Qt学习笔记（十三）列表（QListWidget）

1、简单使用 - 增加、删除、插入

效果图

效果图

链接信号和槽

connect(ui.addBtn, SIGNAL(clicked()), this, SLOT(AddItem()));
connect(ui.deleteBtn, SIGNAL(clicked()), this, SLOT(DeleteItem()));
connect(ui.insertBtn, SIGNAL(clicked()), this, SLOT(InsertItem()));
connect(ui.listWidget, SIGNAL(itemDoubleClicked(QListWidgetItem*)), this, SLOT(ItemDoubleClicked(QListWidgetItem*)));

槽实现

void MyListWindow::AddItem() {
    QString text = ui.lineEdit->text();
    QListWidgetItem *item = new QListWidgetItem;
    item->setText(text);
    if (text != NULL) {
        ui.listWidget->addItem(item);
        ui.lineEdit->clear();
    }
}
void MyListWindow::DeleteItem() {
    QListWidgetItem *currentItem = ui.listWidget->currentItem();
    delete currentItem;
}
void MyListWindow::InsertItem() {
    int index = ui.listWidget->currentRow();
    QString text = ui.lineEdit->text();
    QListWidgetItem *item = new QListWidgetItem;
    item->setText(text);
    if (text != NULL) {
        ui.listWidget->insertItem(index + 1, item);
        ui.lineEdit->clear();
    }   
}
void MyListWindow::ItemDoubleClicked(QListWidgetItem* item) {
    ui.plainTextEdit->clear();
    QString text = item->text();
    ui.plainTextEdit->setPlainText(text);
}

2、右键添加Menu

设置QListWidget策略，并关联右键信号和槽事件，customContextMenuRequested是继承自QWidget的信号。

ui.listWidget->setContextMenuPolicy(Qt::CustomContextMenu);
connect(ui.listWidget, SIGNAL(customContextMenuRequested(const QPoint&)), this, SLOT(ItemMenu(const QPoint&)));

在QtCreater中添加action

image.png

关联action信号和槽事件

connect(ui.actionAdd, SIGNAL(triggered()), this, SLOT(OnMenuAdd()));
connect(ui.actionRemove, SIGNAL(triggered()), this, SLOT(OnMenuRemove()));

实现槽事件

// 右键菜单
void MyListWindow::ItemMenu(const QPoint& pt) {
    QListWidgetItem *selectedItem = ui.listWidget->itemAt(pt);
    QMenu menu;
    menu.addAction(ui.actionAdd);
    if (selectedItem) {
        menu.addAction(ui.actionRemove);
    }   
    menu.exec(ui.listWidget->mapToGlobal(pt));
}
// 右键菜单-添加
void MyListWindow::OnMenuAdd() {
    QListWidgetItem *newitem = new QListWidgetItem("New Item");
    ui.listWidget->addItem(newitem);
}
// 右键菜单-删除
void MyListWindow::OnMenuRemove() {
    QListWidgetItem *item = ui.listWidget->currentItem();
    if (item) {
        delete item;
    }
}

3、QListWidgetItem 双击可编辑

链接信号和槽

connect(ui.listWidget, SIGNAL(itemDoubleClicked(QListWidgetItem*)), this, SLOT(OnItemDoubleClicked(QListWidgetItem *)));

实现槽事件

void MyListWindow::OnItemDoubleClicked(QListWidgetItem *item) {
    item->setFlags(item->flags() | Qt::ItemIsEditable);
}

4、QListWidgetItem 拖拽

自定义QListWidget派生类MyListWidget。

// MyListWidget.h
#include <QListWidget>
#include <QWidgetItem>
#include <QPoint>

class MyListWidget : public QListWidget
{
    Q_OBJECT

private:
    QPoint m_dragPoint;// 开始拖拽的点
    QListWidgetItem  *m_dragItem;// 拖拽的项

protected:
    //重写下面两个函数来完成从该部件中拖拽出去的操作.
    void mousePressEvent(QMouseEvent *event);
    void mouseMoveEvent(QMouseEvent *event);
    //重写下面三个函数来完成接受外来拖拽的操作.
    void dragEnterEvent(QDragEnterEvent *event);
    void dragMoveEvent(QDragMoveEvent *event);
    void dropEvent(QDropEvent *event);

public:
    MyListWidget(QWidget *parent);
    ~MyListWidget();
};

// MyListWidget.cpp
#include "MyListWidget.h"
#include <QMouseEvent>
#include <QApplication>
#include <QDrag>
#include <QMimeData>

MyListWidget::MyListWidget(QWidget *parent)
    : QListWidget(parent)
{
    // 设置可拖拽
    this->setAcceptDrops(true);
}

MyListWidget::~MyListWidget()
{
}

// 从该部件中拖拽出去的操作.
void MyListWidget::mousePressEvent(QMouseEvent *event) {
    //确保左键拖拽.
    if (event->button() == Qt::LeftButton)
    {
        //先保存拖拽的起点.
        m_dragPoint = event->pos();
        //保留被拖拽的项.
        m_dragItem = this->itemAt(event->pos());
    }
    //保留原QListWidget部件的鼠标点击操作.
    QListWidget::mousePressEvent(event);
}
void MyListWidget::mouseMoveEvent(QMouseEvent *event) {
    //确保按住左键移动.
    if (event->buttons() & Qt::LeftButton)
    {
        QPoint temp = event->pos() - m_dragPoint;
        //只有这个长度大于默认的距离,才会被系统认为是形成拖拽的操作.
        if (temp.manhattanLength() > QApplication::startDragDistance())
        {
            QDrag *drag = new QDrag(this);
            QMimeData *mimeData = new QMimeData;
            mimeData->setText(m_dragItem->text());
            drag->setMimeData(mimeData);
            auto action = drag->exec(Qt::CopyAction | Qt::MoveAction);

            if (action == (Qt::CopyAction) || (action == Qt::MoveAction))
            {
                //当成功拖拽后，删除拖拽项.
                auto i = this->takeItem(this->row(m_dragItem));
                delete i;
            }
        }
    }
    QListWidget::mouseMoveEvent(event);
}
// 接受外来拖拽的操作.
void MyListWidget::dragEnterEvent(QDragEnterEvent *event) {
    //设置动作为移动动作.
    event->setDropAction(Qt::MoveAction);
    //然后接受事件.这个一定要写.
    event->accept();
}
void MyListWidget::dragMoveEvent(QDragMoveEvent *event) {
    event->setDropAction(Qt::MoveAction);
    event->accept();
}
void MyListWidget::dropEvent(QDropEvent *event) {
    QString str = event->mimeData()->text();
    if (!str.isEmpty())
    {
        //找到当前鼠标位置在部件中的项.
        auto item = this->itemAt(event->pos());
        //
        if (!item)
            this->addItem(str);
        else
            this->insertItem(this->row(item), str);

        event->setDropAction(Qt::MoveAction);
        event->accept();
    }
}

右键提升可视化控件与自定义类关联起来。

提升控件

简单方法。。。额。。。

image.png

参考：https://blog.csdn.net/qq_37233607/article/details/78630924
未完待续...