將自定義按鈕添加到UINavigationItem LeftBarButtonItem

Question

任何人都可以告訴我爲什麼這段代碼不起作用嗎？

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; 

編輯：

沒有出現在leftBarButtonItem。那就是問題所在。

Answer 1

從文檔：

「當創建自定義按鈕，其與按鈕的類型UIButtonTypeCustom-的幀被設置爲一個按鈕（0 ，0,0,0），在將按鈕添加到您的界面之前，您應該將幀更新爲更合適的值。「

所以，你應該看到的東西，如果你在第2行設置的框架，如：

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

Answer 2

這應該工作

CGRect rect = CGRectMake(10, 0, 30, 30); 
self.backButton = [[UIButton alloc] initWithFrame:rect]; 
[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]; 
self.navigationItem.leftBarButtonItem = backButtonItem; 
self.navigationItem.hidesBackButton = YES;