ios 将segment添加到nav上

/* 初始化导航按钮 */  
{
            credits = [ [ [ UIBarButtonItem alloc ]  
                        initWithTitle:@"Credits"  
                        style: UIBarButtonItemStylePlain  
                        target: appDelegate  
                        action:@selector(credits) ]  
                    autorelease ];  
            self.navigationItem.rightBarButtonItem = credits;  
 
            segmentedControl = [ [ UISegmentedControl 
alloc ] initWithItems: nil ];  
            segmentedControl.segmentedControlStyle = 
UISegmentedControlStyleBar;  
 
            [ segmentedControl insertSegmentWithTitle: 
@"Bunnies" atIndex: 0  
                animated: NO  
            ];  
            [ segmentedControl insertSegmentWithTitle: 
@"Ponies" atIndex: 1  
                animated: NO  
            ];  
 
            [ segmentedControl addTarget: self action: 
@selector(controlPressed:)  
                forControlEvents:UIControlEventValueChanged  
            ];  
 
            self.navigationItem.titleView = segmentedControl;  
            segmentedControl.selectedSegmentIndex = 0;  
        }  
        return self;  
}  
 
- (void)controlPressed:(id) sender {  
        [ self setPage ];  
}  
 
- (void)setPage {  
        int index = segmentedControl.selectedSegmentIndex;  
 
        if (index == 0) {  
            textView.text = @"OMG Bunnies!";  
        } else {  
            textView.text = @"OMG Ponies";  
        }  
}