iOS开发之-iPad-Specific Controllers

Popovers

1. The content of a popover is derived from a view controller object that you provide. Popovers are capable of presenting most types of view controllers

2. Steps to create a popover:

    (1)Create an instance of the UIPopoverController class and initialize it with your view controller object.
    (2)Specify the size of the popover, which you can do in one of two ways:
        Assign a value to the contentSizeForViewInPopover property of the view controller you want to display in the                 popover.
        Assign a value to the popoverContentSize property of the popover controller itself.

    (3)present the popover;

3. Popovers are commonly associated with toolbar buttons, so the presentPopoverFromBarButtonItem:permittedArrowDirections:animated: method is a convenient way to present popovers from your application’s toolbar. You can also associate a popover with a particular part of one of your views using the presentPopoverFromRect:inView:permittedArrowDirections:animated: method.

4. Changes to the content view controller or its size while the popover is visible are automatically animated. You can also change the size (with or without animations) using the setPopoverContentSize:animated: method.

- (IBAction)toolbarItemTapped:(id)sender
{
   MyCustomViewController* content = [[MyCustomViewController alloc] init];
   UIPopoverController* aPopover = [[UIPopoverController alloc]
        initWithContentViewController:content];
   aPopover.delegate = self;
   [content release];
 
   // Store the popover in a custom property for later use.
   self.popoverController = aPopover;
   [aPopover release];
 
   [self.popoverController presentPopoverFromBarButtonItem:sender
        permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];
}

5. You use dismissPopoverAnimated: to dismiss a popover.

6. Popover Controller Delegate

By the time the popoverControllerDidDismissPopover: method of your delegate is called, the popover itself has been removed from the screen. At this point, it is safe to release the popover controller if you do not plan to use it again. You can also use this message to refresh your user interface or update your application’s state.

7. Popover controllers can be reused, so cache popover controllers rather than creating new ones from scratch. 

8. When presenting a popover, specify the UIPopoverArrowDirectionAny constant for the permitted arrow direction whenever possible. 

Split View Controller

1. The UISplitViewController class is a container view controller that manages two panes of information. The first pane has a fixed width of 320 points and a height that matches the visible window height. The second pane fills the remaining space. In a landscape orientation, the split view controller presents the two panes side-by-side with a small divider separating them. In a portrait orientation, the split view controller shows only the second, larger pane and provides a toolbar button for displaying the first pane using a popover

2. A split view controller must always be the root of any interface you create. In other words, you must always install the view from aUISplitViewController object as the root view of your application’s window. 

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
   MyFirstViewController* firstVC = [[[MyFirstViewController alloc]
                     initWithNibName:@"FirstNib" bundle:nil] autorelease];
   MySecondViewController* secondVC = [[[MySecondViewController alloc]
                     initWithNibName:@"SecondNib" bundle:nil] autorelease];
 
   UISplitViewController* splitVC = [[UISplitViewController alloc] init];
   splitVC.viewControllers = [NSArray arrayWithObjects:firstVC, secondVC, nil];
 
   [window addSubview:splitVC.view];
   [window makeKeyAndVisible];
 
   return YES;
}

// Called when rotating to a portrait orientation.
- (void)splitViewController: (UISplitViewController*)svc willHideViewController:(UIViewController *)aViewController withBarButtonItem:(UIBarButtonItem*)barButtonItem forPopoverController: (UIPopoverController*)pc 
{
    barButtonItem.title = @"Root List";
    NSMutableArray *items = [[toolbar items] mutableCopy];
    [items insertObject:barButtonItem atIndex:0];
    [toolbar setItems:items animated:YES];
    [items release];
    self.popoverController = pc;
}
 
// Called when the view is shown again in the split view, invalidating the button and popover controller.
- (void)splitViewController: (UISplitViewController*)svc willShowViewController:(UIViewController *)aViewController invalidatingBarButtonItem:(UIBarButtonItem *)barButtonItem {
 
    NSMutableArray *items = [[toolbar items] mutableCopy];
    [items removeObjectAtIndex:0];
    [toolbar setItems:items animated:YES];
    [items release];
    self.popoverController = nil;
}