为什么我的TabBar按钮不会在iPad上自动显示？

Question

我正在构建一个通用iOS应用程序，iPad版本使用SplitViewController。在popover视图中，我有一个带有两个按钮的UITabBarController。当它在iPhone上运行时，TabBar按钮会正确拉伸以填充视图的整个宽度......

...但是在iPad上，在弹出视图中，按钮不会拉伸以填充整个宽度......

我正在以编程方式创建UITabBarController ......

InspectionTabBarViewController *inspectionTabBarVC;
    InspectionListViewController *inspectionListVC;
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

 if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone) {

        inspectionListVC = [[InspectionListViewController alloc] initWithSunday:NO];
        inspectionListVC.managedObjectContext = self.managedObjectContext;
        UINavigationController *calendarNavVC = [[UINavigationController alloc] initWithRootViewController:inspectionListVC];
        calendarNavVC.title = @"Calendar";

        InspectionMapViewController *mapViewVC = [[InspectionMapViewController alloc] initWithNibName:@"InspectionMapView_iPhone" bundle:nil];
        UINavigationController *mapdNavVC = [[UINavigationController alloc] initWithRootViewController:mapViewVC];
        mapdNavVC.title = @"Map";

        inspectionTabBarVC = [[InspectionTabBarViewController alloc] init];
        [inspectionTabBarVC addChildViewController:calendarNavVC];
        [inspectionTabBarVC addChildViewController:mapdNavVC];
        self.window.rootViewController = inspectionTabBarVC;
    } 
    else 
    {
        inspectionListVC = [[InspectionListViewController alloc] initWithSunday:NO];
        UINavigationController *calendarNavVC = [[UINavigationController alloc] initWithRootViewController:inspectionListVC];
        calendarNavVC.title = @"Calendar";

        InspectionMapViewController *mapViewVC = [[InspectionMapViewController alloc] initWithNibName:@"InspectionMapView_iPad" bundle:nil];
        UINavigationController *mapdNavVC = [[UINavigationController alloc] initWithRootViewController:mapViewVC];
        mapdNavVC.title = @"Map";

        inspectionTabBarVC = [[InspectionTabBarViewController alloc] init];
        [inspectionTabBarVC addChildViewController:calendarNavVC];
        [inspectionTabBarVC addChildViewController:mapdNavVC];

        DetailViewController *detailViewController = [[DetailViewController alloc] initWithNibName:@"DetailViewController_iPad" bundle:nil];
        UINavigationController *detailNavigationController = [[UINavigationController alloc] initWithRootViewController:detailViewController];

        self.splitViewController = [[UISplitViewController alloc] init];
        self.splitViewController.delegate = detailViewController;
        self.splitViewController.viewControllers = [NSArray arrayWithObjects:inspectionTabBarVC, detailNavigationController, nil];

        self.window.rootViewController = self.splitViewController;
        inspectionListVC.detailViewController = detailViewController;
        inspectionListVC.managedObjectContext = self.managedObjectContext;

        detailViewController.detailViewControllerDelegate = inspectionListVC;
    }

    [self.window makeKeyAndVisible];

我还尝试使用以下语句在InspectionTabBarViewController的loadView方法中设置autoResizeMask ...

self.tabBar.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin | UIViewAutoresizingFlexibleBottomMargin | UIViewAutoresizingFlexibleWidth;

......但这也不起作用。如何让UITabBar按钮填充整个视图宽度？

非常感谢您的帮助！

Answer 1

将UITabBar属性itemPositioning更改为UITabBarItemPositioningFill：

self.tabBar.itemPositioning = UITabBarItemPositioningFill;

Swift版本：

tabBar.itemPositioning = .fill

UITabBar itemPositioning reference

Answer 2

实际上可以通过在标签栏上设置setSelectionIndicatorImage来完成。无论iPhone或iPad如何，按钮都会调整为您图像的宽度。

问题在于它不是动态的，每次添加或更改标签栏中的项目数时，您都必须创建另一个图像。

解决方案是在代码中创建图像并按（{tab bar width}/{# of tabbaritems}）计算宽度。

例如：

创建标签栏的位置：

[[self.tabBarController tabBar] setSelectionIndicatorImage:[self selectionIndicatorImage]];

图像方法：

- (UIImage *)selectionIndicatorImage
{
    NSUInteger count    = [[self.tabBarController viewControllers] count];
    CGSize tabBarSize = [[self.tabBarController tabBar] frame].size;
    NSUInteger padding = 2;

    CGSize buttonSize = CGSizeMake( tabBarSize.width / count, tabBarSize.height );

    UIGraphicsBeginImageContext( buttonSize );

    CGContextRef c = UIGraphicsGetCurrentContext();

    [[UIColor colorWithWhite:0.9 alpha:0.1] setFill];

    UIBezierPath *roundedRect = [UIBezierPath bezierPathWithRoundedRect:CGRectMake( padding, padding * 2, buttonSize.width - (padding * 2) , buttonSize.height - ( padding * 2 ) ) cornerRadius:4.0];

    [roundedRect fillWithBlendMode: kCGBlendModeNormal alpha:1.0f];

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

    CGContextRelease( c );

    return image;
}

Answer 3

1. 我们无法动态设置UITabbarItem的大小。
2. 在iPhone中设置（设备宽度/没有Tabbaritems）
3. 在iPad中设置特定宽度

如果你想创建这种类型的视图，那么使用看起来像标签栏按钮的自定义按钮，并按照你的代码添加功能。

Answer 4

我在iOS7中找到了itemWidth（UITabBar的属性）。

UITabBar reference