iPhone SDK : How to add an image to a UIBarButton?

Question

我使用下面的代码在导航栏上创建一个带有图像的按钮。

我可以看到图像，但我也可以看到图像周围按钮的边框。我的问题是，如何去掉按钮边框。我只想看到导航栏上的图像，没有边框。

UIBarButtonItem *settingsBtn = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"icon_prefs.png"] style:UIBarButtonItemStylePlain target:self action:@selector(openSettings:)];
[[self navigationItem] setLeftBarButtonItem:settingsBtn];
[settingsBtn release];

提前致谢。任何指针、进一步阅读的链接或示例表示赞赏。

Answer 1

这是我当前项目之一的代码片段。它为 UIBarButtonItem 加载具有透明度的图像:

UIImage* image = [UIImage imageNamed:@"some-image.png"];
CGRect frame = CGRectMake(0, 0, image.size.width, image.size.height);
UIButton* someButton = [[UIButton alloc] initWithFrame:frame];
[someButton setBackgroundImage:image forState:UIControlStateNormal];
[someButton setShowsTouchWhenHighlighted:YES];
UIBarButtonItem* someBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:someButton];
[self.navigationItem setRightBarButtonItem:someBarButtonItem];
[someBarButtonItem release];
[someButton release];