xamarin - 在 C# 后端中，如何选择分段控件中的元素？

Question

我正在使用自定义控件来创建显示如下的连接按钮:

********************************************
*            *            *                *
*    One     *    Two     *     Three      *
*            *            *                *
********************************************

当我单击按钮时，会触发一个事件:

void OnValueChanged(object sender, EventArgs e)
{
     switch (segControl.SelectedValue)
     {

这运行良好，但我想做的是能够从我的 C# 代码中选择这些按钮之一。

当我查看控件的源代码时，我不知道如何执行此操作。

如果有人对我应该做什么有任何建议，例如以与我单击它相同的方式选择第二个按钮，我将不胜感激。

这是我正在使用的代码:

<local:SegmentedControl ValueChanged="OnValueChanged" SelectedSegment="{Binding CustomPointsSwitch}" x:Name="segControl" HorizontalOptions="End">
   <local:SegmentedControl.Children>
       <local:SegmentedControlOption Text="Two" />
       <local:SegmentedControlOption Text="Four" />
   </local:SegmentedControl.Children>
</local:SegmentedControl>

共享代码

public class SegmentedControl : View, IViewContainer<SegmentedControlOption>
{
    public IList<SegmentedControlOption> Children { get; set; }

    public SegmentedControl()
    {
        Children = new List<SegmentedControlOption>();
    }

    public event ValueChangedEventHandler ValueChanged;

    public delegate void ValueChangedEventHandler(object sender, EventArgs e);

    private string selectedValue;

    public string SelectedValue
    {
        get { return selectedValue; }
        set
        {
            selectedValue = value;
            if (ValueChanged != null)
                ValueChanged(this, EventArgs.Empty);
        }
    }
    public static readonly BindableProperty SelectedSegmentProperty = BindableProperty.Create("SelectedSegment", typeof(int), typeof(SegmentedControl), 0);
    public int SelectedSegment
    {
        get
        {
            return (int)GetValue(SelectedSegmentProperty);
        }
        set
        {
            SetValue(SelectedSegmentProperty, value);
        }
    }
}

public class SegmentedControlOption : View
{
    public static readonly BindableProperty TextProperty = BindableProperty.Create("Text", typeof(string), typeof(SegmentedControlOption), string.Empty);

    public string Text
    {
        get { return (string)GetValue(TextProperty); }
        set { SetValue(TextProperty, value); }
    }
}

iOS 渲染器

public class SegmentedControlRenderer : ViewRenderer<SegmentedControl, UISegmentedControl>
{
    public SegmentedControlRenderer()
    {
    }

    protected override void OnElementChanged(ElementChangedEventArgs<SegmentedControl> e)
    {
        base.OnElementChanged(e);

        var segmentedControl = new UISegmentedControl();
        for (var i = 0; i < e.NewElement.Children.Count; i++)
        {
            segmentedControl.InsertSegment(e.NewElement.Children[i].Text, i, false);
        }

        segmentedControl.ValueChanged += (sender, eventArgs) => {
            e.NewElement.SelectedSegment = (int)segmentedControl.SelectedSegment;
            e.NewElement.SelectedValue = segmentedControl.TitleAt(segmentedControl.SelectedSegment);
        };

        SetNativeControl(segmentedControl);
    }
}

Android 渲染器

public class SegmentedControlRenderer : ViewRenderer<SegmentedControl, RadioGroup>
{

    protected override void OnElementChanged(ElementChangedEventArgs<SegmentedControl> e)
    {
        base.OnElementChanged(e);

        var layoutInflater = (LayoutInflater)Context.GetSystemService(Context.LayoutInflaterService);

        var g = new RadioGroup(Context);
        g.Orientation = Orientation.Horizontal;
        g.CheckedChange += (sender, eventArgs) => {
            var rg = (RadioGroup)sender;
            if (rg.CheckedRadioButtonId != -1)
            {
                var id = rg.CheckedRadioButtonId;
                var radioButton = rg.FindViewById(id);
                var radioId = rg.IndexOfChild(radioButton);
                var btn = (RadioButton)rg.GetChildAt(radioId);
                var selection = (String)btn.Text;
                e.NewElement.SelectedValue = selection;
            }
        };

        for (var i = 0; i < e.NewElement.Children.Count; i++)
        {
            var o = e.NewElement.Children[i];
            var v = (SegmentedControlButton)layoutInflater.Inflate(Resource.Layout.SegmentedControl, null);
            v.Text = o.Text;
            if (i == 0)
                v.SetBackgroundResource(Resource.Drawable.segmented_control_first_background);
            else if (i == e.NewElement.Children.Count - 1)
                v.SetBackgroundResource(Resource.Drawable.segmented_control_last_background);
            g.AddView(v);
        }

        SetNativeControl(g);
    }
}

public class SegmentedControlButton : RadioButton
{
    private int lineHeightSelected;
    private int lineHeightUnselected;
    private Paint linePaint;

    public SegmentedControlButton(Context context, IAttributeSet attributes) : this(context, attributes, Resource.Attribute.segmentedControlOptionStyle)
    {
    }

    public SegmentedControlButton(Context context, IAttributeSet attributes, int defStyle) : base(context, attributes, defStyle)
    {
        Initialize(attributes, defStyle);
    }

    private void Initialize(IAttributeSet attributes, int defStyle)
    {
        var a = this.Context.ObtainStyledAttributes(attributes, Resource.Styleable.SegmentedControlOption, defStyle, Resource.Style.SegmentedControlOption);

        var lineColor = a.GetColor(Resource.Styleable.SegmentedControlOption_lineColor, 0);
        linePaint = new Paint();
        linePaint.Color = lineColor;

        lineHeightUnselected = a.GetDimensionPixelSize(Resource.Styleable.SegmentedControlOption_lineHeightUnselected, 0);
        lineHeightSelected = a.GetDimensionPixelSize(Resource.Styleable.SegmentedControlOption_lineHeightSelected, 0);

        a.Recycle();
    }

    protected override void OnDraw(Canvas canvas)
    {
        base.OnDraw(canvas);

        if (linePaint.Color != 0 && (lineHeightSelected > 0 || lineHeightUnselected > 0))
        {
            var lineHeight = Checked ? lineHeightSelected : lineHeightUnselected;

            if (lineHeight > 0)
            {
                var rect = new Rect(0, Height - lineHeight, Width, Height);
                canvas.DrawRect(rect, linePaint);
            }
        }
    }
}

如果有任何有关如何进行更改的建议，我将不胜感激。还有人知道 Xamarin 是否希望将其制作成表单组件吗？

Answer 1

为什么不在共享 xaml 中设置边距？

<local:SegmentedControl ValueChanged="OnValueChanged" SelectedSegment="{Binding CustomPointsSwitch}" x:Name="segControl" HorizontalOptions="End">
   <local:SegmentedControl.Children>
       <local:SegmentedControlOption Text="Two" Margin="8,0,8,0" />
       <local:SegmentedControlOption Text="Four" Margin="8,0,8,0" />
   </local:SegmentedControl.Children>
</local:SegmentedControl>