Warm-up and pre-fetch: using the Custom Tabs Service

The third part of this guide focuses on speeding up the browser startup via warmup() and prefetching web pages via mayLaunchUrl(). Warming up the browser process can save up to 700ms when opening a link. Pre-rendering content via mayLaunchUrl will make external content open instantly. Together both APIs can greatly improve the user experience of a Custom Tabs integration and are highly recommended.

The required steps are:

1. Check via CustomTabsClient.getPackageName() If the default browser supports Custom Tabs. If yes, bind to the CustomTabsService via CustomTabsClient.bindCustomTabsService().

2. Once connected to the CustomTabsService, in the CustomTabsServiceConnection.onCustomTabsServiceConnected() callback, do:

   a. Warmup the browser process via CustomTabsClient.warmup(). b. Create a new CustomTabsSession via CustomTabsClient.newSession().

3. Optionally, prefetch web pages the user is likely to visit via CustomTabsSession.mayLaunchUrl().

4. When launching a new Custom Tab, pass the CustomTabsSession to the CustomTabsIntent.Builder via the constructor new CustomTabsIntent.Builder(session).

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools">
  …
   <queries>
        <intent>
            <action android:name="android.support.customtabs.action.CustomTabsService" />
        </intent>
    </queries>
</manifest>

Here is a full example for how to connect to a Custom Tabs service:

private CustomTabsClient mClient;
private CustomTabsSession mSession;

private CustomTabsServiceConnection mConnection = new CustomTabsServiceConnection() {
    @Override
    public void onCustomTabsServiceConnected(
            @NonNull ComponentName name,
            @NonNull CustomTabsClient client
    ) {
        mClient = client;
        // Warm up the browser process
        mClient.warmup(0 /* placeholder for future use */);
        // Create a new browser session
        mSession = mClient.newSession(new CustomTabsCallback());
        // Pre-render pages the user is likely to visit
        // you can do this any time while the service is connected
        mSession.mayLaunchUrl("https://developers.android.com", null, null);
    }

    @Override
    public void onServiceDisconnected(ComponentName name) {
        mClient = null;
        mSesssion = null;
    }
};

private void bindCustomTabService(Context context) {
    // Check for an existing connection
    if (mClient != null) {
        // Do nothing if there is an existing service connection
        return;
    }

    // Get the default browser package name, this will be null if
    // the default browser does not provide a CustomTabsService
    String packageName = CustomTabsClient.getPackageName(context, null);
    if (packageName == null) {
        // Do nothing as service connection is not supported
        return;
    }
    CustomTabsClient.bindCustomTabsService(context, packageName, mConnection);
}

@Override
protected void onCreate(Bundle savedInstanceState) {
…
    bindCustomTabService(this);
    findViewById(R.id.button).setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            String url = "https://developers.android.com";
            CustomTabsIntent intent = new CustomTabsIntent.Builder(session)
                    .build();
            intent.launchUrl(MainActivity.this, Uri.parse(url));
        }
    });
}

Next up: Learn how to resize the Custom Tabs experience.