Article directory
I. Overview
In order to display pictures on the Label and obtain corresponding coordinates, corresponding mouse events are required. However, by default, QLabel does not support mouse event functions, such as click events. To realize the click event of QLabel, there are generally two ways: one is to generate a dynamic library file and place it in the D:\ProgramFiles\Qt\5.12.10\msvc2015_64\plugins\designer directory, which can be directly dragged in the designer The other is to directly add the control class and promote the corresponding control to a custom control.
2. Create a new project and add the mylabel class
Add the mylabel class under the project that needs to use the custom control.
The header file and cpp file where the mylibel class is located are as follows:
myLabel.h
#pragma once
#include <QWidget>
#include <QLabel>
#include <QObject>
#include <QEvent>
#include <QMouseEvent>
extern int xlocation;
extern int ylocation;
class mylabel : public QLabel
{
Q_OBJECT // must include this if you use Qt signals/slots
public:
explicit mylabel(QWidget *parent = 0);
signals:
void myClicked(); // 单击产生的信号
void myDoubleClicked(); // 双击产生的信号
private:
void enterEvent(QEvent* event); // 鼠标进入事件
void leaveEvent(QEvent *event); //当鼠离开
void mousePressEvent(QMouseEvent* event); //鼠标按下
void mouseReleaseEvent(QMouseEvent *event);//鼠标释放
void mouseMoveEvent(QMouseEvent *event); //鼠标移动
void mouseDoubleClickEvent(QMouseEvent *event); // 鼠标双击事件
};
mylabel.cpp
#include "myLabel.h"
#include <QDebug>
#include <QMoveEvent>
int xlocation = 0;
int ylocation = 0;
mylabel::mylabel(QWidget *parent) :QLabel(parent)
{
}
//鼠标进入
void mylabel::enterEvent(QEvent *event)
{
qDebug() << "tips:" << "move enter";
emit myDoubleClicked();
}
//鼠离开
void mylabel::leaveEvent(QEvent *event)
{
qDebug() << "tips:" << "mouse leave";
emit myDoubleClicked();
}
//鼠标按下
void mylabel::mousePressEvent(QMouseEvent *event)
{
QString Str = QString("location: X=%1 Y=%2").arg(event->x()).arg(event->y());
xlocation = event->x();
ylocation = event->y();
//判断鼠标是按下左键还是右键
if (event->button() == Qt::LeftButton) {
qDebug() << "tips:" << "mouse press the left button" + Str;
emit myClicked();
}
else {
qDebug() << "tips:" << "mouse press the right button" + Str;
}
}
//鼠标释放
void mylabel::mouseReleaseEvent(QMouseEvent *event)
{
//判断鼠标是按下左键还是右键
if (event->button() == Qt::LeftButton) {
qDebug() << "tips:" << "mouse release the left button";
}
else {
qDebug() << "tips:" << "mouse release the right button";
}
}
//鼠标移动
void mylabel::mouseMoveEvent(QMouseEvent *event)
{
//持续状态 需要用buttons 用与操作符 进行判断
if (event->buttons()&Qt::LeftButton) {
QString Str = QString("location：X=%1 Y=%2").arg(event->x()).arg(event->y());
qDebug() << "tips:" << "mouse move" + Str;
}
}
//当鼠标双击的时候
void mylabel::mouseDoubleClickEvent(QMouseEvent *event)
{
qDebug() << "tips:" << "When the mouse double clicks, the double click signal is issued";
emit myDoubleClicked();
}
3. Improve the Label control
In the UI interface of qt designer, drag the Label control to an appropriate position, then right-click to select the promoted widget , and promote it to the mylabel class we defined.
Note: After the control is promoted, the header file of the control we defined will be automatically included in our ui header file. As you can see, the header file (myLabel.h) directory is in the same directory as ui_MyLabelTest2.h, so it needs to be copied to this directory.
4. Reference and connect the signal
The mouse click event and the execution function are connected through cnnect, and the mouse press event (mousePressEvent), mouse movement event, etc. are protected attributes, so they cannot be directly connected through the signal slot. Here, I mainly want to get the coordinates of the label through the mouse press event, so I use two global variables (xlocation and ylocation) to realize my function.
In addition, the ImshowQImage() function is added to display images on the Label control.
MyLabelTest2::MyLabelTest2(QWidget *parent)
:QMainWindow(parent)
{
ui.setupUi(this);
//ui.label11->setText("hello word");
ImshowQImage();
QObject::connect(ui.label11, &mylabel::myClicked, this, &MyLabelTest2::myLabel_Clicked);
}
void MyLabelTest2::ImshowQImage()
{
QString filename = "D:\\PyProject01\\images\\background.jpg";
QImage image(filename);
//图片自适应label大小
image.scaled(ui.label11->size(), Qt::KeepAspectRatio);
ui.label11->setScaledContents(true);
//显示图片
ui.label11->setPixmap(QPixmap::fromImage(image));
//ui.label_processedImage->resize(ui.label_rawImage->pixmap()->size());
ui.label11->show();
}
void MyLabelTest2::myLabel_Clicked()
{
qDebug() << xlocation << " " << ylocation;
ui.label2->setText(QString::asprintf("(%d,%d)", xlocation,ylocation));
}
5. Effect test
Test our control events by moving the mouse on the Label, pressing, clicking, etc. The test results are as follows:
The final display picture and the corresponding coordinate effect are also realized.
Great, great fun. If you think it is helpful to you, just click three times.
References:
[1] https://blog.csdn.net/lizaijinsheng/article/details/125314092
[2] https://blog.csdn.net/qq_40541268/article/details/85211021
[3] https:// blog.csdn.net/qq_33583069/article/details/109513284
[4] https://blog.csdn.net/augfun/article/details/101083946