实现 QTreeWidget 中子节点勾选状态的递归更新功能只影响跟节点的状态父节点状态不受影响

在 Qt 开发中，QTreeWidget 提供了树形结构的显示和交互功能。为了实现某个子节点勾选或取消勾选时，只影响当前节点及其子节点的状态，同时递归更新父节点的状态以正确显示 Qt::PartiallyChecked 或 Qt::Checked，我们可以借助 Qt 的信号与槽机制进行处理。以下是详细实现及测试分析

1.功能需求分析

我们希望实现如下功能：

1.1勾选或取消勾选某个子节点时：

仅更新当前节点及其子节点状态。
递归更新最顶层父节点状态（Qt::Checked 或 Qt::PartiallyChecked）。

1.2不影响兄弟节点及父节点的兄弟节点状态。

测试场景如下：
场景 1：部分勾选子节点
根节点 A
子节点 A1 [Checked]
子节点 A2 [Unchecked]
结果：根节点 A 的状态为 Qt::PartiallyChecked。
场景 2：全部勾选子节点
根节点 B
子节点 B1 [Checked]
子节点 B2 [Checked]
结果：根节点 B 的状态为 Qt::Checked。
场景 3：多层嵌套
根节点 C
子节点 C1
子节点 C1.1 [Checked]
子节点 C1.2 [Unchecked]
子节点 C2 [Checked]
结果：子节点 C1 的状态为 Qt::PartiallyChecked，根节点 C 的状态为 Qt::PartiallyChecked。

2 效果展示

3.实现步骤

3.1 main.cpp

#include "mainwindow.h"#include <QApplication>int main(int argc, char *argv[])
{QApplication a(argc, argv);MainWindow w;w.show();return a.exec();
}

3.2 main.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H#include <QMainWindow>
#include <QTreeWidget>class MainWindow : public QMainWindow {Q_OBJECTpublic:MainWindow(QWidget *parent = nullptr);~MainWindow();private:QTreeWidget *treeWidget;void setupTree();// checkedCount  子节点中已勾选的数量void updateParentState(QTreeWidgetItem *item,int checkedCount = 0);void updateChildState(QTreeWidgetItem *item, Qt::CheckState state);// 使用 统计节点数量int countDescendants(QTreeWidgetItem *node);//获取当前节点下的勾选状态bool areAllDescendantsChecked(QTreeWidgetItem *node);
private slots:void onItemChanged(QTreeWidgetItem *item, int column);
};#endif // MAINWINDOW_H

3.3 main.cpp

#include "mainwindow.h"MainWindow::MainWindow(QWidget *parent): QMainWindow(parent), treeWidget(new QTreeWidget(this)) {setCentralWidget(treeWidget);setupTree();// 连接信号槽connect(treeWidget, &QTreeWidget::itemChanged, this, &MainWindow::onItemChanged);
}MainWindow::~MainWindow() {}void MainWindow::setupTree() {treeWidget->setColumnCount(1);treeWidget->setHeaderLabel("Tree Example");// 添加根节点 A，及其子节点QTreeWidgetItem *rootA = new QTreeWidgetItem(treeWidget, QStringList("A"));rootA->setCheckState(0, Qt::Unchecked);QTreeWidgetItem *childA1 = new QTreeWidgetItem(rootA, QStringList("A1"));childA1->setCheckState(0, Qt::Unchecked);QTreeWidgetItem *childA2 = new QTreeWidgetItem(rootA, QStringList("A2"));childA2->setCheckState(0, Qt::Unchecked);QTreeWidgetItem *childA3 = new QTreeWidgetItem(childA2, QStringList("A2.1"));childA3->setCheckState(0, Qt::Unchecked);QTreeWidgetItem *childA4 = new QTreeWidgetItem(childA2, QStringList("A2.2"));childA4->setCheckState(0, Qt::Unchecked);// 添加根节点 B，及其子节点QTreeWidgetItem *rootB = new QTreeWidgetItem(treeWidget, QStringList("B"));rootB->setCheckState(0, Qt::Unchecked);QTreeWidgetItem *childB1 = new QTreeWidgetItem(rootB, QStringList("B1"));childB1->setCheckState(0, Qt::Unchecked);QTreeWidgetItem *childB2 = new QTreeWidgetItem(rootB, QStringList("B2"));childB2->setCheckState(0, Qt::Unchecked);QTreeWidgetItem *childB3 = new QTreeWidgetItem(childB2, QStringList("B2.1"));childB3->setCheckState(0, Qt::Unchecked);// 添加根节点 C，及其多层子节点QTreeWidgetItem *rootC = new QTreeWidgetItem(treeWidget, QStringList("C"));rootC->setCheckState(0, Qt::Unchecked);QTreeWidgetItem *childC1 = new QTreeWidgetItem(rootC, QStringList("C1"));childC1->setCheckState(0, Qt::Unchecked);QTreeWidgetItem *childC2 = new QTreeWidgetItem(childC1, QStringList("C1.1"));childC2->setCheckState(0, Qt::Unchecked);QTreeWidgetItem *childC3 = new QTreeWidgetItem(childC1, QStringList("C1.2"));childC3->setCheckState(0, Qt::Unchecked);QTreeWidgetItem *childC31 = new QTreeWidgetItem(childC1, QStringList("C1.3"));childC31->setCheckState(0, Qt::Unchecked);QTreeWidgetItem *childC4 = new QTreeWidgetItem(rootC, QStringList("C2"));childC4->setCheckState(0, Qt::Unchecked);// 添加根节点 D，及其子节点QTreeWidgetItem *rootD = new QTreeWidgetItem(treeWidget, QStringList("D"));rootD->setCheckState(0, Qt::Unchecked);QTreeWidgetItem *childD1 = new QTreeWidgetItem(rootD, QStringList("C1"));childD1->setCheckState(0, Qt::Unchecked);
}void MainWindow::onItemChanged(QTreeWidgetItem *item, int column) {if (column != 0) return;treeWidget->blockSignals(true);// 防止递归调用 信号屏蔽Qt::CheckState state = item->checkState(0);// 更新子节点状态updateChildState(item, state);updateParentState(item);// 更新父节点状态treeWidget->blockSignals(false);// 恢复信号
}void MainWindow::updateChildState(QTreeWidgetItem *item, Qt::CheckState state) {for (int i = 0; i < item->childCount(); ++i) {QTreeWidgetItem *child = item->child(i);child->setCheckState(0, state);updateChildState(child, state);// 递归处理子节点}
}int MainWindow::countDescendants(QTreeWidgetItem *node)
{if (!node) return 0;int count = 0;// 遍历直接子节点for (int i = 0; i < node->childCount(); ++i) {QTreeWidgetItem *child = node->child(i);++count; // 当前子节点计数count += countDescendants(child); // 递归统计子节点的子节点}return count;
}bool MainWindow::areAllDescendantsChecked(QTreeWidgetItem *node)
{if (!node) return false;// 遍历子节点for (int i = 0; i < node->childCount(); ++i) {// 检查当前节点的状态QTreeWidgetItem *child = node->child(i);QString Text = child->text(0);if (child->checkState(0) != Qt::Checked) {return false;}if (!areAllDescendantsChecked(node->child(i))) {return false;}}return true;
}void MainWindow::updateParentState(QTreeWidgetItem *item,int checkedCount) {QTreeWidgetItem *parent = item->parent();if (!parent) return;int childCheckedCount = checkedCount;int partiallyCheckedCount = 0; // 子节点中部分勾选的数量int parentCheckedCount = 0; //检验根节点选择个数（只针对根节点有用）// 遍历所有子节点，统计状态for (int i = 0; i < parent->childCount(); ++i) {QTreeWidgetItem *child = parent->child(i);// 递归更新父节点QString text = child->text(0);if (child->checkState(0) == Qt::Checked) {++checkedCount;if(parent->parent() == nullptr){++parentCheckedCount;}} else if (child->checkState(0) == Qt::PartiallyChecked) {++partiallyCheckedCount;}}// 根据子节点状态更新 根节点状态if(parent->parent() == nullptr ){if (checkedCount == parent->childCount()) {//第二层if(parentCheckedCount == parent->childCount()){//分情况考虑 只考虑第二层节点bool status = false;for (int i = 0; i < parent->childCount(); ++i) {QTreeWidgetItem *child = parent->child(i);status = areAllDescendantsChecked(child);if(!status){break;}}if(status){parent->setCheckState(0, Qt::Checked);}else{parent->setCheckState(0, Qt::PartiallyChecked);}}else if(checkedCount != 0){parent->setCheckState(0, Qt::PartiallyChecked);}else{}} else if (checkedCount > 0 || partiallyCheckedCount > 0) {parent->setCheckState(0, Qt::PartiallyChecked);} else {parent->setCheckState(0, Qt::Unchecked);}}// 递归更新父节点updateParentState(parent,checkedCount);
}