I have a simple view controller (SecondViewController) used to manage a UITextview (I'm building a simple editor) this is the code of the SecondViewController.h

    @interface SecondViewController : UIViewController {
 IBOutlet UITextView *textView;
}
@property (nonatomic,retain) IBOutlet UITextView *textView;
@end

and this is the SecondViewController.m

//
// EditorViewController.m
// Editor
//
// Created by elio d'antoni on 13/01/11.
// Copyright 2011 none. All rights reserved.
//
@implementation SecondViewController
@synthesize textView;
/*
// Implement loadView to create a view hierarchy programmatically, without using a nib.
- (void)loadView {
}
*/
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
[super viewDidLoad];
self.view.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"uiViewBg.png"]];
textView.layer.borderWidth=1;
textView.layer.cornerRadius=5;
textView.layer.borderColor=[[UIColor darkGrayColor] CGColor];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillAppear:) name:UIKeyboardWillShowNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillDisappear:) name:UIKeyboardWillHideNotification object:nil];
}
-(void) matchAnimationTo:(NSDictionary *) userInfo {
NSLog(@"match animation method");
[UIView setAnimationDuration:[[userInfo objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue]];
[UIView setAnimationCurve:[[userInfo objectForKey:UIKeyboardAnimationCurveUserInfoKey] intValue]];
}
-(CGFloat) keyboardEndingFrameHeight:(NSDictionary *) userInfo {
NSLog(@"keyboardEndingFrameHeight method");
CGRect keyboardEndingUncorrectedFrame = 

[[ userInfo objectForKey:UIKeyboardFrameEndUserInfoKey ]
CGRectValue];
CGRect keyboardEndingFrame =
[self.view convertRect:keyboardEndingUncorrectedFrame
fromView:nil];
return keyboardEndingFrame.size.height;
}
-(CGRect) adjustFrameHeightBy:(CGFloat) change
multipliedBy:(NSInteger) direction {
NSLog(@"adjust method");
return CGRectMake(20, 
                  57, 
                  self.textView.frame.size.width, 
                  self.textView.frame.size.height + change * direction);

}
-(void)keyboardWillAppear:(NSNotification *)notification {
NSLog(@"keyboard appear");
[UIView beginAnimations:nil context:NULL];
[self matchAnimationTo:[notification userInfo]];
self.textView.frame =
[self adjustFrameHeightBy:[self keyboardEndingFrameHeight:
[notification userInfo]]
multipliedBy:-1];
[UIView commitAnimations];
}
-(void)keyboardWillDisappear:(NSNotification *) notification {
NSLog(@"keyboard disappear");
[UIView beginAnimations:nil context:NULL];
[self matchAnimationTo:[notification userInfo]];
self.textView.frame =
[self adjustFrameHeightBy:[self keyboardEndingFrameHeight:
[notification userInfo]]
multipliedBy:1];
[UIView commitAnimations];
}
// Override to allow orientations other than the default portrait orientation.
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
return YES;
}

(void)didReceiveMemoryWarning {
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Release any cached data, images, etc that aren't in use.
}
(void)viewDidUnload {
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}
(void)dealloc {
[super dealloc];
}

@end

the problem is that if load the view controller from a tab bar controller the textView doesn't resize when the keyboard appear, but the SAME code works if loaded as a single view based app. I hope I was clear enough. I used the tabBar template provided by xcode no modifications.