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.

这是范例的初始状态：

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

AnnotatedUrl 类定义

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 处理程序实现

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);
}
					
					

运行范例

要运行范例从 Qt Creator ，打开 欢迎 模式，然后选择范例从 范例 。更多信息，拜访 构建和运行范例 .

范例工程 @ code.qt.io

另请参阅 Qt NFC .

内容

• AnnotatedUrl 类定义

• AnnotatedUrl 处理程序实现

• 运行范例