菜鸟学QT之四-------------第一个对话框 .

一、

新建一个工程，选择QT Application，工程名qtFindDlg；注意，BaseDialog选择QDialog，而不是默认的QMainWindow；点击“完成”。

程序完成运行效果如图：

 

上代码finddlg.h:

#ifndef FINDDLG_H
#define FINDDLG_H

#include <QtGui/QDialog>
#include "ui_finddlg.h"
class QCheckBox;
class QLabel;
class QLineEdit;
class QPushButton;

class FindDlg : public QDialog
{
    Q_OBJECT

public:
    FindDlg(QWidget *parent = 0, Qt::WFlags flags = 0);
    ~FindDlg();
signals:
    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:
    Ui::FindDlgClass ui;
    QLabel* m_pQLabel;
    QLineEdit* m_pQLineEdit;
    QCheckBox* m_pQCaseCheckBox;
    QCheckBox* m_pQBackwardCheckBox;
    QPushButton* m_pQFindButton;
    QPushButton* m_pQCloseButton;
};

#endif // FINDDLG_H

#ifndef FINDDLG_H #define FINDDLG_H #include <QtGui/QDialog> #include "ui_finddlg.h" class QCheckBox; class QLabel; class QLineEdit; class QPushButton; class FindDlg : public QDialog { Q_OBJECT public: FindDlg(QWidget *parent = 0, Qt::WFlags flags = 0); ~FindDlg(); signals: 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: Ui::FindDlgClass ui; QLabel* m_pQLabel; QLineEdit* m_pQLineEdit; QCheckBox* m_pQCaseCheckBox; QCheckBox* m_pQBackwardCheckBox; QPushButton* m_pQFindButton; QPushButton* m_pQCloseButton; }; #endif // FINDDLG_H

 

对于所有定义了信号和槽的类，在类定义开始处的Q_OBJECT宏都是必需的。

Signals部分声明了当用户单击Find按钮时对话框所发射的信号。

Signals关键字实际上是一个宏。C++预处理器会在编译程序找到它之前把它转换成标准C++代码。

之后private slots:声明了两个槽。为了实现这两个槽，几乎需要访问这个对话框的所有子窗口部件（控件），所以也就保留了指向这些子窗口部件的指针。关键字slots如同signals一样也是一个宏。

 

下面是finddlg.cpp的代码

#include <QtGui>
#include "finddlg.h"
#include <iostream>
#include <exception>

FindDlg::FindDlg(QWidget *parent, Qt::WFlags flags)
    : QDialog(parent, flags)
{
    ui.setupUi(this);
    try
    {
        m_pQLabel = new QLabel(tr("Find &what:"));
        m_pQLineEdit = new QLineEdit;
        m_pQLabel->setBuddy(m_pQLineEdit);

        m_pQCaseCheckBox = new QCheckBox(tr("Match &case"));
        m_pQBackwardCheckBox = new QCheckBox(tr("Search &backford"));

        m_pQFindButton = new QPushButton(tr("&Find"));
        m_pQFindButton->setDefault(true);
        m_pQFindButton->setEnabled(false);

        m_pQCloseButton = new QPushButton(tr("Cl&ose"));

        connect(m_pQLineEdit, SIGNAL(textChanged(const QString&)), this, SLOT(enableFindButton(const QString&)));
        connect(m_pQFindButton, SIGNAL(clicked()), this, SLOT(findClicked()));
        connect(m_pQCloseButton, SIGNAL(clicked()), this, SLOT(close()));

        QHBoxLayout *topLeftLayout = new QHBoxLayout;
        topLeftLayout->addWidget(m_pQLabel);
        topLeftLayout->addWidget(m_pQLineEdit);

        QVBoxLayout *leftLayout = new QVBoxLayout;
        leftLayout->addLayout(topLeftLayout);
        leftLayout->addWidget(m_pQCaseCheckBox);
        leftLayout->addWidget(m_pQBackwardCheckBox);

        QVBoxLayout *rightLayout = new QVBoxLayout;
        rightLayout->addWidget(m_pQFindButton);
        rightLayout->addWidget(m_pQCloseButton);
        rightLayout->addStretch();

        QHBoxLayout *mainLayout = new QHBoxLayout;
        mainLayout->addLayout(leftLayout);
        mainLayout->addLayout(rightLayout);
        setLayout(mainLayout);

        setWindowTitle(tr("Find"));
        setFixedHeight(sizeHint().height());
    }
    catch(std::bad_alloc& e)
    {
        std::cerr << e.what() << std::endl;
    }
    catch(...)
    {
        std::cerr << "err" << std::endl;
    }
}

FindDlg::~FindDlg()
{
    if (NULL != m_pQLabel)
    {
        delete m_pQLabel;
    }
    if (NULL != m_pQLineEdit)
    {
        delete m_pQLineEdit;
    }
    if (NULL != m_pQCaseCheckBox)
    {
        delete m_pQCaseCheckBox;
    }
    if (NULL != m_pQBackwardCheckBox)
    {
        delete m_pQBackwardCheckBox;
    }
    if (NULL != m_pQFindButton)
    {
        delete m_pQFindButton;
    }
    if (NULL != m_pQCloseButton)
    {
        delete m_pQCloseButton;
    }
}
void FindDlg::findClicked()
{

    QString text = m_pQLineEdit->text();
    Qt::CaseSensitivity cs = m_pQCaseCheckBox->isChecked() ? Qt::CaseInsensitive : Qt::CaseInsensitive;
    if (m_pQBackwardCheckBox->isChecked())
    {
        emit findPrevious(text, cs);
    }
    else
    {
        emit findNext(text, cs);
    }
    return;
}

void FindDlg::enableFindButton(const QString& text)
{
    m_pQFindButton->setEnabled(!text.isEmpty());
    return;
}

#include <QtGui> #include "finddlg.h" #include <iostream> #include <exception> FindDlg::FindDlg(QWidget *parent, Qt::WFlags flags) : QDialog(parent, flags) { ui.setupUi(this); try { m_pQLabel = new QLabel(tr("Find &what:")); m_pQLineEdit = new QLineEdit; m_pQLabel->setBuddy(m_pQLineEdit); m_pQCaseCheckBox = new QCheckBox(tr("Match &case")); m_pQBackwardCheckBox = new QCheckBox(tr("Search &backford")); m_pQFindButton = new QPushButton(tr("&Find")); m_pQFindButton->setDefault(true); m_pQFindButton->setEnabled(false); m_pQCloseButton = new QPushButton(tr("Cl&ose")); connect(m_pQLineEdit, SIGNAL(textChanged(const QString&)), this, SLOT(enableFindButton(const QString&))); connect(m_pQFindButton, SIGNAL(clicked()), this, SLOT(findClicked())); connect(m_pQCloseButton, SIGNAL(clicked()), this, SLOT(close())); QHBoxLayout *topLeftLayout = new QHBoxLayout; topLeftLayout->addWidget(m_pQLabel); topLeftLayout->addWidget(m_pQLineEdit); QVBoxLayout *leftLayout = new QVBoxLayout; leftLayout->addLayout(topLeftLayout); leftLayout->addWidget(m_pQCaseCheckBox); leftLayout->addWidget(m_pQBackwardCheckBox); QVBoxLayout *rightLayout = new QVBoxLayout; rightLayout->addWidget(m_pQFindButton); rightLayout->addWidget(m_pQCloseButton); rightLayout->addStretch(); QHBoxLayout *mainLayout = new QHBoxLayout; mainLayout->addLayout(leftLayout); mainLayout->addLayout(rightLayout); setLayout(mainLayout); setWindowTitle(tr("Find")); setFixedHeight(sizeHint().height()); } catch(std::bad_alloc& e) { std::cerr << e.what() << std::endl; } catch(...) { std::cerr << "err" << std::endl; } } FindDlg::~FindDlg() { if (NULL != m_pQLabel) { delete m_pQLabel; } if (NULL != m_pQLineEdit) { delete m_pQLineEdit; } if (NULL != m_pQCaseCheckBox) { delete m_pQCaseCheckBox; } if (NULL != m_pQBackwardCheckBox) { delete m_pQBackwardCheckBox; } if (NULL != m_pQFindButton) { delete m_pQFindButton; } if (NULL != m_pQCloseButton) { delete m_pQCloseButton; } } void FindDlg::findClicked() { QString text = m_pQLineEdit->text(); Qt::CaseSensitivity cs = m_pQCaseCheckBox->isChecked() ? Qt::CaseInsensitive : Qt::CaseInsensitive; if (m_pQBackwardCheckBox->isChecked()) { emit findPrevious(text, cs); } else { emit findNext(text, cs); } return; } void FindDlg::enableFindButton(const QString& text) { m_pQFindButton->setEnabled(!text.isEmpty()); return; }

 

代码第X行，“12”符号来表示快捷键，可以用来控制焦点。而在第14行设置了行编辑器作为标签的伙伴。所谓伙伴“buddy”，就是一个窗口部件，它可以在按下标签的快捷键时接收焦点。

通过setDefault(true)让Find按钮成为对话框的默认按钮。意为当用户按下Enter键时如同鼠标点击了“Find”按钮。

当用户单击Find按钮时，就会调用findClicked()槽。而该槽将会发射findPrevious()或findNext()信号。emit是Qt中的关键字，像其他QT扩展一样它也会被C++预处理器转换成标准的C++代码。

由于在创建这个对话框中的窗口部件和而已时使用的是new，所以需要写一个能调用delete的析构函数，以便可以删除所创建的每一个窗口部件和布局。但是这样做并不是必需的，因为QT会在删除父对象的时候自动删除其所属的子对象，也就会删除FindDialog中作为期子孙的所有子窗口部件和子布局。但是个人还是比较喜欢自己控制的东西。