AI2 App Inventor: How To Login With Google (MIT)

by Alex Braham 49 views

Hey guys! Ever wanted to build your own Android app but thought it was too complicated? Well, let me introduce you to MIT App Inventor, a super cool platform that lets you create apps using a visual block-based programming language. It's like playing with LEGOs, but instead of building castles, you're building apps! And one of the most common features you might want to include in your app is Google Login. It makes things so much easier for users to sign up and get started. So, let's dive in and see how you can add Google Login to your AI2 App Inventor project.

Why Use Google Login?

Before we get into the how-to, let's quickly talk about why Google Login is such a great feature to have. First off, almost everyone has a Google account. By allowing users to sign in with their existing Google accounts, you're making the sign-up process incredibly simple and convenient. No need for them to remember yet another username and password! This can significantly improve the user experience and encourage more people to use your app.

Another benefit is security. Google handles the authentication process, which means you don't have to worry about storing passwords or implementing complex security measures yourself. This not only saves you a lot of time and effort but also reduces the risk of security vulnerabilities in your app. Plus, Google's security is top-notch, so you can be confident that your users' data is well-protected.

Furthermore, Google Login can provide you with valuable user information, such as their name and email address (with their permission, of course). This information can be used to personalize the user experience, provide targeted content, and improve your app overall. By understanding your users better, you can create an app that truly meets their needs and keeps them coming back for more.

Finally, implementing Google Login can make your app more trustworthy and professional. Users are more likely to trust an app that uses a well-known and reputable authentication provider like Google. This can help you build a strong reputation and attract more users to your app.

Prerequisites

Before we start, make sure you have a few things ready:

  • MIT App Inventor Account: You'll need an account on the MIT App Inventor platform. If you don't have one, head over to http://appinventor.mit.edu/ and sign up. It's free!
  • Basic App Inventor Knowledge: You should be familiar with the basics of using App Inventor, such as creating projects, adding components, and using the block editor.
  • A Google Cloud Project: You'll need a Google Cloud project to enable the Google Sign-In API and get the necessary credentials. Don't worry; I'll walk you through this step by step.

Step-by-Step Guide to Implementing Google Login

Okay, let's get down to the nitty-gritty. Here's how you can add Google Login to your AI2 App Inventor project:

Step 1: Set Up a Google Cloud Project

First, you'll need to create a Google Cloud project. This is where you'll enable the Google Sign-In API and get the credentials needed for your app.

  1. Go to the Google Cloud Console: Open your web browser and go to the Google Cloud Console.
  2. Create a New Project: If you don't already have a project, click on the project dropdown at the top of the page and select "New Project". Give your project a name and click "Create".
  3. Enable the Google Sign-In API: Once your project is created, go to the API Library by clicking on the menu icon (three horizontal lines) in the top-left corner, then selecting "APIs & Services" and "Library". Search for "Google Sign-In API" and click on it. Then, click the "Enable" button.
  4. Create Credentials: Next, you'll need to create credentials for your app. Click on the menu icon again, then select "APIs & Services" and "Credentials". Click the "Create Credentials" button and select "OAuth client ID".
  5. Configure OAuth Consent Screen: You might be prompted to configure the OAuth consent screen. If so, click the "Configure consent screen" button. Choose the "External" user type and click "Create". Fill out the required information, such as the app name, user support email, and developer contact information. You can leave the optional fields blank for now. Click "Save and Continue" until you reach the "Summary" page, then click "Back to Dashboard".
  6. Create OAuth Client ID: Now, go back to the "Credentials" page and click "Create Credentials" again, then select "OAuth client ID". Choose "Android" as the application type. Enter your app's package name and SHA-1 signing certificate fingerprint. You can get these values from your App Inventor project settings (more on that later). Click "Create".
  7. Get Your Client ID: After creating the OAuth client ID, you'll see a dialog box with your client ID. Copy this value; you'll need it later in your App Inventor project.

Step 2: Design Your App Inventor Project

Now that you have your Google Cloud project set up, it's time to design your app in App Inventor.

  1. Create a New Project: Open App Inventor and create a new project. Give it a meaningful name.
  2. Add Components: Drag and drop the following components from the Palette to the Viewer:
    • Button: This will be the "Sign in with Google" button.
    • Label: This will display the user's information after they sign in.
    • Web: This component will be used to communicate with the Google Sign-In API.
    • Activity Starter: This component will be used to start the Google Sign-In activity.
    • Non-visible components: Add notifier and TinyDB. The notifier will be used to display the error or any information. The TinyDB component will be used to save the user information.
  3. Configure Components:
    • Button: Set the Text property to "Sign in with Google".
    • Label: Set the Text property to "".
    • Web: Leave the properties as their default values.
    • Activity Starter: Set the Action property to android.intent.action.VIEW.

Step 3: Implement the Logic with Blocks

Now comes the fun part: implementing the logic using the block editor.

  1. Button Click Event: Create a Button.Click event handler. This event will be triggered when the user clicks the "Sign in with Google" button.
  2. Construct the Google Sign-In URL: Inside the Button.Click event handler, you'll need to construct the Google Sign-In URL. This URL will be used to redirect the user to the Google Sign-In page. Use the following blocks:
set global googleSignInURL to join
  "https://accounts.google.com/o/oauth2/v2/auth?"
  "client_id=" + your_client_id + "&"
  "redirect_uri=urn:ietf:wg:oauth:2.0:oob&"
  "response_type=code&"
  "scope=openid%20email%20profile"

Replace your_client_id with the client ID you obtained from the Google Cloud Console.

  1. Start the Activity: Use the Activity Starter component to start the Google Sign-In activity. Set the DataUri property to the Google Sign-In URL you constructed in the previous step. Then, call the ActivityStarter.StartActivity method.
set ActivityStarter1.DataUri to global googleSignInURL
call ActivityStarter1.StartActivity
  1. Handle the Activity Result: Create an ActivityStarter.AfterActivity event handler. This event will be triggered after the user signs in with Google and is redirected back to your app. Check the Result property to see if the sign-in was successful.
if ActivityStarter1.Result = "OK" then
  set global authorizationCode to get value from text
    ActivityStarter1.ResultUri
    "code="
else
  call Notifier.ShowMessageDialog
    "Sign-in failed" "Error" "Dismiss" cancelable: false
  1. Exchange the Authorization Code for an Access Token: If the sign-in was successful, you'll need to exchange the authorization code for an access token. This token will be used to access the user's Google profile information. Use the Web component to send a POST request to the Google token endpoint.
set Web1.Url to "https://oauth2.googleapis.com/token"
set Web1.RequestHeaders to create list
  create list "Content-Type" "application/x-www-form-urlencoded"
set Web1.PostText to join
  "code=" + global authorizationCode + "&"
  "client_id=" + your_client_id + "&"
  "client_secret=" + your_client_secret + "&"
  "redirect_uri=urn:ietf:wg:oauth:2.0:oob&"
  "grant_type=authorization_code"
call Web1.PostText

Replace your_client_id and your_client_secret with the client ID and client secret you obtained from the Google Cloud Console.

  1. Handle the Web Response: Create a Web.GotText event handler. This event will be triggered when the Web component receives a response from the Google token endpoint. Parse the JSON response to extract the access token.
set global accessToken to get value from json
  Web1.ResponseContent
  "access_token"
  1. Get User Information: Use the access token to get the user's Google profile information. Send a GET request to the Google People API.
set Web1.Url to "https://people.googleapis.com/v1/people/me?personFields=names,emailAddresses"
set Web1.RequestHeaders to create list
  create list "Authorization" "Bearer " + global accessToken
call Web1.Get
  1. Display User Information: Parse the JSON response to extract the user's name and email address. Display this information in the Label component.
set global userName to get value from json
  Web1.ResponseContent
  "names[0].displayName"
set global userEmail to get value from json
  Web1.ResponseContent
  "emailAddresses[0].value"
set Label1.Text to join
  "Name: " + global userName + "\nEmail: " + global userEmail

Step 4: Test Your App

Alright, you've done all the hard work! Now it's time to test your app and make sure everything is working as expected.

  1. Connect to the App Inventor Companion: Open the App Inventor Companion app on your Android device and connect to your project.
  2. Test the Sign-In Process: Click the "Sign in with Google" button. You should be redirected to the Google Sign-In page. Sign in with your Google account.
  3. Verify the Results: If the sign-in is successful, your app should display your name and email address in the Label component.

If you encounter any errors, double-check your code and make sure you've followed all the steps correctly. Pay close attention to the client ID, client secret, and redirect URI. These values must be exactly as they appear in your Google Cloud Console.

Troubleshooting

Sometimes, things don't go as planned. Here are a few common issues you might encounter and how to fix them:

  • "invalid_request" error: This usually means that your client ID or redirect URI is incorrect. Double-check these values in your code and in the Google Cloud Console.
  • "access_denied" error: This means that the user has denied your app access to their Google account. Make sure you're requesting the correct scopes (e.g., openid, email, profile) in your Google Sign-In URL.
  • App crashes or freezes: This could be due to a variety of reasons. Check your code for errors and make sure you're handling exceptions properly. You can also use the App Inventor debugger to step through your code and identify the source of the problem.

Conclusion

And there you have it! You've successfully added Google Login to your AI2 App Inventor project. This is a great way to simplify the sign-up process for your users and improve the overall user experience. Remember to always prioritize security and user privacy when implementing authentication in your app. Have fun building awesome apps with App Inventor!