Operate files through QT drag events

In order to improve the friendly interaction of users , stay QT Sometimes in the application, we need to drag and drop events to realize file shortcut . Here's how to achieve file shortcut by dragging events , First, we need to enable the drag event in the corresponding interface implementation , The corresponding configuration is as follows :

setAcceptDrops(true);

After the drag event is enabled, we can dragEnterEvent Event to determine whether there is a file in the dragged object . By judgment mimeData Include in text/uri-list Format data to determine whether there is a file in the drag object . If the dragged object contains a file , We can continue the follow-up events :

class ImageLoader : public QWidget
{
    
    Q_OBJECT
...    
protected:
    // Drag into event 
    void dragEnterEvent(QDragEnterEvent* event) override;
...
}
void ImageLoader::dragEnterEvent(QDragEnterEvent *event)
{
    
    // This event will be triggered every time a file is dragged onto the control 
    // We can determine whether there is a corresponding file by dragging the data format 
    // Follow up operations are only accepted when there are documents 
    if(event->mimeData()->hasFormat("text/uri-list")){
    
        event->acceptProposedAction();
    }
}

After the control accepts the drag event , We can do that drop The file is processed when it is released , The processing flow is as follows , In the example, we mainly deal with text files and image files , In actual business, we can process files in different formats according to our own business .

class ImageLoader : public QWidget
{
    
    Q_OBJECT
...    
protected:
    // Release dragged event 
    void dropEvent(QDropEvent* event) override;
...
}
void ImageLoader::dropEvent(QDropEvent *event)
{
    
    // If there is no file, do nothing 
    const QMimeData* mimeData = event->mimeData();
    if (!mimeData->hasUrls()) {
    
        return;
    }
    // Perform different operations according to the file type 
    const QUrl url = mimeData->urls().first();
    QMimeType mime = QMimeDatabase().mimeTypeForUrl(url);
    // Print file type 
    qDebug() << mime.name();
    if (mime.inherits("audio/wav")) {
    
        m_image_label->setText(" Audio file ");
    }
    else if(mime.inherits("text/plain"))
    {
    
        QString file_path = url.toLocalFile();
        QFile file(file_path);
        file.open(QIODevice::ReadOnly);
        QByteArray array = file.readAll();
        m_image_label->setText(array);
        file.close();
    }
    else if(mime.inherits("image/png"))
    {
    
        QString file_path = url.toLocalFile();
        QPixmap pixmap(file_path);
        m_image_label->setPixmap(pixmap);
    }
}

The example code of the whole calling process of dragging operation file is as follows , Welcome to :

//imageloader.h
#ifndef IMAGELOADER_H
#define IMAGELOADER_H

#include <QWidget>
#include <QLabel>

namespace Ui {
    
class ImageLoader;
}

class ImageLoader : public QWidget
{
    
    Q_OBJECT

public:
    explicit ImageLoader(QWidget *parent = 0);
    ~ImageLoader();


protected:
    // Drag into event 
    void dragEnterEvent(QDragEnterEvent* event) override;

    // Release dragged event 
    void dropEvent(QDropEvent* event) override;

private:
    QLabel* m_image_label = nullptr;
};
#endif // IMAGELOADER_H

//imageloader.cpp
#include "imageloader.h"
#include "ui_imageloader.h"
#include <QDropEvent>
#include <QMimeData>
#include <QMimeDatabase>
#include <QMimeType>
#include <QHBoxLayout>
#include <QDebug>

ImageLoader::ImageLoader(QWidget *parent) :
    QWidget(parent)
{
    

    m_image_label = new QLabel(this);
    QHBoxLayout* main_layout = new QHBoxLayout(this);
    main_layout->addWidget(m_image_label);
    this->setLayout(main_layout);
    m_image_label->setText(" Drag the file here ");
    // Set the control to receive drag events 
    setAcceptDrops(true);
}

ImageLoader::~ImageLoader()
{
    
}

void ImageLoader::dragEnterEvent(QDragEnterEvent *event)
{
    
    // This event will be triggered every time a file is dragged onto the control 
    // We can determine whether there is a corresponding file by dragging the data format 
    // Follow up operations are only accepted when there are documents 
    if(event->mimeData()->hasFormat("text/uri-list")){
    
        event->acceptProposedAction();
    }
}

void ImageLoader::dropEvent(QDropEvent *event)
{
    
    // If there is no file, do nothing 
    const QMimeData* mimeData = event->mimeData();
    if (!mimeData->hasUrls()) {
    
        return;
    }
    // Perform different operations according to the file type 
    const QUrl url = mimeData->urls().first();
    QMimeType mime = QMimeDatabase().mimeTypeForUrl(url);
    // Print file type 
    qDebug() << mime.name();
    if (mime.inherits("audio/wav")) {
    
        m_image_label->setText(" Audio file ");
    }
    else if(mime.inherits("text/plain"))
    {
    
        QString file_path = url.toLocalFile();
        QFile file(file_path);
        file.open(QIODevice::ReadOnly);
        QByteArray array = file.readAll();
        m_image_label->setText(array);
        file.close();
    }
    else if(mime.inherits("image/png"))
    {
    
        QString file_path = url.toLocalFile();
        QPixmap pixmap(file_path);
        m_image_label->setPixmap(pixmap);
    }
}

The use effect is as follows: :