Question

我的应用程序的一个目标是管理多个自定义输入视图（来自笔尖）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，我只管理单个笔尖+系统键盘）。

换掉键盘时，我想保留使用系统键盘看到的滑入/滑出效果。为了获得自定义键盘和系统键盘的滑动动画，我从文本字段中取出resignFirstResponder并等到键盘被隐藏。然后我执行一个becomeFirstResponder来引入新的键盘。我使用UIKeyboardDidHideNotification作为触发器来触发becomeFirstResponder并加载新键盘。

我看到的问题是UIKeyboardDidHideNotification在执行resignFirstResponder（正如预期）时再次触发两次......再次执行becomeFirstResponder时触发。我怀疑我可以放入一些状态来检测第二个通知，但我想了解一下，为什么第一个反应器会导致它首先触发？

#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

我的猜测是你在前一个字段完全辞去第一个响应者之前正在调用becomeFirstResponder。只是为了看看它是否有帮助，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];
    };
}

Answer 2

@interface MainViewController : UIViewController

@property (nonatomic, retain) IBOutlet UITextField *textField;
@property (nonatomic, retain) IBOutlet UISwitch *keyboardSwitch;
@property (nonatomic, retain) IBOutlet UISwitch *textFieldSwitch;


- (IBAction)toggleKeyboardVisibility;

@end


#import "MainViewController.h"

@implementation MainViewController
@synthesize textField, keyboardSwitch, textFieldSwitch;

- (void)viewDidLoad
{
    [super viewDidLoad];
}

/**
 * Show keyboard as soon as view appears
 *
 */
- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [self.textField becomeFirstResponder];
}

/**
 * Modify the hidden property of our text field
 *
 */
- (IBAction)toggleTextFieldVisibility
{
    if (self.textFieldSwitch.on)
        self.textField.hidden = NO;
    else
        self.textField.hidden = YES;
}

/**
 * Change the first responder status of the keyboard
 *
 */
- (IBAction)toggleKeyboardVisibility
{
    if (self.keyboardSwitch.on)
        [self.textField becomeFirstResponder];
    else
        [self.textField resignFirstResponder];
}

@end

becomeFirstResponder正在触发UIKeyboardDidHideNotification

2 个答案: