deep_link_steps.md

Steps for creating Deep Link

A deep link in Android is a URL that points to a specific location within a mobile app rather than a website. Deep links allow users to directly access specific content or features within an app by clicking on a link, either in a web browser, another app, or even a notification.

In this steps, we are going to create a SecretActivity and deep links that will open this activity when clicked.

Create Activity and define links for it

1. Create Activity

class SecretActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_secret)
    }

    companion object {
        //deep links
        const val SECRET_SCREEN_DEEP_LINK1 = "dlapp://deep-link.demo/secret-screen"
        const val SECRET_SCREEN_DEEP_LINK2 = "http://deep-link.demo/secret-screen"
    }
}

2. Modify MainActivity in the Android Manifest file with the deep links

<activity android:name=".MainActivity" android:exported="true" android:launchMode="singleTask">
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </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="http" android:host="deep-link.demo"
            android:pathPrefix="/secret-screen" />
    </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="dlapp" android:host="deep-link.demo"
            android:pathPrefix="/secret-screen" />
    </intent-filter>
</activity>

Modifications

• android:launchMode="singleTask": We have set the launch mode to singleTask so that if there will be an instance of this activity already present in the current task than that it will be reused. The onNewIntent method of the activity will be called with new Intent.
• intent-filter - Intent filters tell the android which type of intent the activity can handle. Here we define category of BROWSABLE, DEFAULT and VIEW with the deep link schemas to make sure that it will redirect user to this app if the user clicks any of the two deep links.

Deep Links defined for this app

1. dlapp://deep-link.demo/secret-screen
2. http://deep-link.demo/secret-screen

Modify MainActivity to handle the deep links

Here we will modify it such that if this activity is launched with any of the two deep links, then it will redirect it to the SecretActivity

1. Define this method in the MainActvity. It will analyze the given intent and decide whether the activity is opened by the deep links. If it is then it will redirect the user to SecretActivity.

private fun handleIntent(intent: Intent?) = intent?.data?.toString()?.takeIf {
    //check if the uri of the intent is equal to the deep links
    //of the secret screen
    return@takeIf it == SecretActivity.SECRET_SCREEN_DEEP_LINK2 ||
            it == SecretActivity.SECRET_SCREEN_DEEP_LINK1
}?.let {
    //if it is the uri of the secret screen
    //take the user to the secret screen
    Intent(this, SecretActivity::class.java)
        .also(::startActivity)
    return@let
}

2. Call it from two places from the MainActvity.

class MainActivity : AppCompatActivity() {
...

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        handleIntent(intent)
        ...
    } 


    override fun onNewIntent(intent: Intent?) {
        super.onNewIntent(intent)
        //this will be called if there is
        //an instance of MainActivity already exist
        //in the current task
        //with the new intent
        handleIntent(intent)
    }
    

Integration with Notification

We are going to modify the notification action that we made in notification_steps.md to go the SecretActivity.

private fun Context.getEnterAppAction() =
    NotificationCompat.Action.Builder(
        R.drawable.ic_notification,
        "Enter secret screen", //change title (optional)
        PendingIntent.getActivity(
            this,
            ENTER_APP_REQUEST_CODE,
            Intent(
                Intent.ACTION_VIEW,
                Uri.parse(SecretActivity.SECRET_SCREEN_DEEP_LINK1) //give any one of the uri
            ),
            PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE
        )
    )
        .build()

Here we are just changing the Intent creation. We are using Intent.ACTION_VIEW action with one of the two URI that we just created.

That's all.

Challenges

1. Handling redirection : We have to check for the intent that is opening the MainActivity. If it contains the Deep Link URI, we have to redirect the user to the Correct Activity.
2. launchMode : If we don't provide the singleTask launch mode then it will launch the activity in another task. That we don't want. It can be useful if the screen is a separate module / feature.