iOS設置或修改導航欄按鈕、標題

1. 設置導航欄返回按鈕：

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. 設置導航欄背景圖片：

    [self.navigationController.navigationBar setBackgroundImage:[UIImage imageNamed:@"grayNavBack"] forBarMetrics:UIBarMetricsDefault];

3. 取消導航欄橫線：

    [self.navigationController.navigationBar setShadowImage:[UIImage new]];