使用Xamarin开发移动应用示例——数独游戏（七）添加新游戏

项目代码可以从Github下载：https://github.com/zhenl/ZL.Shudu 。代码随项目进度更新。

现在我们增加添加新游戏的功能，创建一个页面，编辑初始局面，并保存到数据库。

我们首先了解一下Xamarin中页面如何跳转。首先，需要为跳转的页面增加路由，这需要在AppShell中增加下面的代码：

        public AppShell()        {            InitializeComponent();            Routing.RegisterRoute(nameof(GameEdit), typeof(GameEdit));            Routing.RegisterRoute(nameof(GameList), typeof(GameList));        }

GameEdit和GameList是两个页面，GameList中显示数据库中现有的游戏列表，GameEdit用来编辑或新建游戏。通过GameList中的新建游戏按钮或者选择列表中现有的项目，可以跳转到GameEdit。在GameEdit中可以返回到GameList。导航的代码如下：

GameList中新建游戏的代码如下：

        async void btn_NewGame_Clicked(object sender, EventArgs e)        {            await Shell.Current.GoToAsync($"{nameof(GameEdit)}?{nameof(GameEdit.ItemId)}=0");        }

GameList中选中现有项目，跳转到GameEdit的代码如下：

        async void Handle_ItemTapped(object sender, ItemTappedEventArgs e)        {            if (e.Item == null)                return;            await Shell.Current.GoToAsync($"{nameof(GameEdit)}?{nameof(GameEdit.ItemId)}={e.Item}");        }

在GameEdit中，还需要定义接收传入的参数，这里传入的参数是ItemId，在GameEdit的声明中使用QueryProperty标记声明传入参数:

    [QueryProperty(nameof(ItemId), nameof(ItemId))]    [XamlCompilation(XamlCompilationOptions.Compile)]    public partial class GameEdit : ContentPage

在接收ItemId时，从数据库中读取相应的记录并初始化页面:

        public string ItemId        {            get            {                return currentId.ToString();            }            set            {                currentId = int.Parse( value);                if (currentId > 0)                {                    var game = App.Database.GetGameAsync(currentId).Result;                    if(game != null) EditGame(game);                }                            }        }

下面是GameList和GameEdit的完整代码。

GameList页面代码：

<?xml version="1.0" encoding="utf-8" ?><ContentPage xmlns="http://xamarin.com/schemas/2014/forms"             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:d="http://xamarin.com/schemas/2014/forms" xmlns:d1="http://xamarin.com/schemas/2014/forms/design"             x:>    <ContentPage.Content>        <StackLayout>            <Button Text="新游戏"  Clicked="btn_NewGame_Clicked"></Button>            <ListView x:Name="MyListView"            d1:ItemsSource="{Binding Items}"            ItemTapped="Handle_ItemTapped"            CachingStrategy="RecycleElement"                   IsVisible="True">                <d:ListView.ItemsSource>                    <x:Array Type="{x:Type x:String}">                                            </x:Array>                </d:ListView.ItemsSource>            </ListView>        </StackLayout>    </ContentPage.Content></ContentPage>

GameList后台代码：

using System;using System.Collections.Generic;using System.Collections.ObjectModel;using System.Linq;using System.Text;using System.Threading.Tasks;using Xamarin.Forms;using Xamarin.Forms.Xaml;namespace ZL.Shudu.Views{    [XamlCompilation(XamlCompilationOptions.Compile)]    public partial class GameList : ContentPage    {        public ObservableCollection<string> Items { get; set; }        public GameList()        {            InitializeComponent();                   }        protected override async void OnAppearing()        {            await RefreshList();        }        public async Task RefreshList()        {            Items = await GetItems();            MyListView.ItemsSource = Items;            MyListView.IsVisible = true;        }        public async Task<ObservableCollection<string>> GetItems()        {            var items = new ObservableCollection<string>();            var lst = await App.Database.GetGamesAsync();            foreach (var obj in lst)            {                items.Add(obj.ID.ToString());            }            return items;        }        async void Handle_ItemTapped(object sender, ItemTappedEventArgs e)        {            if (e.Item == null)                return;            await Shell.Current.GoToAsync($"{nameof(GameEdit)}?{nameof(GameEdit.ItemId)}={e.Item}");        }        async void btn_NewGame_Clicked(object sender, EventArgs e)        {            await Shell.Current.GoToAsync($"{nameof(GameEdit)}?{nameof(GameEdit.ItemId)}=0");        }    }}

GameEdit页面代码：

<?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:>    <ContentPage.Content>        <StackLayout>            <Grid x:Name="myGrid" IsVisible="True" >                <Grid.ColumnDefinitions>                    <ColumnDefinition Width="*" />                    <ColumnDefinition Width="*" />                    <ColumnDefinition Width="*" />                    <ColumnDefinition Width="*" />                    <ColumnDefinition Width="*" />                    <ColumnDefinition Width="*" />                    <ColumnDefinition Width="*" />                    <ColumnDefinition Width="*" />                    <ColumnDefinition Width="*" />                </Grid.ColumnDefinitions>                <Grid.RowDefinitions>                    <RowDefinition Height="25"  />                    <RowDefinition Height="25" />                    <RowDefinition Height="25" />                    <RowDefinition Height="25" />                    <RowDefinition Height="25" />                    <RowDefinition Height="25" />                    <RowDefinition Height="25" />                    <RowDefinition Height="25" />                    <RowDefinition Height="25" />                    <RowDefinition Height="40" x:Name="rowButton" />                    <RowDefinition Height="40" x:Name="rowResult" />                </Grid.RowDefinitions>                        <Button Text="保存" Grid.Row="9" Grid.Column="2"  Grid.ColumnSpan="2" Clicked="btn_Save_Clicked"></Button>                <Button Text="删除" x:Name="btn_Delete" Grid.Row="9" Grid.Column="4"  Grid.ColumnSpan="2" Clicked="btn_Delete_Clicked"></Button>                <Button Text="返回" Grid.Row="9" Grid.Column="6"  Grid.ColumnSpan="2" Clicked="btn_Back_Clicked"></Button>                <Label x:Name="lbMessage" Grid.Row="10" Grid.Column="5" Grid.ColumnSpan="4" Text="" IsVisible="False"></Label>            </Grid>            <Grid x:Name="grdNumber" IsVisible="false">                <Grid.ColumnDefinitions>                    <ColumnDefinition Width="*" />                    <ColumnDefinition Width="*" />                    <ColumnDefinition Width="*" />                    <ColumnDefinition Width="*" />                    <ColumnDefinition Width="*" />                </Grid.ColumnDefinitions>                <Grid.RowDefinitions>                    <RowDefinition Height="*" />                    <RowDefinition Height="*" />                </Grid.RowDefinitions>            </Grid>        </StackLayout>    </ContentPage.Content></ContentPage>

GameEdit后台代码：

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;using Xamarin.Forms;using Xamarin.Forms.Xaml;using ZL.Shudu.Services;namespace ZL.Shudu.Views{    [QueryProperty(nameof(ItemId), nameof(ItemId))]    [XamlCompilation(XamlCompilationOptions.Compile)]    public partial class GameEdit : ContentPage    {        private bool IsSaved=false;        private int currentId = 0;        private static int[,] chess = new int[9, 9];        private Button[,] buttons = new Button[9, 9];        private Button[,] numbuttons = new Button[2, 5];        private Button currentButton;        private Button currentNumBtn;        public string ItemId        {            get            {                return currentId.ToString();            }            set            {                currentId = int.Parse( value);                if (currentId > 0)                {                    var game = App.Database.GetGameAsync(currentId).Result;                    if(game != null) EditGame(game);                }                            }        }        public GameEdit()        {            InitializeComponent();            SetLayout();            SetNumButtons();        }        internal void EditGame(InputGameInfo game)        {            currentId = game.ID;            for (var i = 0; i < 9; i++)                for (var j = 0; j < 9; j++)                {                    chess[i, j] = int.Parse(game.Sudoku.Substring(i * 9 + j, 1));                    buttons[i, j].Text = chess[i, j] > 0 ? chess[i, j].ToString() : "";                    buttons[i, j].IsEnabled = true;                }        }        private void SetNumButtons()        {            var num = 1;            for (var i = 0; i < 2; i++)            {                for (var j = 0; j < 5; j++)                {                    var btn = new Button();                    if (num == 10)                    {                        btn.Text = "清除";                        btn.Clicked += Clear_Clicked;                        btn.FontSize = 15;                    }                    else                    {                        btn.Text = num.ToString();                        btn.Clicked += Num_Clicked;                        btn.FontSize = 16;                    }                    btn.Padding = 0;                    grdNumber.Children.Add(btn, j, i);                    numbuttons[i, j] = btn;                    num++;                }            }        }        private void SetLayout()        {            for (var i = 0; i < 9; i++)            {                for (var j = 0; j < 9; j++)                {                    int m = i / 3;                    int n = j / 3;                    var btn = new Button();                    var c = new Color(0.9, 0.9, 0.9);                    if ((m + n) % 2 == 0)                    {                        c = new Color(0.7, 0.7, 0.7);                    }                    btn.BackgroundColor = c;                    btn.Padding = 0;                    btn.Margin = 0;                    btn.FontSize = 20;                    myGrid.Children.Add(btn, i, j);                    btn.Clicked += Btn_Clicked;                    buttons[i, j] = btn;                }            }        }        private async void btn_Save_Clicked(object sender, EventArgs e)        {            var str = "";            for (var i = 0; i < 9; i++)                for (var j = 0; j < 9; j++)                {                    if (string.IsNullOrEmpty(buttons[i, j].Text))                        chess[i, j] = 0;                    else                        chess[i, j] = int.Parse(buttons[i, j].Text);                    str += chess[i, j].ToString();                }            var newgame = new InputGameInfo            {                Sudoku = str,                InputDate = DateTime.Now            };            if (currentId > 0)            {                newgame.ID = currentId;                await App.Database.UpdateGameAsync(newgame);            }            else            {                currentId = await App.Database.SaveGameAsync(newgame);            }            lbMessage.Text = "保存成功";            lbMessage.IsVisible = true;        }        private void btn_New_Clicked(object sender, EventArgs e)        {            lbMessage.Text = "";            currentId = 0;            for (var i = 0; i < 9; i++)                for (var j = 0; j < 9; j++)                {                    buttons[i, j].Text = "";                    buttons[i, j].IsEnabled = true;                    chess[i, j] = 0;                }        }        private void Btn_Clicked(object sender, EventArgs e)        {            currentButton = sender as Button;            rowResult.Height = 1;            rowButton.Height = 1;            grdNumber.IsVisible = true;        }        private async void btn_Delete_Clicked(object sender, EventArgs e)        {            if (currentId > 0)            {                await App.Database.DeleteGameAsync(new InputGameInfo { ID = currentId });                await Shell.Current.GoToAsync($"///{nameof(GameList)}");            }        }        private void Num_Clicked(object sender, EventArgs e)        {            currentNumBtn = sender as Button;            int x = -1, y = -1;            for (var i = 0; i < 9; i++)            {                for (var j = 0; j < 9; j++)                {                    if (buttons[i, j] == currentButton)                    {                        x = i;                        y = j;                        break;                    }                }            }            var num = int.Parse(currentNumBtn.Text);            currentButton.Text = currentNumBtn.Text;            myGrid.IsVisible = true;            grdNumber.IsVisible = false;            rowResult.Height = 40;            rowButton.Height = 40;                    }        private void Clear_Clicked(object sender, EventArgs e)        {            if (currentButton == null) return;            currentButton.Text = "";            grdNumber.IsVisible = false;            myGrid.IsVisible = true;            rowResult.Height = 40;            rowButton.Height = 40;        }        private async void btn_Back_Clicked(object sender, EventArgs e)        {                        await Shell.Current.GoToAsync($"///{nameof(GameList)}");        }    }}

编辑功能完成了，但还有一个问题，如果输入的游戏无法完成怎么办？这需要增加判断游戏是否可以完成的逻辑，如果无法完成，需要将UsedInGame属性设置为false，避免无效游戏。

在输入新的游戏时，我们需要确保输入的游戏合法并且能够完成，在输入过程中，可能需要随时检查合法性，在保存之前，需要确保游戏合法且可完成，然后才能保存。验证的方法就是使用计算机算法完成数独游戏，如果可以完成，就是合法的，否则就需要修改。相关的算法已经封装在程序包中，实现细节在这里不做讨论，将来会作为独立的文章详细介绍实现过程。可以使用Nuget程序包管理器进行安装：ZL.Sudoku.Lib。使用方法如下：

                var comp = new FindOneSolution(cinp);                var res = comp.Comp();                var fchess = comp.Matrix;

上面算法中，cinp是输入的数独数组，使用Comp方法进行计算，如果res=2，说明计算完成，输出的结果使用Matrix属性获得，也是一个二维数组。如果res=1，说明无法完成，如果是其它值说明输入有错误。

安装完这个程序包后，我们可以改造GameEdit页面。首先增加一个按钮，用来在输入过程中验证是否合法和能够完成。

                <Button Text="检查" x:Name="btn_Check" Grid.Row="9" Grid.Column="0"  Grid.ColumnSpan="2" Clicked="btn_Check_Clicked"></Button>                <Button Text="保存" Grid.Row="9" Grid.Column="2"  Grid.ColumnSpan="2" Clicked="btn_Save_Clicked"></Button>                <Button Text="删除" x:Name="btn_Delete" Grid.Row="9" Grid.Column="4"  Grid.ColumnSpan="2" Clicked="btn_Delete_Clicked"></Button>                <Button Text="返回" Grid.Row="9" Grid.Column="6"  Grid.ColumnSpan="2" Clicked="btn_Back_Clicked"></Button>

后台代码：

      private void btn_Check_Clicked(object sender, EventArgs e)        {            if (btn_Check.Text == "检查")            {                var cinp = getChess();                lastinput = cinp;                var comp = new FindOneSolution(cinp);                var res = comp.Comp();                var fchess = comp.Matrix;                for (var i = 0; i < 9; i++)                {                    for (var j = 0; j < 9; j++)                    {                        var btn = buttons[i, j];                        if (cinp[i, j] > 0)                        {                            btn.Text = cinp[i, j].ToString();                        }                        else                        {                            btn.Text = fchess[i, j] > 0 ? fchess[i, j].ToString() : "";                        }                    }                }                if (res == 0) lbMessage.Text = "不合法";                else if (res == 1) lbMessage.Text = "计算不出来";                else if (res == 2) lbMessage.Text = "计算完成";                else lbMessage.Text = "其它错误";                btn_Check.Text = "继续";            }            else            {                lbMessage.Text = "";                btn_Check.Text = "检查";                for (var i = 0; i < 9; i++)                {                    for (var j = 0; j < 9; j++)                    {                        var btn = buttons[i, j];                        if (lastinput[i, j] > 0)                        {                            btn.Text = lastinput[i, j].ToString();                        }                        else                        {                            btn.Text ="";                        }                    }                }            }        }        private int[,] getChess()        {            var res = new int[9, 9];            for (var i = 0; i < 9; i++)            {                for (var j = 0; j < 9; j++)                {                    var btn = buttons[i, j];                    if(string.IsNullOrEmpty(btn.Text)) res[i,j]= 0;                    else res[i, j]=int.Parse(btn.Text);                }            }            return res;        }

在保存前，也需要进行检查，如果不合法或者无法完成，就提示继续编辑，不能保存：

       private async void btn_Save_Clicked(object sender, EventArgs e)        {            if(btn_Check.Text=="继续") btn_Check_Clicked(null,null);            var str = "";            var chess = getChess();            for (var i = 0; i < 9; i++)                for (var j = 0; j < 9; j++)                {                  str +=  chess[i, j].ToString();                }            var comp = new FindOneSolution(chess);            var res = comp.Comp();            if(res != 2)            {                lbMessage.Text = "不合法或者无法完成的游戏，请修改后保存";                return;            }            var newgame = new InputGameInfo            {                Sudoku = str,                InputDate = DateTime.Now,                UsedInGame = true            };            if (currentId > 0)            {                newgame.ID = currentId;                await App.Database.UpdateGameAsync(newgame);            }            else            {                currentId = await App.Database.SaveGameAsync(newgame);            }            lbMessage.Text = "保存成功";        }

到此，我们的数独游戏基本完成。下一步的工作是增加完成历史列表页面，让玩家查看已经完成的历史，并且能够复盘。