    [super viewWillDisappear:animated]; 
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillShowNotification object:nil]; 
} 

-(void)keyboardWillShow:(NSNotification*)notification{ 
    done.hidden = NO; 
} 

Answer 2

寄存器为UIKeyboardWillShowNotification这样的：

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil]; 

，并在显示方法按钮提供：

-(void) keyboardWillShow:(NSNotification*)notification{ 
    done.hidden = NO; 
} 

不要忘了与去除观察员的dealloc

[[NSNotificationCenter defaultCenter] removeObserver:self]; 

Answer 3

您可以使用UITextFieldDelegate方法来实现这一目标，例如：

-(BOOL)textFieldShouldBeginEditing:(UITextField *)textField 
{ 
    done.hidden = NO;  
    return YES; 
} 

希望这将有助于。