Multiple Buttons on a Navigation Bar

本文详细介绍了如何在iOS导航栏中使用标准图标和按钮,通过使用`UIBarButtonItem`类,展示如何在导航栏右侧放置多个按钮,包括创建自定义视图、使用`initWithCustomView:`初始化方法以及如何利用`UIToolbar`容器来实现这一目标。

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Previously, I wrote about how to use standard icons in your navigation bar. This takes advantage of the nav bar's ability to put a button on the right side. But what if you want to put multiple buttons there? If your title is short enough, you can easily fit 2 or 3 buttons in that space. The nav bar allows you to stick content on the right hand side via the rightBarButtonItem property. On the surface, you might think you can add but one button to this property. But it's not so. There is an initializer for UIBarButtonItem that takes a view:
initWithCustomView:(UIView *)customView
With this, you can create multiple UIButton objects, add them to a UIView, and then create a UIBarButtonItem passing in this parent UIView. The following pseudo-code shows what I mean:
// create the container
UIView* container = [[UIView alloc] init];

// create a button and add it to the container
UIButton* button = [[UIButton alloc] init...];
[container addSubview:button];
[button release];

// add another button
button = [[UIButton alloc] init...];
[container addSubview:button];
[button release];

// now create a Bar button item
UIBarButtonItem* item = [[UIBarButtonItem alloc] initWithCustomView:container];

// set the nav bar's right button item
self.navigationItem.rightBarButtonItem = item;
[item release];

But, what if you want multiple *standard* buttons. Access to the standard buttons/icons is through the UIBarButtonItem class, not UIButton. You can't add UIBarButtonItem objects to a UIView. While there is support to create a UIBarButtonItem object from a UIView-derived object, there does not seem to be a way to do the opposite; there is no way to create a UIView object from a UIBarButtonItem. The only way I found how to deal with multiple UIBarButtonItem objects is to stick them in a toolbar. A UIToolBar is designed to hold multiple UIBarButtonItem objects. Think of a toolbar as your container, instead of the UIView object. And since a UIToolBar is UIView based, it can be added to the right side of a nav bar using the above trick. The following code shows how you can add two standard buttons to the right side:

// create a toolbar to have two buttons in the right
UIToolbar* tools = [[UIToolbar alloc] initWithFrame:CGRectMake(0, 0, 133, 44.01)];

// create the array to hold the buttons, which then gets added to the toolbar
NSMutableArray* buttons = [[NSMutableArray alloc] initWithCapacity:3];

// create a standard "add" button
UIBarButtonItem* bi = [[UIBarButtonItem alloc]
initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:NULL];
bi.style = UIBarButtonItemStyleBordered;
[buttons addObject:bi];
[bi release];

// create a spacer
bi = [[UIBarButtonItem alloc]
initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace target:nil action:nil];
[buttons addObject:bi];
[bi release];

// create a standard "refresh" button
bi = [[UIBarButtonItem alloc]
initWithBarButtonSystemItem:UIBarButtonSystemItemRefresh target:self action:@selector(refresh:)];
bi.style = UIBarButtonItemStyleBordered;
[buttons addObject:bi];
[bi release];

// stick the buttons in the toolbar
[tools setItems:buttons animated:NO];

[buttons release];

// and put the toolbar in the nav bar
self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:tools];
[tools release];

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