在keyboard上面增加toolbar提供便捷操作－保持keyboard

Building an iPhone keyboard toolbar

有各种理由让你想做到把UIToolbar 悬浮于 keyboard ：比如你希望键盘的return是用作换行，而需要另外一个iaaction来触发dismiss keyboard；当然有些时候，这个键未必要出现在keyboard上方，很可能程序就为你提供了，例如在邮件编辑程序中按下上角的send按钮 ，keyboard就消失了

还有一个有用的地方是 聊天的程序，你希望keyboard一直在，方便快速输入：这个在iPhone Messages app就如此的 

mobile Safari app 使用带有toolbar的keyboard 用于各种功能切换 fields 以及 autofilling, 当然也有“done”来隐藏 keyboard:

虽然没有内置的选项用于添加键盘上方的 UIToolbar，但可以很容易地实现。

个人喜欢做 的方式是，把uitoolbar工具栏放在屏幕外，然后键盘上方的正确地进行动画处理。我觉得这看起来更加无缝的用户体验。所以，我将 UIToolbar 添加到视图的控制器，并放置在屏幕的底部以下。在一个正常的竖立面向的 iPhone 应用程序具有状态栏，所以Y 值将在 460。我也喜欢使工具栏部分透明 （约 0.60 的 alpha），以便用户可以看到"下方"工具栏。

视图控制器出现时，我们要响应键盘事件通知使我们可以显示工具栏出现和消失 ：

／／比较重要的代码就是：

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillHide:) name:UIKeyboardWillHideNotification object:nil];

／／

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
 
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillHide:) name:UIKeyboardWillHideNotification object:nil];
}
 
- (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];
 
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillShowNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillHideNotification object:nil];
}

接下来就是动画出现和消失：

- (void)keyboardWillShow:(NSNotification *)notification {
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:0.3];
 
    CGRect frame = self.keyboardToolbar.frame;
    frame.origin.y = self.view.frame.size.height - 260.0;
    self.keyboardToolbar.frame = frame;
 
    [UIView commitAnimations];

我发现 0.3 秒相当匹配了键盘出现 所需的时间量。IPhone 上的键盘的高度是 260 点，所以我们从视图高度减去，并于该位置工具栏添加动画效果。

- (void)keyboardWillHide:(NSNotification *)notification {
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:0.3];
 
    CGRect frame = self.keyboardToolbar.frame;
    frame.origin.y = self.view.frame.size.height; ／／self。view。frame。。。。。
    self.keyboardToolbar.frame = frame;
 
    [UIView commitAnimations];
}

这是另外一个用法：

 

重点还是订阅 UIWindow notifications UIKeyboardWillShowNotification andUIKeyboardWillHideNotification

这些通知能告知键盘的外观、 大小、 位置和动画的详细信息。使用此信息，我们可以到正确的位置与键盘外观，设计动画同步 我们的工具栏。

    if(nil == keyboardToolbar) {
      keyboardToolbar = [[UIToolbar alloc] initWithFrame:CGRectMake(0,0,self.view.bounds.size.width,44)];
      keyboardToolbar.barStyle = UIBarStyleBlackTranslucent;
      keyboardToolbar.tintColor = [UIColor darkGrayColor];
／／／／／／／／
      UIBarButtonItem *barButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(dismissKeyboard:)];

／／适当的空白区域
      UIBarButtonItem *flex = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:nil action:nil];

      UISegmentedControl *control = [[UISegmentedControl alloc] initWithItems:[NSArray arrayWithObjects:
                                           NSLocalizedString(@"Previous",@"Previous form field"),
                                           NSLocalizedString(@"Next",@"Next form field"),                                         
                                           nil]];
      control.segmentedControlStyle = UISegmentedControlStyleBar;
      control.tintColor = [UIColor darkGrayColor];
      control.momentary = YES;
      [control addTarget:self action:@selector(nextPrevious:) forControlEvents:UIControlEventValueChanged];     

      UIBarButtonItem *controlItem = [[UIBarButtonItem alloc] initWithCustomView:control];

      self.nextPreviousControl = control;


      NSArray *items = [[NSArray alloc] initWithObjects:controlItem, flex, barButtonItem, nil];
      [keyboardToolbar setItems:items];
      [control release];
      [barButtonItem release];
      [flex release];
      [items release];      

      keyboardToolbar.frame = CGRectMake(beginCentre.x - (keyboardBounds.size.width/2), 
                         beginCentre.y - (keyboardBounds.size.height/2) - keyboardToolbar.frame.size.height, 
                         keyboardToolbar.frame.size.width, 
                         keyboardToolbar.frame.size.height);        

      [self.view addSubview:keyboardToolbar];   
    }   
  }   

  [UIView beginAnimations:@"RS_showKeyboardAnimation" context:nil]; 
  [UIView setAnimationCurve:animationCurve];
  [UIView setAnimationDuration:animationDuration];

  keyboardToolbar.alpha = 1.0;  
  keyboardToolbar.frame = CGRectMake(endCentre.x - (keyboardBounds.size.width/2), 
                     endCentre.y - (keyboardBounds.size.height/2) - keyboardToolbar.frame.size.height - self.view.frame.origin.y, 
                     keyboardToolbar.frame.size.width, 
                     keyboardToolbar.frame.size.height);

  [UIView commitAnimations];    

接下来就是根据当前control，寻找下一个，然后[(UITextField *) becomeFirstResponder:]

//Asks the delegate if the text field should process the pressing of the return button.

- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
	if (textField == textField1) {
		[textField2 becomeFirstResponder];
	} else if (textField == textField2) {
		[textField3 becomeFirstResponder];
	} else if (textField == textField3) {
		[textField1 becomeFirstResponder];
	}		
	return NO;
}

以上是为了解决：

当文本框之间切换，编程方式或通过用户敲击，notification仍 接收到键盘隐藏/显示通知。这里我们保持纪录，当从一个输入文本框移动到另一个的时候我们要避免无谓的toolbar的动画。

程序下载： TFTest

last hint：sample／UIToolbar-Keyboard；sample／Toolbar For keboardTest