代码示例：
UIImage *image = [UIImage
imageNamed:@"radio_back.png"];
UIButton* button= [[UIButton
alloc] initWithFrame:CGRectMake(0,0, image.size.width,image.size.height)];
button.adjustsImageWhenHighlighted =
YES; //
按按钮时，显示按钮的变化
[button setBackgroundImage:image
forState:UIControlStateNormal];
[button addTarget:self
action:@selector(onBack:)
forControlEvents:UIControlEventTouchUpInside];
UIBarButtonItem* ButtonItem = [[UIBarButtonItem
alloc] initWithCustomView:button] ;
self.navigationItem.leftBarButtonItem = ButtonItem ;
[ButtonItem release] ;
[button release];
UIBarButtonItem虽然有initWithImage,但只是设置前景图，背景框仍在。setBackgroundImage有测试过，但会崩溃就没有深究。