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【qt学习006】Dialogs and MainWindows 小结

2024-07-04 18:00:15   224人阅读

学习《c++GUI Programming with Qt 4》已有一段时间，非常享受这本书的阅读过程，内容简洁清晰，让人一目了然。

马上要学习更难的内容，所以先做个总结，然后再继续前进。

总结的形式尽量简洁，以代码为主，再将一些我认为重要的笔记作为注释添加在代码中。内容大多是摘抄自书本，但也有一些地方属于个人理解。

闲话少谈，下面列出代码：

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// example1:
#include "mainwindow.h"
#include <QApplication>
#include <QLabel>
 
 
 
int main(int argc, char *argv[])
{
 
 
 
         QApplication app(argc, argv); // The QApplication constructor requires argc and argv because Qt supports a few command-line arguments of its own.
 
         QLabel *label = new QLabel("Hello Qt!"); // Widget: control, <span style="background-color: rgb(255, 0, 0);">container</span>, a user interface in a user interface,容器的意思。
         // Buttons, menus, scroll bars, and frames are all examples of widgets. Widgets can contain other widgets
 
         label->show();
 
 
     
        return app.exec(); // passes control of the application on to Qt.
        // At this point, the program enters the event loop. 开始执行，进入事件队列，由操作系统接管
}

 

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// example2:
#include <QApplication>
#include <QLabel>
#include <QHBoxLayout>
#include <QSlider>
#include <QSpinBox>
 
 
int main(int argc, char *argv[])
{
 
    QApplication app(argc, argv);
 
    QWidget *window = new QWidget; // the application‘s <span style="background-color: rgb(255, 0, 0);">main window</span>
    window->setWindowTitle("Enter your age");
 
    // We could pass window to the QSpinBox and QSlider constructors, specifying that these widgets should have window as their parent
    QSpinBox * spinBox = new QSpinBox;
    QSlider *slider = new QSlider(Qt::Horizontal);
    spinBox->setRange(0, 130);
    slider->setRange(0, 130);
<br>    // 信号槽机制，qt核心本质之一
    QObject::connect(spinBox, SIGNAL(valueChanged(int)),
                     slider, SLOT(setValue(int)));
    QObject::connect(slider, SIGNAL(valueChanged(int)),
                     spinBox, SLOT(setValue(int)));
    spinBox->setValue(35);
 
    // a layout manager，多控件时需要有布局管理器来管理各个控件的位置，qt的布局管理器类可以自动化布局，无需用户关心，写复杂的应用程序时可能会需要自己来布局。
    QHBoxLayout *layout = new QHBoxLayout;
    layout->addWidget(spinBox);
    layout->addWidget(slider);
    QVBoxLayout *layout1 = new QVBoxLayout;
    layout1->addWidget(spinBox); // automatically assigns reasonable positions and sizes to the widgets for which it is responsible, based on their needs
    layout1->addWidget(slider);
<br>    // 此处可以将Layout1设置为layout，体验一下不同的布局形式
    window->setLayout(layout1); // an object that sets the size and position of the widgets that lie under its responsibility
    // installs the layout manager on the window
    window->show();
     
    return app.exec();
}

 

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//  dialog boxes
//  example 3
//  学习有感，学一样东西，未必要从最新的地方入手，应该从资料最丰富的地方入手，如学qt4比qt5容易些，因为qt5刚发布，有很多新特性，新手容易混淆，并且遇见问题，因为资料少，无从下手解决。
 
// main.cpp
#include "mainwindow.h"
#include <QApplication>
 
#include "finddialog.h"
 
 
int main(int argc, char *argv[])
{
 
    QApplication app(argc, argv);
 
    FindDialog *dialog = new FindDialog;
    dialog->show();
 
     
    return app.exec();
}
 
 
// finddialog.h
#ifndef FINDDIALOG_H
#define FINDDIALOG_H
 
#include <QDialog>
 
 
// A forward declaration tells the C++ compiler that a class exists, without giving all the detail that a class definition (usually located in a header file of its own) provides
class QCheckBox;
class QLabel;
class QLineEdit;
class QPushButton;
 
class FindDialog: public QDialog
{<br>    // qt核心本质之一
    // qt macro, is necessary for all classes that define signals or slots
    Q_OBJECT
public:
    // The default is a null pointer, meaning that the dialog has no parent.
    FindDialog(QWidget *parent = 0);
 
signals: // qt macro
    void findNext(const QString &str, Qt::CaseSensitivity cs);
    void findPrevious(const QString &str, Qt::CaseSensitivity cs);
private slots:
    void findClicked();
    void enableFindButton(const QString &text);
private:
    QLabel *label;
    QLineEdit *lineEdit;
    QCheckBox *caseCheckBox;
    QCheckBox *backwardCheckBox;
    QPushButton *findButton;
    QPushButton *closeButton;
 
};
 
#endif // FINDDIALOG_H
 
// finddialog.cpp
// Including this header saves us the bother of including every class individually
//  contains the definition of Qt‘s GUI classes
// bad style to include such a big header file from another header file, especially in larger applications.
#include <QtGui>
 
#include "finddialog.h"
 
 FindDialog::FindDialog(QWidget *parent)
     : QDialog(parent) // ??? we pass on the parent parameter to the base class constructor
{
     label = new QLabel(tr("Find &what:"));  // ??? ampersands (‘&‘) to indicate shortcut keys
     lineEdit = new QLineEdit;
     // we set the label‘s buddy to be the line editor.
     // A buddy is a widget that accepts the focus when the label‘s shortcut key is pressed.
     // So when the user presses Alt+W (the label‘s shortcut), the focus goes to the line editor (the label‘s buddy).
     label->setBuddy(lineEdit);
 
     caseCheckBox = new QCheckBox(tr("Match &case"));
     backwardCheckBox = new QCheckBox(tr("Search &backward"));
 
     findButton = new QPushButton(tr("&Find"));
     findButton->setDefault(true);
     findButton->setEnabled(false);
 
     closeButton = new QPushButton(tr("Close"));
 
     connect(lineEdit, SIGNAL(textChanged(const QString &)),
              this, SLOT(enableFindButton(const QString &)));
     connect(findButton, SIGNAL(clicked()),
           this, SLOT(findClicked()));
     connect(closeButton, SIGNAL(clicked()),
          this, SLOT(close()));
 
     QHBoxLayout *topLeftLayout = new QHBoxLayout;
     topLeftLayout->addWidget(label);
     topLeftLayout->addWidget(lineEdit);
 
     QVBoxLayout *leftLayout = new QVBoxLayout;
     leftLayout->addLayout(topLeftLayout);
     leftLayout->addWidget(caseCheckBox);
     leftLayout->addWidget(backwardCheckBox);
 
     QVBoxLayout *rightLayout = new QVBoxLayout;
     rightLayout->addWidget(findButton);
     rightLayout->addWidget(closeButton);
     rightLayout->addStretch(); // a spacer item (or "stretch").
 
     QHBoxLayout *mainLayout = new QHBoxLayout;
     mainLayout->addLayout(leftLayout);
     mainLayout->addLayout(rightLayout);
     setLayout(mainLayout); // the main layout is installed on the dialog
 
     setWindowTitle(tr("Find"));
     setFixedHeight(sizeHint().height());
}
 
 
 void FindDialog::findClicked()
 {
     QString text = lineEdit->text();
     Qt::CaseSensitivity cs =
             caseCheckBox->isChecked() ? Qt::CaseSensitive
                                       : Qt::CaseInsensitive;
     if (backwardCheckBox->isChecked()) {
         emit findPrevious(text, cs);
     } else {
         emit findNext(text, cs); //The emit keyword is specific to Qt
     }
 }
 
 void FindDialog::enableFindButton(const QString &text)
 {
     findButton->setEnabled(!text.isEmpty());
 }

 

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// example 4
// signals and slots
//
// connect(sender, SIGNAL(signal), receiver, SLOT(slot));
// sender and receiver are POINTERS to QObjects and where signal and slot are function // signatures WITHOUT PARAMETER names
// To successfully connect a signal to a slot (or to another signal), they must have the // same parameter types in the same order:
 
// connect(ftp, SIGNAL(rawCommandReply(int, const QString &)),
//       this, SLOT(processReply(int, const QString &)));
//  signals and slots mechanism don‘t limit to qt gui programming.
 
 
// example 5
// 跳过了qt designer 几小节
// Qt‘s container widgets are widgets that contain other widgets, such as QFrame, // QGroupBox
// QFrame can also be used on its own to simply draw lines and serves as the base class // for many other widget classes, including QToolBox and QLabel.
 
 
// example 6: main windows
// complete with menus, toolbars, status bar, and as many dialogs as the application requires
// mainWdinows（Chapter3）这一章有点难度，比起之前的章节，这一章的知识点有些跳跃，需要写出一个完整的程序，包括布局、对象之间的继承、信号与槽的设置以及一些特殊的函数使用等等一些内容<br>// 另外章节的设置也有问题，这一章需要使用的类，在前两章由qt designer实现，无法直接在本章使用，需要自己去完善。
//　如果学懂了 这一章，应该可以独立设计一个记事本。

 


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