MvvmCross框架下iOS端实现非全屏自定义Dialog弹窗求助

最简便的实现方式不需要自定义MvvmCross的Presenter，仅需修改你现有ViewController的布局逻辑即可，完全复用你已有的ViewModel层代码，不会出现断言报错问题。

核心改动逻辑 #

• 保留你现有UIModalPresentationStyle.OverFullScreen的配置，这是iPhone端实现自定义非全屏弹窗的基础
• 将弹窗根视图的背景改为半透明蒙层，替代原有的白色背景，透出下层页面内容
• 取消弹窗容器formView的全屏约束，改为固定尺寸居中展示

修改后完整iOS View代码 #

[MvxModalPresentation(WrapInNavigationController = false,
    ModalTransitionStyle = UIModalTransitionStyle.CrossDissolve,
    ModalPresentationStyle = UIModalPresentationStyle.OverFullScreen)]
class MessageDialogView : MvxViewController<MessageDialogViewModel>
{
    public override void ViewDidLoad()
    {
        // 根视图改为半透明蒙层，透出下层页面
        View.BackgroundColor = UIColor.Black.ColorWithAlpha(0.5f);
        base.ViewDidLoad();

        var formView = new UIView();
        formView.BackgroundColor = UIColor.Black;
        // 可选：加圆角和Android端弹窗效果对齐
        formView.Layer.CornerRadius = 12f;
        formView.ClipsToBounds = true;

        var message = new UILabel() { Text = ViewModel.Message };
        formView.Add(message);
        message.TextColor = UIColor.White;
        message.Font = message.Font.WithSize(20f);
        message.Lines = 0; // 支持多行文本自动换行

        var btnClose = new UIButton(UIButtonType.RoundedRect);
        btnClose.SetTitle("Close", UIControlState.Normal);
        btnClose.Font = btnClose.Font.WithSize(20f);
        btnClose.SetTitleColor(UIColor.Clear.FromHex(0x00D0F7), UIControlState.Normal);
        formView.Add(btnClose);

        var set = this.CreateBindingSet<MessageDialogView, MessageDialogViewModel>();
        set.Bind(btnClose).To(vm => vm.CloseCommand);
        // 可选：点击半透明蒙层也关闭弹窗，可解除下面注释
        // var tapGesture = new UITapGestureRecognizer();
        // set.Bind(tapGesture).To(vm => vm.CloseCommand);
        // View.AddGestureRecognizer(tapGesture);
        set.Apply();

        View.Add(formView);

        View.SubviewsDoNotTranslateAutoresizingMaskIntoConstraints();
        formView.SubviewsDoNotTranslateAutoresizingMaskIntoConstraints();

        // formView不再撑满全屏，改为固定宽度、居中显示
        View.AddConstraints(
            formView.WithSameCenterX(View),
            formView.WithSameCenterY(View),
            formView.Width().EqualTo(300f),
            // 小屏设备自动适配宽度，左右留20dp边距避免溢出
            formView.Width().LessThanOrEqualTo(View.Width()).Minus(40f)
        );

        formView.AddConstraints(
            message.AtTopOf(formView, 20f),
            message.AtLeftOf(formView, 16f),
            message.AtRightOf(formView, 16f),

            btnClose.Below(message, 20f),
            btnClose.AtRightOf(formView, 16f),
            btnClose.AtBottomOf(formView, 16f)
        );
    }
}

内容的提问来源于stack exchange，提问作者Jim Wilcox