UITextFile获取焦点但不显示软键盘

UITextfield获取焦点时，进入textFieldShouldBeginEditing方法，在这个方法中注册通知：

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

//隐藏系统键盘

- (void)keyboardWillShow:(NSNotification *)Notification{
    UIWindow* tempWindow = [[[UIApplication sharedApplication] windows] objectAtIndex:1];
    [tempWindow setAlpha:0];
}