GPlayServices #0: Configure the GoogleApiClient with Google Play Services.

A little snippet to connect your app with the Google Play Services API.

To use the Google Play Services API you have to follow these steps:(this blog doesn't cover these topics) :

• Set Up Google Play Services SDK
• Register your app in Google Developers Console to activate the API

Now you can build your code.

First of all, create an instance of GoogleApiClient using the GoogleApiClient.Builder.

    /**
     * Called when activity gets visible. A connection to Drive services need to
     * be initiated as soon as the activity is visible. Registers
     * {@code ConnectionCallbacks} and {@code OnConnectionFailedListener} on the
     * activities itself.
     */
    @Override
    protected void onResume() {
        super.onResume();
        if (mGoogleApiClient == null) {
            mGoogleApiClient = new GoogleApiClient.Builder(this)
                    .addApi(Drive.API) 
                    .addScope(Drive.SCOPE_FILE)
                    .addScope(Drive.SCOPE_APPFOLDER)
                    .addConnectionCallbacks(this)
                    .addOnConnectionFailedListener(this)
                    .build();
        }
        mGoogleApiClient.connect();
    }

We have to implement the callback interfaces.

    /**
     * Called when {@code mGoogleApiClient} is connected.
     */
    @Override
    public void onConnected(Bundle connectionHint) {
        Log.i(TAG, "GoogleApiClient connected");
    }

    /**
     * Called when {@code mGoogleApiClient} is disconnected.
     */
    @Override
    public void onConnectionSuspended(int cause) {
        Log.i(TAG, "GoogleApiClient connection suspended");
    }

    /**
     * Called when {@code mGoogleApiClient} is trying to connect but failed.
     * Handle {@code result.getResolution()} if there is a resolution is
     * available.
     */
    @Override
    public void onConnectionFailed(ConnectionResult result) {
        Log.i(TAG, "GoogleApiClient connection failed: " + result.toString());
        if (mResolvingError) {
            // Already attempting to resolve an error.
            return;
        }else {
            if (!result.hasResolution()) {
                mResolvingError = true;
                // show the localized error dialog.
                GooglePlayServicesUtil.getErrorDialog(result.getErrorCode(), this, 0).show();
                return;
            }
            try {
                mResolvingError = true;
                result.startResolutionForResult(this, REQUEST_CODE_RESOLUTION);
            } catch (IntentSender.SendIntentException e) {
                Log.e(TAG, "Exception while starting resolution activity", e);
            }
        }
    }

With this simple code we can try to connect.

Our code will fail and we will receive a call to onConnectionFailed() with the SIGN_IN_REQUIRED error.
This error happens because the user account has not been specified.

It is very simple to handle this error.
Inside the ConnectionResult we can find a PendingIntent to resolve the issue.
In this case the intent will launch the activity to select an account to be used.

    public void onConnectionFailed(ConnectionResult result) {
       //......
       result.startResolutionForResult(this, REQUEST_CODE_RESOLUTION);   
    }

    Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == REQUEST_CODE_RESOLUTION) {
            mResolvingError = false;
            if (resultCode == RESULT_OK) {
                // Make sure the app is not already connected or attempting to connect
                if (!mGoogleApiClient.isConnecting() &&
                        !mGoogleApiClient.isConnected()) {
                    mGoogleApiClient.connect();
                }
            }
        }
    }

You can find more info here.

After choosing the account, the app asks us to authorize the access:

At this point we can connect the GoogleApiClient and use it for our scopes.