问题
I've been developing an iPhone app that uses a UIToolbar (in the context of a UINavigationController) to display a small status icon at the bottom of the screen. The toolbar will eventually also have action icons associated with it (think Mail application).
I'm running into an issue where it appears that each UIViewController pushed onto the navigation controller's stack is expected to have its own set of items for the toolbar to display, and as a result, the "status" item fades out and back in for each view transition.
Is there a way to have a single persistent item in the toolbar? I also tried adding the item in the navigation controller's initializer (I subclassed UINavigationController for this approach), but it's still no go.
回答1:
Instead of using the navigation controller's toolbar, add one directly to the window and resize the navigation controller's view's frame to avoid it. That single global toolbar will then always be visible.
If you're using the Navigation-based Application template, and are using Interface Builder, the following steps should do it:
- Open up your app delegate's .h file.
- Add an
IBOutlet UIToolbar * toolbar;to the app delegate's instance variables. - Switch to the .m file.
- Find the line that reads
[window addSubview:[navigationController view]];and add after it:CGRect frame = navigationController.view.frame;frame.size.height -= toolbar.frame.size.height;navigationController.view.frame = frame; - Add code to release
toolbarin the-deallocmethod. - Open MainWindow.xib.
- Open the window.
- Drag a toolbar onto the bottom of the window.
- Connect the toolbar to the app delegate's toolbar outlet
- Now set up the toolbar—add whatever items you need to it, then create whatever outlets and actions you need in the app delegate and connect them.
Since the toolbar is part of the window, not part of the navigation controller, the navigation controller shouldn't touch it.
回答2:
As you push new views onto your navigation controller the views in the toolbar will be replaced with the views from the toolbar of the view on the top of the stack.
Even if you have a static view (a view that does not change when you push a new controller), the view will still appear to be new because of the animation apple includes when you push a new view controller onto the stack.
回答3:
I found this works for me:
CGFloat height = [self.toolbar frame].size.height;
CGRect rootBounds = self.window.rootViewController.view.bounds;
CGRect frame = CGRectMake(0, CGRectGetHeight(rootBounds) - height, CGRectGetWidth(rootBounds), height);
[self.toolbar setFrame:frame];
[self.navigationController.view addSubview:self.toolbar];
来源：https://stackoverflow.com/questions/1072080/persistent-uibarbuttonitem-in-uitoolbar