Question

I’m using the PayPal MECL library to:

• Display the “Pay with PayPal”-button in Activity A
• Initiate the payment process in Activity B

For obvious reasons, I don’t want to initialize the PayPal library twice (once for every activity), as this takes time and unnecessarily makes the user wait.

How can I share a reference to the library between my two Activities?

This is my code (present in both Activity A and B) at the moment (taken from the PayPal example):

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    //...

    //Show PayPal-Button
    initializePayPal();

}

public void initializePayPal() {
    //Time to launch the library but first we need to initialize
    setSupportProgressBarIndeterminateVisibility(true);

    //Create a separate thread to do the initialization
    Thread libraryInitializationThread = new Thread() {
        public void run() {
            //Initialize the library
            initLibrary();

            // The library is initialized so let's launch it by notifying our handler
            if (PayPal.getInstance().isLibraryInitialized()) {
                hRefresh.sendEmptyMessage(INITIALIZE_SUCCESS);
            }
            else {
                hRefresh.sendEmptyMessage(INITIALIZE_FAILURE);
            }
        }
    };
    libraryInitializationThread.start();
}

private void initLibrary() {
    // This is the main initialization call that takes in your Context, the Application ID, the server you would like to connect to, and your PayPalListener
    PayPal.fetchDeviceReferenceTokenWithAppID(this, CompletePaymentActivity.appID, CompletePaymentActivity.server, new ResultDelegate());

    // -- These are required settings.
    PayPal.getInstance().setLanguage(SharedFunctions.getCurrentLocaleString()); // Sets the language for the library.
    // --
}

// This handler will allow us to properly update the UI. You cannot touch Views from a non-UI thread.
Handler hRefresh = new Handler(){
    @Override
    public void handleMessage(Message msg) {
        switch(msg.what){
            case INITIALIZE_SUCCESS:
                //We have initialized the application, close the dialog and show the PayPal Button
                setSupportProgressBarIndeterminateVisibility(false);
                showPayPalButton();
                break;
            case INITIALIZE_FAILURE:
                //Initialization failure, close the dialog, update the page and show a toast
                setSupportProgressBarIndeterminateVisibility(false);
                Toast.makeText(mContext, mContext.getString(R.string.paypal_initialization_failed), Toast.LENGTH_LONG).show();
                finish();
                break;
        }
    }
};

public void showPayPalButton() {
    //...

    PayPal pp = PayPal.getInstance();
    // get the checkoutbutton
    launchPayPalButton = pp.getCheckoutButton(this, PayPal.BUTTON_194x37,
            CheckoutButton.TEXT_PAY);
    //...
}

Answer 1

I ended up declaring a class that extends Application, where I initialize the library once and from which it can be used by all activities.