Linux中进程之间通信有,pipe,signal,消息队列,共享内存,信号量,socket.
Qt中提供的进程间通信有如下几种:
1.TCP/IP
跨平台的QNetwork提供了众多的类来实现网络编程.比如QNetworkAccessManger,Qftp等来使用指定的应用程序协议.
2.共享内存
在Linux中也有这个通信方式,通信方式是非常常用额,也比较简单.本文用共享内存来举例.
3.D-Bus
QtDBus模块是一个Unix库,可以使用D-Bus协议来实现进程间的通信
4.Qt通信协议(QCOP)
QCopChannel实现客户端程序使用有名管道来进行消息传输的协议.QCopChannel仅仅在在做嵌入式Linux上才能够使用.
新建一个Gui应用项目,
#include <QtGui/QApplication>
#include "dialog.h"
#include <QTextCodec>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QTextCodec::setCodecForTr(QTextCodec::codecForName("UTF-8"));
Dialog w;
w.show();
return a.exec();
}
dialog.h
#ifndef DIALOG_H
#define DIALOG_H
#include <QDialog>
#include <QSharedMemory>
namespace Ui {
class Dialog;
}
class Dialog : public QDialog
{
Q_OBJECT
public:
explicit Dialog(QWidget *parent = 0);
~Dialog();
private:
Ui::Dialog *ui;
void detach();
QSharedMemory shareMemory;
public slots:
void loadFromFile();
void loadFromMemory();
private slots:
void on_pushButton_clicked();
void on_pushButton_2_clicked();
};
#endif // DIALOG_H
dialog.cpp
#include "dialog.h"
#include "ui_dialog.h"
#include <QFileDialog>
#include <QBuffer>
#include <QDebug>
Dialog::Dialog(QWidget *parent) :
QDialog(parent),
ui(new Ui::Dialog)
{
ui->setupUi(this);
shareMemory.setKey("Linux_Google");
}
Dialog::~Dialog()
{
delete ui;
}
void Dialog::loadFromFile()
{
if(shareMemory.isAttached()) /* 判断该进程是否已经连接到共享内存段 */
detach();
ui->label->setText(tr("选择一个图片文件"));
QString fileName = QFileDialog::getOpenFileName(0,QString(),QString(tr("Images(*.png *.jpg)")));
QImage image;
if(!image.load(fileName))
{
ui->label->setText(tr("选择的文件不是图片文件,选择图片文件"));
return;
}
ui->label->setPixmap(QPixmap::fromImage(image));
QBuffer buffer; /* QBuffer用来暂存图片 */
buffer.open(QBuffer::ReadWrite);
QDataStream out(&buffer); /* QDataStream从数据流冲去读取buffer数据 */
out << image;
int size = buffer.size();
if(!shareMemory.create(size)){ /* 自动将该内存段连接到本进程上 */
ui->label->setText(tr("无法创建共享内存段"));
return;
}
shareMemory.lock();
char *to = (char *)shareMemory.data(); /* 强制转换一个地址 */
const char *from=buffer.data().data();
memcpy(to,from,qMin(shareMemory.size(),size));
shareMemory.unlock();
}
void Dialog::loadFromMemory()
{
if(!shareMemory.attach()){
ui->label->setText(tr("无法连接到共享内存段,请先添加一张图片"));
return;
}
QBuffer buffer;
QDataStream in(&buffer);
QImage image;
shareMemory.lock();
buffer.setData((char*)shareMemory.constData(), shareMemory.size());
buffer.open(QBuffer::ReadOnly);
in >> image;
shareMemory.unlock();
shareMemory.detach();
ui->label->setPixmap(QPixmap::fromImage(image));
}
void Dialog::detach()
{
if (!shareMemory.detach())
ui->label->setText(tr("无法从共享内存中分离"));
}
void Dialog::on_pushButton_clicked()
{
loadFromFile();
}
void Dialog::on_pushButton_2_clicked()
{
loadFromMemory();
}
界面效果如下:
文章出自:Linux_Google