c# - Xamarin Forms 相对布局不会堆叠

Question

使用以下代码:

<ScrollView Orientation="Vertical" Padding="0">
            <RelativeLayout BackgroundColor="Red" Padding="0">
                <BoxView Color="Blue" WidthRequest="100" HeightRequest="100" 
                RelativeLayout.XConstraint="{ConstraintExpression Type=Constant, Constant=0}" 
                RelativeLayout.YConstraint="{ConstraintExpression Type=Constant, Constant=0}" />
            </RelativeLayout>
            <RelativeLayout BackgroundColor="Green" Padding="0">
                <BoxView Color="Yellow" WidthRequest="100" HeightRequest="100" 
                RelativeLayout.XConstraint="{ConstraintExpression Type=Constant, Constant=0}" 
                RelativeLayout.YConstraint="{ConstraintExpression Type=Constant, Constant=0}" />
            </RelativeLayout>
        </ScrollView>

但出于某种原因，每个新的相对布局都没有堆叠，而是像这样占据了整个屏幕:

为什么它们不能垂直堆叠？堆栈布局通常只会在垂直或水平方向上采用其子元素的组合高度，但相对布局不会发生这种情况。我错过了什么？

Answer 1

试试这个布局。我在 ScrollView 中添加了 StackLayout，在 RelativeLayouts 中添加了 VerticalOptions="Start"。

<?xml version="1.0" encoding="UTF-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" x:Class="TestChat.ChatPage">
    <ContentPage.Content>
<ScrollView Orientation="Vertical" Padding="0">
    <StackLayout>
            <RelativeLayout BackgroundColor="Red" Padding="0" VerticalOptions="Start">
                <BoxView Color="Blue" WidthRequest="100" HeightRequest="100" 
                RelativeLayout.XConstraint="{ConstraintExpression Type=Constant, Constant=0}" 
                RelativeLayout.YConstraint="{ConstraintExpression Type=Constant, Constant=0}" />
            </RelativeLayout>
            <RelativeLayout BackgroundColor="Green" Padding="0" VerticalOptions="Start">
                <BoxView Color="Yellow" WidthRequest="100" HeightRequest="100" 
                RelativeLayout.XConstraint="{ConstraintExpression Type=Constant, Constant=0}" 
                RelativeLayout.YConstraint="{ConstraintExpression Type=Constant, Constant=0}" />
            </RelativeLayout>
            </StackLayout>
        </ScrollView>
    </ContentPage.Content>
</ContentPage>