objective-c - 即使 UIResponder 对象放弃其第一响应者状态，键盘也不会关闭

Question

我设法自定义了 UIAlertView，将两个 UITextFields 作为其内部的 subview ，但不知何故键盘坏了。

当我试图解雇它并让第一响应者辞职时，它什么也没做，只是呆在那里。

这是我的代码，嗯，只有相关部分(这是我放在 UIAlertView 子类中的部分):

#pragma mark -
#pragma mark UIView

- (void)layoutSubviews
{
    [super layoutSubviews];

    NSArray *subviews = [self subviews];
    UIView *backgroundView = [subviews objectAtIndex:0];
    CGRect firstFrame = [[subviews objectAtIndex:2] frame];
    CGRect backgroundFrame = [backgroundView frame];
    CGFloat displacement = kTextHeight * 2 + kPadding * 3;
    CGFloat pivot = firstFrame.origin.y + firstFrame.size.height;
    CGRect nameFrame = CGRectMake(firstFrame.origin.x,
            pivot + kPadding,
            kTextWidth, kTextHeight);
    CGRect descriptionFrame = CGRectMake(firstFrame.origin.x,
            pivot + kTextHeight + kPadding * 2,
            kTextWidth, kTextHeight);

    if (_nameField == nil && _descriptionField == nil) {
        // first UITextField
        _nameField = [[UITextField alloc] initWithFrame:CGRectZero];
        [_nameField setPlaceholder:kNamePlaceholder];
        [_nameField setBorderStyle:UITextBorderStyleRoundedRect];
        [_nameField setDelegate:self];
        // second UITextField
        _descriptionField =
                [[UITextField alloc] initWithFrame:CGRectZero];
        [_descriptionField setPlaceholder:kDescriptionPlaceholder];
        [_descriptionField setBorderStyle:UITextBorderStyleRoundedRect];
        [_descriptionField setDelegate:self];
        [self addSubview:_nameField];
        [self addSubview:_descriptionField];
    }
    // set the new frames to each text field
    [_nameField setFrame:nameFrame];
    [_descriptionField setFrame:descriptionFrame];
    // increment background image-view height by "displacement"
    backgroundFrame.size.height += displacement;
    [backgroundView setFrame:backgroundFrame];
    // displace by "diplacement" every subview positioned after "pivot"
    for (UIView *view in subviews) {
        CGRect viewRect = [view frame];

        if (viewRect.origin.y > pivot)
            [view setFrame:CGRectOffset(viewRect, 0., displacement)];
    }
}

- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event
{
    return YES;
}

#pragma mark -
#pragma mark <UITextFieldDelegate>

- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
    [textField resignFirstResponder];
    return NO;
}

这是我的一大块代码:

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

static CGFloat kTextWidth = 260.;
static CGFloat kTextHeight = 25.;
static CGFloat kPadding = 10.;
static NSString *kNamePlaceHolder = @"Name";
static NSString *kDescriptionPlaceHolder = @"Description";

// interfaces

@interface AppDelegate: NSObject <UIApplicationDelegate>
{
    UIWindow *_window;
}
- (void)showAlertView;
@end

@interface AlertView: UIAlertView <UITextFieldDelegate>
{
    UITextField *_nameField;
    UITextField *_descriptionField;
}
@end

// implementations

@implementation AppDelegate

#pragma mark -
#pragma mark NSObject

- (void)dealloc
{
    [_window release];
    [super dealloc];
}

#pragma mark -
#pragma mark AppDelegate

- (void)showAlertView
{
    AlertView *alertView = [[[AlertView alloc] initWithTitle:@"Title"
            message:@"Body" delegate:nil
            cancelButtonTitle:@"Ok" otherButtonTitles:nil] autorelease];
    [alertView show];
}

#pragma mark -
#pragma mark <UIApplicationDelegate>

- (BOOL)            application:(UIApplication *)application
  didFinishLaunchingWithOptions:(NSDictionary *)options
{
    _window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    [_window setBackgroundColor:[UIColor whiteColor]];
    [_window makeKeyAndVisible];
    [NSTimer scheduledTimerWithTimeInterval:3. target:self
            selector:@selector(showAlertView) userInfo:nil repeats:NO];
    return YES;
}
@end

@implementation AlertView

#pragma mark -
#pragma mark NSObject

- (void)dealloc
{
    [_nameField setDelegate:nil];
    [_descriptionField setDelegate:nil];
    [_nameField release];
    [_descriptionField release];
    [super dealloc];
}

#pragma mark -
#pragma mark UIView

- (void)layoutSubviews
{
    [super layoutSubviews];

    NSArray *subviews = [self subviews];
    UIView *backgroundView = [subviews objectAtIndex:0];
    CGRect firstFrame = [[subviews objectAtIndex:2] frame];
    CGRect backgroundFrame = [backgroundView frame];
    CGFloat displacement = kTextHeight * 2 + kPadding * 3;
    CGFloat pivot = firstFrame.origin.y + firstFrame.size.height;
    CGRect nameFrame = CGRectMake(firstFrame.origin.x,
            pivot + kPadding,
            kTextWidth, kTextHeight);
    CGRect descriptionFrame = CGRectMake(firstFrame.origin.x,
            pivot + kTextHeight + kPadding * 2,
            kTextWidth, kTextHeight);

    if (_nameField == nil && _descriptionField == nil) {
        // first UITextField
        _nameField = [[UITextField alloc] initWithFrame:CGRectZero];
        [_nameField setPlaceholder:kNamePlaceholder];
        [_nameField setBorderStyle:UITextBorderStyleRoundedRect];
        [_nameField setDelegate:self];
        // second UITextField
        _descriptionField =
                [[UITextField alloc] initWithFrame:CGRectZero];
        [_descriptionField setPlaceholder:kDescriptionPlaceholder];
        [_descriptionField setBorderStyle:UITextBorderStyleRoundedRect];
        [_descriptionField setDelegate:self];
        [self addSubview:_nameField];
        [self addSubview:_descriptionField];
    }
    // set the new frames to each text field
    [_nameField setFrame:nameFrame];
    [_descriptionField setFrame:descriptionFrame];
    // increment background image-view height by "displacement"
    backgroundFrame.size.height += displacement;
    [backgroundView setFrame:backgroundFrame];
    // displace by "diplacement" every subview positioned after "pivot"
    for (UIView *view in subviews) {
        CGRect viewRect = [view frame];

        if (viewRect.origin.y > pivot)
            [view setFrame:CGRectOffset(viewRect, 0., displacement)];
    }
}


- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event
{
    return YES;
}

#pragma mark -
#pragma mark <UITextFieldDelegate>

- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
    [textField resignFirstResponder];
    return NO;
}
@end

int main(int argc, char **argv)
{
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    int retVal = UIApplicationMain(argc, argv, nil,
            NSStringFromClass([AppDelegate class]));
    [pool drain];
    return retVal;
}

Answer 1

我的解决方案是覆盖 UIAlertView 子类中的 becomeFirstResponder:

- (BOOL)becomeFirstResponder
{
    // For some unkown reason UIAlertView can be first responder. Disabling
    // this completely fixes this bug http://stackoverflow.com/q/6866932/434423
    // BTW, overriding "canBecomeFirstResponder" to return "NO" doesn't work,
    // this is why we override this instead of "canBecomeFirstResponder".
    return NO;
}

我会发布我所有的代码，以备不时之需。正确处理 UIAlertView 自定义。

---

CustomizableAlertView.h

@class UIAlertView;

@interface CustomizableAlertView: UIAlertView
{
    UIView *_customSubview;
}
@property (nonatomic, retain) UIView *customSubview;
@end

---

CustomizableAlertView.m

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
#import <QuartzCore/QuartzCore.h>

#import "CustomizableAlertView.h"

static CGFloat kVerticalPadding = 10.;
static CGFloat kMinHorizontalPadding = 12.;
static NSString *kTransformKeyPath = @"transform";

@interface CustomizableAlertView (Private)

- (void)centerViewOnKeyboardDismissal:(UIControl *)control;
@end

@implementation CustomizableAlertView

#pragma mark -
#pragma mark NSObject

- (void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
    [_customSubview release];
    [super dealloc];
}

#pragma mark -
#pragma mark NSObject (NSKeyValueObserving)

- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context
{
    // Make sure we are observing kTransformKeyPath from self
    if (_customSubview != nil && self == object &&
            [keyPath isEqualToString:kTransformKeyPath]) {
        // We should remove the observing object to avoid a recursion
        [self removeObserver:self forKeyPath:kTransformKeyPath];

        CGFloat displacement =
                [_customSubview frame].size.height / 2. + kVerticalPadding;

        [self setTransform:
                CGAffineTransformMakeTranslation(.0, -displacement)];
        // Resume the observation
        [self addObserver:self forKeyPath:kTransformKeyPath options:0
                context:NULL];
    }
}

#pragma mark -
#pragma mark UIResponder

- (BOOL)becomeFirstResponder
{
    // For some unkown reason UIAlertView can be first responder. Disabling
    // this completely fixes this bug http://stackoverflow.com/q/6866932/434423
    // BTW, overriding "canBecomeFirstResponder" to return "NO" doesn't work,
    // this is why we override this instead of "canBecomeFirstResponder".
    return NO;
}

#pragma mark -
#pragma mark UIView

- (void)layoutSubviews
{
    [super layoutSubviews];

    NSArray *subviews = [self subviews];
    UIView *messageView = nil;
    UIView *backgroundView = nil;

    // Perform a pattern search instead of depending on UIAlertView internal
    // structure.
    // This fetches the background view.
    for (UIView *view in subviews) 
        if ([view isKindOfClass:[UIImageView class]]) {
            backgroundView = view;
            break;
        }
    // Perform a pattern search instead of depending on UIAlertView internal
    // structure
    // This fetches the view that we'll use as an anchor.
    for (UIView *view in subviews)
        if ([view isKindOfClass:[UILabel class]] &&
                [[(UILabel *)view text] isEqualToString:[self message]]) {
            messageView = view;
            break;
        }
    if (backgroundView == nil || messageView == nil)
        // Abort if there were no matches
        return;

    CGRect bounds = [self bounds];
    CGRect messageFrame = [messageView frame];
    CGRect backgroundFrame = [backgroundView frame];
    CGRect customFrame = [_customSubview frame];
    CGFloat displacement = customFrame.size.height  + kVerticalPadding * 2.;
    CGFloat pivot = messageFrame.origin.y + messageFrame.size.height;

    // increment background image-view height by "displacement"
    backgroundFrame.size.height += displacement;
    [backgroundView setFrame:backgroundFrame];
    // displace by "diplacement" every subview positioned after "pivot"
    for (UIView *view in subviews) {
        CGRect viewRect = [view frame];

        if (viewRect.origin.y > pivot)
            [view setFrame:CGRectOffset(viewRect, .0, displacement)];
    }

    CGFloat maxWidth = bounds.size.width - kMinHorizontalPadding * 2.;

    if (customFrame.size.width > maxWidth)
        customFrame.size.width = maxWidth;
    [_customSubview setFrame:CGRectOffset(customFrame,
            (bounds.size.width - customFrame.size.width) / 2.,
            pivot + kVerticalPadding)];
    if ([_customSubview superview] == nil)
        [self addSubview:_customSubview];
}

- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event
{
    // perform hit-test for every subview
    for (UIView *view in [self subviews])
        if ([view pointInside:[self convertPoint:point toView:view]
                withEvent:event])
            return YES;
    return NO;
}

#pragma mark -
#pragma mark UIAlertView

- (void)show
{
    NSNotificationCenter *defaultCenter = [NSNotificationCenter defaultCenter];

    [defaultCenter addObserver:self
        selector:@selector(centerViewOnKeyboardDismissal:)
        name:UITextFieldTextDidEndEditingNotification object:nil];
    [defaultCenter addObserver:self
            selector:@selector(centerViewOnKeyboardDismissal:) 
            name:UITextViewTextDidEndEditingNotification object:nil];
    // Dammit! we need to observe value-changes for the property "transform" to
    // handle properly the UIAlertView relocation.
    // We need to hang this onto "show" because UIAlertView's designated
    // initializer is imposible to override due to its variadic parameter (...).
    [self addObserver:self forKeyPath:kTransformKeyPath options:0 context:NULL];
    [super show];
}

- (void)dismissWithClickedButtonIndex:(NSInteger)buttonIndex
                             animated:(BOOL)animated
{
    // Cease to observe kTransformKeyPath upon dismissal
    [self removeObserver:self forKeyPath:kTransformKeyPath];
    [super dismissWithClickedButtonIndex:buttonIndex animated:animated];
}

#pragma mark -
#pragma mark CustomizableAlertView

@synthesize customSubview = _customSubview;

- (void)centerViewOnKeyboardDismissal:(UIControl *)control
{
    CGRect bounds = [[self superview] bounds];

    [self setCenter:CGPointMake(CGRectGetMidX(bounds), CGRectGetMidY(bounds))];
}
@end