iphone - 如何以编程方式在右上角创建一个信息按钮？

我正在尝试执行此操作，但该按钮未显示:

// Create a Button to get Help
UIButton *helpButton =  [UIButton buttonWithType:UIButtonTypeInfoDark ] ;
CGRect buttonRect = helpButton.frame;

// Calculate the top right corner
buttonRect.origin.x = self.tableView.frame.size.width - buttonRect.size.width - 8;
buttonRect.origin.y = self.tableView.frame.size.height - buttonRect.size.height - 8;
[helpButton setFrame:buttonRect];

[helpButton addTarget:self action:@selector(doHelp:)
forControlEvents:UIControlEventTouchUpInside];
[helpButton setEnabled:TRUE];
[self.tableView addSubview:helpButton];

我究竟做错了什么？

更新
修复代码适用于任何有兴趣的人:

// Create a Button to get Help
UIButton *helpButton =  [UIButton buttonWithType:UIButtonTypeInfoDark ] ;
CGRect buttonRect = helpButton.frame;

// CALCulate the bottom right corner
buttonRect.origin.x = self.view.frame.size.width - buttonRect.size.width - 8;
buttonRect.origin.y = buttonRect.size.height - 8;
[helpButton setFrame:buttonRect];

[helpButton addTarget:self action:@selector(doHelp:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:helpButton];

最佳答案

尝试将其添加到self.view而不是self.tableview