import os
import sys
from qgis.gui import *
from qgis.core import *
from qgis.PyQt.QtCore import *
from qgis.PyQt.QtWidgets import *


class MapViewer(QMainWindow):
    def __init__(self, shapefile):
        QMainWindow.__init__(self)
        self.setWindowTitle("Map Viewer")

        canvas = QgsMapCanvas()
        canvas.setCanvasColor(Qt.white)
        canvas.show()

        project = QgsProject.instance()
        project.read(r'E:/data/1.Natural_Earth/Test.qgz')

        layer = QgsVectorLayer(shapefile, "layer1", "ogr")
        if not layer.isValid():
            raise IOError("Invalid shapefile")

        # project.addMapLayer(layer)
        # canvas.setExtent(layer.extent())
        # canvas.setLayers([layer])
        layers = project.mapLayers().values()
        canvas.setLayers(layers)

        layout = QVBoxLayout()
        layout.addWidget(canvas)

        contents = QWidget()
        contents.setLayout(layout)
        self.setCentralWidget(contents)


if __name__ == "__main__":
    QgsApplication.setPrefixPath("qgis", True)
    qgs = QgsApplication([], True)
    qgs.initQgis()

    viewer = MapViewer("./data/Counties.shp")
    viewer.show()
    exitCode = qgs.exec()

    qgs.exitQgis()