- Qt 5.15
- Qt Bluetooth
- QML Bluetooth Picture Push Example
- Qt 5.15.18 Reference Documentation

# QML Bluetooth Picture Push Example

An example showing the use Bluetooth Object Push Profile (OPP).

The Bluetooth Picture Push example shows how to use the QBluetoothTransferManager API. The example transfers a local image to a remote device. Unfortunately this example cannot be used on Android as Qt does not support the Object Push Profile (OPP) on this platform.

On the first user interface page the application scans for remote Bluetooth devices. The user must select the appropriate device to continue:

The next page presents a list of image files on the device. The files must be located under QStandardPaths::PicturesLocation}:

Once the picture was selected the UI shows the progress of the file transfer:

#### Running the Example

To run the example from Qt Creator, open the Welcome mode and select the example from Examples. For more information, visit Building and Running an Example.

#### Device Discovery

The device discovery uses the BluetoothDiscoveryModel to detect the remote devices. Each discovery is displayed as an entry in a list. Once a device was selected the device address is stored in the `root` element. More details about the `root` element will follow further below.

         ListView {
             model: BluetoothDiscoveryModel {
                 discoveryMode: BluetoothDiscoveryModel.DeviceDiscovery
                 onErrorChanged: {
                     if (error == BluetoothDiscoveryModel.NoError)
                         return;
                     if (error == BluetoothDiscoveryModel.PoweredOffError)
                         titleLabel.text = "Bluetooth turned off";
                     else
                         titleLabel.text = "Cannot find devices";
                 }
             }

             delegate: Button {
                 width: listView.width + 2
                 text: model.name
                 onClicked: root.remoteDevice = model.remoteAddress
             }
         }

#### File Selection

The file is selected with the help of FolderListModel. Once again the selected file is stored in the `root` element:

             model: FolderListModel {
                 folder: "file://"+SystemPictureFolder
                 showDirs: false
             }

             delegate: Rectangle {
                 Text {
                     text: model.fileName
                 }
                 MouseArea {
                     id: mArea
                     anchors.fill: parent
                     onClicked: {
                         print ("path: " + model.filePath + " " + model.fileName)
                         root.fileName = model.filePath
                     }
                 }
             }

#### Root Element

The already mentioned `root` element collects the necessary pieces of data for the picture transfer. Once the file name has been set it triggers the file transfer:

     Image {
         id: root
         property string remoteDevice;
         property string fileName;
         onFileNameChanged: {
             fileTransfer.initTransfer(remoteDevice, fileName);
             loader.source = "FileSending.qml"
         }
         onFileNameChanged: {
             fileTransfer.initTransfer(remoteDevice, fileName);
             loader.source = "FileSending.qml"
         }

#### File Transfer

The file transfer is implemented in C++:

     void FileTransfer::initTransfer(QString address, QString fileName)
     {
         qDebug() << "Begin sharing file: " << address << fileName;
         QBluetoothAddress btAddress = QBluetoothAddress(address);
         QBluetoothTransferRequest request(btAddress);
         QFile *file = new QFile(fileName);
         reply = manager.put(request, file);
         connect(reply, SIGNAL(transferProgress(qint64,qint64)), this, SLOT(updateProgress(qint64,qint64)));
     }

and exposed to QML via a context property:

         QQuickView view;
         FileTransfer fileTransfer;
         view.rootContext()->setContextProperty("fileTransfer", QVariant::fromValue(&fileTransfer));

Example project @ code.qt.io

See also Qt Bluetooth.