将按钮添加到底部工具栏

I have the following code:

我有以下代码:

self.shareButton=[[UIButton alloc] initWithFrame:CGRectMake(0.0, 0.0, 35, 35)];
[shareButton setBackgroundColor:[UIColor blueColor]];
[shareButton setBackgroundImage:[UIImage imageNamed:@"share_button"] forState:UIControlStateNormal];
[shareButton setBackgroundImage:[UIImage imageNamed:@"share_button_pressed"] forState:UIControlStateHighlighted];
[shareButton addTarget:self action:@selector(shareButtonPressed:) forControlEvents:UIControlEventTouchUpInside];
[self.navigationController setToolbarItems:[NSArray arrayWithObject:shareButton] animated:YES];
self.sha