Custom Barcode Invoker Example

Files:

• custombarcodeinvoker/assets/main.qml
• custombarcodeinvoker/src/BarcodeInvoker.cpp
• custombarcodeinvoker/src/BarcodeInvoker.hpp
• custombarcodeinvoker/src/main.cpp
• custombarcodeinvoker/custombarcodeinvoker.pro
• custombarcodeinvoker/translations/custombarcodeinvoker.pro

Description

The Custom Barcode Invoker example allows the user to scan barcodes via a Card through the InvokeManager by issuing scan requests.

Overview

In this example we'll learn how to use the InvokeManager class to issue barcode scanning requests to the BarcodeScanner Card and retrieve the decoded barcode data from the Card.

The UI

The simplistic UI of this sample application consists of a Button to issue requests, and a Label to display the request results.

    Container {
        layout: DockLayout {
        }

        background: Color.Black

        Container {
            horizontalAlignment: HorizontalAlignment.Fill
            verticalAlignment: VerticalAlignment.Fill

            bottomPadding: 20

            layout: DockLayout {
            }

            // The background image
            ImageView {
                horizontalAlignment: HorizontalAlignment.Fill
                verticalAlignment: VerticalAlignment.Fill
                imageSource: "asset:///images/background.png"
            }
        }

        Container {
            horizontalAlignment: HorizontalAlignment.Fill
            verticalAlignment: VerticalAlignment.Fill

            topPadding: 20
            leftPadding: 20
            bottomPadding: 20

            layout: DockLayout {
            }

            //Button to invoke the barcodescanner card - for this to work
            //you have to have barcodescanner sample on device
            Button {
                horizontalAlignment: HorizontalAlignment.Center
                verticalAlignment: VerticalAlignment.Top

                text: qsTr("Scan Barcode")
                onClicked: {
                    _barcodeInvoker.onInvokeButtonClicked()
                }
            }
            //displays barcode data
            Label {
                horizontalAlignment: HorizontalAlignment.Left
                verticalAlignment: VerticalAlignment.Bottom

                text: qsTr("Barcode: %1").arg(_barcodeInvoker.barcode)
                textStyle.color: Color.White
            }
        }
    }

When the Button is clicked, the request is sent and the barcodescanner card is invoked and transitions over the parent to begin barcode scanning. Once the barcode is read and decoded, the card sends a cardDone() signal to the requesting parent, transitions off screen and is pooled to await subsequent invokation requests. The Label's text property is bound to the BarcodeInvoker barcode property, which gets updated when barcodeChanged() signal is emited.

    BarcodeInvoker::BarcodeInvoker(QObject* parent)
        : QObject(parent)
    {
        bool ok = connect(new InvokeManager(this), SIGNAL(childCardDone(const bb::system::CardDoneMessage&)),
                          this, SLOT(onChildCardDone(const bb::system::CardDoneMessage&)));
        Q_ASSERT(ok);
        Q_UNUSED(ok);
    }

Constructor initializes InvokeManager and hooks into the signal/slot mechanism to receive childCardDone() signals from the invoked Card.

    void BarcodeInvoker::onInvokeButtonClicked() const
    {
        InvokeManager* imanager = qobject_cast<InvokeManager*>(sender());

        InvokeRequest invokeRequest;
        invokeRequest.setTarget("com.example.CustomBarcodeScanner");
        invokeRequest.setAction("community.action.SCANBARCODE");

        const InvokeTargetReply *invokeReply = imanager->invoke(invokeRequest);

        if (!invokeReply)
            qWarning() << "failed to sent invoke request message";
    }

    void BarcodeInvoker::onChildCardDone(const bb::system::CardDoneMessage &message)
    {
        setBarcode(message.data());
    }

    QString BarcodeInvoker::barcode() const
    {
        return m_barcode;
    }

    void BarcodeInvoker::setBarcode(const QString &barcode)
    {
        if (m_barcode == barcode)
            return;

        m_barcode = barcode;
        Q_EMIT barcodeChanged();
    }

The onInvokeButtonClicked() method creates InvokeRequest and invokes the request via InvokeManager. Once the card finishes processing the onChildCardDone() is invoked and sets the barcode textual data from the result, which than emits a barcodeChanged() signal via the setBarcode() method for the QML to update the Label's text property.