如何在QFileSystemModel中更新文件信息？

Question

首先，这个问题与另一个问题相似，主要区别在于，我不想每次更新一个文件时都替换整个模型。在

在真实世界的例子中，我的应用程序只打开了几个文件，所以我基本上只是想了解如何更新一个特定的QFileSystemModel项的信息（大小、修改日期），下面您可以使用一些mcve，正如您在我尝试使用setData失败的代码中看到的那样：

import sys
import os

from PyQt5.Qt import *  # noqa


class DirectoryTreeWidget(QTreeView):

    def __init__(self, path=QDir.currentPath(), *args, **kwargs):
        super().__init__(*args, **kwargs)

        self.init_model(path)
        self.expandsOnDoubleClick = False
        self.header().setSectionResizeMode(0, QHeaderView.ResizeToContents)
        self.setAutoScroll(True)

    def init_model(self, path):
        self.extensions = ["*.*"]
        self.path = path
        model = QFileSystemModel(self)
        model.setRootPath(QDir.rootPath())
        model.setReadOnly(False)
        model.setFilter(QDir.AllDirs | QDir.NoDot | QDir.AllEntries)
        self.setModel(model)
        self.set_path(path)

    def set_path(self, path):
        self.path = path
        model = self.model()
        index = model.index(str(self.path))

        if os.path.isfile(path):
            self.setRootIndex(model.index(
                os.path.dirname(str(self.path))))
            self.scrollTo(index)
            self.setCurrentIndex(index)
        else:
            self.setRootIndex(index)


class Foo(QWidget):

    def __init__(self, path):
        super().__init__()

        self.path = path

        self.tree_view = DirectoryTreeWidget(path=".")
        self.tree_view.show()
        bt = QPushButton(f"Update {path}")
        bt.pressed.connect(self.update_file)

        layout = QVBoxLayout()
        layout.addWidget(self.tree_view)
        layout.addWidget(bt)

        self.setLayout(layout)

        # New file will automatically refresh QFileSystemModel
        self.create_file()

    def create_file(self):
        with open(self.path, "w") as f:
            data = "This new file contains xx bytes"
            f.write(data.replace("xx", str(len(data))))

    def update_file(self):
        model = self.tree_view.model()

        # Updating a file won't refresh QFileSystemModel, the question is,
        # how can we update that particular item to be refreshed?
        data = "The file updated is much larger, it contains xx bytes"
        with open(self.path, "w") as f:
            f.write(data.replace("xx", str(len(data))))

        # file_info = self.obj.model.fileInfo(index)
        # file_info.refresh()
        index = model.index(self.path)
        model.setData(index, model.data(index))
        QMessageBox.about(None, "Info", f"{self.path} updated, new size is {len(data)}")


def main():
    app = QApplication(sys.argv)
    foo = Foo("foo.txt")
    foo.setMinimumSize(640, 480)
    foo.show()
    sys.exit(app.exec_())


if __name__ == "__main__":
    main()

所以问题是，如何实现update_file更新特定文件foo.txt的信息？在

目标是只更新该文件而不替换整个模型，如图所示here，而且一旦该模型项被更新，那么该项就不会在视图中排序/移动了。在

Answer 1

qtv5.9.4引入了环境变量QT_FILESYSTEMMODEL_WATCH_FILES，为了解决QTBUG-46684，您可以在changelog中阅读更多关于它的信息：

QTBUG-46684 It is now possible to enable per-file watching by setting the environment variable QT_FILESYSTEMMODEL_WATCH_FILES, allowing to track for example changes in file size.

因此，要使示例正常工作，只需将envar设置为非空值，即：

import sys
import os

from PyQt5.Qt import *  # noqa


class DirectoryTreeWidget(QTreeView):

    def __init__(self, path=QDir.currentPath(), *args, **kwargs):
        super().__init__(*args, **kwargs)

        self.init_model(path)
        self.expandsOnDoubleClick = False
        self.header().setSectionResizeMode(0, QHeaderView.ResizeToContents)
        self.setAutoScroll(True)

    def init_model(self, path):
        os.environ["QT_FILESYSTEMMODEL_WATCH_FILES"] = '1'

        self.extensions = ["*.*"]
        self.path = path
        model = QFileSystemModel(self)
        model.setRootPath(QDir.rootPath())
        model.setReadOnly(False)
        model.setFilter(QDir.AllDirs | QDir.NoDot | QDir.AllEntries)
        self.setModel(model)
        self.set_path(path)

    def set_path(self, path):
        self.path = path
        model = self.model()
        index = model.index(str(self.path))

        if os.path.isfile(path):
            self.setRootIndex(model.index(
                os.path.dirname(str(self.path))))
            self.scrollTo(index)
            self.setCurrentIndex(index)
        else:
            self.setRootIndex(index)


class Foo(QWidget):

    def __init__(self, path):
        super().__init__()

        self.path = path

        self.tree_view = DirectoryTreeWidget(path=".")
        self.tree_view.show()
        bt = QPushButton(f"Update {path}")
        bt.pressed.connect(self.update_file)

        layout = QVBoxLayout()
        layout.addWidget(self.tree_view)
        layout.addWidget(bt)

        self.setLayout(layout)
        self.create_file()

    def create_file(self):
        with open(self.path, "w") as f:
            data = "This new file contains xx bytes"
            f.write(data.replace("xx", str(len(data))))

    def update_file(self):
        model = self.tree_view.model()

        data = "The file updated is much larger, it contains xx bytes"
        with open(self.path, "w") as f:
            f.write(data.replace("xx", str(len(data))))

        index = model.index(self.path)
        model.setData(index, model.data(index))
        QMessageBox.about(None, "Info", f"{self.path} updated, new size is {len(data)}")


def main():
    app = QApplication(sys.argv)
    foo = Foo("foo.txt")
    foo.setMinimumSize(640, 480)
    foo.show()
    sys.exit(app.exec_())


if __name__ == "__main__":
    main()

几点意见：

• 你需要设置这个环境变量before initializing the model。在
• 不过，这个特性的代价是潜在的重载。缓存文件将被监视，如果环境变量开启。在