Deep linking loads multiple instances of app on android

[mklilley]

I am creating my app using Ionic and am testing the app on Android version 5.1.1.

I find that using the plugin does indeed allow the app to be launched when I click on a particular link which is lovely, thanks.

The issue is that if I already have the app open and then I click on a link inside of e.g. whatsapp, then a new instance of the app loads inside of whatsapp instead of using the already open app. This creates a strange user experience because in order to return to whatsapp I have to navigate backwards several times , whereas I would expect to just be able to switch from my app back to whatsapp using the familiar square button that allows you to see all open apps.

Thanks for taking to time to develop this plugin, it is very useful, I am just trying to understand if this is intended behaviour or a bug.

Thanks,

Matt

[nikDemyankov]

Thanks for the kind words :)

I don't have a whatsapp, but tried to reproduce it with the Inbox app and couldn't. What I did:

1. Created a new Ionic app.

2. In the config.xml added:

   <universal-links>
     <host name="sometest.com" scheme="https" />
   </universal-links>

3. Launched the app on the device: ionic run android --device.

4. Pressed "home" button, so it would stay alive.

5. Send myself an email with the http://sometest.com/path/ url in it.

6. Opened Inbox app and pressed on the link. As a result - application launched.

7. Pressed back button - returned to the Inbox app.

Also, can navigate back to the Inbox app by clicking on the square button.

Can you please provide a step-by-step guide on how I can try to reproduce it?

then a new instance of the app loads inside of whatsapp instead of using the already open app

Feels like whatsapp opened url link in his inner webview instead of launching your app. Especially if you can't see it in recent apps list. Android app can't launch another application inside of himself.

[mklilley]

Hi.

Thanks for getting back to me so quickly.

Yes you are right it does appear as if whatsapp is loading it as some kind of internal webview. I guess that is a separate discussion of why it does that.

If I email myself a link in the gmail app (I dont have inbox) I get different behaviour this time. The app loads as a proper app outside of gmail (not in some kind of internal webview). However, if I already have the app open it duplicates the app, so that if i look at my recent apps there are two versions of it open.

Just in case this was something strange i did for my app I did the following

1. ionic start test tabs
2. cd test
3. ionic platform add android
4. cordova plugin add cordova-universal-links-plugin
5. Added the following to config.xml after the end of </feature>

<universal-links> <host name="test.com" scheme="https"> </host> </universal-links>
6) ionic run android --device
7) hit home button
8) Go to gmail and click on a link https://test.com
9) Hit the recent apps button to show what you see in the attached image

You see there are two copies. The one that was loaded on step 6 is apparently ignored when i click on the link in gmail.

What do you think?

Thanks again,

Matt

[TonivdW]

I have also tested this and find that both Whatsapp and Gmail behave the same (Android 4.4). If I click the link then the app opens. In the open apps view, the logo of WhatsApp/Gmail is shown, but the screenshot is that of my app. So I find no difference in behavior between Gmail and WhatsApp.
(I was about to open an issue for the following, but I think it just as well fits in this issue) What I find strange/unwanted is that when I subsequently tap the WhatsApp or Gmail icon on the homescreen my app is shown. If I navigated within my app 6 pages deep, then I have to press the back button 6 times in order to get back to the app that opened it. I would like the app in which the link is clicked to spawn my app as a seperate process, instead of embedding it within the 'parent' app. Is this something Universal Links can decide, or is this an Android issue?

[nikDemyankov]

@mklilley thanks for the step-by-step guide, that helped.

After some experiments and debugging I found, that this is an Android feature, not a plugin bug. I'll explain why and how it can be changed.

At first I tried to use Inbox app. I launched my TestApp, then pressed home button, then in the Inbox app pressed the link. As a result - existing instance of the TestApp was launched, no new instance is created.

Then I used Gmail app, and suddenly it created a new instance of the TestApp. Which is strange, since application is the same, link is the same. The only thing that has changed is the app, in what the link was pressed. This means, that they are sending different types on Intents to the Android. Intent from the Inbox doesn't lead to creation of the TestApp's new instance.

To confirm that I launched the app in debug mode from the AndroidStudio and placed a break point in the MainActivity onCreate() method. It should be called every time the instance of the application is created. Then I reproduced the steps with Inbox and Gmail. As a result I saw, that for the Gmail version I get the break point hit. So yes - for some reason the Intent from this app creates new instance of the TestApp.

After looking into AndroidManifest.xml of the TestApp I found the following preference:

<activity
            android:name="MainActivity"
            android:launchMode="singleTop"
....>

From the android documentation you can find, that singleTop allows creation of several instances of the activity. And since our launching (MainActivity) is the one that get's targeted by the Intent from the other app - it can be created several times.

To prevent that from happening you can change singleTop to singleInstance. Although, in the docs:

standard is the default mode and is appropriate for most types of activities. SingleTop is also a common and useful launch mode for many types of activities. The other modes — singleTask and singleInstance — are not appropriate for most applications, since they result in an interaction model that is likely to be unfamiliar to users and is very different from most other applications.

But in the case of Ionic/Cordova apps, which consist only of one activity and all navigation is executed within the WebView - that can be fine. But make sure to test it carefully.

[nikDemyankov]

@TonivdW I think in your case the problem is the same, as I described above. This is an Android behaviour, not a plugin thing. In some way - yes, plugin can be considered as responsible for that, since it add's the feature for launching the app from the link. But it can't control what Intents it receives and if new instance of the app is created.

As an experiment, you can try to add android:allowTaskReparenting="true" to the AndroidManifest.xml:

<activity
  android:name="MainActivity"
  android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale"
  android:label="@string/activity_name"
  android:launchMode="singleInstance"
  android:allowTaskReparenting="true"
  android:theme="@android:style/Theme.Black.NoTitleBar"
  android:windowSoftInputMode="adjustResize">

[mklilley]

@nikDemyankov This works like a charm, thank you so much! It is thanks to people like you that people like me can get anywhere with making apps.

You are a star!

Matt

[nikDemyankov]

@mklilley thanks :)

[TonivdW]

@nikDemyankov My testing shows that setting allowTaskReparenting is not needed. I switched android:launchMode from the default (singleTop) to what you mentioned above (singleInstance) and that alone did the trick. The app is now started outside the context of the calling app just like it should (for my purpose)
Like @mklilley I want to thank you for writing this fantastic plugin!

[nikDemyankov]

@TonivdW Thanks :) I'll update the readme, so if someone will hit the same issue - they would know why and how to fix it. Created an issue for that so I would not forget. Leaving this one open for the newcomers, will close it when the docs are updated.

[TonivdW]

Unfortunately I encountered and issue with changing the lauchmode to singleInstance...
I also use phonegap-plugin-push to receive push notifications in my app, and when the app has singleInstance set, it will not be brought to the foreground upon receiving a notification. The app works ok, and receives and handles the notification, but stays in the background.
I have now changed it back to SingleTop and then push notifications start working again, but then Universal Links starts misbehaving again of course.
Do you think the author of phonegap-plugin-push can change something to their plugin to change this behavior?

[nikDemyankov]

Don't know, I think you should ask him... But my guess, is that it will require some experiments with PushHandleActivity or GCMIntentService.

[TonivdW]

The reason I was asking you is that the universal links plugin does manage the app to be brought to the foreground, even if the setting is singleInstance, so I was guessing your code also has to actively make that happen. Or is it the OS that is doing this? In that case the OS apparently is handling push notifications differently than universal links.
(But I will also open an issue in the push plugin queue.)