Create-Deep-Links-and-Android-App-Links-to-Your-App-Content

This Tutorial will discuss how to create a deep link and prepare your app to implement the android app links feature.

This Tutorial discusses the following:

How Android System Deals with URLs ?
Create Deep Links
Test Your Deep Link
How to accomplish this using the App Links Assistant in Android Studio.
Dive in the details of each line of code so you could have the whole picture of what is going on.
How to customize the Android App Links as per your needs.

This is a part of Android App Links Series.

How Android System Deals with URLs ?

As We mentioned earlier in a previous tutorial (Deep-Links-vs-Android-App-Links), Deep links make navigation easier within your app and from external app through the use of URLs.

These URLs could be either:

a URL link that you click on from anywhere in your mobile
OR an imbedded URL called from another app (You can't see the URLs) like the Share Button in any app

In either case, Android System will deals with them similarly. Let's see how Android System deals with a URLs:

First Step: Android System will open the user's preferred app that can handle the URI, if one is designated.
Second Step: if there is no preferred app and there is Only One App could handle this URL, Android System will open this app immediately.
Third Step: if there is no preferred app and there are more than One App could handle this URL, Android System will show a dialog containing all apps that could handle this URL.

Create Deep Links ?

Step One: Add Intent Filters for Incoming Intents

As We discussed in the previous tutorial (Allow-Other-Apps-to-Start-Your-Activity), If you want your app to be accessible by other apps, You have to allow this in your manifest file by declaring <intent-filter>. You could use any Action, Category, and Data Type which satisfies your needs.

If you didn't read the Allow-Other-Apps-to-Start-Your-Activity tutorial yet, I recomment you to have a quick look on it now

https://github.com/KarimRedaHassan/Allow-Other-Apps-to-Start-Your-Activity/blob/master/README.md#allow-other-apps-to-open-a-certain-activity-in-your-app

NOTE: Android App Links is an Ownership-Verified Deep Link with some obligatory specifications

If you are intending to use Android App Links, there are some essential declarations to be made for your deep link in the <intent-filter> as following:

Declare ACTION_VIEW, So your app could be accessible from Google Search.
Declare BROWSABLE category, So your app could be accessible from a web browser.
Declare DEFAULT category, So your app could be accessible Implicit Intents.
At Least Declare one tag which must include the android:scheme.

Below is the minimum requirements in the <intent-filter> which must be declared for a Deep Link. In Normal Scenarios, You at least specify the android:host or your app will respond for all URLs starts with http scheme

    <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="http" />
    </intent-filter>

Step Two: Read From Incoming Intent

Prepare your activity to receive the intent data as we discuss in the previous tutorial (Allow-Other-Apps-to-Start-Your-Activity),

Below is a code snippet from Android Documentation to handle an incomming intent. In normal cases, we don't write this code only, we have to do some checks and directions to the code.

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    Intent intent = getIntent();
    String action = intent.getAction();
    Uri data = intent.getData();
}

If you didn't read the Allow-Other-Apps-to-Start-Your-Activity tutorial yet, I recomment you to have a quick look on it now

https://github.com/KarimRedaHassan/Allow-Other-Apps-to-Start-Your-Activity/blob/master/README.md#allow-other-apps-to-open-a-certain-activity-in-your-app

Step Three: Test your Deep Link

After you do the previous two steps, you have to test your work to see if it acts as you intended or not. Android Debug Bridge adb is oferring an easy way to test your deep links. Simply, use the below coommand to test if any activity could resolve the intent.

    adb shell am start
    -W -a android.intent.action.VIEW
    -d <URI> <PACKAGE>

If you are asking how could I use this command or where, We will talk about it in deep details

First, to use the adb, the easiest way is to use the terminal tab in your android studio. You will find it in the bottom bar which contains "Version Control, Logcat, TODO, Terminal, Build, Profiler, Run".

Second, to start communicating with the adb, You have to define its path in your local disk. Normally, you will find your adb in this path sdk/platform-tools/adb. For Example, here is my path

    /Volumes/HDD/Android/sdk/platform-tools/adb

Third, here is a quick hint about the adb commands,

"am" refers to Activity Manager
"start" is used to start Activity specified by the following intent parameters.
"-W" is used to tell the shell to wait for launch to complete
"-a" is used to define the action
"-d" is used to define the data URL
after the data URL, specify the package that you need to test on.

So, in other words, your are using the android debug bridge "adb" to tell the Activity manager "am" to start an Activity "start" and wait for the launch to complete "-W" and use these parameters to the calling intent (action "-a", data URL "-d").

Here is my complete adb command

    /Volumes/HDD/Android/sdk/platform-tools/adb shell am start -W -a android.intent.action.VIEW -d https://www.smarkiz.com com.smarkiz.baseproject

You will have the following response

    Starting: Intent { act=android.intent.action.VIEW dat=https://www.smarkiz.com pkg=com.smarkiz.baseproject }

If the activity failed to resolve your Intent, You will receive the following:

    Error: Activity not started, unable to resolve Intent { act=android.intent.action.VIEW dat=https://www.smarkiz.com flg=0x10000000 pkg=com.smarkiz.baseproject }

If The activity could resolve your Intent, You will receive the following:

    Status: ok
    Activity: com.smarkiz.baseproject/.ui.settings.SettingsActivity
    ThisTime: 220
    TotalTime: 246
    WaitTime: 271
    Complete

For All Available adb commands, Please refer to the Android Documentations below

https://developer.android.com/studio/command-line/adb.html#am

Create Android App Link using App Links Assistant

You could follow the exact same steps mentioned in the previous section and considered the obligatory declarations to create a valid Deep Link which could be upgraded to an Android App Link.

OR You could easily use the App Links Assistant.

Step One: Add intent filters

Tools > App Links Assistant > Open URL Mapping Editor > press the (+) button > Fill required details > OK.

Now you have created a valid Deep Link and magically added the necessary <intent-filter> to your manifest file.

Step Two: Handle incoming links

Tools > App Links Assistant > Select Activity > Choose The Activity associated with the Deep Link > OK.

Now you have inserted a template code to your activity to handle the incoming intent. You should start modify this code to match your needs

    // ATTENTION: This was auto-generated to handle app links.
    Intent appLinkIntent = getIntent();
    String appLinkAction = appLinkIntent.getAction();
    Uri appLinkData = appLinkIntent.getData();

Step Three: Verify your ownership to this host to upgrade the Deep Link to Android App Link

Tools > App Links Assistant > Open Digital Asset Links File Generator > Fill required details > Generate Digital Asset Links File

Now you have created the required json file to attach your app with your website. Simply, copy the generated json text into a file and upload it to this exact destination at your website. This file will help Google to verify that you are the owner of this website

    https://www.your.domain/.well-known/assetlinks.json

Step Four: Enable link handling verification for your app

Tools > App Links Assistant > Open Digital Asset Links File Generator > Link And Verify

Now You have added a single line to your manifest file which is android:autoVerify="true". This will enable link handling verification for your app. This should be added to every <intent-filter> in your manifest file which intended to handle an Android App Link.

Step Five: Test your App Links

Tools > App Links Assistant > Test App Links

Now you should test your work and check if the Android App Link is working fine as intended by providing the URL and click "Run Test". The Response will indicate either if this URL maps to any activity or not.