Xamarin.Forms 动态布局取决于屏幕方向或大小

Question

Xamarin.Forms 是否已经包含一个控件/布局，它根据屏幕方向或大小对其内容进行排序？

我想要的：如果屏幕有足够的空间，两个堆栈布局是水平排列的。 当屏幕发生变化时，屏幕没有足够的水平空间，两个堆栈布局应该垂直排列。

我不想在后面的代码中这样做。

我搜索仅使用 xaml 的解决方案。

Answer 1

我猜你不能只使用 XAML 来实现这一点。 当然，您将需要一些 c# 代码。 Xamarin.Forms 上的 XAML 设计为响应式的，您通常以相对模式（而不是绝对模式）定义视图属性。

您可以在本主题中看到您想要的行为示例，我们可以看到屏幕根据设备方向更改 StackLayout 的方向（您可以将其用作编写自己的布局组件的指南）

纵向模式下的屏幕：

横向模式下的屏幕：

这是通过以下 XAML 完成的：

<?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="ResponsiveLayout.StackLayoutPageXaml"
Title="Stack Photo Editor - XAML">
    <ContentPage.Content>
        <StackLayout Spacing="10" Padding="5" Orientation="Vertical"
        x:Name="outerStack"> <!-- can change orientation to make responsive -->
            <ScrollView>
                <StackLayout Spacing="5" HorizontalOptions="FillAndExpand"
                    WidthRequest="1000">
                    <StackLayout Orientation="Horizontal">
                        <Label Text="Name: " WidthRequest="75"
                            HorizontalOptions="Start" />
                        <Entry Text="deer.jpg"
                            HorizontalOptions="FillAndExpand" />
                    </StackLayout>
                    <StackLayout Orientation="Horizontal">
                        <Label Text="Date: " WidthRequest="75"
                            HorizontalOptions="Start" />
                        <Entry Text="07/05/2015"
                            HorizontalOptions="FillAndExpand" />
                    </StackLayout>
                    <StackLayout Orientation="Horizontal">
                        <Label Text="Tags:" WidthRequest="75"
                            HorizontalOptions="Start" />
                        <Entry Text="deer, tiger"
                            HorizontalOptions="FillAndExpand" />
                    </StackLayout>
                    <StackLayout Orientation="Horizontal">
                        <Button Text="Save" HorizontalOptions="FillAndExpand" />
                    </StackLayout>
                </StackLayout>
            </ScrollView>
            <Image  Source="deer.jpg" />
        </StackLayout>
    </ContentPage.Content>
</ContentPage>

一些 C# 用于根据设备的方向更改 outerStack 的方向：

protected override void OnSizeAllocated (double width, double height){
    base.OnSizeAllocated (width, height);
    if (width != this.width || height != this.height) {
        this.width = width;
        this.height = height;
        if (width > height) {
            outerStack.Orientation = StackOrientation.Horizontal;
        } else {
            outerStack.Orientation = StackOrientation.Vertical;
        }
    }
}

我希望它对你有帮助。

Answer 2

据我所知，这是不可能的。 我基本上做了你想要的“手动”。 不过，这并不太难。 首先，您必须将堆栈布局包装在另一个StackLayout中

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="App.Views.TestPage">
    <ContentPage.Content>
        <StackLayout x:Name="OuterStackLayout">
            <StackLayout>
                <!-- Inner stack layout 1 -->
            </StackLayout>
            <StackLayout>
                <!-- Inner stack layout 2 -->
            </StackLayout>
        </StackLayout>
    </ContentPage.Content>
</ContentPage>

接下来，您必须覆盖OnSizeAllocated并根据您的屏幕方向设置外部OuterStackLayout.Orientation

protected override void OnSizeAllocated(double width, double height)
{
    base.OnSizeAllocated(width, height);

    if (SizeHasChanged(width, height)) // elided, just compare width, height with the stored values
    {
        StoreSize(width, height); // store in private members

        if (IsLandscape)
        {
            this.OuterStackLayout.Orientation = StackOrientation.Horizontal;
        }
        else
        {
            this.OuterStackLayout.Orientation = StackOrientation.Vertical;
        }
    }
}

public bool IsLandscape => _width > _height;

也许您将不得不摆弄内部StackLayout的水平选项或其他布局参数，但基本上应该这样做。

Answer 3

选项 #1 '方向状态' - 纵向和横向。 在视觉状态管理器中使用“OrientationStates”，如下所示：

内部 .XAML 文件

<Grid x:Name="myGrid"
        Margin="10,30,10,10">
    <VisualStateManager.VisualStateGroups>
        <VisualStateGroup x:Name="OrientationStates">

            <!-- Row & Column Definitions of Grid - [2 Rows, 1 Col = Portrait] & [1 Row, 2 Cols = Landscape] -->
            <VisualState x:Name="Portrait">
                <VisualState.Setters>
                    <Setter Property="Grid.RowDefinitions"
                            Value="*,*" />
                    <Setter Property="Grid.ColumnDefinitions"
                            Value="*" />
                </VisualState.Setters>
            </VisualState>

            <VisualState x:Name="Landscape">
                <VisualState.Setters>
                    <Setter Property="Grid.RowDefinitions"
                            Value="*" />
                    <Setter Property="Grid.ColumnDefinitions"
                            Value="*,*" />
                </VisualState.Setters>
            </VisualState>

        </VisualStateGroup>
    </VisualStateManager.VisualStateGroups>

    <!-- Change position of stack layouts in grid, to match above stated orientation requirement -->
    <StackLayout x:Name="firstStackLayout">
        <Entry Placeholder="Enter first words" />
        <Button Text="Nothing Happens" />

        <VisualStateManager.VisualStateGroups>
            <VisualStateGroup>

                <VisualState x:Name="Portrait">
                    <VisualState.Setters>
                        <Setter Property="Grid.Row" Value="0" />
                        <Setter Property="Grid.Column" Value="0" />
                    </VisualState.Setters>
                </VisualState>

                <VisualState x:Name="Landscape">
                    <VisualState.Setters>
                        <Setter Property="Grid.Row" Value="0" />
                        <Setter Property="Grid.Column" Value="0" />
                    </VisualState.Setters>
                </VisualState>

            </VisualStateGroup>
        </VisualStateManager.VisualStateGroups>
    </StackLayout>

    <StackLayout x:Name="secondStackLayout">
        <Entry Placeholder="Enter last words" />
        <Button Text="Still Nothing Happens" />

        <VisualStateManager.VisualStateGroups>
            <VisualStateGroup>

                <VisualState x:Name="Portrait">
                    <VisualState.Setters>
                        <Setter Property="Grid.Row" Value="1" />
                        <Setter Property="Grid.Column" Value="0" />
                    </VisualState.Setters>
                </VisualState>

                <VisualState x:Name="Landscape">
                    <VisualState.Setters>
                        <Setter Property="Grid.Row" Value="0" />
                        <Setter Property="Grid.Column" Value="1" />
                    </VisualState.Setters>
                </VisualState>

            </VisualStateGroup>
        </VisualStateManager.VisualStateGroups>
    </StackLayout>
</Grid>

在 CodeBehind 中添加了“OnSizeAllocated()”函数，如下所示：

内部 .XAML.CS 文件

public partial class RegisterPage : ContentPage
{
    public RegisterPage()
    {
        InitializeComponent();
    }

    protected override void OnSizeAllocated(double width, double height)
    {
        base.OnSizeAllocated(width, height);

        var state = (width > height) ? "Landscape" : "Portrait";

        // Call the 'Portrait' & 'Landscape' States in .XAML File
        VisualStateManager.GoToState(myGrid, state);
        VisualStateManager.GoToState(firstStackLayout, state);
        VisualStateManager.GoToState(secondStackLayout, state);
    }
}

[或者]

选项 #2 灵丹妙药 - 您唯一的 .XAML 文件解决方案。

“方向触发器” - 纵向和横向。

在 Visual State 的“状态触发器”中使用“OrientationStateTriggers”，如下所示：

内部 .XAML 文件

<Grid Margin="10,30,10,10">
    <VisualStateManager.VisualStateGroups>
        <VisualStateGroup>

            <!-- Row & Column Definitions of Grid - [2 Rows, 1 Col = Portrait] & [1 Row, 2 Cols = Landscape] -->
            <VisualState x:Name="gridPortrait">

                <VisualState.StateTriggers>
                    <OrientationStateTrigger Orientation="Portrait" />
                </VisualState.StateTriggers>

                <VisualState.Setters>
                    <Setter Property="Grid.RowDefinitions"
                            Value="*,*" />
                    <Setter Property="Grid.ColumnDefinitions" Value="*" />
                </VisualState.Setters>

            </VisualState>

            <VisualState x:Name="gridLandscape">

                <VisualState.StateTriggers>
                    <OrientationStateTrigger Orientation="Landscape" />
                </VisualState.StateTriggers>

                <VisualState.Setters>
                    <Setter Property="Grid.RowDefinitions"
                            Value="*" />
                    <Setter Property="Grid.ColumnDefinitions"
                            Value="*,*" />
                </VisualState.Setters>

            </VisualState>

        </VisualStateGroup>
    </VisualStateManager.VisualStateGroups>

    <!-- Change position of stack layouts in grid, to match above stated orientation requirement -->
    <StackLayout>
        <Entry Placeholder="Enter first words" />
        <Button Text="Nothing Happens" />

        <VisualStateManager.VisualStateGroups>
            <VisualStateGroup>

                <VisualState x:Name="myPortraitState">

                    <VisualState.StateTriggers>
                        <OrientationStateTrigger Orientation="Portrait" />
                    </VisualState.StateTriggers>

                    <VisualState.Setters>
                        <Setter Property="Grid.Row" Value="0" />
                        <Setter Property="Grid.Column" Value="0" />
                    </VisualState.Setters>

                </VisualState>

                <VisualState x:Name="myLandscapeState">

                    <VisualState.StateTriggers>
                        <OrientationStateTrigger Orientation="Landscape" />
                    </VisualState.StateTriggers>

                    <VisualState.Setters>
                        <Setter Property="Grid.Row" Value="0" />
                        <Setter Property="Grid.Column" Value="0" />
                    </VisualState.Setters>

                </VisualState>

            </VisualStateGroup>
        </VisualStateManager.VisualStateGroups>
    </StackLayout>

    <StackLayout>
        <Entry Placeholder="Enter last words" />
        <Button Text="Still Nothing Happens" />

        <VisualStateManager.VisualStateGroups>
            <VisualStateGroup>
                <VisualState x:Name="myPortraitState">
                    <VisualState.StateTriggers>
                        <OrientationStateTrigger Orientation="Portrait" />
                    </VisualState.StateTriggers>
                    <VisualState.Setters>
                        <Setter Property="Grid.Row" Value="1" />
                        <Setter Property="Grid.Column" Value="0" />
                    </VisualState.Setters>
                </VisualState>
                <VisualState x:Name="myLandscapeState">
                    <VisualState.StateTriggers>
                        <OrientationStateTrigger Orientation="Landscape" />
                    </VisualState.StateTriggers>
                    <VisualState.Setters>
                        <Setter Property="Grid.Row" Value="0" />
                        <Setter Property="Grid.Column" Value="1" />
                    </VisualState.Setters>
                </VisualState>

            </VisualStateGroup>
        </VisualStateManager.VisualStateGroups>
    </StackLayout>
</Grid>