我们有时候想发送自定义事件
1：创建自定义事件，首先我们需要知道它的条件
1：自定义事件需要继承QEvent
2：事件的类型需要在 QEvent::User 和 QEvent::MaxUser 范围之间，在QEvent::User之前 是预留给系统的事件
3：使用sendEvent() 和 postEvent()发送自定义消息
4：接受自定义消息，通过 重写 customEvent 或者 使用 eventFilter事件 来处理
2：注册自定义事件ID
在注册自定义事件的时候我们有两种方法
一：使用QEvent::registerEventType()，这个是系统会帮助我们注册ID，如果错误 返回-1
二：我们自定义 取QEvent::User 和QEvent::MaxUser 之间的值
方法一：
QEvent::Type CustomEvent::m_eventType = (QEvent::Type)QEvent::registerEventType();
方法二：
const int CustomEventBaseID = QEvent::User;
const int TextEventID = CustomEventBaseID + 1;
3：自定义事件
class CustomEvent :public QEvent
{
public:
CustomEvent();
virtual ~CustomEvent();
static QEvent::Type eventType();
private:
static QEvent::Type m_eventType;
};
QEvent::Type CustomEvent::m_eventType = (QEvent::Type)QEvent::registerEventType();//1、注册自定义事件类型
CustomEvent::CustomEvent()
:QEvent(eventType()) //2、指定事件类型
{
}
CustomEvent::~CustomEvent()
{
}
QEvent::Type CustomEvent::eventType()
{
return m_eventType;
}
4:发送自定义事件
postEvent 方法：异步发送，向事件队列中 的发送一个指定接受者事件
不需要手动释放事件的内存，QT框架自动释放
sendEvent方法：此方法是阻塞发送的，它发送对象事件，等待对象处理结束返回；
需要手动释放事件的内存
5：自定义事件处理
写自定义事件 void customEvent(QEvent* event) override;
写事件过滤器 bool eventFilter(QObject* watched, QEvent* event) override;
还需要将对象添加到事件过滤器中
源码：
.h
#pragma once
#include <QtWidgets/QWidget>
#include "ui_CustomEventTest.h"
#include <QEvent>
#include <QDebug>
//自定义事件
class CustomEvent :public QEvent
{
public:
CustomEvent();
virtual ~CustomEvent();
void SetText(const QString& str);
QString GetText() const;
void SetNumber(int number);
int GetNumber() const;
static QEvent::Type eventType();
private:
QString m_str;
int m_number;
static QEvent::Type m_eventType;
};
class CustomTwoEvent :public QEvent
{
public:
CustomTwoEvent();
virtual ~CustomTwoEvent();
void SetStr(const QString& str);
QString GetStr() const;
void SetNumber(int number);
int GetNumber() const;
private:
QString m_str;
int m_number;
};
//测试自定义事件
class CustomEventTest : public QWidget
{
Q_OBJECT
public:
CustomEventTest(QWidget *parent = nullptr);
~CustomEventTest();
private slots:
//测试自定义事件一
void on_btn1_1_clicked();
void on_btn2_1_clicked();
void on_btn3_1_clicked();
void on_btn4_1_clicked();
protected:
void customEvent(QEvent* event) override;
private slots:
//测试自定义事件二
void on_btn5_1_clicked();
void on_btn6_1_clicked();
void on_btn7_1_clicked();
void on_btn8_1_clicked();
protected:
bool eventFilter(QObject* watched, QEvent* event) override;
private:
Ui::CustomEventTestClass ui;
};
.cpp
#include "CustomEventTest.h"
/************************自定义事件一********************************/
QEvent::Type CustomEvent::m_eventType = (QEvent::Type)QEvent::registerEventType();//1、注册自定义事件类型
CustomEvent::CustomEvent()
:QEvent(eventType()) //2、指定事件类型
{
}
CustomEvent::~CustomEvent()
{
}
void CustomEvent::SetText(const QString& str)
{
m_str = str;
}
QString CustomEvent::GetText() const
{
return m_str;
}
void CustomEvent::SetNumber(int number)
{
m_number = number;
}
int CustomEvent::GetNumber() const
{
return m_number;
}
QEvent::Type CustomEvent::eventType()
{
return m_eventType;
}
/************************自定义事件一********************************/
/************************自定义事件二********************************/
const int CustomEventBaseID = QEvent::User;
const int TextEventID = CustomEventBaseID + 1;
CustomTwoEvent::CustomTwoEvent()
:QEvent(QEvent::Type(TextEventID))
{
}
CustomTwoEvent::~CustomTwoEvent()
{
}
void CustomTwoEvent::SetStr(const QString& str)
{
m_str = str;
}
QString CustomTwoEvent::GetStr() const
{
return m_str;
}
void CustomTwoEvent::SetNumber(int number)
{
m_number = number;
}
int CustomTwoEvent::GetNumber() const
{
return m_number;
}
/************************自定义事件二********************************/
/************************测试自定义事件********************************/
CustomEventTest::CustomEventTest(QWidget *parent)
: QWidget(parent)
{
ui.setupUi(this);
qApp->installEventFilter(this);
}
CustomEventTest::~CustomEventTest()
{
}
void CustomEventTest::on_btn1_1_clicked()
{
QString str = QStringLiteral("自定义事件一 我是post 发送指针");
CustomEvent* event = new CustomEvent;
event->SetText(str);
event->SetNumber(1);
qApp->postEvent(this, event);
}
void CustomEventTest::on_btn2_1_clicked()
{
QString str = QStringLiteral("自定义事件一 我是post 发送局部变量");
CustomEvent event;
event.SetText(str);
event.SetNumber(2);
//会出现崩溃
qApp->postEvent(this, &event);
}
void CustomEventTest::on_btn3_1_clicked()
{
QString str = QStringLiteral("自定义事件一 我是send 发送指针");
CustomEvent* event = new CustomEvent;
event->SetText(str);
event->SetNumber(3);
qApp->sendEvent(this, event);
delete event;
}
void CustomEventTest::on_btn4_1_clicked()
{
QString str = QStringLiteral("自定义事件一 我是send 发送局部变量");
CustomEvent event;
event.SetText(str);
event.SetNumber(4);
qApp->sendEvent(this, &event);
}
void CustomEventTest::on_btn5_1_clicked()
{
QString str = QStringLiteral("自定义事件二 我是post 发送指针");
CustomTwoEvent* event = new CustomTwoEvent;
event->SetStr(str);
event->SetNumber(5);
qApp->postEvent(this, event);
}
void CustomEventTest::on_btn6_1_clicked()
{
QString str = QStringLiteral("自定义事件二 我是post 发送局部变量");
CustomTwoEvent event;
event.SetStr(str);
event.SetNumber(6);
//会出现崩溃
qApp->postEvent(this, &event);
}
void CustomEventTest::on_btn7_1_clicked()
{
QString str = QStringLiteral("自定义事件二 我是send 发送指针");
CustomTwoEvent* event = new CustomTwoEvent;
event->SetStr(str);
event->SetNumber(7);
qApp->sendEvent(this, event);
delete event;
}
void CustomEventTest::on_btn8_1_clicked()
{
QString str = QStringLiteral("自定义事件二 我是send 发送局部变量");
CustomTwoEvent event;
event.SetStr(str);
event.SetNumber(8);
qApp->sendEvent(this, &event);
}
void CustomEventTest::customEvent(QEvent* event)
{
if (event->type() == CustomEvent::eventType())
{
CustomEvent* e = dynamic_cast<CustomEvent*>(event);
if (e->GetNumber() == 1)
ui.btn1->setText(e->GetText());
else if (e->GetNumber() == 2)
ui.btn2->setText(e->GetText());
else if (e->GetNumber() == 3)
ui.btn3->setText(e->GetText());
else if (e->GetNumber() == 4)
ui.btn4->setText(e->GetText());
}
}
bool CustomEventTest::eventFilter(QObject* watched, QEvent* event)
{
if (event->type() == TextEventID)
{
CustomTwoEvent* e = dynamic_cast<CustomTwoEvent*>(event);
if (e->GetNumber() == 5)
ui.btn5->setText(e->GetStr());
else if (e->GetNumber() == 6)
ui.btn6->setText(e->GetStr());
else if (e->GetNumber() == 7)
ui.btn7->setText(e->GetStr());
else if (e->GetNumber() == 8)
ui.btn8->setText(e->GetStr());
event->accept();
}
return QWidget::eventFilter(watched,event);
}
/************************测试自定义事件********************************/
错误：在上面的代码中，当我们post 局部变量的时候会出现错误
QCoreApplication::removePostedEvent: Event of type 65535 deleted while posted to CustomEventTest CustomEventTestClass
原因：postEvent 只能在堆上创建，系统会自动释放
参考博客：
Qt 自定义事件
Qt中的事件- 自定义事件
Qt事件：自定义事件
