Opening UI for QGIS plugin

Question

I am trying to develop my first simple QGIS plugin, which just loads all shapefiles from a folder into the current project by opening a window and click there a button "import". the importing does work, if I click the thumbnail of the plugin in the QGIS toolbar. But it does not open the user interface with my created button in qt designer. What am I doing wrong?

import os
from qgis.PyQt.QtCore import QCoreApplication
from qgis.core import QgsProject, QgsVectorLayer
from PyQt5.QtWidgets import QAction
from PyQt5.QtGui import QIcon


def load_shapefiles():
    path = "C:/Users/Giaco/Desktop/windkraft"
    for file_name in os.listdir(path):
        if file_name.endswith(".shp"):
            layer_name = os.path.splitext(file_name)[0]
            layer_path = os.path.join(path, file_name)
            layer = QgsVectorLayer(layer_path, layer_name, "ogr")
            if not layer.isValid():
                print("Layer failed to load: " + layer_name)
            QgsProject.instance().addMapLayer(layer)
    print("Shapefiles loaded successfully")

class LoadShapefiles:
    def __init__(self, iface):
        self.iface = iface

    def initGui(self):
        # Create action that will start plugin configuration
        self.action = self.create_action(
            "Load Shapefiles",
            "icon.png",
            "Load shapefiles into current project",
            self.run)

        # Add toolbar button and menu item
        self.iface.addToolBarIcon(self.action)
        self.iface.addPluginToMenu("&Load Shapefiles", self.action)

    def create_action(self, text, icon, description, function):
        action = QAction(QCoreApplication.translate("LoadShapefiles", text), self.iface.mainWindow())
        action.setIcon(QIcon(os.path.join(os.path.dirname(__file__), icon)))
        action.setToolTip(QCoreApplication.translate("LoadShapefiles", description))
        action.triggered.connect(function)
        return action

    def unload(self):
        self.iface.removeToolBarIcon(self.action)
        self.iface.removePluginMenu("&Load Shapefiles", self.action)

    def run(self):
        load_shapefiles()

Answer 1

Working as written. I do not see any definition of an interface to open. I do not see any attempts to open an interface.

But it does not open the user interface with my created button in qt designer. What am I doing wrong?

To open an interface you would want to add calls to the run function or something that run calls. The following is one possibility.

def run(self):
  self.my_window = MyWidget()
  self.my_window.show()
  # Run the dialog event loop
  result = self.my_window.exec_()

With a minimal example of use of the .ui file.

import os
from PyQt5 import uic
import PyQt5.QtWidgets as qtw
DESIGNER, _ = uic.loadUiType(os.path.join(
    os.path.dirname(__file__), 'my_widget.ui'))

class MyWidget(qtw.QDialog,DESIGNER):
  def __init__(self):
    super(MyWidget, self).__init__(None)
        self.setupUi(self)

Answer 2

There is a plugin called "plugin builder" which will create boilerplate plugin code that works.

The documentation is at http://g-sherman.github.io/Qgis-Plugin-Builder/ and the "plugin builder" plugin can be installed from the plugin repository in QGIS.

This does not answer your question directly, but may be very helpful.