android - Xamarin Forms: How to open an app from another app?

Question

I have 2 applications ( A and B ) developed using Xamarin.Forms. I need to open app A from app B.

I have tried like below as per this thread:

In the view

var appname = @"otherappId";
var result = await DependencyService.Get<IAppHandler>().LaunchApp(appname);

Interface

public interface IAppHandler
{
    Task<bool> LaunchApp(string uri);
}

Android

[Activity(Label = "OpenAppAndroid")]
public class OpenAppAndroid : Activity, IAppHandler
{
    public Task<bool> LaunchApp(string uri)
    {
        bool result = false;

        try
        {
            var aUri = Android.Net.Uri.Parse(uri.ToString());
            var intent = new Intent(Intent.ActionView, aUri);
            Xamarin.Forms.Forms.Context.StartActivity(intent);
            result = true;
        }
        catch (ActivityNotFoundException)
        {
            result = false;
        }

        return Task.FromResult(result);
    }
}

IOS

public class OpenAppiOS : IAppHandler
{
    public Task<bool> LaunchApp(string uri)
    {
        try
        {
            var canOpen = UIApplication.SharedApplication.CanOpenUrl(new NSUrl(uri));

            if (!canOpen)
                return Task.FromResult(false);

            return Task.FromResult(UIApplication.SharedApplication.OpenUrl(new NSUrl(uri)));

        }
        catch (Exception ex)
        {
            return Task.FromResult(false);
        }
    }

1. For android, I am getting System.NullReferenceException: 'Object reference not set to an instance of an object.' when running the project. I don't know what is app name in the code? I have tried with the package name.

2. Also if the android app is not installed on the device, it needs to open the Play Store to download the app.

3. I didn't test the iOS part because Mac is not available. Is the above code work for iOS? Also if the app is not installed on the iPhone, need to open the AppStore to download the app.

4. Also, I like to implement the same for UWP.

Reference: https://forums.xamarin.com/discussion/92666/detect-and-open-another-app-on-device Is it possible to open another app in my app with xamarin.form?

Answer 1

Xamarin.Forms.Forms.Context is out of date since XF 2.5 . So you could use Android.App.Application.Context instead of it or use the plugin Plugin.CurrentActivity

So you could modify the code in Android like following

using System.Threading.Tasks;
using Android.App;
using Android.Content;
using Android.Content.PM;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using App14;
using App14.Droid;
using Xamarin.Forms;

[assembly: Dependency(typeof(OpenAppAndroid))]
namespace App14.Droid
{
    public class OpenAppAndroid : IAppHandler
    {
        public Task<bool> LaunchApp(string packageName)
        {


            bool result = false;

            try
            {

                PackageManager pm = Android.App.Application.Context.PackageManager;

                if (IsAppInstalled(packageName))
                {
                    
                    Intent intent = pm.GetLaunchIntentForPackage(packageName);
                    if (intent != null)
                    {
                      
                        intent.SetFlags(ActivityFlags.NewTask);
                        Android.App.Application.Context.StartActivity(intent);
                    }
                }

                else
                {
                  
                    Intent intent = pm.GetLaunchIntentForPackage("the package name of play store on your device");
                    if (intent != null)
                    {

                        intent.SetFlags(ActivityFlags.NewTask);
                        Android.App.Application.Context.StartActivity(intent);
                    }
                }
            }
            catch (ActivityNotFoundException)
            {
                result = false;
            }

            return Task.FromResult(result);
        }


        private bool IsAppInstalled(string packageName)
        {
            PackageManager pm = Android.App.Application.Context.PackageManager;
            bool installed = false;
            try
            {
                pm.GetPackageInfo(packageName, PackageInfoFlags.Activities);
                installed = true;
            }
            catch (PackageManager.NameNotFoundException e)
            {
                installed = false;
            }

            return installed;
        }

    }
}

For iOS you could refer Launch Another IOS App from Xamarin Forms App .