我正在尝试添加带有背景图像的选取器，因此我使用了相对布局，并在相对布局内添加了图像和选取器。 我的问题是我在 IOS 环境中有一个边界，而我在 android 设备中有一个底线。 我在 Normal Entry 中遇到了这个问题并解决了，但我在选择器中使用了相同的场景但无法正常工作。

这是代码

<RelativeLayout Margin="0,0,0,0"
                                    Padding="0,0,0,0"
                                    >
                        <Image Source="input_mobile_code_brown.png"
                               x:Name="img"

                               RelativeLayout.XConstraint =
                    "{ConstraintExpression Type=RelativeToParent,
                         Property=Width,
                         Factor=0,
                         Constant=0}"
                RelativeLayout.YConstraint =
                    "{ConstraintExpression Type=RelativeToParent,
                         Property=Height,
                         Factor=0,
                         Constant=0}"
                                  RelativeLayout.WidthConstraint =
                    "{ConstraintExpression Type=RelativeToParent,

                         Property=Width,
                         Factor=1,
                         Constant=0}"
               RelativeLayout.HeightConstraint =
                    "{ConstraintExpression Type=RelativeToParent,

                         Property=Height,
                         Factor=1,
                         Constant=0}"
                               />
                        <Picker BackgroundColor="Transparent"
                                x:Name="picker" 
                                Margin="10,0,0,0"

                RelativeLayout.XConstraint =
                    "{ConstraintExpression Type=RelativeToParent,
                         Property=Width,
                         Factor=0,
                         Constant=0}"
                RelativeLayout.YConstraint =
                    "{ConstraintExpression Type=RelativeToParent,
                         Property=Height,
                         Factor=0,
                         Constant=0}"
                RelativeLayout.WidthConstraint =
                    "{ConstraintExpression Type=RelativeToView,
                         ElementName=img,
                         Property=Width,
                         Factor=1,
                         Constant=0}"
               RelativeLayout.HeightConstraint =
                    "{ConstraintExpression Type=RelativeToView,
                         ElementName=img,
                         Property=Height,
                         Factor=1,
                         Constant=0}"
            />
                    </RelativeLayout>

• 这是结果

我需要从 IOS 中删除默认边框

所以我在IOS做了一个customRenderer

protected override void OnElementChanged(ElementChangedEventArgs<Picker> e)
{
    base.OnElementChanged(e);
    var view = e.NewElement as CustomPicker;
    this.Control.BorderStyle=  UITextBorderStyle.None;
}

但在IOS中仍然没有去除边框

最佳答案

预期的答案是

<local:CustomPicker x:Name="modePicker" ...

 public class BorderlessPickerRenderer : PickerRenderer
 {
    public static void Init() { }
    protected override void OnElementChanged(ElementChangedEventArgs<Picker> e)
    {
        base.OnElementChanged(e);
        if (e.OldElement == null)
        {
            Control.Background = null;

            var layoutParams = new MarginLayoutParams(Control.LayoutParameters);
            layoutParams.SetMargins(0, 0, 0, 0);
            LayoutParameters = layoutParams;
            Control.LayoutParameters = layoutParams;
            Control.SetPadding(0, 0, 0, 0);
            SetPadding(0, 0, 0, 0);
        }
    }
}

以上渲染器适用于 Android

对于 iOS -

protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        base.OnElementPropertyChanged(sender, e);

        Control.Layer.BorderWidth = 0;
        Control.BorderStyle = UITextBorderStyle.None;
    }

对于 UWP -

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

        if (Control != null)
        {
            Control.BorderThickness = new Windows.UI.Xaml.Thickness(0);
            Control.Margin = new Windows.UI.Xaml.Thickness(0);
            Control.Padding = new Windows.UI.Xaml.Thickness(0);
        }
    }

关于ios - 如何在 IOS 中删除选择器边框，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/45704768/