弹出键盘时，让table向上移动

原文链接：iphone 中弹出输入法键盘的时候，让table向上移动。

#pragma mark UITextFieldDelegate

- (BOOL)textFieldShouldBeginEditing: (UITextField *)textField
{
[UIView beginAnimations: nil context: nil];
self.tableView.contentInset = UIEdgeInsetsMake(0, 0, 280, 0);
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:textField.tag - tag_index_cell_start inSection: 0];
[self.tableView scrollToRowAtIndexPath: indexPath 
  atScrollPosition: UITableViewScrollPositionBottom 
  animated: YES];
[UIView commitAnimations];
return YES;
}