Iphone 向导航控制器添加第三个按钮

我已经在导航控制器上添加了两个按钮，一个是右按钮，另一个是左按钮，我想在右按钮之前添加第三个按钮。怎么做

 UIButton *logo_btn =  [UIButton buttonWithType:UIButtonTypeCustom];
 [logo_btn setBackgroundImage:[UIImage imageNamed:@"logo-57.png"]  forState:UIControlStateNormal];

[logo_btn setFrame:CGRectMake(-2, 0, 47, 47)];

UIBarButtonItem *btnItem1 = [[UIBarButtonItem alloc] initWithCustomView:logo_btn];
self.navigationItem.leftBarButtonItem = btnItem1;

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这就是我在左边添加一个按钮的方式

iOS 5帮助您在导航栏上创建2个以上的按钮

self.navigationItem.leftBarButtonItems = [NSArray arrayWithObjects:uibarbuttonInstance1, uibarbuttonInstance2, nil];

右边的按钮也一样

self.navigationItem.rightBarButtonItems = [NSArray arrayWithObjects:uibarbuttonInstance1, uibarbuttonInstance2, nil];

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iOS 5帮助您在导航栏上创建2个以上的按钮

self.navigationItem.leftBarButtonItems = [NSArray arrayWithObjects:uibarbuttonInstance1, uibarbuttonInstance2, nil];

右边的按钮也一样

self.navigationItem.rightBarButtonItems = [NSArray arrayWithObjects:uibarbuttonInstance1, uibarbuttonInstance2, nil];

用过这个。你会知道的。用过这个。你会知道的。