如何以编程方式检查iOS应用程序中是否存在键盘？

Question

我需要在我的iOS应用中检查键盘可见性的条件。伪代码：if(keyboardIsPresentOnWindow) {    //Do action 1}else if (keyboardIsNotPresentOnWindow) {    //Do action 2}如何检查这种情况？

Answer 1

…或采取简单的方法：

输入textField时，它成为第一响应者，并出现键盘。您可以使用来检查键盘的状态[myTextField isFirstResponder]。如果返回YES，则键盘处于活动状态。

Answer 2

drawonward的代码非常接近，但与UIKit的命名空间冲突，因此可以更易于使用。

@interface KeyboardStateListener : NSObject {

    BOOL _isVisible;

}

+ (KeyboardStateListener *)sharedInstance;

@property (nonatomic, readonly, getter=isVisible) BOOL visible;

@end

static KeyboardStateListener *sharedInstance;

@implementation KeyboardStateListener

+ (KeyboardStateListener *)sharedInstance

{

    return sharedInstance;

}

+ (void)load

{

    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

    sharedInstance = [[self alloc] init];

    [pool release];

}

- (BOOL)isVisible

{

    return _isVisible;

}

- (void)didShow

{

    _isVisible = YES;

}

- (void)didHide

{

    _isVisible = NO;

}

- (id)init

{

    if ((self = [super init])) {

        NSNotificationCenter *center = [NSNotificationCenter defaultCenter];

        [center addObserver:self selector:@selector(didShow) name:UIKeyboardDidShowNotification object:nil];

        [center addObserver:self selector:@selector(didHide) name:UIKeyboardWillHideNotification object:nil];

    }

    return self;

}

@end

Answer 3

UIKeyboardListener当您知道键盘不可见时，请创建一个，例如通过[UIKeyboardListener shared]从调用applicationDidFinishLaunching。

@implementation UIKeyboardListener

+ (UIKeyboardListener) shared {

    static UIKeyboardListener sListener;    

    if ( nil == sListener ) sListener = [[UIKeyboardListener alloc] init];

    return sListener;

}

-(id) init {

    self = [super init];

    if ( self ) {

        NSNotificationCenter        *center = [NSNotificationCenter defaultCenter];

        [center addObserver:self selector:@selector(noticeShowKeyboard:) name:UIKeyboardDidShowNotification object:nil];

        [center addObserver:self selector:@selector(noticeHideKeyboard:) name:UIKeyboardWillHideNotification object:nil];

    }

    return self;

}

-(void) noticeShowKeyboard:(NSNotification *)inNotification {

    _visible = true;

}

-(void) noticeHideKeyboard:(NSNotification *)inNotification {

    _visible = false;

}

-(BOOL) isVisible {

    return _visible;

}

@end