走进 Prism for Xamarin.Forms

一、使用环境

OS：Win 10 16273

VS：VS2017- 15.3.4

Xamarin：4.6.3.4，nuget：2.4

Android Emulator：Visual Studio for Android Emulator（相比 Android Emulator不用下载SDK，而且启动快）

二、安装 Prism 模块

工具——扩展和更新——搜索 Prism Template Pack——安装

三、开始搞起

1.先建个项目

2.添加页面

Views文件夹右键——添加——新建项，弹出来的对话框先选中左边的 Prism 节点

确定后，你会发现 App.xaml.cs 文件里注入了新建的页面， ViewModels 文件夹下也多出了 ViewModel ，Views 新添加的文件也是和 ViewModel 绑定好的

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage
    x:Class="SD.Xamarin.Views.LoginPage"
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    xmlns:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms"
    Title="Login"
    prism:ViewModelLocator.AutowireViewModel="True">

    <ContentPage.ToolbarItems>
        <ToolbarItem Text="Regist" />
    </ContentPage.ToolbarItems>

    <StackLayout
        Padding="20"
        Spacing="20"
        VerticalOptions="Center">

        <Entry Placeholder="Username" Text="{Binding Username}" />
        <Entry
            IsPassword="true"
            Placeholder="Password"
            Text="{Binding Password}" />

        <Button
            BackgroundColor="#77D065"
            Command="{Binding LoginCommand}"
            Text="Login"
            TextColor="White" />
    </StackLayout>

</ContentPage>

public class LoginPageViewModel : BindableBase
    {
        private readonly INavigationService _navigationService;
        private readonly IEventAggregator _eventAggregator;
        private readonly IPageDialogService _pageDialogService;


        private string _username;

        public string Username
        {
            get { return _username; }
            set
            {
                _username = value;
                RaisePropertyChanged();
            }
        }

        private string _password;

        public string Password
        {
            get { return _password; }
            set
            {
                _password = value;
                RaisePropertyChanged();
            }
        }

        private ICommand _loginCommand;

        public ICommand LoginCommand
        {
            get { return _loginCommand ?? new DelegateCommand(Login); }
            set { _loginCommand = value; }
        }

        public LoginPageViewModel(INavigationService navigationService, IEventAggregator eventAggregator, IPageDialogService pageDialogService)
        {
            _navigationService = navigationService;
            _eventAggregator = eventAggregator;
            _pageDialogService = pageDialogService;
        }

        private async void Login()
        {
            if (!string.IsNullOrEmpty(Username) && !string.IsNullOrEmpty(Password))
            {
                await _navigationService.NavigateAsync(nameof(DataCabinPage));
            }
            else
            {
                await _pageDialogService.DisplayAlertAsync("Error", "Wrong Username or Password", "OK!");
            }
        }
    }

3.添加一个 Master 页面作为主页面

<?xml version="1.0" encoding="utf-8" ?>
<MasterDetailPage
    x:Class="SD.Xamarin.Views.MasterPage"
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    xmlns:behaviors="clr-namespace:Prism.Behaviors;assembly=Prism.Forms"
    xmlns:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms"
    xmlns:views="clr-namespace:SD.Xamarin.Views;assembly=SD.Xamarin"
    Title="Master"
    prism:ViewModelLocator.AutowireViewModel="True">

    <MasterDetailPage.Master>
        <NavigationPage Title="Required Foo" Icon="hamburger.png">
            <x:Arguments>
                <views:DataCabinPage />
            </x:Arguments>
        </NavigationPage>
    </MasterDetailPage.Master>

</MasterDetailPage>

 Master里的子页面

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage
    x:Class="SD.Xamarin.Views.DataCabinPage"
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    xmlns:behaviors="clr-namespace:Prism.Behaviors;assembly=Prism.Forms"
    xmlns:prism="clr-namespace:Prism.Mvvm;assembly=Prism.Forms"
    Title="DataCabin"
    prism:ViewModelLocator.AutowireViewModel="True">

    <ContentPage.ToolbarItems>
        <ToolbarItem Command="GoBackCommand" Text="Back" />
    </ContentPage.ToolbarItems>

    <ListView
        x:Name="listView"
        CachingStrategy="RecycleElement"
        GroupDisplayBinding="{Binding Key}"
        GroupShortNameBinding="{Binding Key}"
        IsGroupingEnabled="True"
        ItemsSource="{Binding DataCabinsGrouped}"
        SelectedItem="{Binding SelectedDataCabin}">

        <ListView.Behaviors>
            <behaviors:EventToCommandBehavior Command="{Binding ItemTappedCommand}" EventName="ItemTapped" />
        </ListView.Behaviors>

        <ListView.GroupHeaderTemplate>
            <DataTemplate>
                <ViewCell>
                    <StackLayout Orientation="Horizontal">
                        <Image Source="hamburger.png" />
                        <Label
                            FontSize="18"
                            Text="{Binding Key}"
                            TextColor="DeepSkyBlue"
                            VerticalTextAlignment="Center" />
                    </StackLayout>
                </ViewCell>
            </DataTemplate>
        </ListView.GroupHeaderTemplate>

        <ListView.ItemTemplate>
            <DataTemplate>
                <ViewCell>
                    <Label
                        Text="{Binding Name}"
                        TextColor="White"
                        VerticalTextAlignment="Center" />
                </ViewCell>
            </DataTemplate>
        </ListView.ItemTemplate>

    </ListView>

</ContentPage>

public class DataCabinPageViewModel : BindableBase
    {
        private readonly INavigationService _navigationService;
        private readonly IEventAggregator _eventAggregator;
        private readonly IPageDialogService _pageDialogService;

        private DataCabinModel _selectedDataCabin;

        public DataCabinModel SelectedDataCabin
        {
            get { return _selectedDataCabin; }
            set
            {
                _selectedDataCabin = value;
                RaisePropertyChanged();
            }
        }

        private ObservableCollection<DataCabinModel> _dataCabins;

        public ObservableCollection<DataCabinModel> DataCabins
        {
            get { return _dataCabins; }
            set
            {
                _dataCabins = value;
                RaisePropertyChanged();
            }
        }

        private ObservableCollection<GroupingModel<string, DataCabinModel>> _dataCabinsGrouped;

        public ObservableCollection<GroupingModel<string, DataCabinModel>> DataCabinsGrouped
        {
            get { return _dataCabinsGrouped; }
            set
            {
                _dataCabinsGrouped = value;
                RaisePropertyChanged();
            }
        }

        private ICommand _itemTappedCommand;

        public ICommand ItemTappedCommand
        {
            get { return _itemTappedCommand ?? new DelegateCommand(ItemTapped); }
            set { _itemTappedCommand = value; }
        }

        private ICommand _goBackCommand;

        public ICommand GoBackCommand
        {
            get { return _goBackCommand ?? new DelegateCommand(GoBack); }
            set { _goBackCommand = value; }
        }

        public DataCabinPageViewModel(INavigationService navigationService, IEventAggregator eventAggregator, IPageDialogService pageDialogService)
        {
            _navigationService = navigationService;
            _eventAggregator = eventAggregator;
            _pageDialogService = pageDialogService;

            DataCabins = new ObservableCollection<DataCabinModel>()
            {
                new DataCabinModel(){Id=1,Name = "T1",GroupName="G1",DisplayType= DataCabinType.Chart},
                new DataCabinModel(){Id=2,Name = "T2",GroupName="G1",DisplayType= DataCabinType.Grid},
                new DataCabinModel(){Id=3,Name = "T3",GroupName="G2",DisplayType= DataCabinType.Guage},
                new DataCabinModel(){Id=4,Name = "T4",GroupName="G2",DisplayType= DataCabinType.Map}
            };

            var grouped = from menuItem in DataCabins
                          orderby menuItem.Id
                          group menuItem by menuItem.GroupName into menuItemGroup
                          select new GroupingModel<string, DataCabinModel>(menuItemGroup.Key, menuItemGroup);

            DataCabinsGrouped = new ObservableCollection<GroupingModel<string, DataCabinModel>>(grouped);
        }

        private async void ItemTapped()
        {
            switch (SelectedDataCabin.DisplayType)
            {
                case DataCabinType.Chart:
                    await _navigationService.NavigateAsync("/Master/Navigation/" + nameof(ChartPage));
                    break;
                case DataCabinType.Grid:
                    await _navigationService.NavigateAsync("/Master/Navigation/" + nameof(GridPage));
                    break;
                case DataCabinType.Guage:
                    await _navigationService.NavigateAsync("/Master/Navigation/" + nameof(GuagePage));
                    break;
                case DataCabinType.Map:
                    await _navigationService.NavigateAsync("/Master/Navigation/" + nameof(MapPage));
                    break;
                default:
                    throw new ArgumentOutOfRangeException();
            }

        }

        private void GoBack()
        {
            _navigationService.NavigateAsync(nameof(DataCabinPage));
        }
    }

App.xaml

public partial class App : PrismApplication
    {
        public App(IPlatformInitializer initializer = null) 
            : base(initializer)
        { }

        protected override void OnInitialized()
        {
            InitializeComponent();

            NavigationService.NavigateAsync(nameof(LoginPage));
        }

        protected override void RegisterTypes()
        {
            Container.RegisterTypeForNavigation<NavigationPage>("Navigation");

            Container.RegisterTypeForNavigation<RegistPage>();
            Container.RegisterTypeForNavigation<LoginPage>();
            Container.RegisterTypeForNavigation<MasterPage>("Master");
            Container.RegisterTypeForNavigation<ChartPage>();
            Container.RegisterTypeForNavigation<GridPage>();
            Container.RegisterTypeForNavigation<GuagePage>();
            Container.RegisterTypeForNavigation<MapPage>();
            Container.RegisterTypeForNavigation<DataCabinPage>();
        }
    }

这是最终的 App 文件，注意其中的NavigationPage 和MasterPage 后边都加了参数，用来导航用的，因为想要汉堡包样式 

汉堡包的图片是从官方例子复制的，需要放到

Android：

IOS：直接 Resources 文件夹下

导航的写法  await _navigationService.NavigateAsync("/Master/Navigation/" + nameof(ChartPage));  这里就是App.xaml.cs 文件里注册时的那个参数，本来想把前边也写出nameof 的方式，但是发现直接失败了，就只能这样了

其他的代码都很建单，也没写什么逻辑，就不贴了，大概就是这个样子，嗯，下一步就要引入 syncfusion 的控件才行了，这样才好看，也能有很多控件用（主要是实在不知道写什么业务）

动态图

四、模拟器

工具——Visual Studio Emulator for Android 弹出的里边选择一个下载就好了，是基于Hyper-V 的，需要确定你的机器支持

窗口——其他窗口——Xamarin.Forms Previewer 也是可以预览的，但是用了Prism 后，App.xaml.cs 里的构造函数变了，然后就显示不了了~~

 

五、遇到的问题

1.F5 运行后，执行了 编译——部署，然后就停了，不能像WPF 项目一样实时Debug ，也不知道需要配置什么，这样一旦出错，就得一点点试，很不舒服

2.点击主页后跳转到子页面，再弹出汉堡包跳转第二个，再跳转第三个后 程序就崩溃了，也不知道为什么 

3.有时页面的ToolbarItem 不显示，但是放到汉堡包里的那个就显示，不知道怎么搞的，

以上问题有知道的，请多指教啊

六、总结

Xamarin 整合到VS 里后，环境配置相比刚出来时好配置好多，VS Emulator 的加入也省去了下载 Android SDK时的困难，而且还特别大，虽然VS的某些功能还是需要FQ下载。

WP已死，没必要开发，UWP 肯定是回到桌面的 UWP 开发比较好，调试和用法更好用，而且还可以查看虚拟树什么的，好方便的。

CM框架也要出4.0了，到时再试试CM

七、参考例子

Prism：https://github.com/PrismLibrary/Prism-Samples-Forms

Xamarin：https://github.com/xamarin/xamarin-forms-samples