[英]Trying to paint on a QLabel fails (cannot call member function 'virtual void QLabel::paintEvent(QPaintEvent*)' without object)
[英]cannot call member function 'virtual void ThreadBase::doTask()' without object
如何从ThreadBase.h调用虚拟函数以在pthread_create中运行的静态指针函数中使用此函数?
当我编译它时,显示->“无法在没有对象的情况下调用成员函数'virtual void ThreadBase :: doTask()'”
非常感谢。
// ThreadBase.h
class ThreadBase {
public:
ThreadBase();
void sayName();
virtual void doTask() = 0; // --> dotask()
static void *run( void *para );
void start();
};
// ThreadBase.cpp
#include <iostream>
#include "ThreadBase.h"
#include "ThreadEncoder.h"
#include "pthread.h"
using namespace std;
ThreadBase :: ThreadBase()
{
}
void ThreadBase :: sayName() {
cout << "I am a RobnertsQ" << endl;
}
void *ThreadBase :: run( void *para ) {
cout << "run()" << endl;
while( false ) {
doTask(); // -> ***My problem
// ( delaySleep )
}
}
void ThreadBase :: start() {
pthread_t thread_encoder;
pthread_create( &thread_encoder, NULL, &ThreadEncoder :: run, NULL);
}
// ThreadEncoder.h
#include <iostream>
using namespace std;
class ThreadEncoder : public ThreadBase {
public:
ThreadEncoder();
ThreadEncoder( int );
void doTask();
protected:
string getFullName() {
return "ThreadEncoder";
}
};
// ThreadEncoder.cpp
#include <iostream>
#include "ThreadBase.h"
#include "ThreadEncoder.h"
using namespace std;
ThreadEncoder :: ThreadEncoder()
{
cout << "ThreadEncoder default " << endl;
}
ThreadEncoder :: ThreadEncoder( int delaySleep )
{
cout << "ThreadEncoder delaySleep = " << delaySleep << endl;
}
void ThreadEncoder :: doTask() {
cout << "ThreadEncoder doTask !!!" << endl;
// main.cpp
#include <iostream>
#include "ThreadBase.h"
#include "ThreadEncoder.h"
//#include "ThreadGps.h"
using namespace std;
int main(){
ThreadEncoder te;
te.start();
}
你能建议我做什么吗? 谢谢。
将对doTask的调用更改为:
static_cast<ThreadBase*>(para)->doTask();
并调用pthread_create来:
pthread_create( &thread_encoder, NULL, &ThreadEncoder :: run, this);
原因:线程启动时,pthread_create的第四个参数将作为参数传递给ThreadBase :: run方法。
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