UIKeyboardWillShowNotification & UIKeyboardDidShowNotification 报错键盘高度

Question

以下代码（抱歉，篇幅较长）在 iOS 4.3（可能还有其他版本）下显示了一个奇怪的行为。在此示例中，三个UITextFields 具有三个不同大小的键盘。如果您开始编辑一个文本字段，然后触摸“返回”关闭键盘，则每次使用UIKeyboardFrameBeginUserInfoKey 在UIKeyboardWillShowNotification 和UIKeyboardDidShowNotification 中正确返回键盘大小。

见下文：

- (void) keyboardWillShowNotification:(NSNotification *)aNotification

和

- (void) keyboardDidShowNotification:(NSNotification *)aNotification

请注意，这是预期的行为。

action                 reported keyboard size  expected keyboard size  
---------------------  ----------------------  ----------------------
touch one    & return  100                     100
touch two    & return  200                     200
touch normal & return  216                     216
n            & return  keyboard size(n)        keyboard size(n)

意外行为是，如果您开始编辑文本字段，则会报告第一个键盘的大小（预期）。当您触摸第二个文本字段（不触摸返回）时，将报告（意外）第一个键盘的大小，而不是第二个键盘的大小。当您触摸第三个文本字段（不触摸返回）时，将报告第二个键盘大小的大小（意外）而不是第三个的大小。第二次到第 n 次，它似乎报告的是前一个键盘的大小，而不是将要显示的那个。

action        reported keyboard size  expected keyboard size  
------------  ----------------------  ----------------------
touch one     100                     100
touch two     100                     200
touch normal  200                     216
touch one     216                     100
n             keyboard size(n-1)      keyboard size(n)

在我发送错误报告之前，我只是想确保我没有看过任何东西。

仅供参考，当我尝试做正确的事情时（使用UIKeyboardWillShowNotification 或UIKeyboardDidShowNotification 和UIKeyboardFrameBeginUserInfoKey 来获取键盘的大小）时，我在移动视图时遇到了这个问题，以便文本字段被键盘可见。参考：

How to make a UITextField move up when keyboard is present?

iOS Library: Text, Web, and Editing Programming Guide for iOS --> Managing the Keyboard

iOS Library: Scroll View Programming Guide for iOS --> Creating and Configuring Scroll Views

BugVC.h

#import <UIKit/UIKit.h>

@interface BugVC : UIViewController <UITextFieldDelegate> {
    UITextField *oneTF;
    UITextField *twoTF;
    UITextField *normalTF;
    UILabel *keyboardWillShowNotificationL;
    UILabel *keyboardDidShowNotificationL;
}

- (void) oneReturnTouchDown:(id)sender;
- (void) twoReturnTouchDown:(id)sneder;
- (void) keyboardWillShowNotification:(NSNotification *)aNotification;
- (void) keyboardDidShowNotification:(NSNotification *)aNotification;

@end

BugVC.m

#import "BugVC.h"

@implementation BugVC

- (id) init
{
    if ( !(self = [super init]) )
    {
        return self;
    }

    // = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
    // One text field with 100 height keyboard
    oneTF = [[UITextField alloc] initWithFrame:CGRectMake(10, 10, 300, 30)];
    oneTF.borderStyle = UITextBorderStyleRoundedRect;
    oneTF.text = @"100";
    oneTF.delegate = self;
    // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    // Custom input view for the above text field
    UIView *oneInputView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 100)];
    oneInputView.backgroundColor = [UIColor redColor];
    UIButton *oneReturnB = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    oneReturnB.frame = CGRectMake(10, 10, 300, 30);
    [oneReturnB setTitle:@"return" forState:UIControlStateNormal];
    [oneReturnB addTarget:self
                   action:@selector(oneReturnTouchDown:)
         forControlEvents:UIControlEventTouchDown];
    [oneInputView addSubview:oneReturnB];
    oneTF.inputView = oneInputView;
    [oneInputView release];
    [self.view addSubview:oneTF];

    // = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
    // Two text field with 200 height keyboard
    twoTF = [[UITextField alloc] initWithFrame:CGRectMake(10, 50, 300, 30)];
    twoTF.borderStyle = UITextBorderStyleRoundedRect;
    twoTF.text = @"200";
    twoTF.delegate = self;
    // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    // Custom input view for the above text field
    UIView *twoInputView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 200)];
    twoInputView.backgroundColor = [UIColor blueColor];
    UIButton *twoReturnB = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    twoReturnB.frame = CGRectMake(10, 10, 300, 30);
    [twoReturnB setTitle:@"return" forState:UIControlStateNormal];
    [twoReturnB addTarget:self
                   action:@selector(twoReturnTouchDown:)
         forControlEvents:UIControlEventTouchDown];
    [twoInputView addSubview:twoReturnB];
    twoTF.inputView = twoInputView;
    [twoInputView release];
    [self.view addSubview:twoTF];

    // = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
    // normal text field with normal keyboard (216 height keyboard)
    normalTF = [[UITextField alloc] initWithFrame:CGRectMake(10, 90, 300, 30)];
    normalTF.borderStyle = UITextBorderStyleRoundedRect;
    normalTF.text = @"normal";
    normalTF.delegate = self;
    [self.view addSubview:normalTF];

    // = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
    // Label that displays the keyboard height from keyboardWillShowNotification
    keyboardWillShowNotificationL = [[UILabel alloc] initWithFrame:CGRectMake(10, 130, 300, 30)];
    keyboardWillShowNotificationL.font = [UIFont systemFontOfSize:14];
    keyboardWillShowNotificationL.text = @"keyboardWillShowNotification kbHeight:";
    [self.view addSubview:keyboardWillShowNotificationL];

    // = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
    // Label that displays the keyboard height from keyboardDidShowNotification
    keyboardDidShowNotificationL = [[UILabel alloc] initWithFrame:CGRectMake(10, 170, 300, 30)];
    keyboardDidShowNotificationL.font = [UIFont systemFontOfSize:14];
    keyboardDidShowNotificationL.text = @"keyboardDidShowNotification kbHeight:";
    [self.view addSubview:keyboardDidShowNotificationL];

    // = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
    // Register for keyboard notifications.
    [[NSNotificationCenter defaultCenter]
     addObserver:self
        selector:@selector(keyboardWillShowNotification:)
            name:UIKeyboardWillShowNotification object:nil];

    [[NSNotificationCenter defaultCenter]
     addObserver:self
        selector:@selector(keyboardDidShowNotification:)
            name:UIKeyboardDidShowNotification object:nil];

    return self;
}

- (void) dealloc
{
    // = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
    // Deregister for keyboard notifications
    [[NSNotificationCenter defaultCenter]
     removeObserver:self
               name:UIKeyboardWillShowNotification object:nil];

    [[NSNotificationCenter defaultCenter]
     removeObserver:self
               name:UIKeyboardDidShowNotification object:nil];

    [oneTF release];
    [twoTF release];
    [normalTF release];
    [keyboardWillShowNotificationL release];
    [keyboardDidShowNotificationL release];

    [super dealloc];
}

- (BOOL) textFieldShouldReturn:(UITextField *)textField
{
    [textField resignFirstResponder];

    return YES;
}

- (void) oneReturnTouchDown:(id)sender
{
    [oneTF.delegate textFieldShouldReturn:oneTF];
}

- (void) twoReturnTouchDown:(id)sneder
{
    [twoTF.delegate textFieldShouldReturn:twoTF];
}

- (void) keyboardWillShowNotification:(NSNotification *)aNotification
{
    NSDictionary *info = [aNotification userInfo];
    CGFloat kbHeight =
        [[info objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size.height;

    NSString *string = [[NSString alloc] initWithFormat:@"keyboardWillShowNotification kbHeight: %.2f", kbHeight];
    NSLog(@"%@", string);
    keyboardWillShowNotificationL.text = string;
    [string release];
}

- (void) keyboardDidShowNotification:(NSNotification *)aNotification
{
    NSDictionary *info = [aNotification userInfo];
    CGFloat kbHeight =
        [[info objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size.height;

    NSString *string = [[NSString alloc] initWithFormat:@"keyboardDidShowNotification kbHeight: %.2f", kbHeight];
    NSLog(@"%@", string);
    keyboardDidShowNotificationL.text = string;
    [string release];
}

@end

Answer 1

如this question 中所述，start frame（由UIKeyboardFrameBeginUserInfoKey 键入）是键盘位于动画开头 的位置。 UIKeyboardFrameEndUserInfoKey 应该给你end frame。大概帧之间的大小也不同。

关键参考：http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UIWindow_Class/UIWindowClassReference/UIWindowClassReference.html#//apple_ref/doc/constant_group/Keyboard_Notification_User_Info_Keys