Annotated URL Example

An example showing reading from formatted NFC Data Exchange Format (NDEF) messages.

The Annotated URL example displays the contents of specifically formatted NFC Data Exchange Format (NDEF) messages read from an NFC Tag. The NDEF message should contain a URI record, an optional image/* MIME record, and one or more localized Text records.

這是範例的初始狀態：

In this example the NFC Tag used contains a text record. The UI gets updated accordingly to:

AnnotatedUrl 類定義

The AnnotatedUrl class wraps the QNearFieldManager , the class providing the NFC Tag detection functionality. NDEF messages are read by the QNearFieldManager and forwarded to a handler contained in the AnnotatedUrl class. After parsing the NDEF message the class emits the signal AnnotatedUrl::annotatedUrl(const QUrl &url, const QString &title, const QPixmap &pixmap). The UI reacts to the signal displaying the contents of the NDEF message.

class AnnotatedUrl : public QObject
{
    Q_OBJECT
public:
    explicit AnnotatedUrl(QObject *parent = 0);
    ~AnnotatedUrl();
signals:
    void annotatedUrl(const QUrl &url, const QString &title, const QPixmap &pixmap);
public slots:
    void targetDetected(QNearFieldTarget *target);
    void targetLost(QNearFieldTarget *target);
    void handleMessage(const QNdefMessage &message, QNearFieldTarget *target);
    void handlePolledNdefMessage(QNdefMessage message);
private:
    QNearFieldManager *manager;
};

AnnotatedUrl 處理程序實現

NFC messages read by the QNearFieldManager are forwarded to AnnotatedUrl::handleMessage. The callback signature details can be read in QNearFieldManager::registerNdefMessageHandler .

void AnnotatedUrl::handleMessage(const QNdefMessage &message, QNearFieldTarget *target)
{

Because NFC messages are composed of several NDEF records, looping through all of the records allows the extraction of the 3 parameters to be displayed in the UI: the Uri, the Title and the Pixmap:

    for (const QNdefRecord &record : message) {
        if (record.isRecordType<QNdefNfcTextRecord>()) {
            QNdefNfcTextRecord textRecord(record);
            title = textRecord.text();
            QLocale locale(textRecord.locale());
        } else if (record.isRecordType<QNdefNfcUriRecord>()) {
            QNdefNfcUriRecord uriRecord(record);
            url = uriRecord.uri();
        } else if (record.typeNameFormat() == QNdefRecord::Mime &&
                   record.type().startsWith("image/")) {
            pixmap = QPixmap::fromImage(QImage::fromData(record.payload()));
        }

Finally after having extracted the parameters of the NFC message the corresponding signal is emitted so that the UI can handle it.

    }
    emit annotatedUrl(url, title, pixmap);
}

運行範例

要運行範例從 Qt Creator ，打開歡迎模式，然後選擇範例從範例。更多信息，拜訪構建和運行範例 .

文件：

另請參閱 Qt NFC .