Dynamically Change icon (like iCal icon) (iPhone OS 3.1)

Question

I'd like to be able to change the icon in a tab bar to reflect the current date...rather, I'd like to have a background image, with the date as a number on top of that—basically what the iCal icon on OS X does. Is there a way to create the number on that icon, or is this not possible?

Answer 1

musicwind95 wrote:
when I create the new tab, how do I know which one it's replacing?
I'm not sure you've seen the view hierarchy yet. Are you sure you set the "View Mode" switch to the Center position in the MainWindow.xib window (see the instructions for displaying the small-icon view hierarchy in my May 22 post).
If you're looking at the hierarchy (with all the nodes of the tree expanded), note each view controller owns a UITabBarItem object. This point is often misunderstood, since we see the tab bar items on the tab bar. But each tab bar item is a child of its controller, and the address of the tab bar item is stored in the 'tabBarItem' property of that controller. So when we replace the tab bar item in this line of the example:
- (void)awakeFromNib {
self.tabBarItem = tabItem;
We're setting the 'tabBarItem' property of 'self' to the address of a new tab bar item. Therefore we're changing the tab bar item for the controller which received the awakeFromNib message. If that controller is connected as the first child of the tab bar controller, we'll be changing tab bar item #1. If that controller is the second child, we'll be changing tab bar item #2, etc.
Of course if more than one view controller is an instance of the same custom class, e.g. FirstViewController is the class for both the first and third controllers, the tab bar items for both #1 and #3 will be reset when the respective controllers receive the awakeFormNib message. In that case we'd need a way to know whether 'self' was the address of the first or third controller. That could be done in several ways. For example, we could tag each controller's original tab bar item in IB. Then we might do something like the following to ensure the item replacement code only runs for the controller object which owns tab bar item #1:
- (void)awakeFromNib {
if (self.tabBarItem.tag == 1) {
// replace tab bar item
Once again, the above if-condition would only be needed if the first controller and one or more other controllers were of the same class.
Would this code be better off in the app delegate or the view controller?
The code belongs in a method of the view controller which wants its tab bar item to be replaced.
I've created the tab bar in IB (or rather, I started with a Tab Bar template), so I don't have a view controller for the tab bar itself.
Referring again to the small-icon view hierarchy in the MainWindow.xib window, note the tab bar is connected directly to the tab bar controller. The tab bar controller is the controller for the tab bar.
... In at least two of the tabs that I'm working in, I'm displaying a table view that leads to a navigational hierarchy. How would I set that up?
This time it's essential to be able to see the small-icon view hierarchy in the MainWindow.xib window. So please follow the instructions in my May 22 post in case you haven't done so already. Next, follow these steps (which assume tabs 3 and 4 will each bring up a table view under a nav bar which is controlled by a nav bar controller):
Add a new UIViewController subclass in Xcode for the tab 3 controller. Check both Options so the new class will be a subclass of UITableViewController, and a matching XIB file will be created;
Name the subclass ThirdViewController (name it whatever you want, but the class will be referred to as ThirdViewController here);
Open MainWindow.xib, make sure the XIB window is visible (Window->Document) and its View Mode switch is in the Center position, then expand the small icon tree so you can see all the view controllers under the Tab Bar Controller;
Drag a UINavigationController object into the XIB window, and drop it onto the Tab Bar Controller icon. If you only had two controllers to start with, the Nav Controller object should now be in the last (3rd) position. If you already had a third controller, drag the Nav Controller icon to place it under the second controller. The Nav Controller icon should now be in the third position;
Expand the Nav Controller subtree, and select the Root View Controller icon;
Open the Identity Inspector and set the Class of the Root View Controller to ThirdViewController;
Open the Attributes Inspector and set the Nib Name to ThirdViewController;
If you checked "With XIB for user interface" when making the ThirdViewController class in the first step, ThirdViewController.xib should already be setup correctly; i.e. File's Owner will be set the ThirdViewController class, the 'view' outlet of File's Owner will be connected to a Table View object, and the Table View's delegate and dataSource outlets will be connected to File's Owner;
Open ThirdViewController.xib, select the Table View and locate the Simulated User Interface Elements group;
Set Top Bar to Navigation Bar. This optional setting will paint a dummy nav bar in the Table View editor window and cause the size of the Table View to be adjusted to fit. The dummy nav bar is just a placeholder for the real one which will be created at runtime. You can't place controls on the dummy bar; it's just to help you see how the screen will look;
Repeat the above steps to add a nav controller at position 4, making a FourthViewController class for the root controller;
If you now have too many tab positions, you can delete each extra controller by selecting its icon and selecting Edit->Delete.
That should complete the project skeleton, and you should now be able to Build and Go. You won't see the table views though, until you set up the data source methods in the respective controller implementations.
- Ray