UWP(Universal Windows Platform)介绍 — 快速上手

Tuesday, May 08, 2018

1. Xaml

1.1. XAML 简介

XAML 概述
主要用于创建可视的 UI 元素.
Xaml 的基本语法基于 XML.
声明一个 namespace 的别名:

xmlns:controls="using:Common.Controls"

使用 namespace 中声明的类:

<controls:MyControl />

可重用的资源(Resource),
x:Key

<Style x:Key="TextBlock_Style" />

控件元素的 Name,

x:Name

Xaml:

<MyControl x:Name="myControl" />

C#:

private MyControl myControl;

本地化
x:Uid

<TextBlock x:Uid="sampleText" />

1.2. 最基础的控件(Control) – TextBlock, Button

<Page x:Class="MyPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <StackPanel>
        <TextBlock Text="UWP Introduction" />
        <Button Content="UWP Introduction" Click="Button_Click" />
    </StackPanel>
</Page>

2. MVVM

MVVM 详细介绍

View <=> ViewModel <=> Model

View 尽量只包含 UI 展示的内容, View 大部分使用 Xaml 语言完成;
ViewModel 应尽量不包含业务处理逻辑, 而是通过调用 Model 里的函数完成动作;
Model 应尽量包含所有的业务数据和逻辑, 并尽量不依赖 View 和 ViewModel;

3. ViewModel 与 Model 的交互

3.1. ViewModel 操控 Model 的数据

ViewModel:

public class ViewModel
{
    private Model model;
    private ChangeA()
    {
        this.model.A = "A";
    }
}

Model:

public class Model
{
    public string A { get; set; }
    public string B { get; set; }
}

3.2. Model 通知 ViewModel – event

ViewModel:

public class ViewModel
{
private Model model;
    private ChangeA()
    {
        r.BEventArgs += this.Handler;
    }
    private void Handler(object sender, EventArgs e)
    {
        AnyActions();
    }
}

Model:

public delegate void BChangedHandler(object sender, EventArgs e);

public class Model
{
    public string A { get; set; }
    private string _B;
    public string B
    {
        get { return this._B; }
        set
        {
            this._B = value;
            if (BEventArgs != null)
            {
                BEventArgs(this, new EventArgs());
            }
        }
    }
    public event BChangedHandler BEventArgs;
}

4. View 与 ViewModel 的交互

4.1. 数据绑定

数据绑定概述
只有 DependencyProperty 可以被绑定
绑定在 Public 的 Property
谨慎重构

4.1.1. 绑定在 ViewModel

View:

<TextBlock Text={Binding SampleText} />

ViewModel:

public string SampleText { get; set; }

4.1.2. 绑定在其它 Control

View:

<TextBlock x:Name="TextBlock1" Text="SampleText" />
<Button Content="{Binding ElementName=TextBlock1, Path= Text}" />

4.1.3. 指定 DataContext

public ViewModelClass ViewModel { get; set; }

...
SpecifiedControl.DataContext = ViewModel;
...

5. (View 与 ViewModel) 实现消息通知 – INotifyPropertyChanged

当 SampleText 发生变化时, 会通知到绑定在该 property 的 DependencyProperty

public class MyControlViewModel : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        public void Notify(string propName)
        {
            if (this.PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propName));
            }
        }

        private string _sampleText;
        public string SampleText
        {
            get
            {
                return _sampleText;
            }
            set
            {
                _sampleText = value;
                Notify(nameof(SampleText));
            }
        }
    }

或者继承 ViewModelBase

public class ViewModelBase : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;

        public void Notify(string propName)
        {
            if (this.PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propName));
            }
        }
    }

6. (View 与 ViewModel) ListView 绑定到实现了消息通知的源 – ObservableCollection

ListView

在 ListView 中实现绑定到具有消息通知的 ItemSource

View:

<ListView ItemsSource="{Binding Items}">

ViewModel:

public ObservableCollection<Recording> Items { get; set; }

ObservableCollection 只在 Item 添加\移除, 整个列表刷新时才产生消息通知;
如果需要在 item Recording 的内容发生变化时通知界面, 需要由 Recording 实现 INotifyPropertyChanged.

7. (View) ListView 的 Item 模板(DataTemplate | UserControl)

7.1. DataTemplate

View:

<ListView ItemsSource="{Binding Items}">
    <ListView.ItemTemplate>
        <DataTemplate DataType="local:Recording">
            <StackPanel Orientation="Horizontal">
                <TextBlock Text="{Binding A}" />
                <TextBlock Text="{Binding B}" />
            </StackPanel>
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

ViewModel:

public ObservableCollection<RecordingViewModel> Items { get; set; }

public class RecordingViewModel : INotifyPropertyChanged
{
    ...
    Implement INotifyPropertyChanged
    ...

    private Recording _recording;

    public string A
    {
        get
        {
            return this._recording.A;
        }
        set
        {
            this._recording.A = value;
            Notify(nameof(A));
        }
    }

    public string B { get; set; } = this._recording.B;

    public RecordingViewModel (Recording recording)
    {
        this._recording = recording;
    }
}

Model:

public class Recording
{
    public string A { get; set; }
    public string B { get; set; }
    public string C { get; set; }
    ... ...
}

比较:

分离 ViewModel/Model

7.2. UserControl

7.2.1. DependencyProperty

Dependency Properties Overview
只有 DependencyProperty 能绑定到其它 property, 只有绑定能实现消息通知到 View
具有优先级

View:

<control:MyControl Text="App is on searching" IsSearching="{Binding ViewModel.IsSearching}" />

ViewModel:

public class MyControl
{
...
public static readonly DependencyProperty IsSearchingProperty =
    DependencyProperty.Register
    (
        "IsSearching", typeof(Boolean),
        typeof(MyControl), null
    );

public bool IsSearching
{
    get { return (bool)GetValue(IsSearchingProperty); }
    set { SetValue(IsSearchingProperty, value); }
}
...
}

8. (ViewModel 与 Model) 数据转换 – IValueConverter

可以使用IValueConverter来进行 ViewModel 和 Model 之间的数据转换.

public class ShowAllButtonVisibilityConverter:IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, string language)
        {
            if (value is IList)
            {
                int count = (value as IList).Count;
                if (count > 3)
                {
                    return Windows.UI.Xaml.Visibility.Visible;
                }
            }
            return Windows.UI.Xaml.Visibility.Collapsed;
        }

        public object ConvertBack(object value, Type targetType, object parameter, string language)
        {
            if (value is IList)
            {
                int count = (value as IList).Count;
                if (count > 3)
                {
                    return Windows.UI.Xaml.Visibility.Visible;
                }
            }
            return Windows.UI.Xaml.Visibility.Collapsed;
        }

9. (View) 修改 Control 的 Style

9.1. 在 Control 里定制 Style

View:

<TextBlock Foreground="Red" Text="SampleText" />

9.2. 使用统一的 Style – ResourceDictionary

View:

<Window.Resources>
    <ResourceDictionary>
        <Style TargetType="TextBlock" x:Key="ImportantText">
            <Setter Property="Foreground" Value="Red" />
        </Style>
    </ResourceDictionary>
</Window.Resources>
...
<TextBlock Text="SampleText" Style={StaticResource ImportantText} />

9.3. 使用 ThemeResource

View:

<Window.Resources>
    <ResourceDictionary>
        <ResourceDictionary.ThemeDictionaries>
            <ResourceDictionary x:Key="Light">
                <Style TargetType="TextBlock" x:Key="ImportantText">
                    <Setter Property="Foreground" Value="Red" />
                </Style>
            </ResourceDictionary>

            <ResourceDictionary x:Key="Dark">
                <Style TargetType="TextBlock" x:Key="ImportantText">
                    <Setter Property="Foreground" Value="Yellow" />
                </Style>
            </ResourceDictionary>

            <ResourceDictionary x:Key="HighContrast">
                <Style TargetType="TextBlock" x:Key="ImportantText">
                    <Setter Property="Foreground" Value="Black" />
                </Style>
            </ResourceDictionary>
        </ResourceDictionary.ThemeDictionaries>
    </ResourceDictionary>
</Window.Resources>
...
<TextBlock Text="SampleText" Style={ThemeResource ImportantText} />

10. 使用 Panel

10.1. Grid

特点:

默认 Height/Width 等于父级元素;

建议:

在 Grid 中定义子元素的布局大小;
以比例显示;

10.2. StackPanel

特点:

可以超越父元素边界;
Height 或 Width 随 Panel 内的元素变化;

建议:

灵活使用 Padding 和比例;
在父级元素给 StackPanel 的 Width 或 Height 一个值, 以防止 Control 越界;

11. (View) 自适应 UI (Adaptive UI)

使用 VisualStateManager.VisualStateGroup

<VisualStateGroup>
    <VisualState x:Name="WideLayout">
        <VisualState.StateTriggers>
            <AdaptiveTrigger x:Name="WideLayoutTrigger" MinWindowWidth="1280" />
        </VisualState.StateTriggers>
        <VisualState.Setters>
            <Setter Target="SystemUpdateSideGrid.Width" Value="800" />
            <Setter Target="SystemUpdateSideGrid.Grid.Row" Value="0" />
        </VisualState.Setters>
    </VisualState>

    <VisualState x:Name="MidLayout">
        <VisualState.StateTriggers>
            <AdaptiveTrigger x:Name="MidLayoutTrigger" MinWindowWidth="700" />
        </VisualState.StateTriggers>
        <VisualState.Setters>
            <Setter Target="SystemUpdateSideGrid.Width" Value="400" />
            <Setter Target="SystemUpdateSideGrid.Grid.Row" Value="1" />
        </VisualState.Setters>
    </VisualState>
    ...
</VisualStateGroup>

12. 布局原则

不显式设定元素的尺寸;
不使用屏幕坐标指定元素的位置;
容器内子元素共享可用的空间;
可嵌套的布局容器;

13. 本地化(Localization)

使用 x:Uid, 元素的唯一标记符

    <TextBlock x:Uid="S_TextBlock1" />

使用 Resources File

    <data name="S_TextBlock1.Text" xml:space="preserve">
        <value>Sample text</value>
    </data>

14. 命名方式

大驼峰 big camel-case: firstName

小驼峰 little camel-case: FirstName

Class: big camel-case
Property: big camel-case
Field: little camel-case with prefix “_”
Control in Xaml: little camel-case

15. 注意

谨慎重命名 ViewModel 中的 Property, 因为 Xaml 中的 Binding 名称不会跟随重构;