OAuth2Helper.java

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package com.google.appinventor.components.runtime.util;
 
import java.io.IOException;
 
import com.google.api.client.googleapis.auth.oauth2.GoogleCredential;
import com.google.api.client.googleapis.extensions.android2.auth.GoogleAccountManager;
 
import android.accounts.Account;
import android.accounts.AccountManager;
import android.accounts.AccountManagerFuture;
import android.accounts.AuthenticatorException;
import android.accounts.OperationCanceledException;
import android.app.Activity;
import android.content.SharedPreferences;
 
import android.os.Bundle;
import android.os.Looper;
import android.util.Log;
 
 
public class OAuth2Helper {  
 
  public static final String TAG = "OAuthHelper";
  public static final String PREF_AUTH_TOKEN      = "authToken";
  public static final String PREF_ACCOUNT_NAME = "accountName";
  
  private static String errorMessage = "Error during OAuth";
 
  public OAuth2Helper () {}
 
  public String getRefreshedAuthToken(Activity activity, String authTokenType) {
    Log.i(TAG, "getRefreshedAuthToken()");
 
    if (isUiThread()) 
      throw new IllegalArgumentException("Can't get authtoken from UI thread");
 
    // Get the saved account name, possibly null
    SharedPreferences settings = activity.getPreferences(Activity.MODE_PRIVATE);
    String accountName = settings.getString(PREF_ACCOUNT_NAME, null);
 
    // Get the saved authToken, possibly null. We save even though we refresh it every time
    String authToken = settings.getString(PREF_AUTH_TOKEN, null);
 
    // Initialize credential with the saved authToken.
    GoogleCredential credential = new GoogleCredential();
    credential.setAccessToken(authToken);
 
    // Tell AccountManager to get the authToken and user account name. This is 
    //  where all the details of the OAuth flow are hidden.
    AccountManagerFuture<Bundle> future = 
      getAccountManagerResult(activity, credential, authTokenType, accountName); 
 
    // Extract and save the authToken and account name
    try {
 
      Bundle authTokenBundle = future.getResult();
      authToken = authTokenBundle.get(AccountManager.KEY_AUTHTOKEN).toString();
 
      persistCredentials(settings, 
          authTokenBundle.getString(AccountManager.KEY_ACCOUNT_NAME), 
          authToken);
    } catch (OperationCanceledException e) {
      e.printStackTrace();
      OAuth2Helper.resetAccountCredential(activity);
      errorMessage = "Error: operation cancelled";
    } catch (AuthenticatorException e) {
      e.printStackTrace();
      errorMessage = "Error: Authenticator error";
    } catch (IOException e) {
      e.printStackTrace();
      errorMessage = "Error: I/O error";
    }    
 
    // Return the authToken or null
    return authToken;
  }
 
  private AccountManagerFuture<Bundle> getAccountManagerResult(Activity activity, 
      GoogleCredential credential, 
      String authTokenType, 
      String accountName) {
 
    AccountManagerFuture<Bundle> future = null; 
    GoogleAccountManager accountManager = new GoogleAccountManager(activity);
 
    // Force the return of fresh token by invalidating the current token
    // Doing this on every OAuth request, avoids the need to determine whether the
    // authToken has expired, usually after 1 hour, and then getting 
    // another one using the refresh token.
 
    accountManager.invalidateAuthToken(credential.getAccessToken());
    AccountManager.get(activity).invalidateAuthToken(authTokenType, null);
 
    // Try to get the user's account by account name. Might return null
 
    Account account = accountManager.getAccountByName(accountName);
 
    // Here is where AccountManager may prompt user to select an account
    if (account != null) {
 
      // We have the user's account at this point, so AccountManager simply returns the token
      Log.i(TAG, "Getting token by account");
      future = accountManager.getAccountManager().getAuthToken(account, authTokenType, true, null, null);
 
    } else {
 
      // AccountManager uses 'features' to get the authToken, possibly prompting the user to choose an account
      Log.i(TAG, "Getting token by features, possibly prompting user to select an account");
      future = accountManager.getAccountManager().getAuthTokenByFeatures(GoogleAccountManager.ACCOUNT_TYPE,
          authTokenType, null, activity, null, null, null, null);      
    }
 
    // Return the whole bundle containing the authToken, account name, and other data.
    return future;
  }
 
  private boolean isUiThread() {
    return Looper.getMainLooper().getThread().equals(Thread.currentThread());
  }
 
 
  private void persistCredentials(SharedPreferences settings, String accountName, String authToken) {
    Log.i(TAG, "Persisting credentials, acct =" + accountName);
    SharedPreferences.Editor editor = settings.edit();
    editor.putString(PREF_ACCOUNT_NAME, accountName);
    editor.putString(PREF_AUTH_TOKEN, authToken);
    editor.commit();
  }
 
  public static void resetAccountCredential(Activity activity) {
    Log.i(TAG, "Reset credentials");
    SharedPreferences settings = activity.getPreferences(Activity.MODE_PRIVATE);
    SharedPreferences.Editor editor2 = settings.edit();
    editor2.remove(PREF_AUTH_TOKEN);
    editor2.remove(PREF_ACCOUNT_NAME);
    editor2.commit();
  }
  
  public static String getErrorMessage() {
    Log.i(TAG, "getErrorMessage = " + errorMessage);
    return errorMessage;
  }
}