为什么qtreeview.scrollto()最初不工作?

下面的代码只显示计算机驱动器的树视图。每次选择一个新的文件/文件夹时,视图都会滚动以使新的选择可见。

问题 一 :当这项工作时,启动应用程序后的初始选择不会触发滚动。为什么?

问题 二 :如果说明:

self.my_view.scrollTo(index, QAbstractItemView.EnsureVisible)
self.my_view.resizeColumnToContents(0)

倒置:

self.my_view.resizeColumnToContents(0)
self.my_view.scrollTo(index, QAbstractItemView.EnsureVisible)

第一列的大小也不会在初始显示时进行调整,只会在之后进行调整。为什么?

import sys
from PyQt5.QtCore import Qt, QModelIndex, QDir
from PyQt5.QtWidgets import QApplication, QTreeView, QMainWindow, QFileSystemModel, QAbstractItemView


class MyWindow(QMainWindow):
    def __init__(self):
        super().__init__()

        # Instance variables
        self.my_view = QTreeView()
        self.my_model = QFileSystemModel()

        # Init FS model to show all computer drives
        model_root_path = str(self.my_model.myComputer())
        self.my_model.setRootPath(model_root_path)

        # Init tree view
        self.my_view.setModel(self.my_model)
        self.my_view.setRootIndex(self.my_model.index(model_root_path))
        self.my_view.setSelectionMode(QAbstractItemView.SingleSelection)
        self.my_view.setSelectionBehavior(QAbstractItemView.SelectRows)

        # Connect selection change events to custom slot
        select_model = self.my_view.selectionModel()
        select_model.currentRowChanged.connect(self.current_row_changed)

        # Main window
        self.setCentralWidget(self.my_view)
        self.setGeometry(200, 200, 800, 600)

        # Select initial row on view
        focus_path = QDir.currentPath()
        focus_index = self.my_model.index(focus_path)
        self.my_view.setCurrentIndex(focus_index)

    def current_row_changed(self):
        """Current row of the model has changed"""

        # Scroll view to new row
        index = self.my_view.selectionModel().currentIndex()
        self.my_view.scrollTo(index, QAbstractItemView.EnsureVisible)
        self.my_view.resizeColumnToContents(0)

        # Show path of current row in window title
        absolute_path = self.my_model.filePath(index)
        self.setWindowTitle(absolute_path)


def main():
    a = QApplication(sys.argv)
    mw = MyWindow()
    mw.show()
    sys.exit(a.exec_())

if __name__ == '__main__':
    main()

`

编辑 :在使用了@ekhometo提供的良好解决方案后,我上面的示例代码工作正常。然而,另一段代码仍然没有:

import os
import sys

from PyQt5.QtCore import pyqtSignal, QTimer, QDir, Qt
from PyQt5.QtWidgets import QMainWindow, QGridLayout, QWidget, QTreeView, QAbstractItemView, QFileSystemModel, \
    QApplication


class AppWindow(QMainWindow):

    default_folder_path = "."

    def __init__(self):
        super().__init__()
        self.folder_view = FolderTreeView()
        self.folder_view.folder_has_changed.connect(self.folder_changed)
        self.build_ui()
        self.show()

        # Select initial folder
        self.select_initial_folder()

    def build_ui(self):
        main_widget = QWidget()
        layout = QGridLayout(main_widget)
        layout.addWidget(self.folder_view)
        self.setCentralWidget(main_widget)
        self.setGeometry(200, 100, 800, 600)

    def select_initial_folder(self):
        folder_index = self.folder_view.get_index(AppWindow.default_folder_path)
        if folder_index.isValid():
            self.folder_view.select_folder(folder_index)

    def folder_changed(self, folder_path):
        if not os.path.isdir(folder_path):
            print("Non existing folder:", folder_path)
            return


class FolderTreeView(QTreeView):
    folder_has_changed = pyqtSignal(str)

    def __init__(self):
        super().__init__()
        self.folder_tree_model = FolderTreeModel()
        self.setModel(self.folder_tree_model)
        self.setSelectionMode(QAbstractItemView.SingleSelection)
        self.setSelectionBehavior(QAbstractItemView.SelectRows)

    def select_folder(self, folder_index):
        self.setCurrentIndex(folder_index)

    def currentChanged(self, current, previous):
        super(FolderTreeView, self).currentChanged(current, previous)

        # Scroll the view to current item and resize folder name column
        QTimer.singleShot(50, lambda: self.delayed_scroll(current))

        # Emit signal for other uses
        self.folder_has_changed.emit(self.folder_tree_model.filePath(current))

    def delayed_scroll(self, index):
        self.scrollTo(index, QAbstractItemView.EnsureVisible)
        self.resizeColumnToContents(0)

    def get_index(self, folder_path):
        return self.folder_tree_model.index(folder_path)


class FolderTreeModel(QFileSystemModel):
    def __init__(self):
        super().__init__()
        self.setFilter(QDir.AllDirs | QDir.NoDotAndDotDot)
        self.setRootPath("")


def main():
    app = QApplication(sys.argv)
    window = AppWindow()
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()