Question

I want to initialize my tab bar controller programmatically, but I just get a blank screen with the code I have. I tried to imitate TheElements sample app, and stuff seems comparable going line-by-line, but obviously something’s wrong. Any suggestions?

In main.m:

#import <UIKit/UIKit.h>

int main(int argc, char *argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    int retVal = UIApplicationMain(argc, argv, nil, @"DubbleWrapAppDelegate");
    [pool release];
    return retVal;
}

In DubbleWrapAppDelegate.h:

@interface DubbleWrapAppDelegate : NSObject <UIApplicationDelegate, UITabBarControllerDelegate> {
    UIWindow *window;
    UITabBarController *tabBarController;
}

@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) IBOutlet UITabBarController *tabBarController;

@end

In DubbleWrapAppDelegate.m:

@implementation DubbleWrapAppDelegate

@synthesize window;
@synthesize tabBarController;


- init {
    if (self = [super init]){
        // initialize to nil
        window = nil;
        tabBarController = nil;
    }
    return self;
}

- (void)applicationDidFinishLaunching:(UIApplication *)application {

    SafeTableViewController *vc1 = [[SafeTableViewController alloc] initWithStyle:UITableViewStylePlain];
    [vc1 setSafeItems:[SafeItem knownSafeItems]]; // Set the list of known SafeItems:
    UINavigationController *nc1;
    nc1 = [[UINavigationController alloc] initWithRootViewController:vc1];
    [vc1 release];


    BoxXRayTableViewController *vc2 = [[BoxXRayTableViewController alloc] initWithStyle:UITableViewStylePlain];
    UINavigationController *nc2;
    nc2 = [[UINavigationController alloc] initWithRootViewController:vc2];
    [vc2 release];

    AboutLibertyViewController *vc3 = [[AboutLibertyViewController alloc] init];
    UINavigationController *nc3;
    nc3 = [[UINavigationController alloc] initWithRootViewController:vc3];
    [vc3 release];

    NSArray* controllers = [NSArray arrayWithObjects:nc1, nc2, nc3, nil];

    tabBarController = [[UITabBarController alloc] init];
    tabBarController.viewControllers = controllers;
    [controllers release];

    // Add the tab bar controller's current view as a subview of the window
    window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
    [window setBackgroundColor:[UIColor redColor]];
    [window addSubview:tabBarController.view];
    [window makeKeyAndVisible];

    [nc1 release];
    [nc2 release];
    [nc3 release];
}

The plist is set so that there is no NIB file referenced.

Answer 1

You should hold on to the window object. You marked it as autorelease, so it is released at the next application loop.

Don’t call autorelease on window:

window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];