Integrate Android App with Google Cloud Function

Easy, it is not – when authentication is required for the function

You need to update the Server client id the string.xml file:

Advertisements

<string name="server_client_id">YOUR_SERVER_CLIENT</string>

Then you need to add credentials for your app in the Google Cloud console:

Enable Google Sign in

	<application>
	….
	<meta-data
	android:name="com.google.android.geo.API_KEY"
	android:value="@string/google_maps_key" />
	</application>
	<uses-permission android:name="android.permission.INTERNET" />

view raw AndroidManifest.xml hosted with ❤ by GitHub

implementation 'com.google.android.gms:play-services-auth:19.0.0'

view raw build.gradle (module) hosted with ❤ by GitHub

	dependencies {
	…
	classpath 'com.google.gms:google-services:4.3.4'
	}

view raw build.gradle (project) hosted with ❤ by GitHub

private GoogleSignInClient mGoogleSignInClient;

view raw GSI1.java hosted with ❤ by GitHub

	GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
	.requestIdToken(getString(R.string.server_client_id))
	.requestEmail()
	.build();
	mGoogleSignInClient = getClient(this, gso);

view raw GSI2.java hosted with ❤ by GitHub

	@Override
	public void onActivityResult(int requestCode, int resultCode, Intent data) {
	super.onActivityResult(requestCode, resultCode, data);
	if (requestCode == RC_SIGN_IN) {
	Task<GoogleSignInAccount> task = GoogleSignIn.getSignedInAccountFromIntent(data);
	handleSignInResult(task);
	}
	}

view raw GSI3.java hosted with ❤ by GitHub

	private void handleSignInResult(Task<GoogleSignInAccount> completedTask) {
	try {
	GoogleSignInAccount account = completedTask.getResult(ApiException.class);
	updateUI(account);
	} catch (ApiException e) {
	e.printStackTrace();
	updateUI(null);
	}
	}
	@Override
	public void onStart() {
	super.onStart();
	GoogleSignInAccount account = getLastSignedInAccount(this);
	updateUI(account);
	}

view raw GSI4.java hosted with ❤ by GitHub

	private void updateUI(@Nullable GoogleSignInAccount account) {
	if (account != null) {
	String idToken = account.getIdToken();
	// call function with the token
	callGcpFunction(idToken);
	} else {
	signIn();
	}
	}
	private void signIn() {
	Intent signInIntent = mGoogleSignInClient.getSignInIntent();
	startActivityForResult(signInIntent, RC_SIGN_IN);
	}

view raw GSI5.java hosted with ❤ by GitHub

Advertisements

On Google side, configure the permissions of the function to have the invoker role.

And finally, call the HTTP url of the cloud function with the id token:

URL url = new URL("https://<place the function url here>");
HttpURLConnection con = (HttpURLConnection) url.openConnection();
con.setRequestMethod("POST");
con.setRequestProperty("Authorization", "Bearer " + idtoken);
con.setRequestProperty("Content-Type", "application/json; utf-8");
con.setRequestProperty("Accept", "application/json");
con.setDoOutput(true);

// Read the output:
try (BufferedReader br = new BufferedReader(
        new InputStreamReader(con.getInputStream(), "utf-8"))) {
    StringBuilder response = new StringBuilder();
    String responseLine = null;
    while ((responseLine = br.readLine()) != null) {
        response.append(responseLine.trim());
    }
    System.out.println(response.toString());
}

Advertisements