ios - becomeFirstResponder 正在触发 UIKeyboardDidHideNotification

Question

我的应用程序的一个目标是管理多个自定义输入 View (来自 nibs)以及常规系统键盘。一个或另一个将永远存在。 (在示例代码中，我只管理一个 Nib + 系统键盘)。

更换键盘时，我想保留您在系统键盘上看到的滑入/滑出效果。为了获得自定义键盘和系统键盘的滑动动画，我从文本字段中 resignFirstResponder 并等到键盘被隐藏。然后我执行 becomeFirstResponder 以引入新键盘。我使用 UIKeyboardDidHideNotification 作为触发 becomeFirstResponder 并加载新键盘的触发器。

我看到的问题是 UIKeyboardDidHideNotification 触发了两次……一次是在执行 resignFirstResponder 时(如预期的那样)，另一次是在执行 becomeFirstResponder 时。我怀疑我可以设置某种状态来检测第二个通知，但我想了解，为什么 becomeFirstResponder 首先导致它触发？

#import "DemoViewController.h"

@interface DemoViewController ()
@property (strong, nonatomic) IBOutlet UITextField *dummyTextField;
@end

@implementation DemoViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    [[UITextField appearance] setKeyboardAppearance:UIKeyboardAppearanceDark];

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardDidHide:) name:UIKeyboardDidHideNotification object:nil];

    [self showNormalKeyboard];
    [_dummyTextField becomeFirstResponder];
}

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

-(void)keyboardDidHide:(NSNotification*) notification {
    NSLog(@"Keyboard hidden: %@", notification);
    // Executing this next line causes the notification to fire again
    [_dummyTextField becomeFirstResponder];
}

-(void)showAlternateKeyboard{
    _dummyTextField.inputView = [[[NSBundle mainBundle] loadNibNamed:@"AlternateKeyboardView" owner:self options:nil] lastObject];
    [_dummyTextField resignFirstResponder];
}

-(void)showNormalKeyboard{
    _dummyTextField.inputView = nil;
    [_dummyTextField resignFirstResponder];
}

// This is a button on the DemoViewController screen
// that is always present.
- (IBAction)mainButtonPressed:(UIButton *)sender {
    NSLog(@"Main Screen Button Pressed!");
}

// This is a button from the Custom Input View xib
// but hardwired directly into here
- (IBAction)alternateKeyboardButtonPressed:(UIButton *)sender {
    NSLog(@"Alternate Keyboard Button Pressed!");
}

// This is a UISwitch on the DemoViewController storyboard
// that selects between the custom keyboard and the regular
// system keyboard
- (IBAction)keyboardSelectChanged:(UISwitch *)sender {
    if (sender.on){
        [self showAlternateKeyboard];
    } else {
        [self showNormalKeyboard];
    }
}

@end

Answer 1

我的猜测是您在前一个字段完全完成辞去第一响应者之前调用了 becomeFirstResponder。只是为了看看它是否有帮助，请尝试添加一些延迟性能:

-(void)keyboardDidHide:(NSNotification*) notification {
    NSLog(@"Keyboard hidden: %@", notification);
    dispatch_async(dispatch_get_main_queue(), ^{
        [_dummyTextField becomeFirstResponder];
    };
}