Xamarin.Forms中DependencyService的使用

在Xamarin.Forms中，我们经常会根据各个平台的特性特殊处理一些需求，比如：读取应用的版本号。

在此也以读取应用版本号为例，练习DependencyService用法：

创建IPlatformInfoService接口：

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Text;
 4
 5 namespace XFPractice.Service
 6 {
 7     public interface IPlatformInfoService
 8     {
 9
10         /// <summary>
11         /// 获取应用版本
12         /// </summary>
13         /// <returns></returns>
14         string GetAppVersion();
15
16     }
17 }

在Android创建ImpDroidService实现IPlatformInfoService接口：

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 using System.Text;
 5
 6 using Android.App;
 7 using Android.Content;
 8 using Android.Content.PM;
 9 using Android.OS;
10 using Android.Runtime;
11 using Android.Views;
12 using Android.Widget;
13 using Xamarin.Forms;
14 using XFPractice.Service;
15
16
17 [assembly: Dependency(typeof(XFPractice.Droid.ImpService.ImpDroidService))]
18 namespace XFPractice.Droid.ImpService
19 {
20     public class ImpDroidService: IPlatformInfoService
21     {
22         public string GetAppVersion()
23         {
24             var context = Android.App.Application.Context;
25             var packageInfo = context.PackageManager.GetPackageInfo(
26                 context.PackageName, PackageInfoFlags.Configurations);
27             return packageInfo.VersionName;
28         }
29     }
30 }

在iOS创建ImpiOSService实现IPlatformInfoService接口：

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 using System.Text;
 5
 6 using Foundation;
 7 using UIKit;
 8 using Xamarin.Forms;
 9 using XFPractice.Service;
10
11
12 [assembly: Dependency(typeof(XFPractice.iOS.ImpService.ImpiOSService))]
13 namespace XFPractice.iOS.ImpService
14 {
15     public class ImpiOSService : IPlatformInfoService
16     {
17         public string GetAppVersion()
18         {
19             var version = NSBundle.MainBundle.ObjectForInfoDictionary("CFBundleVersion");
20             return version.ToString();
21         }
22     }
23 }

使用：

1  private readonly IPlatformInfoService _platformService;
2
3  _platformService = DependencyService.Get<IPlatformInfoService>();
4
5  var AppVersion = _platformService.GetAppVersion();

这样我们就能读取到App的版本了。

原文地址：https://www.cnblogs.com/devin_zhou/p/8313352.html