MainWindow来自Qt中main.cpp的代码

Question

想要了解MainWindow和main.cpp之间代码的差异。具体而言，需要如何修改main.cpp中专门编写的代码块，使其成为mainwindow.cpp和mainwindow.h的一部分。

例如，我正在尝试修改此answer中的代码，以便在MainWindow中使用。

的main.cpp

#include <QtWidgets>
#include <QtNetwork>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    //setup GUI (you could be doing this in the designer)
    QWidget widget;
    QFormLayout layout(&widget);
    QLineEdit lineEditName;
    QLineEdit lineEditGender;
    QLineEdit lineEditRegion;
    auto edits = {&lineEditName, &lineEditGender, &lineEditRegion};
    for(auto edit : edits) edit->setReadOnly(true);
    layout.addRow("Name:", &lineEditName);
    layout.addRow("Gender:", &lineEditGender);
    layout.addRow("Region:", &lineEditRegion);
    QPushButton button("Get Name");
    layout.addRow(&button);

    //send request to uinames API
    QNetworkAccessManager networkManager;
    QObject::connect(&networkManager, &QNetworkAccessManager::finished,
                 [&](QNetworkReply* reply){
        //this lambda is called when the reply is received
        //it can be a slot in your GUI window class
        //check for errors
        if(reply->error() != QNetworkReply::NoError){
            for(auto edit : edits) edit->setText("Error");
            networkManager.clearAccessCache();
        } else {
            //parse the reply JSON and display result in the UI
            QJsonObject jsonObject=     QJsonDocument::fromJson(reply->readAll()).object();
            QString fullName= jsonObject["name"].toString();
            fullName.append(" ");
            fullName.append(jsonObject["surname"].toString());
            lineEditName.setText(fullName);
            lineEditGender.setText(jsonObject["gender"].toString());
            lineEditRegion.setText(jsonObject["region"].toString());
        }
        button.setEnabled(true);
        reply->deleteLater();
        });
     //url parameters
    QUrlQuery query;
    query.addQueryItem("amount", "1");
    query.addQueryItem("region", "United States");
    QUrl url("http://uinames.com/api/");
    url.setQuery(query);
    QNetworkRequest networkRequest(url);
    //send GET request when the button is clicked
    QObject::connect(&button, &QPushButton::clicked, [&](){
        networkManager.get(networkRequest);
        button.setEnabled(false);
        for(auto edit : edits) edit->setText("Loading. . .");
    });

    widget.show();
    return a.exec();
}

修改

添加了相同答案的计时器部分;请演示如何使用计时器的这个版本

QTimer timer;
QObject::connect(&timer, &QTimer::timeout, [&](){
    networkManager.get(networkRequest);
    button.setEnabled(false);
    for(auto edit : edits) edit->setText("Loading. . .");
});
timer.start(60000); //60000 msecs = 60 secs

我很难将networkManager修改为类成员，如何构造代码以及如何替换lambda函数。

如果有人可以为我提供所有必需的修改，以获得更好的理解，那就太棒了。

Answer 1

您可能希望将用户界面和控制器（业务逻辑）分离为单独的类。

main()的主体实例化ui和控制器并连接它们。每5秒获取一次新结果的计时器。计时器也可以滚动到Controller中 - 我将其分离出来作为向现有类添加功能而不修改它的示例。

的main.cpp

// https://github.com/KubaO/stackoverflown/tree/master/questions/into-mainwin-39643510
#include "mainwindow.h"
#include "controller.h"

int main(int argc, char *argv[])
{
   QApplication app{argc, argv};
   MainWindow ui;
   Controller ctl;
   QTimer timer;
   timer.start(5*1000);
   QObject::connect(&timer, &QTimer::timeout, &ctl, &Controller::get);

   QObject::connect(&ctl, &Controller::busy, &ui, [&]{ ui.setState(MainWindow::Loading); });
   QObject::connect(&ui, &MainWindow::request, &ctl, &Controller::get);
   QObject::connect(&ctl, &Controller::error, &ui, [&]{ ui.setState(MainWindow::Error); });
   QObject::connect(&ctl, &Controller::values, &ui, &MainWindow::setFields);
   ui.show();
   return app.exec();
}

控制器对用户界面一无所知，只处理请求。每次处理请求时，它都会发出busy信号。

如果您希望为多个活动请求提供更好的反馈，则只有在没有待处理请求且添加新请求时才需要发出busy信号，并且idle信号将会发出在最后一个请求完成时发出，并且没有更多的待处理请求。

或者Controller.h

#ifndef CONTROLLER_H
#define CONTROLLER_H

#include <QtNetwork>

class Controller : public QObject {
   Q_OBJECT
   QNetworkAccessManager manager{this};
   QNetworkRequest request;
   Q_SLOT void onReply(QNetworkReply *);
public:
   explicit Controller(QObject * parent = nullptr);
   Q_SLOT void get();
   Q_SIGNAL void busy();
   Q_SIGNAL void error(const QString &);
   Q_SIGNAL void values(const QString & name, const QString & gender, const QString & region);
};

#endif // CONTROLLER_H

controller.cpp

#include "controller.h"

Controller::Controller(QObject *parent) : QObject(parent)
{
   QUrlQuery query;
   query.addQueryItem("amount", "1");
   query.addQueryItem("region", "United States");
   QUrl url("http://uinames.com/api/");
   url.setQuery(query);
   request = QNetworkRequest(url);
   connect(&manager, &QNetworkAccessManager::finished, this, &Controller::onReply);
}

void Controller::onReply(QNetworkReply * reply) {
   if (reply->error() != QNetworkReply::NoError) {
      emit error(reply->errorString());
      manager.clearAccessCache();
   } else {
      //parse the reply JSON and display result in the UI
      auto jsonObject = QJsonDocument::fromJson(reply->readAll()).object();
      auto fullName = jsonObject["name"].toString();
      fullName.append(" ");
      fullName.append(jsonObject["surname"].toString());
      emit values(fullName, jsonObject["gender"].toString(), jsonObject["region"].toString());
   }
   reply->deleteLater();
}

void Controller::get() {
   emit busy();
   manager.get(request);
}

用户界面不知道任何业务逻辑，它提供的API足以让业务逻辑使用它。它可以处于以下三种状态之一：Normal状态，其中结果可见，Loading状态显示繁忙反馈，Error状态显示错误信息。 setFields广告位将状态返回到Normal。

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QtWidgets>

class MainWindow : public QWidget {
  Q_OBJECT
  QFormLayout layout{this};
  QLineEdit lineEditName;
  QLineEdit lineEditGender;
  QLineEdit lineEditRegion;
  QPushButton button{"Get Name"};
  QLineEdit * edits[3] = {&lineEditName, &lineEditGender, &lineEditRegion};
public:
  enum State { Normal, Loading, Error };
  explicit MainWindow(QWidget * parent = nullptr);
  Q_SLOT void setFields(const QString & name, const QString & gender, const QString & region);
  Q_SLOT void setState(State);
  Q_SIGNAL void request();
};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"

MainWindow::MainWindow(QWidget *parent) : QWidget(parent)
{
   for(auto edit : edits) edit->setReadOnly(true);
   layout.addRow("Name:", &lineEditName);
   layout.addRow("Gender:", &lineEditGender);
   layout.addRow("Region:", &lineEditRegion);
   layout.addRow(&button);
   connect(&button, &QPushButton::clicked, this, &MainWindow::request);
}

void MainWindow::setFields(const QString & name, const QString & gender, const QString & region) {
   setState(Normal);
   lineEditName.setText(name);
   lineEditGender.setText(gender);
   lineEditRegion.setText(region);
}

void MainWindow::setState(MainWindow::State state) {
   if (state == Normal) {
      for (auto edit : edits) edit->setEnabled(true);
      button.setEnabled(true);
   }
   else if (state == Loading) {
      for (auto edit : edits) edit->setEnabled(false);
      button.setEnabled(false);
   }
   else if (state == Error) {
      for (auto edit : edits) edit->setText("Error...");
      button.setEnabled(true);
   }
}

Answer 2

您可以将所有这些代码放在QMainWindow的构造函数中，并按原样保留lambda函数。

另一种更干净的方法是将这些lambda函数转换为私有槽。使用这种方式，您应该将networkManager定义为QMainWindow类的类成员，并且它应该在堆内存中而不是堆栈中分配。要完成此操作，只需定义QNetworkManager*类成员并在QMainWindow构造函数中初始化它。

this->networkManager = new QNetworkManager(this);

初始化后，您可以在QMainWindow课程的所有广告位中使用它。

一个简单的经验法则是：lambda函数中的所有共享变量和主范围都应该是这样的类成员。

代码。 （我测试了它并且工作正常）

<强>的main.cpp

#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

<强> mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    ui->lineEditGender->setReadOnly(true);
    ui->lineEditRegion->setReadOnly(true);
    ui->lineEditName->setReadOnly(true);

    networkManager = new QNetworkAccessManager(this);

    connect(networkManager, &QNetworkAccessManager::finished, this, &MainWindow::onNetworkManagerFinished);
    connect(ui->btnGetName, &QPushButton::clicked, this, &MainWindow::onBtnGetNameClicked);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::onNetworkManagerFinished(QNetworkReply *reply)
{
    if(reply->error() != QNetworkReply::NoError){
        ui->lineEditName->setText("Error");
        ui->lineEditGender->setText("Error");
        ui->lineEditRegion->setText("Error");

        networkManager->clearAccessCache();
    } else {
        //parse the reply JSON and display result in the UI
        QJsonObject jsonObject = QJsonDocument::fromJson(reply->readAll()).object();
        QString fullName= jsonObject["name"].toString();
        fullName.append(" ");
        fullName.append(jsonObject["surname"].toString());
        ui->lineEditName->setText(fullName);
        ui->lineEditGender->setText(jsonObject["gender"].toString());
        ui->lineEditRegion->setText(jsonObject["region"].toString());
    }
    ui->btnGetName->setEnabled(true);
    reply->deleteLater();
}

void MainWindow::onBtnGetNameClicked()
{
    QUrlQuery query;
    query.addQueryItem("amount", "1");
    query.addQueryItem("region", "United States");
    QUrl url("http://uinames.com/api/");
    url.setQuery(query);
    QNetworkRequest networkRequest(url);

    //send GET request when the button is clicked
    networkManager->get(networkRequest);
    ui->btnGetName->setEnabled(false);

    ui->lineEditName->setText("Loading. . .");
    ui->lineEditGender->setText("Loading. . .");
    ui->lineEditRegion->setText("Loading. . .");
}

<强> mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QNetworkAccessManager>
#include <QNetworkReply>
#include <QNetworkRequest>
#include <QUrlQuery>
#include <QJsonDocument>
#include <QJsonObject>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private slots:
    void onNetworkManagerFinished(QNetworkReply* reply);
    void onBtnGetNameClicked();

private:
    Ui::MainWindow *ui;
    QNetworkAccessManager *networkManager;
};

#endif // MAINWINDOW_H