iOS tip：让你的footTableView的UILabel居中

如果你需要编写一个软件，同时支持portrait&landscape，你会遇到一个问题：当屏幕旋转后，如果才能确保一些可视化的things依然居中呢。下面是一个简单的例子，无论设备是否旋转，UITableView的footer中的UILabel保持居中的方法。

 1     //create the uiview container 2     UIView *tfooterView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, _tableView.frame.size.width, 45)]; 3     tfooterView.autoresizingMask = UIViewAutoresizingFlexibleWidth; 4     //create the uilabel for the text 5     UILabel *label3 = [[UILabel alloc] initWithFrame:CGRectMake(_tableView.frame.size.width/2-120, 0, 240, 35)]; 6     label3.backgroundColor = [UIColor clearColor]; 7     label3.font = [UIFont systemFontOfSize:12]; 8     label3.numberOfLines = 2; 9     label3.lineBreakMode = UILineBreakModeWordWrap;10     label3.textAlignment = UITextAlignmentCenter;11     label3.text = @"Some text you want centered in your tableFooterView.";12     label3.autoresizingMask = UIViewAutoresizingFlexibleRightMargin | UIViewAutoresizingFlexibleLeftMargin;13     //add the label to the view14     [tfooterView addSubview:label3];15     //add the view to the uitableview footer16     _tableView.tableFooterView = tfooterView;