QFileOpenEvent Class

Detailed Description

File open events will be sent to the QApplication::instance() when the operating system requests that a file or URL should be opened. This is a high-level event that can be caused by different user actions depending on the user's desktop environment; for example, double clicking on an file icon in the Finder on macOS.

This event is only used to notify the application of a request. It may be safely ignored.

macOS Example

In order to trigger the event on macOS, the application must be configured to let the OS know what kind of file(s) it should react on.

For example, the following Info.plist file declares that the application can act as a viewer for files with a PNG extension:

 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
 <plist version="1.0">
 <dict>
     <key>CFBundleDocumentTypes</key>
     <array>
         <dict>
             <key>CFBundleTypeExtensions</key>
             <array>
                 <string>png</string>
             </array>
             <key>CFBundleTypeRole</key>
             <string>Viewer</string>
         </dict>
     </array>
 </dict>
 </plist>

The following implementation of a QApplication subclass shows how to handle QFileOpenEvent to open the file that was, for example, dropped on the Dock icon of the application.

 #include <QApplication>
 #include <QDebug>
 #include <QFileOpenEvent>
 #include <QPushButton>

 class MyApplication : public QApplication
 {
 public:
     MyApplication(int &argc, char **argv)
         : QApplication(argc, argv)
     {
     }

     bool event(QEvent *event) override
     {
         if (event->type() == QEvent::FileOpen) {
             QFileOpenEvent *openEvent = static_cast<QFileOpenEvent *>(event);
             const QUrl url = openEvent->url();
             if (url.isLocalFile()) {
                 QFile localFile(url.toLocalFile());
                 // read from local file
             } else if (url.isValid()) {
                 // process according to the URL's schema
             } else {
                 // parse openEvent->file()
             }
         }

         return QApplication::event(event);
     }
 };

Note how QFileOpenEvent::file() is not guaranteed to be the name of a local file that can be opened using QFile. The contents of the string depend on the source application.