iOS设置或修改导航栏按钮、标题

1. 设置导航栏返回按钮：

    UIButton * button = [UIButton buttonWithType:UIButtonTypeCustom];
    button.frame = CGRectMake(0, 0, 44, 30);
    [button setImage:[UIImage imageNamed:@"leftArrow"] forState:UIControlStateNormal];
    button.imageView.contentMode = UIViewContentModeScaleAspectFit;
    [button addTarget:self action:@selector(DismissViewController:) forControlEvents:UIControlEventTouchUpInside];
    self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:button];

2. 设置导航栏背景图片：

    [self.navigationController.navigationBarsetBackgroundImage:[UIImageimageNamed:@"grayNavBack"]forBarMetrics:UIBarMetricsDefault];

3. 取消导航栏横线：

    [self.navigationController.navigationBarsetShadowImage:[UIImagenew]];