dynamically adding and removing widgets in PyQt

Question

using PyQt, I am trying to create an interface for which I can add or remove widget dynamically. I want to define a separate class for the widget that will be added or remov

Answer 1

Here is a little change that will make the button delete itself once clicked:

from PyQt4 import QtGui, QtCore
import sys

class Main(QtGui.QMainWindow):
    def __init__(self, parent = None):
        super(Main, self).__init__(parent)

        # main button
        self.addButton = QtGui.QPushButton('button to add other widgets')
        self.addButton.clicked.connect(self.addWidget)

        # scroll area widget contents - layout
        self.scrollLayout = QtGui.QFormLayout()

        # scroll area widget contents
        self.scrollWidget = QtGui.QWidget()
        self.scrollWidget.setLayout(self.scrollLayout)

        # scroll area
        self.scrollArea = QtGui.QScrollArea()
        self.scrollArea.setWidgetResizable(True)
        self.scrollArea.setWidget(self.scrollWidget)

        # main layout
        self.mainLayout = QtGui.QVBoxLayout()

        # add all main to the main vLayout
        self.mainLayout.addWidget(self.addButton)
        self.mainLayout.addWidget(self.scrollArea)

        # central widget
        self.centralWidget = QtGui.QWidget()
        self.centralWidget.setLayout(self.mainLayout)

        # set central widget
        self.setCentralWidget(self.centralWidget)

    def addWidget(self):
        self.scrollLayout.addRow(TestButton()) 


class TestButton(QtGui.QPushButton):
  def __init__( self, parent=None):
      super(TestButton, self).__init__(parent)
      self.setText("I am in Test widget")
      self.clicked.connect(self.deleteLater)


app = QtGui.QApplication(sys.argv)
myWidget = Main()
myWidget.show()
app.exec_()

This way it shouldn't mem leak when deleted and the button can actually be used for stuff. I follow this pattern for progress bars by the dozens for downloads and chunks monitoring and it works just fine even with threading and multi processing. And not the easy QThreads...

Answer 2

Actually, it does work. Problem is, your Test widget has a QPushButton without any layout management. So it can't calculate its minimumSize with taking the button into consideration. When you put that widget in a layout, it just shrinks to 0 (since a QWidget has no default minimumSize) and you don't see anything.

You have two choices, either you manually manage layout and enter a needless world of pain, or you rely on layout managers. In general, you should prefer the latter.

I would re-write your script like this (Although I'm not sure why you use QFormLayout, I leave it as it is.):

from PyQt4 import QtGui, QtCore
import sys

class Main(QtGui.QMainWindow):
    def __init__(self, parent = None):
        super(Main, self).__init__(parent)

        # main button
        self.addButton = QtGui.QPushButton('button to add other widgets')
        self.addButton.clicked.connect(self.addWidget)

        # scroll area widget contents - layout
        self.scrollLayout = QtGui.QFormLayout()

        # scroll area widget contents
        self.scrollWidget = QtGui.QWidget()
        self.scrollWidget.setLayout(self.scrollLayout)

        # scroll area
        self.scrollArea = QtGui.QScrollArea()
        self.scrollArea.setWidgetResizable(True)
        self.scrollArea.setWidget(self.scrollWidget)

        # main layout
        self.mainLayout = QtGui.QVBoxLayout()

        # add all main to the main vLayout
        self.mainLayout.addWidget(self.addButton)
        self.mainLayout.addWidget(self.scrollArea)

        # central widget
        self.centralWidget = QtGui.QWidget()
        self.centralWidget.setLayout(self.mainLayout)

        # set central widget
        self.setCentralWidget(self.centralWidget)

    def addWidget(self):
        self.scrollLayout.addRow(Test())


class Test(QtGui.QWidget):
  def __init__( self, parent=None):
      super(Test, self).__init__(parent)

      self.pushButton = QtGui.QPushButton('I am in Test widget')

      layout = QtGui.QHBoxLayout()
      layout.addWidget(self.pushButton)
      self.setLayout(layout)



app = QtGui.QApplication(sys.argv)
myWidget = Main()
myWidget.show()
app.exec_()

Answer 3

If u want to say , delete a widget whenever a button is clicked , or during any event of ur program , use the deleteLater() method :self.yourwidget.deleteLater()

self.button.clicked.connect(delete_widget);

def delete_widget(self):
     self.widget.deleteLater();

self.widget.deleteLater();

Using the above function makes that widget dissappear from the Application