Is There a Custom Url Scheme for the Built-In Contacts App

Is there a custom URL scheme for the built-in Contacts app?

If there were a public URL scheme, Apple would have documented it in the URL Scheme Reference.

Your options are:

ABNewPersonViewController or ABUnknownPersonViewController
Direct modification of the address book. (archived link)

WP8 Contact Store Launch App

Afaik it's not possible yet. We cannot launch app from people hub.

Windows Phone 8 Custom Contact Store & Extended Properties

URL scheme to call the Microsoft Edge App?

I try with microsoft-edge:some website and it works. I test the following page in Firefox on Android and it can open Microsoft Edge when I click the link:

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title></title>
</head>
<body>
    <a href="microsoft-edge:https://www.google.com">link</a>
</body>
</html>

android custom url scheme..?

I think the problem is with the Action you defined.
There is a "android.intent.action.VIEW" which is what I think you want.

<activity android:name=".Gallery1" android:label="@string/app_name" android:launchMode="singleTask" android:screenOrientation="portrait">
        <intent-filter>
            <action android:name="android.intent.action.VIEW" />
            <category android:name="android.intent.category.DEFAULT" />
            <category android:name="android.intent.category.BROWSABLE" />
            <data android:scheme="cedemo" android:host="com.cedemo.scan" />

        </intent-filter>
</activity>

Try that and I bet will resolve correctly. I only made this assumption because you included the browsable category which is usually used by the Browser, which does not know of any of your custom actions. If you do want the GALLERY action as you have implied then just create 2 filters

<activity android:name=".Gallery1" android:label="@string/app_name" android:launchMode="singleTask" android:screenOrientation="portrait">
        <intent-filter>
            <action android:name="android.intent.action.GALLERY" />
            <category android:name="android.intent.category.DEFAULT" />
            <category android:name="android.intent.category.BROWSABLE" />
            <data android:scheme="cedemo" android:host="com.cedemo.scan" />

        </intent-filter>
        <intent-filter>
            <action android:name="android.intent.action.VIEW" />
            <category android:name="android.intent.category.DEFAULT" />
            <category android:name="android.intent.category.BROWSABLE" />
            <data android:scheme="cedemo" android:host="com.cedemo.scan" />

        </intent-filter>
</activity>

So within the contents of your activity you can do something like:

// Value should be "toto" as in your example
String value = getData().getQueryParameter("X");

Is There a Custom Url Scheme for the Built-In Contacts App