コントロールを見つけるにはRelativeLayoutを使用できます。私はあなたのための例を書いて、シナリオに合わせてRelativeLayoutを編集することができます。
<RelativeLayout Margin="0,20,0,0">
<Image Source="pickerbackgroundimage.png" Aspect="AspectFit" 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}"
/>
<Picker BackgroundColor="Transparent" x:Name="picker"
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>
それは、iOSとAndroid上でこのように動作します:それは作品
感謝を:) –