覆蓋 Xamarin.IOS 中的后退按鈕導航

Question

我正在嘗試使用 Xamarin.IOS 框架覆蓋 IOS 的默認后退按鈕行為。 我的 ViewController 中有一堆對象，我的要求是當用戶按回導航到前一個 ViewController 時，我只會在我的堆棧為空時導航，否則我將留在該屏幕（ViewController）中。 為此，我嘗試了幾件事，例如覆蓋 ViewWillDisappear 並將 PopViewController 設置為 false，但我無法做到這一點。 請指導。

public override void ViewWillDisappear(bool animated)
    {
        Stack<Object> st = vPage.uContentStack;
        if (st.Count != 0)
        {
            Object pop_obj = st.Pop();
            if (st.Count != 0)
            {
                NavigationController.PopViewController(false);// Here trying to stop navigating back
                Object peek_obj = st.Peek();
                vPage.ContentUpdateOnBackPress(pop_obj, peek_obj);
            }
            else
            {
                NavigationController.PopViewController(true);
            }

        }
        else
        {
            NavigationController.PopViewController(true);
        }
        base.ViewWillDisappear(animated);
    }

Answer 1

您可以在特定的ViewController 中自定義導航欄

public override void ViewWillAppear(bool animated)
    {
        base.ViewWillAppear(animated);
       
        NavigationController.NavigationBar.Hidden = true;
        double height = IsiphoneX();
        UIView backView = new UIView()
        {
            BackgroundColor = UIColor.White,
            Frame = new CGRect(0, 20, UIScreen.MainScreen.Bounds.Width, height),
        };
        UIButton backBtn = new UIButton()
        {
            Frame = new CGRect(20, height - 44, 40, 44),
            Font = UIFont.SystemFontOfSize(18),
        };
        backBtn.SetTitle("<", UIControlState.Normal);
       // backBtn.SetBackgroundImage(UIImage.FromBundle("xx.png"),UIControlState.Normal); or you can set image here 
        backBtn.SetTitleColor(UIColor.FromRGB(60,140,250), UIControlState.Normal);
        backBtn.AddTarget(this, new Selector("GoBack"), UIControlEvent.TouchUpInside);
        UILabel titleLabel = new UILabel()
        {
            Frame = new CGRect(UIScreen.MainScreen.Bounds.Width / 2 - 75, 0, 150, height),
            Font = UIFont.SystemFontOfSize(20),
            Text = "xxx",
            TextAlignment = UITextAlignment.Center,
            TextColor = UIColor.Black,
            Lines = 0,
        };
        UILabel line = new UILabel()
        {
            Frame = new CGRect(0, height, UIScreen.MainScreen.Bounds.Width, 0.5),
            BackgroundColor = UIColor.Black,
        };

        backView.AddSubview(backBtn);
        backView.AddSubview(titleLabel);
        backView.AddSubview(line);
        View.AddSubview(backView);
    }
    double IsiphoneX()
    {
        double height = 44;
        if (UIDevice.CurrentDevice.CheckSystemVersion(11, 0))
        {
            if (UIApplication.SharedApplication.Delegate.GetWindow().SafeAreaInsets.Bottom > 0.0)
            {
                height = 64;
            }
        }
        return height;
    }
    [Export("GoBack")]
    void GoBack()
    {
       //handle logic here
    }
    public override void ViewWillDisappear(bool animated)
    {
        base.ViewWillDisappear(animated);

        NavigationController.NavigationBar.Hidden = false;
    }

在此解決方案中，您可以設置導航欄的樣式，例如標題的文本顏色或后退按鈕的圖標。