导航标题被条形按钮隐藏

UILabel

titleView

// CUSTOMIZE NAVIGATION BAR TITLE LABEL
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0.0, 0.0, 320.0, 44.0)];
[label setBackgroundColor:[UIColor clearColor]];
[label setFont:[UIFont boldSystemFontOfSize:20.0]];
[label setAdjustsFontSizeToFitWidth:YES];
[label setTextAlignment:UITextAlignmentCenter];
[[self navigationItem] setTitleView:label];
[label release];