第45课 - 创建查找对话框以及功能实现

1、查找对话框 

查找对话框是应用程序中的常用部件 

目标： 

         开发一个可以在不同项目间复用的查找对话框 

 

查找对话框需求分析

       －可复用软件部件 

       －查找文本框中的指定字符串 

       －能够指定查找方向 

       －支持大小写敏感查找 

        - 点击关闭按钮后隐藏 

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查找对话框的架构与设计 

查找对话框的界面布局 

2、编程实验 

查找对话框界面开发  

FindDialog.h

#ifndef _FINDDIALOG_H_
#define _FINDDIALOG_H_

#include <QDialog>
#include <QGridLayout>
#include <QHBoxLayout>
#include <QLabel>
#include <QLineEdit>
#include <QPushButton>
#include <QRadioButton>
#include <QCheckBox>
#include <QGroupBox>

class FindDialog : public QDialog
{
    Q_OBJECT

protected:
    QGroupBox m_radioGrpBx;

    QGridLayout m_layout;
    QHBoxLayout m_hbLayout;

    QLabel m_findLbl;
    QLineEdit m_findEdit;
    QPushButton m_findBtn;
    QPushButton m_closeBtn;
    QCheckBox m_matchChkBx;
    QRadioButton m_forwardBtn;
    QRadioButton m_backwardBtn;

public:
    explicit FindDialog(QWidget* parent = 0);
    bool event(QEvent* evt);
    
signals:
    
public slots:
    
};

#endif // _FINDDIALOG_H_

FindDialog.cpp

#include "FindDialog.h"
#include <QEvent>

FindDialog::FindDialog(QWidget *parent) : QDialog(parent, Qt::WindowCloseButtonHint | Qt::Drawer)
{
    m_findLbl.setText("Find What:");
    m_findBtn.setText("Find Next");
    m_closeBtn.setText("Close");
    m_matchChkBx.setText("Match Case");
    m_backwardBtn.setText("Backward");
    m_forwardBtn.setText("Forward");
    m_forwardBtn.setChecked(true);
    m_radioGrpBx.setTitle("Direction");

    m_hbLayout.addWidget(&m_forwardBtn);
    m_hbLayout.addWidget(&m_backwardBtn);

    m_radioGrpBx.setLayout(&m_hbLayout);

    m_layout.setSpacing(10);
    m_layout.addWidget(&m_findLbl, 0, 0);
    m_layout.addWidget(&m_findEdit, 0, 1);
    m_layout.addWidget(&m_findBtn, 0, 2);
    m_layout.addWidget(&m_matchChkBx, 1, 0);
    m_layout.addWidget(&m_radioGrpBx, 1, 1);
    m_layout.addWidget(&m_closeBtn, 1, 2);

    setLayout(&m_layout);
    setWindowTitle("Find");
}

bool FindDialog::event(QEvent* evt)
{
    if( evt->type() == QEvent::Close )
    {
        hide();

        return true;
    }

    return QDialog::event(evt);
}

3、查找功能的实现 

文本查找功能的核心思想 

      1. 获取当前光标的位置并作为起始点 

      2. 向后（向前）查找目标第一次出现的位置 

      3. 通过目标位置以及目标长度在文本框中进行标记 

 

QString类中提供了子串查找的相关函数 

        - indexOf 

                从指定位置向后查找目标子串的下标位置 

        - lastIndexOf 

                从指定位置向前查找目标子串的下标位置 

QString类中查找函数所使用的下标位置 

Qt中的光标信息类QTextCursor 

          - 文本框中的光标是一个QTextCursor对象 

          - 所有与光标相关的信息都通过QTextCursor描述 

               • 如：光标位置，文本选择，等等 

查找算法流程图 

              

MainWindow与FindDialog之间的关系图 

4、编程实验 

查找功能的实现 

FindDialog.h

#ifndef _FINDDIALOG_H_
#define _FINDDIALOG_H_

#include <QDialog>
#include <QGridLayout>
#include <QHBoxLayout>
#include <QLabel>
#include <QLineEdit>
#include <QPushButton>
#include <QRadioButton>
#include <QCheckBox>
#include <QGroupBox>
#include <QPlainTextEdit>
#include <QPointer>

class FindDialog : public QDialog
{
    Q_OBJECT

protected:
    QGroupBox m_radioGrpBx;

    QGridLayout m_layout;
    QHBoxLayout m_hbLayout;

    QLabel m_findLbl;
    QLineEdit m_findEdit;
    QPushButton m_findBtn;
    QPushButton m_closeBtn;
    QCheckBox m_matchChkBx;
    QRadioButton m_forwardBtn;
    QRadioButton m_backwardBtn;

    QPointer<QPlainTextEdit> m_pText;

    void initControl();
    void connectSlot();
protected slots:
    void onFindClicked();
    void onCloseClicked();
public:
    explicit FindDialog(QWidget* parent = 0, QPlainTextEdit* pText = 0);
    void setPlainTextEdit(QPlainTextEdit* pText);
    QPlainTextEdit* getPlainTextEdit();
    bool event(QEvent* evt);  
};

#endif // _FINDDIALOG_H_

FindDialog.cpp

#include "FindDialog.h"
#include <QEvent>
#include <QTextCursor>
#include <QMessageBox>

FindDialog::FindDialog(QWidget *parent, QPlainTextEdit* pText)
    : QDialog(parent, Qt::WindowCloseButtonHint | Qt::Drawer)
{
    initControl();
    connectSlot();
    setLayout(&m_layout);
    setWindowTitle("Find");
    setPlainTextEdit(pText);
}

void FindDialog::initControl()
{
    m_findLbl.setText("Find What:");
    m_findBtn.setText("Find Next");
    m_closeBtn.setText("Close");
    m_matchChkBx.setText("Match Case");
    m_backwardBtn.setText("Backward");
    m_forwardBtn.setText("Forward");
    m_forwardBtn.setChecked(true);
    m_radioGrpBx.setTitle("Direction");

    m_hbLayout.addWidget(&m_forwardBtn);
    m_hbLayout.addWidget(&m_backwardBtn);

    m_radioGrpBx.setLayout(&m_hbLayout);

    m_layout.setSpacing(10);
    m_layout.addWidget(&m_findLbl, 0, 0);
    m_layout.addWidget(&m_findEdit, 0, 1);
    m_layout.addWidget(&m_findBtn, 0, 2);
    m_layout.addWidget(&m_matchChkBx, 1, 0);
    m_layout.addWidget(&m_radioGrpBx, 1, 1);
    m_layout.addWidget(&m_closeBtn, 1, 2);

}

void FindDialog::connectSlot()
{
    connect(&m_findBtn, SIGNAL(clicked()), this, SLOT(onFindClicked()));
    connect(&m_closeBtn, SIGNAL(clicked()), this, SLOT(onCloseClicked()));
}

void FindDialog::setPlainTextEdit(QPlainTextEdit* pText)
{
    m_pText = pText;
}

QPlainTextEdit* FindDialog::getPlainTextEdit()
{
    return m_pText;
}

bool FindDialog::event(QEvent* evt)
{
    if( evt->type() == QEvent::Close )
    {
        hide();

        return true;
    }

    return QDialog::event(evt);
}

void FindDialog::onFindClicked()
{
    QString target = m_findEdit.text();

    if( (m_pText != NULL) && (target != "") )
    {
        QString text = m_pText->toPlainText();
        QTextCursor c = m_pText->textCursor();
        int index = -1;

        if( m_forwardBtn.isChecked() )
        {
            index = text.indexOf(target, c.position(), m_matchChkBx.isChecked() ? Qt::CaseSensitive : Qt::CaseInsensitive);

            if( index >= 0 )
            {
                c.setPosition(index);
                c.setPosition(index + target.length(), QTextCursor::KeepAnchor);

                m_pText->setTextCursor(c);
            }
        }

        if( m_backwardBtn.isChecked() )
        {
            index = text.lastIndexOf(target, c.position() - text.length() - 1, m_matchChkBx.isChecked() ? Qt::CaseSensitive : Qt::CaseInsensitive);

            if( index >= 0 )
            {
                c.setPosition(index + target.length());
                c.setPosition(index, QTextCursor::KeepAnchor);

                m_pText->setTextCursor(c);
            }
        }

        if( index < 0 )
        {
            QMessageBox msg(this);

            msg.setWindowTitle("Find");
            msg.setText("Can not find \"" + target + "\" any more...");
            msg.setIcon(QMessageBox::Information);
            msg.setStandardButtons(QMessageBox::Ok);

            msg.exec();
        }
    }
}

void FindDialog::onCloseClicked()
{
    close();
}

使用该查找对话框类

MainWindow.h

QSharedPointer<FindDialog> m_pFindDlg;

MainWindowUI.cpp

MainWindow::MainWindow() : m_pFindDlg(new FindDialog(this, &mainEditor))
{
    //mainEditor为文本编辑框对象
}

                                           高亮显示的颜色问题下节课介绍

5、小结 

查找对话框可以作用一个可复用的软件部件进行开发 

查找对话框继承自QDialog类 

查找对话框的界面通过布局管理器相互嵌套完成 

查找对话框的设计与实现是GUI学习中的经典范例 

 

QString中提供了不同的子串查找方式 

QTextCursor对象保存了文本框中光标的相关信息

QString对象和QTextCurosr对象协作实现查找功能 

查找对话框与文本框的弱耦合关系满足了可复用的需求