QTreeWidget Item懒加载

本文主要是介绍QTreeWidget Item懒加载，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

前言

qt界面加载，数据较多时是比较慢的，treeWidget加载数据，跟tableWidget类似思路，先加载部分。

QTreeWidget常用属性设置

    m_treeWidget->setColumnCount(1); //设置列数//m_treeWidget->headerItem()->setHidden(true);//隐藏表头m_treeWidget->header()->setDefaultSectionSize(20);//默认行高m_treeWidget->setMinimumWidth(200);//设置默认最小列宽m_treeWidget->setColumnWidth(0, 100);//设置第0列列宽//需加 #include <QStyleFactory>m_treeWidget->setStyle(QStyleFactory::create("windows"));//显示节点虚线 - +//m_treeWidget->header()->setSectionResizeMode(QHeaderView::Stretch);//设置列宽自动分均//m_treeWidget->setEditTriggers(QAbstractItemView::NoEditTriggers);//禁止编辑m_treeWidget->setSelectionBehavior(QAbstractItemView::SelectRows);//以行为单位选择m_treeWidget->header()->setStyleSheet("QHeaderView::section{background-color:rgb(216,226,236);}""border:0px solid rgb(254,254,254);");//设置表头背景色QStringList headList;headList << "表头0" <<"表头1";m_treeWidget->setHeaderLabels(headList);//设置表头//需加 #include <QHeaderView>m_treeWidget->header()->setDefaultAlignment(Qt::AlignRight | Qt::AlignVCenter);//表头默认局右m_treeWidget->headerItem()->setTextAlignment(0, Qt::AlignLeft | Qt::AlignVCenter);//表头0列居左

QTreeWidget源码

直接分享示例代码

.h文件

#ifndef MyTREEWIDGET_H
#define MyTREEWIDGET_H#include <QWidget>#include <QTreeWidget>
#include <QTreeWidgetItem>
#include <QMap>class MyTreeWidget:public QWidget
{
public:MyTreeWidget(QWidget* parent= nullptr);~MyTreeWidget();void InitTree();void LoadTreeData();void MakeData();QString GetStr();QTreeWidgetItem*  SetItemText(QTreeWidgetItem* item, QString str);protected:void showEvent(QShowEvent *event) override;void hideEvent(QHideEvent *event) override;
private:bool m_bShow;int m_itemShowCnt;QTreeWidget* m_treeWidget;QTreeWidgetItem* m_topItem_1;QTreeWidgetItem* m_topItem_2;QMap<QString,QStringList> m_map;
};#endif // MyTREEWIDGET_H

.cpp文件

#include "mytreewidget.h"
#include <QVBoxLayout>
#include <QScrollBar>
#include <QTime>
#include <QDebug>
#include <QHeaderView>
#include <QStyleFactory>
#include <QThread>
MyTreeWidget::MyTreeWidget(QWidget* parent):QWidget(parent)
{resize(200,500);qsrand(time(NULL));m_bShow = false;
}MyTreeWidget::~MyTreeWidget()
{}void MyTreeWidget::InitTree()
{QVBoxLayout* vbox =new QVBoxLayout;vbox->setMargin(0);m_treeWidget = new QTreeWidget(this);m_treeWidget->setColumnCount(1); //设置列数//m_treeWidget->headerItem()->setHidden(true);//隐藏表头m_treeWidget->header()->setDefaultSectionSize(20);//默认行高m_treeWidget->setMinimumWidth(200);//设置默认最小列宽m_treeWidget->setColumnWidth(0, 100);//设置第0列列宽//需加 #include <QStyleFactory>m_treeWidget->setStyle(QStyleFactory::create("windows"));//显示节点虚线 - +//m_treeWidget->header()->setSectionResizeMode(QHeaderView::Stretch);//设置列宽自动分均//m_treeWidget->setEditTriggers(QAbstractItemView::NoEditTriggers);//禁止编辑m_treeWidget->setSelectionBehavior(QAbstractItemView::SelectRows);//以行为单位选择
//    m_treeWidget->header()->setStyleSheet(
//                "QHeaderView::section{background-color:rgb(216,226,236);}"
//                "border:0px solid rgb(254,254,254);");//设置表头背景色QStringList headList;headList << "表头0" <<"表头1";m_treeWidget->setHeaderLabels(headList);//设置表头//需加 #include <QHeaderView>m_treeWidget->header()->setDefaultAlignment(Qt::AlignRight | Qt::AlignVCenter);//表头默认局右m_treeWidget->headerItem()->setTextAlignment(0, Qt::AlignLeft | Qt::AlignVCenter);//表头0列居左vbox->addWidget(m_treeWidget);setLayout(vbox);m_topItem_1 = new  QTreeWidgetItem(m_treeWidget);m_topItem_2 = new  QTreeWidgetItem(m_treeWidget);m_topItem_1->setText(0,"ProJect");m_topItem_2->setText(0,"TestCase");m_treeWidget->addTopLevelItem(m_topItem_1);m_treeWidget->addTopLevelItem(m_topItem_2);m_itemShowCnt = 30;//设置默认item加载数量//展开加载connect(m_treeWidget,&QTreeWidget::itemExpanded,this,[=](QTreeWidgetItem *item){if(item != m_topItem_1 && item != m_topItem_2 && item->childCount() == 1)//初次展开则加载{QMap<QString,QStringList>::iterator itor =  m_map.find(item->text(0));if(itor == m_map.end())return;QStringList strList = itor.value();for (int i=1;i!=strList.length(); i++)//从第0个已经加载{SetItemText(item, itor.value().at(i));}};});//折叠connect(m_treeWidget,&QTreeWidget::itemCollapsed,this,[=](QTreeWidgetItem *item){qDebug()<<"折叠";});//绑定滚动条，根据滚动条值改变来加载connect(m_treeWidget->verticalScrollBar(),&QScrollBar::valueChanged,[=](int value){int currentItemCnt = m_topItem_1->childCount();//已加载topItem数量//滚动条移动到底端且未加载完if(value == m_treeWidget->verticalScrollBar()->maximum() && currentItemCnt < m_map.size()){QMap<QString,QStringList>::iterator itor =  m_map.begin();for (int i=0; i<currentItemCnt; i++){if(itor == m_map.end())break;itor++;}for (int i=0;itor!=m_map.end(); itor++,i++){if(i > m_itemShowCnt)break;//每次滚动条滑到底时，再加载一些item数量QTreeWidgetItem*  item = SetItemText(m_topItem_1, itor.key());//默认先加载一个SetItemText(item, itor.value().at(0));//默认先加载一个}}});//线程加载数据QThread* thread = new QThread();connect(thread, &QThread::started, thread, [=]()mutable{qDebug()<<"started!";MakeData();thread->quit();}, Qt::DirectConnection);//这里要加 Qt::DirectConnection 在线程执行connect(thread, &QThread::finished, this, [=]()mutable{thread->wait();thread->deleteLater();qDebug()<<"finished!";LoadTreeData();});thread->start();
}void MyTreeWidget::MakeData()
{int topItem = 1000;int item = 1000;for (int i=0; i<topItem;i++){QStringList strList;for (int j=0; j<item;j++){strList.append(QString::number(j) + GetStr());}m_map.insert(QString::number(i) + GetStr(),strList);}qDebug()<<"MakeData:"<<m_map.size();
}void MyTreeWidget::LoadTreeData()
{QMap<QString,QStringList>::iterator itor =  m_map.begin();for (int i=0; itor != m_map.end(); itor++,i++) {if(i > m_itemShowCnt)break;//只加载默认item数量QTreeWidgetItem* item = SetItemText(m_topItem_1, itor.key());SetItemText(item, itor.value().at(0));}
}void MyTreeWidget::showEvent(QShowEvent *event)
{if(!m_bShow){InitTree();m_bShow = true;}
}void MyTreeWidget::hideEvent(QHideEvent *event)
{}QTreeWidgetItem*  MyTreeWidget::SetItemText(QTreeWidgetItem *item, QString str)
{QTreeWidgetItem* childItem = new QTreeWidgetItem;item->addChild(childItem);childItem->setText(0,str);return childItem;
}QString MyTreeWidget::GetStr()
{int length = rand()%15+5;const char ch[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";int size = sizeof(ch);char* str = new char[length + 1];int num = 0;int i;for (i = 0; i < length; ++i){num = rand() % (size - 1);str[i] = ch[num];}str[i] = '\0';QString res(str);//return res;return "《"+res+"》";
}