使用 PyQt5 拖放 QLabels

Question

我正在尝试使用 PyQt5 将 Qlabel 拖放到另一个 Qlabel 上：

from PyQt5.QtWidgets import QApplication, QWidget, QToolTip, QPushButton, QMessageBox, QHBoxLayout, QVBoxLayout, QGridLayout,QFrame, QComboBox, QLabel, QLineEdit
from PyQt5.QtGui import QIcon, QFont, QPixmap, QImage
import sys


class my_label(QLabel):
    def __init__(self,title,parent):
        super().__init__(title,parent)
        self.setAcceptDrops(True)

    def dragEnterEvent(self,event):
        if event.mimeData().hasFormat("text/plain"):
            event.accept()
        else:
            event.ignore()
    def dropEvent(self,event):
        self.setText(event.mimeData().text())


class application(QWidget):

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

    def initUI(self):


        label = my_label("drop there",self)
        label.resize(100,100)
        label.move(190,65)

        label_to_drag = QLabel("drag this",self)
        #label_to_drag.setDragEnabled(True)    #doesn't work with QLabel        
        self.show()


    def closeEvent(self,event):
        message = QMessageBox.question(self,"Message","Quit ?",QMessageBox.Yes | QMessageBox.No,QMessageBox.No)

        if message == QMessageBox.Yes:
            event.accept()
        else:
            event.ignore()

app = QApplication(sys.argv)
fenetre = application()
sys.exit(app.exec_())

我想让我的第一个标签“可拖动”，通过调用setDragEnabled(True) 方法（就像我为 QLineEdit 所做的那样），并将它放在第二个标签上以更改他的文本。从另一个应用程序删除文本工作正常，但我找不到如何在我自己的应用程序中拖动 QLabel ... 我错过了什么 ？

编辑：修改代码以尝试拖放图像：

class DraggableLabel(QLabel):
def __init__(self,parent,image):
    super(QLabel,self).__init__(parent)
    self.setPixmap(QPixmap(image))    
    self.show()
def mousePressEvent(self, event):
    if event.button() == Qt.LeftButton:
        self.drag_start_position = event.pos()

def mouseMoveEvent(self, event):
    if not (event.buttons() & Qt.LeftButton):
        return
    if (event.pos() - self.drag_start_position).manhattanLength() < QApplication.startDragDistance():
        return
    drag = QDrag(self)
    mimedata = QMimeData()
    mimedata.setText(self.text())

    drag.setMimeData(mimedata)
    pixmap = QPixmap(self.size())
    painter = QPainter(pixmap)
    painter.drawPixmap(self.rect(), self.grab())
    painter.end()
    drag.setPixmap(pixmap)
    drag.setHotSpot(event.pos())
    drag.exec_(Qt.CopyAction | Qt.MoveAction)

   class my_label(QLabel):
    def __init__(self,title,parent):
        super().__init__(title,parent)
        self.setAcceptDrops(True)

    def dragEnterEvent(self,event):
        if event.mimeData().hasFormat("text/plain"):
            print("event accepted")
            event.accept()
        else:
            print("event rejected")
            event.ignore()
    def dropEvent(self,event):
        if event.mimeData().hasImage():
            self.setPixmap(QPixmap.fromImage(QImage(event.mimeData().imageData())))

class application(QWidget):

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

    def initUI(self):

        label_to_drag = DraggableLabel(self,"index.jpg")

        label = my_label("drop there",self)
        label.resize(100,100)
        label.move(190,65)



        self.show()

当我将DraggableLabel（显示图像）放在my_label 上时，该事件被接受，但hasImage() 总是返回false...是我设置图像的方式错误吗？

Answer 1

对于QLabel，您必须从头开始创建所有内容，为此您可以遵循docs 的示例。

在下面的示例中，我放置了一个示例，其中一个类只接受拖放，另一个类只接受拖动，以便您可以看到每个部分并更好地理解。

import sys

from PyQt5.QtWidgets import QApplication, QLabel, QWidget
from PyQt5.QtGui import QDrag, QPixmap, QPainter, QCursor
from PyQt5.QtCore import QMimeData, Qt


class DraggableLabel(QLabel):
    def mousePressEvent(self, event):
        if event.button() == Qt.LeftButton:
            self.drag_start_position = event.pos()

    def mouseMoveEvent(self, event):
        if not (event.buttons() & Qt.LeftButton):
            return
        if (event.pos() - self.drag_start_position).manhattanLength() < QApplication.startDragDistance():
            return
        drag = QDrag(self)
        mimedata = QMimeData()
        mimedata.setText(self.text())
        drag.setMimeData(mimedata)
        pixmap = QPixmap(self.size())
        painter = QPainter(pixmap)
        painter.drawPixmap(self.rect(), self.grab())
        painter.end()
        drag.setPixmap(pixmap)
        drag.setHotSpot(event.pos())
        drag.exec_(Qt.CopyAction | Qt.MoveAction)

class DropLabel(QLabel):
    def __init__(self, *args, **kwargs):
        QLabel.__init__(self, *args, **kwargs)
        self.setAcceptDrops(True)

    def dragEnterEvent(self, event):
        if event.mimeData().hasText():
            event.acceptProposedAction()

    def dropEvent(self, event):
        pos = event.pos()
        text = event.mimeData().text()
        self.setText(text)
        event.acceptProposedAction()


class Widget(QWidget):
    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):
        label = DropLabel("drop there",self)
        label.setGeometry(190, 65, 100,100)

        label_to_drag = DraggableLabel("drag this",self)  
        self.show()

if __name__ == '__main__':
    app = QApplication(sys.argv)
    w = Widget()
    w.show()
    sys.exit(app.exec_())

---

更新：

不要将QDrag与QMimeData混淆，如果你想使用imageData()你必须将它设置为setImageData()，如docs所示：

class DraggableLabel(QLabel):
    def __init__(self,parent,image):
        super(QLabel,self).__init__(parent)
        self.setPixmap(QPixmap(image))    
        self.show()
    def mousePressEvent(self, event):
        if event.button() == Qt.LeftButton:
            self.drag_start_position = event.pos()

    def mouseMoveEvent(self, event):
        if not (event.buttons() & Qt.LeftButton):
            return
        if (event.pos() - self.drag_start_position).manhattanLength() < QApplication.startDragDistance():
            return
        drag = QDrag(self)
        mimedata = QMimeData()
        mimedata.setText(self.text())
        mimedata.setImageData(self.pixmap().toImage())

        drag.setMimeData(mimedata)
        pixmap = QPixmap(self.size())
        painter = QPainter(pixmap)
        painter.drawPixmap(self.rect(), self.grab())
        painter.end()
        drag.setPixmap(pixmap)
        drag.setHotSpot(event.pos())
        drag.exec_(Qt.CopyAction | Qt.MoveAction)

class my_label(QLabel):
    def __init__(self,title,parent):
        super().__init__(title,parent)
        self.setAcceptDrops(True)

    def dragEnterEvent(self,event):
        if event.mimeData().hasImage():
            print("event accepted")
            event.accept()
        else:
            print("event rejected")
            event.ignore()
    def dropEvent(self,event):
        if event.mimeData().hasImage():
            self.setPixmap(QPixmap.fromImage(QImage(event.mimeData().imageData())))