Question

我使用Qt5的连接功能有问题。我在这里发布了一些代码来快速查看：

void MainWindow::onMessage(const Message* message) {


        try {
            const TextMessage* textMessage = dynamic_cast<const TextMessage*> (message);
            std::string text = "";




        if (textMessage != NULL) {
                text = textMessage->getText();

            } else {
                text = "NOT A TEXTMESSAGE!"; 
            }

            int fieldIndex=message->getIntProperty("field");
            QString qstr = QString::fromStdString(text);



            switch(fieldIndex)
            {

            case 0:ui->lineEdit->setText(qstr);break;
            case 1:ui->lineEdit_2->setText(qstr);break;
            case 2:ui->lineEdit_3->setText(qstr);break;
            case 3:ui->lineEdit_4->setText(qstr);break;
            case 4:ui->lineEdit_5->setText(qstr);break;
            case 5:ui->lineEdit_6->setText(qstr);break;
            case 6:ui->lineEdit_7->setText(qstr);break;
            case 7:ui->lineEdit_8->setText(qstr);break;
            case 8:ui->lineEdit_9->setText(qstr);break;
            }




            connect(ui->lineEdit_4,SIGNAL(textChanged(qstr)),ui->widget_diagram2,SLOT(upDateDatas(qstr)));

            }catch (CMSException& e) {
            e.printStackTrace();
        }

}

正如您所看到的，我正在尝试将lineEdit_4生成的信号textChanged与ui对象widget_diagram2连接，并执行slot upDateDatas（qstr）。但是发生了一些不好的事情，因为我收到了这条消息：

QObject::connect: No such signal QLineEdit::textChanged(qstr) in mainwindow.cpp:97
QObject::connect:  (sender name:   'lineEdit_4')
QObject::connect:  (receiver name: 'widget_diagram2')

个人我不知道为什么......错误在哪里？

void MainWindow::upDateDatas(QString qstr){

 bool ok;
 double value0=qstr.toDouble(&ok); 
 double key = QDateTime::currentDateTime().toMSecsSinceEpoch()/1000.0;
  static double lastPointKey = 0;
   if (key-lastPointKey > 0.01) // at most add point every 10 ms
   {

     ui->widget_diagram2->graph(0)->addData(key, value0);
     ui->widget_diagram2->graph(0)->removeDataBefore(key-8);
     ui->widget_diagram2->graph(0)->rescaleValueAxis();
     lastPointKey = key;
   }
  ui->widget_diagram2->xAxis->setRange(key+0.25, 8, Qt::AlignRight);
  //ui->widget_diagram2->replot();
}

这是错误：

QObject::connect: No such slot QCustomPlot::upDateDatas(QString) in mainwindow.cpp:97
QObject::connect:  (sender name:   'lineEdit_4')
QObject::connect:  (receiver name: 'widget_diagram2')

.h文件：

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QTimer>
#include <activemq/library/ActiveMQCPP.h>
#include <decaf/lang/Thread.h>
#include <decaf/lang/Runnable.h>
#include <decaf/util/concurrent/CountDownLatch.h>
#include <decaf/lang/Integer.h>
#include <decaf/lang/Long.h>
#include <decaf/lang/System.h>
#include <activemq/core/ActiveMQConnectionFactory.h>
#include <activemq/util/Config.h>
#include <cms/Connection.h>
#include <cms/Session.h>
#include <cms/TextMessage.h>
#include <cms/BytesMessage.h>
#include <cms/MapMessage.h>
#include <cms/ExceptionListener.h>
#include <cms/MessageListener.h>
#include "qcustomplot.h"
#include "IfacomAmqReceiver.h"

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow, public MessageListener
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

    void connectionReceiver();
    void onMessage(const Message*);
    void setupDiagram();
    IfacomAmqReceiver* m_IfacomAmqListener;


private:
    Ui::MainWindow *ui;


private slots:

   void upDateDatas(QString);
};

#endif // MAINWINDOW_H

Answer 1

你调用connect（）是错误的。它应该是：

connect(ui->lineEdit_4, SIGNAL(textChanged(QString)),
        ui->widget_diagram2, SLOT(upDateDatas(QString)));

注意内部连接你应该传递类型而不是变量名。常量引用const type &没问题，但理想情况下应该省略type - 它可以节省输入，而且connect内部也可以。

调试开始时SIGNAL失败

1 个答案: