结合以上的答案，可以为UIButtonTypeSystem提供以下解决方案:

if (_button.enabled)
{
    [UIView setAnimationsEnabled:NO];
    [_button setTitle:@"title" forState:UIControlStateNormal];
    [UIView setAnimationsEnabled:YES];
}
else // disabled
{
    [UIView setAnimationsEnabled:NO];
    _button.enabled = YES;
    [_button setTitle:@"title" forState:UIControlStateNormal];
    _button.enabled = NO;
    [UIView setAnimationsEnabled:YES];
}

这适用于自定义按钮:

[UIView setAnimationsEnabled:NO];
[_button setTitle:@"title" forState:UIControlStateNormal];
[UIView setAnimationsEnabled:YES];

对于系统按钮，你需要在重新启用动画之前添加这个(谢谢@Klaas):

[_button layoutIfNeeded];

所以我找到了可行的解决方案:

_logoutButton.titleLabel.text = NSLocalizedString(@"Logout",);
[_logoutButton setTitle:_logoutButton.titleLabel.text forState:UIControlStateNormal];

首先我们改变按钮的标题，然后调整这个标题的按钮大小

在Swift中，你可以使用:

UIView.performWithoutAnimation {
    self.someButtonButton.setTitle(newTitle, forState: .normal)
    self.someButtonButton.layoutIfNeeded()
}

请注意:

当_button的"buttonType"为"UIButtonTypeSystem"时，以下代码无效:

[UIView setAnimationsEnabled:NO];
[_button setTitle:@"title" forState:UIControlStateNormal];
[UIView setAnimationsEnabled:YES];

当_button的"buttonType"为"UIButtonTypeCustom"时，上述代码有效。

Xhacker Liu扩展转换为Swift 3:

extension UIButton {
    func setTitleWithoutAnimation(title: String?) {
        UIView.setAnimationsEnabled(false)

        setTitle(title, for: .normal)

        layoutIfNeeded()
        UIView.setAnimationsEnabled(true)
    }
}