iphone - 将自定义按钮添加到 UINavigationItem LeftBarButtonItem

Question

谁能告诉我为什么这段代码不起作用？

self.backButton = [UIButton buttonWithType:UIButtonTypeCustom];
[self.backButton setImage:[UIImage imageNamed:@"back_arrow.png"]
                 forState:UIControlStateNormal];
self.backButton.contentMode = UIViewContentModeCenter;
[self.backButton addTarget:self
                    action:@selector(backButtonAction:)
          forControlEvents:UIControlEventTouchUpInside];

UIBarButtonItem *backButtonItem = [[UIBarButtonItem alloc] initWithCustomView:self.backButton];
[navigationItem setLeftBarButtonItem:backButtonItem animated:NO];
navigationItem.hidesBackButton = YES;

编辑:
leftBarButtonItem 上没有显示任何内容.那就是问题所在。

Answer 1

从文档:

"When creating a custom button—that is a button with the type UIButtonTypeCustom—the frame of the button is set to (0, 0, 0, 0) initially. Before adding the button to your interface, you should update the frame to a more appropriate value."

因此，如果您在第 2 行设置框架，您应该会看到一些内容，例如:

self.backButton.frame = CGRectMake(0, 0, 40, 20);