Get the source for this example here
A number of blog posts in this site include sample code that I am writing into an Android app as kind of a kitchen sink sandbox app to demonstrate how the code runs.
I hadn’t tried using deep links before and I thought it would be really cool if I could have HTML links in my blog content that could open my Android apps directly to code samples related to my blog posts.
A bit of Google foo and some reading up on the Android docs and especially the Code Labs tutorial showed that it was perhaps not as difficult as I imagined.
Simply put, all that is needed is:
Let’s make a basic example app.
Create a new Android app, with the default MainActivity that gets generated for you. Then add a new activity that will be our deep linking entry point. I’ve called mine DeepLinkActivity.
In my example, when the DeepLinkActivity is launched via an external intent, it simply restarts the MainActivity and passes along the action and data from the originating intent, along with some intent flags to basically restart the activity stack.
This is the point where you could really do anything you like though based on whatever data the intent was initiated with.
public class DeepLinkActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Generate a new intent to launch our main activity
// with the given action and data, and tell it to
// clear and restart a fresh instance.
Intent intent = new Intent(this, MainActivity.class);
intent.setAction(getIntent().getAction());
intent.setData(getIntent().getData());
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(intent);
// Finish this activity as well.
finish();
}
}
Next we need to add the new DeepLinkActivity to the manifest, along with some filters to allow it to be resolved when we want to trigger it.
Add the following inside the application tag of your manifest.
<activity
android:name=".DeepLinkActivity"
android:exported="true">
<intent-filter>
<data
android:scheme="deeplink"
android:host="io.github.marcelbraghetto.deeplinking"
/>
<action android:name="android.intent.action.VIEW" />
<category android:name="android.intent.category.DEFAULT" />
<category android:name="android.intent.category.BROWSABLE" />
</intent-filter>
</activity>
Note that:
In this example, we will simply take the default MainActivity and add a bit of extra code to examine the contents of the intent that was used to launch it.
There will be two launch conditions for the MainActivity class:
We are just going to display the text of the intent data, or a default message if the MainActivity was launched by the user:
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TextView textView = (TextView) findViewById(R.id.main_text);
String action = getIntent().getAction();
Uri data = getIntent().getData();
// If we were started by an ACTION_VIEW, then
// grab the content of the passed in data and
// display it to the user.
if(Intent.ACTION_VIEW.equals(action) && data != null) {
textView.setText(data.getLastPathSegment());
} else {
// Otherwise it was a regular launch, just
// show a default message.
textView.setText(getString(R.string.default_launch_message));
}
}
}
That’s pretty much it for the app.
The next step is launching the app from somewhere else. There is some good information here about launching from a web link.
The idea is to attempt to initiate the intent, and launch the app that can handle it (based on the intent filters). The addition of a browser_fallback_url property will redirect the user if they don’t have an app installed that can handle the intent.
Here is the link that should launch the example app if it is installed, or navigate to Google:
<a href="intent://io.github.marcelbraghetto.deeplinking/Hi%20from%20Marcel%27s%20blog!#Intent;scheme=deeplink;package=io.github.marcelbraghetto.deeplinking;S.browser_fallback_url=https%3A%2F%2Fgoogle.com;end">Tap me to launch directly into the Android app</a>
This example link will attempt to resolve to an activity that has:
Check our sample manifest to see how these properties align to allow the app to be the resolved intent handler.
If you have the example app installed you can tap here to trigger a deep link - only works if you are browsing on an Android device!
This was just a super simple example, but the concept is quite handy for surfacing app content via the web. You can also use http schemes and setup your intent filters to recognise particular url patterns and therefore appear in the list of suggested apps that can handle those particular urls (alongside your browser).