原文:
c#开发移动APP-Xamarin入门扩展
这节主要演示了如何通过添加第二个屏幕来跟踪应用程序的call历史来扩展Phoneword应用程序。最终如下:
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按如下步骤扩展Phoneword
在Phoneword项目右键新建Content Page,命名为CallHistoryPage
修改后CallHistoryPage.xaml如下：
<?xml version="1.0" encoding="UTF-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:local="clr-namespace:Phoneword;assembly=Phoneword"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="Phoneword.CallHistoryPage"
Title="Call History">
<ContentPage.Padding>
<OnPlatform x:TypeArguments="Thickness">
<On Platform="iOS" Value="20, 40, 20, 20" />
<On Platform="Android, UWP" Value="20" />
</OnPlatform>
</ContentPage.Padding>
<StackLayout>
<ListView ItemsSource="{x:Static local:App.PhoneNumbers}" />
</StackLayout>
</ContentPage>
双击Phoneword项目的App.xaml.cs文件
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添加PhoneNumbers属性的声明，在App构造函数中初始化该属性，并将MainPage属性初始化为NavigationPage。PhoneNumbers被用于存储应用程序打的每个电话号码
using System.Collections.Generic;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
[assembly: XamlCompilation(XamlCompilationOptions.Compile)]
namespace Phoneword
{
public partial class App : Application
{
public static IList<string> PhoneNumbers { get; set; }
public App()
{
InitializeComponent();
PhoneNumbers = new List<string>();
MainPage = new NavigationPage(new MainPage());
}
...
}
}
双击Phoneword项目的MainPage.xaml文件
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在StackLayout控件的末尾添加一个按钮控件，该按钮被用于导航到拨打历史页面
<StackLayout VerticalOptions="FillAndExpand"
HorizontalOptions="FillAndExpand"
Orientation="Vertical"
Spacing="15">
...
<Button x:Name="callButton" Text="Call" IsEnabled="false" Clicked="OnCall" />
<Button x:Name="callHistoryButton" Text="Call History" IsEnabled="false"
Clicked="OnCallHistory" />
</StackLayout>
打开隐藏文件MainPage.xaml.cs，添加OnCallHistory事件处理程序方法，并修改OnCall事件处理程序方法，将转换后的电话号码添加到App.PhoneNumbers集合中，并且如果dialer变量不为null时使能callHistoryButton
using System;
using Xamarin.Forms;
namespace Phoneword
{
public partial class MainPage : ContentPage
{
...
async void OnCall(object sender, EventArgs e)
{
...
if (dialer != null) {
App.PhoneNumbers.Add (translatedNumber);
callHistoryButton.IsEnabled = true;
dialer.Dial (translatedNumber);
}
...
}
async void OnCallHistory(object sender, EventArgs e)
{
await Navigation.PushAsync (new CallHistoryPage ());
}
}
}
下节剖析该扩展
