Simple use of qtreeview of QT (including source code + comments)

One 、QTreeView Operation example diagram

1. Example of adding and deleting nodes

The following figure shows an example of adding and deleting nodes , This includes adding top-level nodes 、 Add child nodes 、 Remove nodes and other operations ; The source code is in the third section of this article （ The source code contains detailed comments ）.

2. Get and modify the value of the node

The following figure shows the operation of nodes on node values , This includes getting values 、 Set values, etc ; The source code is in the third section of this article （ The source code contains detailed comments ）.

Two 、QTreeView（ Personal understanding ）

Here we will QTreeView and QTableView Compare the

1. Both are similar MVC（Model View Controller） Pattern , It all includes Delegate, Please check out Qt The realization of agent （ Button chapter ）、Qt The realization of agent （ General controls ）;
2. Use both QStandardItemModel Storing data ;
3. QTreeView There is also an inheritance QTreeWidget Subclasses of ;
4. QTreeView The only difference is that I can operate item Child nodes of .

3、 ... and 、 Source code

CMainWindow.h

#ifndef CMAINWINDOW_H
#define CMAINWINDOW_H

#include <QMainWindow>
#include <QStandardItemModel> // Data model class 

namespace Ui {
    
class CMainWindow;
}

class CMainWindow : public QMainWindow
{
    
    Q_OBJECT

public:
    explicit CMainWindow(QWidget *parent = 0);
    ~CMainWindow();

private slots:

    /** * @brief on_getCurNodeDataBtn_clicked  Get current node value  */
    void on_getCurNodeDataBtn_clicked();

    /** * @brief on_setCurNodeDataBtn_clicked  Set the current node value  */
    void on_setCurNodeDataBtn_clicked();

    /** * @brief on_addTopNodeBtn_clicked  Add top-level nodes  */
    void on_addTopNodeBtn_clicked();

    /** * @brief on_addChildNodeBtn_clicked  Add child nodes  */
    void on_addChildNodeBtn_clicked();

    /** * @brief on_removeCurNodeBtn_clicked  Remove the current node  */
    void on_removeCurNodeBtn_clicked();

private:
    Ui::CMainWindow     *ui;

    QStandardItemModel  *m_pModel;      // Data model object pointer 
};

CMainWindow.cpp

#include "CMainWindow.h"
#include "ui_CMainWindow.h"

CMainWindow::CMainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::CMainWindow)
{
    
    ui->setupUi(this);
    // Set the window title 
    this->setWindowTitle("QTreeView Simple use ");

    //=============== Data model （QStandardItemModel）===============
    // Create the data model object space and specify the parent object 
    m_pModel = new QStandardItemModel(ui->treeView);
    // Set the data model to the tree view 
    ui->treeView->setModel(m_pModel);
    // Set the average score of horizontal header column 
    ui->treeView->header()->setSectionResizeMode(QHeaderView::Stretch);
    // Add column headings 
    m_pModel->setHorizontalHeaderLabels(QStringList() << "one" << "two");

}

CMainWindow::~CMainWindow()
{
    
    //!  Destructor :
    //!  Some of my friends will find that I don't destruct model、m_pFilterModel object ,
    //!  That's because I specified the parent object when I got the object space ,
    //!  When its parent object is destructed , The object whose child object is a pointer will be destructed first .
    delete ui;
}

void CMainWindow::on_getCurNodeDataBtn_clicked()
{
    
    // Get the current row and column 
    QModelIndex curIndex = ui->treeView->currentIndex();
    int row = curIndex.row();
    int column = curIndex.column();

    // The current location contains -1 Value returns 
    if( -1 == row || -1 == column)
    {
    
        return;
    }

    /// Do not get item The situation of ///
    ///  Use... Only when you need to get text 
    //!  adopt index Get value , default data What you get is Qt::DisplayRole Value ,
    //!  Generally speaking, the value obtained is the displayed value 
    ui->valueEdit->setText(curIndex.data().toString());

}

void CMainWindow::on_setCurNodeDataBtn_clicked()
{
    
    // Get the current row and column 
    QModelIndex curIndex = ui->treeView->currentIndex();
    int row = curIndex.row();
    int column = curIndex.column();

    // The current location contains -1 Value returns 
    if( -1 == row || -1 == column)
    {
    
        return;
    }

    /// Need to get item The situation of ///
    /// \brief curItem  When you need to get specific item/ Use... In position 
    ///  Setting up item value 

    QStandardItem *curItem;
    int parentRow = curIndex.data(Qt::UserRole + 1).toInt();
    // Judge the top-level node value and select the corresponding operation 
    if(-1 == parentRow)
    {
    
        curItem = m_pModel->item(row, column);
    }
    else
    {
    
        // Get the top-level node of the current location 
        QStandardItem *parentItem = m_pModel->item(parentRow);
        // Get child nodes from top-level nodes 
        curItem = parentItem->child(row, column);
    }

    // Get the value in the value edit box and set it to item On 
    curItem->setText(ui->valueEdit->text());
}

void CMainWindow::on_addTopNodeBtn_clicked()
{
    
    int index = m_pModel->rowCount();
    QList<QStandardItem *> topList;
    // Add top-level nodes to the linked list container 
    topList << new QStandardItem(QString(" Top level nodes :%1-1").arg(index + 1))
            << new QStandardItem(QString(" Top level nodes :%1-2").arg(index + 1));

    //!  Set up Qt::UserRole + n：  User defined values 
    //!  When n When values are different , Equivalent to different key values , Similarly, different keys can set different values 
    //!  Set here data To get the top-level node value , Judge and make corresponding operation through this value 
    topList[0]->setData(-1, Qt::UserRole + 1); // Set parent node row , The duty of -1 Is currently the top-level node 
    topList[1]->setData(-1, Qt::UserRole + 1);
    // Add top-level nodes 
    m_pModel->appendRow(topList);
}

void CMainWindow::on_addChildNodeBtn_clicked()
{
    
    // Get the current row and column 
    QModelIndex curIndex = ui->treeView->currentIndex();
    int row = curIndex.row();
    int column = curIndex.column();
    int parentRow = curIndex.data(Qt::UserRole + 1).toInt();

    // The current row and column values contain -1 Value or when the current node is not a top-level node 
    if( -1 == row || -1 == column || -1 != parentRow)
    {
    
        return;
    }

    // Gets the first... Of the specified row item
    QStandardItem *curTopItem = m_pModel->item(row);

    // Add child nodes to the top-level nodes 
    QList<QStandardItem *> childList;
    childList << new QStandardItem(QString(" Child node :%1-1").arg(curTopItem->rowCount()))
              << new QStandardItem(QString(" Child node :%1-2").arg(curTopItem->rowCount()));
    // Set up item Of data
    childList[0]->setData(row, Qt::UserRole + 1);
    childList[1]->setData(row, Qt::UserRole + 1);
    // Add child nodes 
    curTopItem->appendRow(childList);
}

void CMainWindow::on_removeCurNodeBtn_clicked()
{
    
    // Get the current row and column 
    QModelIndex curIndex = ui->treeView->currentIndex();
    int row = curIndex.row();
    int column = curIndex.column();

    // The current row and column values contain -1 Value or when the current node is not a top-level node 
    if( -1 == row || -1 == column)
    {
    
        return;
    }

    int parentRow = curIndex.data(Qt::UserRole + 1).toInt();
    // Judge the top-level node value and select the corresponding removal operation 
    if(-1 == parentRow)
    {
    
        m_pModel->removeRow(row);
    }
    else
    {
    
        // To remove a child node, you need to find its top-level node 
        QStandardItem *parentItem = m_pModel->item(parentRow);
        parentItem->removeRow(row);
    }

}

Four 、 expand ： Acquisition and judgment of superior nodes

The judgment of nodes in this paper is through data Set the... For user-defined value operations , There's another way , By getting the current location QModelIndex Object gets the of its parent object QModelIndex Judge , The code is as follows （ The code below applies only to this article ）：
Tips ： It is said that the following methods are not rigorous , For example, when you manually specify the parent object .

void CMainWindow::parentIndex()
{
    
    // Get the... Of the current node QModelIndex object 
    QModelIndex index = ui->treeView->currentIndex();
    // Get the parent object of the current node QModelIndex object 
    QModelIndex parentIndex = index.parent();
    // Determine the row and column values of the parent node , The parent node row and column values of the top-level node are -1
    if(-1 == parentIndex.row() || -1 == parentIndex.column())
    {
    
        qDebug() << " The current node is a top-level node ";
    }
    else
    {
    
        qDebug() << " The current node is a child node ";
    }

}

summary

QTreeView When determining the node position, you should pay attention to , And to set a child node, you need to get the line to its parent node ; Each child node can only pass through its parent node with the row position of 0 Of item To set ;QTreeView Set the proxy method and QTableView equally , It should be noted that , The columns set will run through the child nodes （ The corresponding columns of child nodes will also take effect ）.
Another week , We will continue to move bricks tomorrow , come on. ！

Related articles

Qt And QTableView Simple use （ Including source code + notes ）
Qt The realization of agent （ Button chapter , Including source code + notes ）
Qt The realization of agent （ General controls , Including source code + notes ）
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Qt And QSortFilterProxyModel Simple use （QTableView Search function , Including source code + notes ）

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notes ： This paper summarizes the problems encountered by the author in the process of programming , The content is for reference only , If there are any mistakes, please point out .
notes ： If there is any infringement , Please contact the author for deletion