Android Browser Helper / Multi Domain Trusted Web Activities (TWA) Demo

This demo app shows how a developer can configure the TWA Launcher Activity in their Android Manifest to launch a Trusted Web Activity that supports multiple origins.

What are the use-cases?

Sometimes developers use different domains for different parts of their application. A developer could use login.example.com when users are logging in into their service or checkout.example.com in their shopping cart experience.

When using Trusted Web Activities, developers want to maintain the user in full screen when navigating across those domains.

TWAs offer this possiblity, by allowing developers to add additional trusted origins, when launching the Trusted Web Activity. All origins must be validated using Digital Asset Links.

How to enable Multi Domain TWAs

The first step to enable additional origins is the ensure that the asset_statements declaration contains all origins to be validated. Example:

    <string name="asset_statements">
    [{
        \"relation\": [\"delegate_permission/common.handle_all_urls\"],
        \"target\": {
            \"namespace\": \"web\",
            \"site\": \"https://github.com\"
        }
    }],
    [{
        \"relation\": [\"delegate_permission/common.handle_all_urls\"],
        \"target\": {
            \"namespace\": \"web\",
            \"site\": \"https://www.google.com\"
        }
    }],
    [{
        \"relation\": [\"delegate_permission/common.handle_all_urls\"],
        \"target\": {
            \"namespace\": \"web\",
            \"site\": \"https://www.wikipedia.com\"
        }
    }],
    </string>

The second step is to create a string-array, inside src/main/values/strings.xml, with containing the extra origins to be validated. Adding the origin referenced in the launch URL is not necessary:

    <string-array name="additional_trusted_origins">
        <item>https://www.google.com</item>
        <item>https://www.wikipedia.com</item>
    </string-array>

The last step to add support for multiple domains is achieved by adding an extra meta-tag to AndroidManifest.xml,, inside the activity tag for the Launcher Activity:

<activity android:name="com.google.androidbrowserhelper.trusted.LauncherActivity"
     ...
    <meta-data android:name="android.support.customtabs.trusted.ADDITIONAL_TRUSTED_ORIGINS"
        android:value="@array/additional_trusted_origins" /> 
    ...
</activity>

Finally, don't forget that each origin must have its own assetlinks file, connecting the origin to the the application. The file for each domain will look exacly the same.