//UIToolBar  是导航控制器默认隐藏的工具条    //设置UIToolBar的隐藏状态    self.navigationController.toolbarHidden = NO;        //如何找到UIToolBar   self.navigationController.toolbar    //UIToolBar高度：44        //设置UIToolBar类型:barStyle    self.navigationController.toolbar.barStyle = UIBarStyleDefault;    //设置UIToolBar的颜色:barTintColor    self.navigationController.toolbar.barTintColor = [UIColor redColor];    //设置UIToolBar的图片    [self.navigationController.toolbar setBackgroundImage:[UIImage imageNamed:@"toolBar.png"] forToolbarPosition:UIToolbarPositionBottom barMetrics:UIBarMetricsDefault];        //UIBarButtonItem  文字类型    UIBarButtonItem *wordButton = [[UIBarButtonItem alloc] initWithTitle:@"button" style:UIBarButtonItemStylePlain target:self action:@selector(barButtonClick:)];        //UIBarButtonItem  图片类型    UIBarButtonItem *imageButton = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"itemImage.png"] style:UIBarButtonItemStylePlain target:self action:@selector(imageButtonClick:)]; //UIBarButtonItem 系统类型 UIBarButtonItem *systemButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemBookmarks target:self action:@selector(systemButtonClick:)]; //创建空格 //会均分掉空白部分，空格的点击事件不会实现，无效 UIBarButtonItem *space = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:self action:@selector(spaceClick:)]; //向UIToolBar上面添加按钮 self.toolbarItems //需要接收数组：数组里面的元素必须是UIBarButtonItem类型 self.toolbarItems = @[space, wordButton, space, imageButton, space, systemButton, space];