May 4, 2009

Using Standard Toolbar and Navbar Buttons

In an article several months back, I discussed how to use standard Tab bar buttons. These are icons provided by Apple for you to use in the tab bar. But tab bars are not the only container that offers system-provided icons. There are standard icons available for toolbars and navigation bars. Recently I wanted to make use of a system icon, but it took me some time to find what icons were standard and how to use them. Even though it is fairly trivial, I would like to share this information, if nothing else but to save people a few minutes of needless searching. If you feel weird about using system-provided icons, don't. Apple is very keen on developers making use of the standard icons and encourages it in the HIG. However, Apple is also adamant about the consistent use of these icons. If your application uses a standard icon in a way unintended for that icon, then it is likely your app will get rejected from the app store. For example, if you are using the standard Contacts icon to bring up a list of contact lens providers, ding! Here is the section in the HIG that lists the standard icons and their intended uses. This gives you an idea to what is available, but doesn't help you coding one of them up. You have to know how to reference each of these in your code. For this, you have to look at the UIBarButtonItem class reference. If you go to the Constants section, you will see the UIBarButtonSystemItem enumerations which define the values for all the system icons.

For nav bars

To put a system icon on the navigation bar, you have several choices for the location. At the most basic level, you can put the icon on the left or the right. If you require more refinement, it's quite easy to do with subviews, but that technique is well-documented and outside the scope of this article. Here is the simple code for putting the standard refresh icon in the left position:
self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc]
                                      initWithBarButtonSystemItem:UIBarButtonSystemItemRefresh
                                      target:self
                                      action:@selector(refresh:)];

The first parameter is the enum from the UIBarButtonItem reference. The target/action parameters specify the method to call when the button is hit.

For toolbars

Adding the standard icons to a toolbar is a little more involved, but still straight-forward. Toolbars also take UIBarButtonItem objects, but instead of assigning them to specific locations, you must add them to an NSArray object first (in the order you want them) and then add the array to the toolbar object.

// create the toolbar object
UIToolBar* toolbar = [[UIToolBar alloc] init];

// create an array to hold the buttons
NSMutableArray* buttons = [[NSMutableArray alloc] init];

// create a standard button
UIBarButtonItem* button = [[UIBarButtonItem alloc]
initWithBarButtonSystemItem:UIBarButtonSystemItemRefresh
target:self
action:@selector(refresh:)];

// stick it in the array
[buttons addObject:button];

// add more buttons
//...

// add the array to the toolbar
toolbar.items = buttons;

// done with the buttons array
[buttons release];

2 comments:

  1. Raly good and usefull overview. Thanks for you time

    ReplyDelete