第三讲 对话框的创建

// finddialog.h 头文件

#ifndef FINDDIALOG_H

#define FINDDIALOG_H

#include <QDialog>

class QCheckBox;
class QLabel;
class QLineEdit;
class QPushButton;

class FindDialog : public QDialog
{
    Q_OBJECT  // Q_OBJECT为Qt的宏，定义了信号与槽的类必须含有该宏

public:
    FindDialog(QWidget *parent = 0);

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:
    QLabel *label;
    QLineEdit *lineEdit;
    QCheckBox *caseCheckBox;
    QCheckBox *backwardCheckBox;
    QPushButton *findButton;
    QPushButton *closeButton;
};
#endif

// finddialog.cpp
#include <QLabel>
#include <QLineEdit>
#include <QCheckBox>
#include <QPushButton>
#include <QHBoxLayout>
#include <QVBoxLayout>
#include "finddialog.h"

FindDialog::FindDialog(QWidget *parent)
: QDialog(parent)
{
    label = new QLabel(tr("Find &what:")); // 设置快捷键 Alt+W
    lineEdit = new QLineEdit;
    // 设置lineEdit为label的伙伴，当按下快捷时，程序的焦点会转移到lineEdit上
    label->setBuddy(lineEdit);

    caseCheckBox = new QCheckBox(tr("Match &case"));  // 设置快捷键 Alt+C
    backwardCheckBox = new QCheckBox(tr("Search &backward")); // 设置快捷键 Alt+B

    findButton = new QPushButton(tr("&Find"));
    // 设置findButton为整个对话框(只有在对话框中才有默认按钮)的默认按钮
    // (那么如果用户在对话框中敲击回车键，这个推动按钮将被按下)
    findButton->setDefault(true);  
    // 禁用按钮，当禁用时不会与用户发生交换，显示为灰色
    findButton->setEnabled(false); 
    closeButton = new QPushButton(tr("Close"));

    /* 设置信号与槽的连接 */
    // 设置lineEdit与findButton之间的通信
    connect(lineEdit, SIGNAL(textChanged(const QString &)),
        this, SLOT(enableFindButton(const QString &)));
    // 当findButton被点击时，调用findClicked()函数
    connect(findButton, SIGNAL(clicked()),
        this, SLOT(findClicked()));
    // 当点击closeButton按钮时调用close()函数，隐藏对话框
    connect(closeButton, SIGNAL(clicked()),
        this, SLOT(close()));

    /* 对话框的布局设置 */
    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();

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

    setWindowTitle(tr("Find"));

    // 设置高度固定且高度为Qt建议的大小，在QtWidget类中含有建议大小属性 
    setFixedHeight(sizeHint().height()); 

}

void FindDialog::findClicked()
{
    // 该函数获取lineEdit的text与caseCheckBox的选项设置，
    // 再根据backwardCheckBox的选项来选择发送向前查找或者
    // 向后查找信号
    QString text = lineEdit->text();
    Qt::CaseSensitivity cs =
        caseCheckBox->isChecked() ? Qt::CaseSensitive
        : Qt::CaseInsensitive;
    // emit为Qt的关键字，为Qt的扩展语法，表示发送信号的含义
    // 在这里可能会发送findPrevious或者findNext信号，但是
    // 由于没有设置相应的槽接受，所以不会调用其他函数
    if (backwardCheckBox->isChecked())
        emit findPrevious(text, cs);
    else
        emit findNext(text, cs);
}

void FindDialog::enableFindButton(const QString &text)
{
    findButton->setEnabled(!text.isEmpty());
}

// main.cpp
#include <QApplication>
#include "finddialog.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    FindDialog *dialog = new FindDialog;
    dialog->show();
    return app.exec();
}