RelativeLayout

使用 Constraints 佈局其子女的 Layout。

RelativeLayout 用於相對於佈局或兄弟檢視的屬性定位和調整檢視。與 AbsoluteLayout 不同，RelativeLayout 沒有移動錨的概念，並且沒有相對於佈局的底邊或右邊定位元素的設施。RelativeLayout 確實支援其自身邊界之外的定位元素。

XAML 中的 RelativeLayout，如下所示：

<RelativeLayout>
    <BoxView Color="Red" x:Name="redBox"
        RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent,
            Property=Height,Factor=.15,Constant=0}"
        RelativeLayout.WidthConstraint="{ConstraintExpression
            Type=RelativeToParent,Property=Width,Factor=1,Constant=0}"
        RelativeLayout.HeightConstraint="{ConstraintExpression
            Type=RelativeToParent,Property=Height,Factor=.8,Constant=0}" />
    <BoxView Color="Blue"
        RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToView,
            ElementName=redBox,Property=Y,Factor=1,Constant=20}"
        RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToView,
            ElementName=redBox,Property=X,Factor=1,Constant=20}"
        RelativeLayout.WidthConstraint="{ConstraintExpression
            Type=RelativeToParent,Property=Width,Factor=.5,Constant=0}"
        RelativeLayout.HeightConstraint="{ConstraintExpression
            Type=RelativeToParent,Property=Height,Factor=.5,Constant=0}" />
</RelativeLayout>

使用此程式碼可以完成相同的佈局：

layout.Children.Add (redBox, Constraint.RelativeToParent ((parent) => {
        return parent.X;
    }), Constraint.RelativeToParent ((parent) => {
        return parent.Y * .15;
    }), Constraint.RelativeToParent((parent) => {
        return parent.Width;
    }), Constraint.RelativeToParent((parent) => {
        return parent.Height * .8;
    }));
layout.Children.Add (blueBox, Constraint.RelativeToView (redBox, (Parent, sibling) => {
        return sibling.X + 20;
    }), Constraint.RelativeToView (blueBox, (parent, sibling) => {
        return sibling.Y + 20;
    }), Constraint.RelativeToParent((parent) => {
        return parent.Width * .5;
    }), Constraint.RelativeToParent((parent) => {
        return parent.Height * .5;
    }));