android - Replacing in call app

Question

Background

I'm trying to develop a really simple in call app to replace the stock version. Basically, I just want to answer incoming calls and present the user with a really simple customized UI. There is no need for outgoing calls or any fancy stuff.

Searching the web I've found package android.telecom.incallservice (available in API 23). This service is implemented by any app that wishes to provide the user-interface for managing phone calls.

It seems promising but I'm having trouble getting it to work. I've created simple service extending InCallService and declared it in my manifest as described by the docs. However, I would expect to be able to change the default phone app in the settings to my own, but I can only find the stock phone app.

Code

This is the manifest declaration from the docs. I've replaced BIND_IN_CALL_SERVICE with BIND_INCALL_SERVICE since I guess this is a typo.

<service android:name="your.package.YourInCallServiceImplementation" android:permission="android.permission.BIND_INCALL_SERVICE">
    <meta-data android:name="android.telecom.IN_CALL_SERVICE_UI" android:value="true" />
    <intent-filter>
        <action android:name="android.telecom.InCallService"/>
    </intent-filter>
</service>

Questions

1. Is it even possible for third-party app to replace the default in call app?

2. Are there any sample implementations using this API out there I may use as a reference? I've found the google implementation, but this is a system app which makes use of some permissions that are not available for other apps (ex: android.permission.MODIFY_PHONE_STATE).

3. Am I correct in the assumption that after providing a correct InCallService manifest registration and a stub implementation I could expect to find my app under Default Apps -> Phone? Do I need to declare something else?

Thanks.

Answer 1

1. Is it even possible for third-party app to replace the default in call app?

Yes, starting with API 23 it is possible.

2. Are there any sample implementations using this API out there I may use as a reference? I've found the google implementation, but this is a system app which makes use of some permissions that are not available for other apps (ex: android.permission.MODIFY_PHONE_STATE).

The only one I'm aware of, is the sample I created https://github.com/arekolek/simple-phone that was already mentioned in the other answer as well.

3. Am I correct in the assumption that after providing a correct InCallService manifest registration and a stub implementation I could expect to find my app under Default Apps -> Phone? Do I need to declare something else?

Actually, no.

Like mentioned in another answer on the topic, you don't need InCallService at all to appear on that list.

What you need though, is to register an activity with two intent filters, one with a tel Uri scheme, and one with an empty scheme (having just one of them is not enough):

<intent-filter>
    <action android:name="android.intent.action.DIAL" />
    <data android:scheme="tel" />
</intent-filter>
<intent-filter>
    <action android:name="android.intent.action.DIAL" />
</intent-filter>

It is vaguely mentioned in the docs, and stated explicitly in AOSP code.

That is enough to appear on that list. Only then, to provide the UI for the call, will you actually need the InCallService.