SingleTask activity, but opened through two different applications

Question

This image was quite helpful for understanding the functionality offered by the launhmode singleTask, taken from here

however, I understood this in case of the same application, I am having issues understanding what if both tasks belong to two different Applications

Confusing Scenario(fictional),

• I was going through an app and the app offered an action to send emails, I selected 'send email' option.
• My phone's default 'email app' will be picked and its activity (which is declared as singletask) will be opened.

• While I was typing my email content, I switched to some chat app and the app gets crashed and offered me an option to report an issue over email to the developer, Now when I will select 'Report' , my email app(which is the same default email app ) will be opened.

• Now as the Email app's root activity is singletask, will my content which I wrote will be visible to me?

The main thing is this time, the tasks/stacks belong to two different apps.

Answer 1

Even though you are using 2 different applications, it will work in the expected way:

• if your singleTask activity already exists, that copy will be used, with the method onNewIntent() being called
• if it does not exist, it will be launched as per normal

More technically, reproducing the definition from your link:

The system creates a new task and instantiates the activity at the root of the new task. However, if an instance of the activity already exists in a separate task, the system routes the intent to the existing instance through a call to its onNewIntent() method, rather than creating a new instance. Only one instance of the activity can exist at a time.

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This can easily be verified by making an activity a target for sharing text and singleTask in the manifest:

    <activity
        android:name=".MainActivity"
        android:launchMode="singleTask">
        <intent-filter>
            <action android:name="android.intent.action.SEND" />
            <category android:name="android.intent.category.DEFAULT" />
            <data android:mimeType="text/plain" />
        </intent-filter>
        <intent-filter>
            <action android:name="android.intent.action.SEND_MULTIPLE" />
            <category android:name="android.intent.category.DEFAULT" />
            <data android:mimeType="image/*" />
        </intent-filter>
    </activity>

Now add some logging to the onCreate() and onNewIntent() methods and do some scenario testing.

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Something I found particularly useful when testing the various launchmodes is the following ADB command:

• adb dumpsys activity activities

This outputs a lot of text (it may help to reboot the phone before doing this - adb reboot) showing details of the activity task stacks. This can be used to show you that your singleTask activity "rehomes" itself as it gets launched via different applications.

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As for the question about the emails, I think that will depend on which email client you are using, but I would hope that they handle the onNewIntent() method correctly, and save the current draft before displaying your new email.