Python Qt5 : Drag and drop examples - part 001.

This tutorial si about drag and drop with PyQt5 and Python 3.9.6.

The drag and drop feature is very intuitive for the user.

The widgets should respond to the drag and drop events in order to store the data dragged into them. 

• DragEnterEvent provides an event which is sent to the target widget as dragging action enters it.
• DragMoveEvent is used when the drag and drop action is in progress.
• DragLeaveEvent is generated as the drag and drop action leaves the widget.
• DropEvent, on the other hand, occurs when the drop is completed. The event’s proposed action can be accepted or rejected conditionally.

Let's see two example, first is a drag and drop for one button:

#!/usr/bin/python
import sys
from PyQt5.QtCore import Qt, QMimeData
from PyQt5.QtGui import QDrag
from PyQt5.QtWidgets import QPushButton, QWidget, QApplication

class Button(QPushButton):

    def __init__(self, title, parent):
        super().__init__(title, parent)

    def mouseMoveEvent(self, e):

        if e.buttons() != Qt.RightButton:
            return

        mimeData = QMimeData()

        drag = QDrag(self)
        drag.setMimeData(mimeData)
        drag.setHotSpot(e.pos() - self.rect().topLeft())
        dropAction = drag.exec_(Qt.MoveAction)

    def mousePressEvent(self, e):
        super().mousePressEvent(e)
        if e.button() == Qt.LeftButton:
            print('press')


class Example(QWidget):

    def __init__(self):
        super().__init__()

        self.initUI()

    def initUI(self):

        self.setAcceptDrops(True)

        self.button = Button('Button', self)
        self.button.move(100, 65)

        self.setWindowTitle('Drag and drop with mouse - right click to move Button!')
        self.setGeometry(300, 300, 550, 450)

    def dragEnterEvent(self, e):
        e.accept()

    def dropEvent(self, e):
        position = e.pos()
        self.button.move(position)

        e.setDropAction(Qt.MoveAction)
        e.accept()

def main():
    
    app = QApplication(sys.argv)
    ex = Example()
    ex.show()
    app.exec_()

if __name__ == '__main__':
    main()

... this source code is for a drag and drop for a image file:

import sys, os
from PyQt5.QtWidgets import QApplication, QWidget, QLabel, QVBoxLayout
from PyQt5.QtCore import Qt
from PyQt5.QtGui import QPixmap


class ImageLabel(QLabel):
    def __init__(self):
        super().__init__()

        self.setAlignment(Qt.AlignCenter)
        self.setText('\n\n Drop Image Here \n\n')
        self.setStyleSheet('''
            QLabel{
                border: 3px dashed #bbb
            }
        ''')

    def setPixmap(self, image):
        super().setPixmap(image)

class AppDemo(QWidget):
    def __init__(self):
        super().__init__()
        
        self.setWindowTitle('Drag and drop one image to this window!')
        self.setGeometry(300, 300, 550, 450)

        self.setAcceptDrops(True)

        mainLayout = QVBoxLayout()

        self.photoViewer = ImageLabel()
        mainLayout.addWidget(self.photoViewer)

        self.setLayout(mainLayout)

    def dragEnterEvent(self, event):
        if event.mimeData().hasImage:
            event.accept()
        else:
            event.ignore()

    def dragMoveEvent(self, event):
        if event.mimeData().hasImage:
            event.accept()
        else:
            event.ignore()

    def dropEvent(self, event):
        if event.mimeData().hasImage:
            event.setDropAction(Qt.CopyAction)
            file_path = event.mimeData().urls()[0].toLocalFile()
            self.set_image(file_path)

            event.accept()
        else:
            event.ignore()

    def set_image(self, file_path):
        self.photoViewer.setPixmap(QPixmap(file_path))

app = QApplication(sys.argv)
demo = AppDemo()
demo.show()
sys.exit(app.exec_())