125 lines
3.1 KiB
Markdown
125 lines
3.1 KiB
Markdown
#qt
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### **背景**
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deleteLater 是 [QObject](https://so.csdn.net/so/search?q=QObject&spm=1001.2101.3001.7020) 类对象的成员函数，用于延迟删除一个 QObject 类对象，且对 QObject 类对象的删除推荐使用 deleteLater 而非 delete 。
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### **deleteLater**
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####
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**①．概述**
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deleteLater 依赖于[事件循环](https://so.csdn.net/so/search?q=%E4%BA%8B%E4%BB%B6%E5%BE%AA%E7%8E%AF&spm=1001.2101.3001.7020)，调用 deleteLater 后本质是发送了一个 DeferrerDelete 事件，在事件循环处理中把对象删除。
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#### **②．代码示例**
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``` cpp
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demo = new QtClassDemo(this);
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demo->deleteLater();
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demo = nullptr;
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```
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![[Pasted image 20240806155949.png]]
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### **deleteLater 和 delete**
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####
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①．deleteLater 会在当前对象的所有事件处理完成后再删除对象
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``` cpp
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demo = new QtClassDemo(this);
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demo->setObjectName("demo");
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qApp->postEvent(demo, new CustomEvent("hello"));
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qApp->postEvent(demo, new CustomEvent("world"));
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demo->deleteLater();
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demo = nullptr;
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```
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![[Pasted image 20240806160009.png]]
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#### ②．delete 则是立即删除对象，对象的既有事件不再处理
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``` cpp
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demo = new QtClassDemo(this);
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demo->setObjectName("demo");
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qApp->postEvent(demo, new CustomEvent("hello"));
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qApp->postEvent(demo, new CustomEvent("world"));
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delete demo;
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demo = nullptr;
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```
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![[Pasted image 20240806160020.png]]
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#### ③．deleteLater 后依然可以访问和操作对象，直到再次回到事件循环
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``` cpp
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demo = new QtClassDemo(this);
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demo->setObjectName("demo");
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demo->deleteLater();
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qDebug() << demo->objectName();
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demo = nullptr;
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```
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![[Pasted image 20240806160032.png]]
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### **deleteLater 和 QSharedPointer**
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####
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①．概述
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[智能指针](https://so.csdn.net/so/search?q=%E6%99%BA%E8%83%BD%E6%8C%87%E9%92%88&spm=1001.2101.3001.7020)可以传入自定义的删除器，对于继承自 QObject 的类对象可以传入 deleteLater 。
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#### ②．代码示例
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``` cpp
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QSharedPointer<QtClassDemo> demoClass(new QtClassDemo(this), &QObject::deleteLater);
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```
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###
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**deleteLater 和 moveToThread**
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####
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①．概述
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**moveToThread 的本质是把 QObject 对象的事件循环移动到子线程进行处理**：
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``` cpp
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qDebug() << "主线程:"<< QThread::currentThread();
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QThread * workThread = new QThread;
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demo = new QtClassDemo(nullptr);
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demo->setObjectName("demo");
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demo->moveToThread(workThread);
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workThread->start();
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bool QtClassDemo::event(QEvent * event)
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{
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qDebug() << "事件处理线程:"<< QThread::currentThread() << event->type();
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return QObject::event(event);
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}
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```
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![[Pasted image 20240806160059.png]]
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#### ②．利用 deleteLater 进行资源清理
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``` cpp
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//工作对象工作完成，停止线程
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QObject::connect(workObject,&WorkObject::workFinished,[&](){
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workThread->quit();
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workThread->wait();
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});
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//工作线程停止，删除工作对象
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QObject::connect(workThread,&QThread::finished,workObject,&WorkObject::deleteLater );
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//工作对象销毁，删除工作线程
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QObject::connect(workObject,&WorkObject::destroyed,workThread,&QThread::deleteLater );
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``` |