为啥在 QTreeView 中展开可能无法正常工作？
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【中文标题】为啥在 QTreeView 中展开可能无法正常工作？【英文标题】：Why expanding in QTreeView may work incorrectly?为什么在 QTreeView 中展开可能无法正常工作？ 【发布时间】：2020-04-05 11:02:59 【问题描述】：我正在尝试创建一个小应用程序，它将查找、读取和导出一些 *.xml 文档。应用程序必须读取分层文件夹结构并在窗体上的 QTreeView 中将其可视化。为了更好地管理，我希望它在应用程序启动时扩展树视图的所有对象。我已经尝试了许多不同的解决方案，例如：
void expandChildren(const QModelIndex &index, QTreeView *view)
if (!index.isValid())
return;
int childCount = index.model()->rowCount(index);
for (int i = 0; i < childCount; i++)
const QModelIndex &child = index.child(i, 0);
expandChildren(child, view);
if (!view->isExpanded(index))
view->expand(index);
来自一些论坛和嵌入式解决方案，例如 QTreeView::expandRecursively 和 QTreeView::expandAll，但我没有达到我想要的。
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QFileSystemModel>
#include <QDebug>
#include <QDirModel>
#include <QTreeView>
QT_BEGIN_NAMESPACE
namespace Ui class MainWindow;
QT_END_NAMESPACE
class MainWindow : public QMainWindow
Q_OBJECT
QModelIndex fs_index;
QModelIndex child_1_index;
QModelIndex child_2_index;
QModelIndex child_3_index;
QFileSystemModel *fs_model = new QFileSystemModel;
public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
private slots:
void on_treeView_clicked(const QModelIndex &index);
void on_pushButton_2_clicked();
void on_pushButton_clicked();
private:
Ui::MainWindow *ui;
void expandChildren(const QModelIndex &index, QTreeView *view)
if (!index.isValid())
return;
int childCount = index.model()->rowCount(index);
for (int i = 0; i < childCount; i++)
const QModelIndex &child = index.child(i, 0);
expandChildren(child, view);
if (!view->isExpanded(index))
view->expand(index);
;
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
, ui(new Ui::MainWindow)
ui->setupUi(this);
QString str_root_path;
QDir dir;
qDebug() << "Current user's home folder is: " <<QDir::home().path();
str_root_path = QDir::home().path() + "/AppData/Local/app/settings";
qDebug() << "Settings storing folder id: " << str_root_path;
dir.setPath(str_root_path);
if (!dir.exists())
qDebug() << "Settings folder doesn't exist.";
return;
if (!dir.isReadable())
qDebug() << "Folder found. Read access denied. Check access rights.";
return;
qDebug() << "Folder found. Read access granted. Reading...";
ui->treeView->setModel(fs_model);
fs_index = fs_model->index(str_root_path);
qDebug() << fs_model->fileName(fs_index);
fs_model->setRootPath(str_root_path);
QStringList filter;
filter << "*.xml";
fs_model->setNameFilters(filter);
fs_model->setFilter( QDir::AllDirs | QDir::Files | QDir::NoDotAndDotDot);
ui->treeView->setRootIndex(fs_index);
ui->treeView->setCurrentIndex(fs_index);
for (int i = 1; i < fs_model->columnCount(); i++)
ui->treeView->setColumnHidden(i, true);
ui->treeView->show();
qDebug().nospace() << "View loaded. Expanding....";
ui->treeView->setExpanded(fs_index, true);
int fs_index_rows = fs_model->rowCount(fs_index);
qDebug().nospace() << "Number of found profiles:" << fs_index_rows;
for (int i = 0; i < fs_index_rows; ++i)
child_1_index = fs_model->index(i,0,fs_index);
ui->treeView->setExpanded(child_1_index, true);
int child_1_index_rows = fs_model->rowCount(child_1_index);
qDebug().nospace() << "Step #" << i+1 << " Object name: " << fs_model->fileName(child_1_index) << ". Num of children: " << child_1_index_rows;
for (int j = 0; j < child_1_index_rows; ++j)
child_2_index = ui->treeView->model()->index(j,0,child_1_index);
//qDebug() << child_2_index;
ui->treeView->setExpanded(child_2_index, true);
int child_2_index_rows = ui->treeView->model()->rowCount(child_2_index);
qDebug().nospace() << "Step #" << i+1 << "/" << j+1 << " Object name: " << fs_model->fileName(child_1_index) << "/" << fs_model->fileName(child_2_index) << ". Num of children: " << child_2_index_rows;
for (int k = 0; k < child_2_index_rows; ++k)
child_3_index = ui->treeView->model()->index(k,0,child_2_index);
ui->treeView->setExpanded(child_3_index, true);
int child_3_index_rows = ui->treeView->model()->rowCount(child_3_index);
qDebug().nospace() << "Step #" << i+1 << "/" << j+1 << "/" << k+1 << " Object name: " << fs_model->fileName(child_1_index) << "/" << fs_model->fileName(child_2_index) << "/" << fs_model->fileName(child_3_index) << ". Num of children: " << child_3_index_rows;
如果我将该代码粘贴到连接到“pushbutton_Clicked”信号的插槽，例如，每次单击都会将树视图扩展为一个深度级别（如果我连接 QTreeView::expandRecursively 或 QTreeView:: expandAll 到“pushbutton_Clicked”）。我尝试调试应用程序的每一步，但我发现每个新的索引对象都无法获得父文件系统模型的索引。
请帮助我理解，错误在哪里以及如何修复它。
我是 Qt 编程新手，知识还不全面，但我仍在搜索、阅读和尝试理解。
提前谢谢你，对英语不好表示抱歉。
app的所有代码：
main.cpp
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QFileSystemModel>
#include <QDebug>
#include <QDirModel>
#include <QTreeView>
QT_BEGIN_NAMESPACE
namespace Ui class MainWindow;
QT_END_NAMESPACE
class MainWindow : public QMainWindow
Q_OBJECT
QModelIndex fs_index;
QFileSystemModel fs_model;
public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
private slots:
void on_treeView_clicked(const QModelIndex &index);
void on_pushButton_2_clicked();
void on_pushButton_clicked();
private:
Ui::MainWindow *ui;
void expandChildren(const QModelIndex &index, QTreeView *view)
if (!index.isValid())
return;
int childCount = index.model()->rowCount(index);
for (int i = 0; i < childCount; i++)
const QModelIndex &child = index.child(i, 0);
// Recursively call the function for each child node.
expandChildren(child, view);
if (!view->isExpanded(index))
view->expand(index);
void expand_the_tree(const QModelIndex &root_index, QTreeView *view)
qDebug() << fs_model.canFetchMore(root_index);
while (fs_model.canFetchMore(root_index) == true)
fs_model.fetchMore(root_index);
qDebug().nospace() << "Model fetched on root layer.";
QModelIndex child_1_index;
QModelIndex child_2_index;
QModelIndex child_3_index;
view->expand(root_index);
int root_index_rows = fs_model.rowCount(root_index);
qDebug().nospace() << "Number of found profiles:" << root_index_rows;
for (int i = 0; i < root_index_rows; ++i)
child_1_index = fs_model.index(i,0,root_index);
view->expand(child_1_index);
expandChildren(child_1_index, view);
int child_1_index_rows = fs_model.rowCount(child_1_index);
qDebug().nospace() << "Step #" << i+1 << " Object name: " << fs_model.fileName(child_1_index) << ". Num of children: " << child_1_index_rows;
for (int j = 0; j < child_1_index_rows; ++j)
child_2_index = fs_model.index(j,0,child_1_index);
//qDebug() << child_2_index;
view->expand(child_2_index);
int child_2_index_rows = fs_model.rowCount(child_2_index);
qDebug().nospace() << "Step #" << i+1 << "/" << j+1 << " Object name: " << fs_model.fileName(child_1_index) << "/" << fs_model.fileName(child_2_index) << ". Num of children: " << child_2_index_rows;
for (int k = 0; k < child_2_index_rows; ++k)
child_3_index = fs_model.index(k,0,child_2_index);
view->expand(child_3_index);
int child_3_index_rows = fs_model.rowCount(child_3_index);
qDebug().nospace() << "Step #" << i+1 << "/" << j+1 << "/" << k+1 << " Object name: " << fs_model.fileName(child_1_index) << "/" << fs_model.fileName(child_2_index) << "/" << fs_model.fileName(child_3_index) << ". Num of children: " << child_3_index_rows;
;
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QApplication>
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
, ui(new Ui::MainWindow)
ui->setupUi(this);
QString str_root_path;
QDir dir;
qDebug() << "Current user's home folder is: " <<QDir::home().path();
str_root_path = QDir::home().path() + "/AppData/Local/app/settings";
qDebug() << "Preset's storing folder id: " << str_root_path;
dir.setPath(str_root_path);
if (!dir.exists())
qDebug() << "Settings folder doesn't exist.";
return;
if (!dir.isReadable())
qDebug() << "Folder found. Read access denied. Check access rights.";
return;
qDebug() << "Folder found. Read access granted. Reading...";
fs_index = fs_model.index(str_root_path);
qDebug() << fs_model.fileName(fs_index);
fs_model.setRootPath(str_root_path);
QStringList filter;
filter << "*.xml";
fs_model.setNameFilters(filter);
fs_model.setFilter( QDir::AllDirs | QDir::Files | QDir::NoDotAndDotDot);
ui->treeView->setModel(&fs_model);
ui->treeView->setRootIndex(fs_index);
ui->treeView->setCurrentIndex(fs_index);
qDebug() << fs_model.canFetchMore(fs_index);
for (int c = 1; c < fs_model.columnCount(); c++)
ui->treeView->setColumnHidden(c, true);
qDebug().nospace() << "View loaded. Expanding....";
expand_the_tree(fs_index, ui->treeView);
MainWindow::~MainWindow()
delete ui;
void MainWindow::on_treeView_clicked(const QModelIndex &index)
qDebug() << index;
void MainWindow::on_pushButton_2_clicked()
expandChildren(fs_index, ui->treeView);
void MainWindow::on_pushButton_clicked()
expand_the_tree(fs_index, ui->treeView);
mainwindow.ui
<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
<class>MainWindow</class>
<widget class="QMainWindow" name="MainWindow">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>712</width>
<height>635</height>
</rect>
</property>
<property name="windowTitle">
<string>MainWindow</string>
</property>
<widget class="QWidget" name="centralwidget">
<widget class="QTreeView" name="treeView">
<property name="geometry">
<rect>
<x>20</x>
<y>60</y>
<width>311</width>
<height>531</height>
</rect>
</property>
</widget>
<widget class="QTableView" name="tableView">
<property name="geometry">
<rect>
<x>370</x>
<y>60</y>
<width>321</width>
<height>531</height>
</rect>
</property>
</widget>
<widget class="QPushButton" name="pushButton">
<property name="geometry">
<rect>
<x>20</x>
<y>600</y>
<width>75</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>Refresh</string>
</property>
</widget>
<widget class="QPushButton" name="pushButton_2">
<property name="geometry">
<rect>
<x>110</x>
<y>600</y>
<width>75</width>
<height>23</height>
</rect>
</property>
<property name="text">
<string>Retrieve all</string>
</property>
</widget>
</widget>
</widget>
<resources/>
<connections/>
</ui>
【问题讨论】：
【参考方案1】：这是整个代码吗？可以提供主要的吗？
无论如何我无法编译你的代码，第 29 行：
ui->treeView->setModel(fs_model);
调用不存在的函数treeView。
无论如何，如果你想做一个 UI，我建议你使用 QML，你可以看看 qt 中已经完成的示例。
树模型https://doc-snapshots.qt.io/qt5-5.11/qtquickcontrols-filesystembrowser-example.html
您可以在打开 Qt creator 时查看并运行它们。点击welcome，然后点击example，最后输入tree
一旦您有了基本代码，您就可以根据需要对其进行修改。
【讨论】：
QTreeView 确实有 setModel 方法，因为它继承自 QAbstractItemView：doc.qt.io/qt-5/qtreeview-members.html 不，是ui没有方法treeView。无论如何，如果您有其他代码要发布，请将其放在这里，以便我可以尝试:) mmm，你好像没用过Qt Designer(MOC)，明显OP加了一个QTreeView，名字叫treeView，通过ui访问：ui->treeView
1.我读过树模型。 2. 是的，“treeView”是表单上的 QTreeView 对象，通过 UI 访问。 3.问题出在模型子索引的“rowCount”响应中。谷歌什么也没给...
我已经添加了整个代码。 .canFetchMode 返回 false，但当目录不为空且对象出现在 treeView 中时，.rowCount 继续返回零行...以上是关于为啥在 QTreeView 中展开可能无法正常工作？的主要内容，如果未能解决你的问题，请参考以下文章
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