第三十七课深度解析QMap与QHash

Posted 2020-08-31 谱写赞歌

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一、QMap深度解析

1、QMap是一个以升序键顺序存储键值对的数据结构

（1）QMap原型为class QMap<K, T>模板

（2）、QMap中的键值对根据key进行了排序

（3）、QMap中的key类型必须重载operator < (小于操作符)

2、QMap使用实例一

3、QMap使用实例二

4、QMap的注意事项

（1）、通过key获取Value时

A、当key存在，返回对应的Value

B、当key不存在，返回值类型所对应的“零”值

（2）、插入键值对时

A、当key存在，更新Value的值

B、当key不存在，插入新的键值对

#include <QtCore/QCoreApplication>
#include <QDebug>
#include <QMap>
#include<QMapIterator>//迭代器

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    
    QMap<QString, int> map;
    map["key 2"] = 2;
    map["key 0"] = 0;
    map.insert("key 1", 1);

   //map.insert("key 1", 4);//前面已有key 1，所有这里会更新key的键值为4

    QList<QString> list = map.keys();

    for(int i=0; i<list.count(); i++)
    {
        qDebug() << list[i];//打印排序好的key 0、key 1、key 2
    }

    QList<int> vlist = map.values();

    for(int i=0; i<vlist.count(); i++)
    {
        qDebug() << vlist[i];//打印0、1、2
    }



    QMapIterator<QString,int> it(map);//it指向第一个元素之前的位置
    while(it.hasNext())
    {
        it.next();
        qDebug() << it.key() << ":" << it.value() ;
    }


    return a.exec();
}

QMap.cpp

二、QHash深度解析

1、QHash是Qt中的哈希数据结构

（1）、QHash原型为class QHash<K, T>模板

（2）、QHash中的键值对在内部无序排列

（3）、QHash中的Key类型必须重载operator ==

（4）、QHash中的Key对象必须重载全局哈希函数（qHash()）

2、QHash使用示例

#include <QtCore/QCoreApplication>
#include <QDebug>
#include <QHash>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    
    QHash<QString, int> map;
    map["key 2"] = 2;
    map["key 0"] = 0;
    map.insert("key 1", 1);

   //map.insert("key 1", 4);//前面已有key 1，所有这里会更新key的键值为4

    QList<QString> list = map.keys();

    for(int i=0; i<list.count(); i++)
    {
        qDebug() << list[i];//打印排序好的key 0、key 1、key 2
    }

    QList<int> vlist = map.values();

    for(int i=0; i<vlist.count(); i++)
    {
        qDebug() << vlist[i];//打印0、1、2
    }



    QHash<QString,int>::const_iterator i;

    for(i=map.constBegin(); i!=map.constEnd(); ++i)
    {
        qDebug() << i.key() << ":" << i.value() ;
    }

    return a.exec();
}

QHash.cpp

三、QMap和QHash的对比分析

1、QMap和QHash的接口相同，可直接替换使用

（1）、QHash的查找速度明显快于QMap

（2）、QHash占用的存储空间明显多于QMap

（3）、QHash以任意的方式存储元素

（4）、QMap以Key顺序存储元素

（5）、QHash的键类型必须提供operator == () 和 qHash(key)函数

（6）、QMap的键类型必须提供operator <

QString MainWindow::showFileDialog(QFileDialog::AcceptMode mode, QString title)
{
    QString ret = "";
    QFileDialog fd;
    QStringList filters;
    QMap<QString, QString> map;

    const char* fileArray[][2]=
    {

        {"Text(*.txt)",    ".txt"},
        {"All Files(*.*)",   "*" },
        {NULL,               NULL}

    };

    for(int i=0; fileArray[i][0] != NULL; i++)
    {
        filters.append(fileArray[i][0]);
        map.insert(fileArray[i][0], fileArray[i][1]);
    }

    fd.setWindowTitle(title);
    fd.setAcceptMode(mode);


    fd.setNameFilters(filters);

    if(mode==QFileDialog::AcceptOpen)
    {
        fd.setFileMode(QFileDialog::ExistingFile);
    }

    if(fd.exec()==QFileDialog::Accepted)
    {
        ret = fd.selectedFiles()[0];

        QString posix = map[fd.selectedNameFilter()];//把下拉中选中的后缀对应键值取出

        if(posix != "*" && !ret.endsWith(posix))
        {
            ret += posix;
        }
    }

    return ret;
}

自动加入后缀名

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMenuBar>
#include <QMenu>
#include <QAction>
#include <QString>
#include <QtGui/QMainWindow>
#include <QToolBar>
#include <QIcon>
#include <QSize>
#include <QStatusBar>
#include <QLabel>
#include <QPlainTextEdit>
#include <QFileDialog>
class MainWindow : public QMainWindow
{
    Q_OBJECT
private:
        QPlainTextEdit mainEdit;
        QLabel statusLabel;
        QString m_filePath;//记得在构造函数里初始化
        bool m_isTextChanged;//构造函数里初始化为false

        MainWindow(QWidget *parent = 0);
        MainWindow(const MainWindow& obj);
        MainWindow* operator = (const MainWindow& obj);
        bool construct();

        bool initMenuBar();//菜单栏
        bool initToolBar();//工具栏
        bool initStatusBar();//状态栏
        bool initinitMainEditor();//编辑窗口

        bool initFileMenu(QMenuBar* mb);//文件菜单
        bool initEditMenu(QMenuBar* mb);//编辑菜单
        bool initFormatMenu(QMenuBar* mb);//格式菜单
        bool initViewMenu(QMenuBar* mb);//视图菜单
        bool initHelpMenu(QMenuBar* mb);//帮助菜单

        bool initFileToolItem(QToolBar* tb);//工具选项
        bool initEditToolItem(QToolBar* tb);
        bool initFormatToolItem(QToolBar* tb);
        bool initViewToolItem(QToolBar* tb);


        bool makeAction(QAction*& action,QMenu* menu, QString text, int key);//菜单项
        bool makeAction(QAction*& action,QToolBar* tb, QString tip, QString icon);

        QString showFileDialog(QFileDialog::AcceptMode mode, QString title);//文件对话框
        void showErrorMessage(QString message);//错误消息对话框
        int showQuesstionMessage(QString message);//问题消息对话框
        QString saveCurrentData(QString path = "");
        void preEditorChanged();

private slots:
        void onFileNew();
        void onFileOpen();
        void onFlieSave();
        void onFileSaveAs();
        void onTextChanged();
public:
     static MainWindow* NewInstance();
    ~MainWindow();
};

#endif // MAINWINDOW_H

MainWindow.h

#include "MainWindow.h"
#include <QDebug>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), statusLabel(this)
{
    m_filePath = "";
    m_isTextChanged = false;
    setWindowTitle("NotePad-[New]");
}

bool MainWindow::construct()
{
    bool ret = true;
    ret = ret && initMenuBar();
    ret = ret && initToolBar();
    ret = ret && initStatusBar();
    ret = ret && initinitMainEditor();
    return ret;
}
MainWindow* MainWindow::NewInstance()
{
    MainWindow* ret = new MainWindow();

    if((ret==NULL) || (!ret->construct()))
    {
        delete ret;
        ret = NULL;
    }

    return ret;
}
bool MainWindow::initMenuBar()//菜单栏
{
    bool ret = true;

    QMenuBar* mb = menuBar();//一定要注意是menuBar()，这是普通成员函数，不是构造函数

    ret = ret && initFileMenu(mb);//传一个参数是为了在initFileMenu()函数将menu加入菜单栏
    ret = ret && initEditMenu(mb);
    ret = ret && initFormatMenu(mb);
    ret = ret && initViewMenu(mb);
    ret = ret && initHelpMenu(mb);

    return ret;

}

bool MainWindow::initToolBar()//工具栏
{
    bool ret = true;

    QToolBar* tb = addToolBar("Tool Bar");
    //tb->setMovable(false);
    //tb->setFloatable(false);
    tb->setIconSize(QSize(16,16));

    ret = ret && initFileToolItem(tb);
    tb->addSeparator();
    ret = ret && initEditToolItem(tb);
    tb->addSeparator();
    ret = ret && initFormatToolItem(tb);
    tb->addSeparator();
    ret = ret && initViewToolItem(tb);

    return ret;
}

bool MainWindow::initStatusBar()//状态栏
{
    bool ret = true;

    QStatusBar* sb = statusBar();

    QLabel* label = new QLabel("Made By LGC");

    if(label != NULL)
    {
        statusLabel.setMinimumWidth(200);
        statusLabel.setAlignment(Qt::AlignHCenter);
        statusLabel.setText("Ln:1    Col:1");


        label->setMinimumWidth(200);
        label->setAlignment(Qt::AlignHCenter);

        sb->addPermanentWidget(new QLabel());//单纯加入分隔符
        sb->addPermanentWidget(&statusLabel);
        sb->addPermanentWidget(label);
    }
    else
    {
        ret = false;
    }
    return ret;
}
bool MainWindow::initinitMainEditor()//编辑窗口
{
    bool ret = true;

    mainEdit.setParent(this);
    setCentralWidget(&mainEdit);

    connect(&mainEdit, SIGNAL(textChanged()), this, SLOT(onTextChanged()));

    return ret;
}

/************************************************文件菜单********************************************************/
bool MainWindow::initFileMenu(QMenuBar* mb)
{
    bool ret = true;

    QMenu* menu = new QMenu("File(&F)");//创建文件菜单，（&F）是为了可以Alt+F打开
    ret = (menu != NULL);
    if(ret)
    {
        QAction* action = NULL;

        //New
        ret = ret &&  makeAction(action, menu, "New(&N)",Qt::CTRL + Qt::Key_N);
        if(ret)
        {
           connect(action, SIGNAL(triggered()), this, SLOT(onFileNew()));
           menu->addAction(action);
        }

        menu->addSeparator();

        //Open
        ret = ret &&  makeAction(action,  menu,"Open(&O)...",Qt::CTRL + Qt::Key_O);
        if(ret)
        {
           connect(action, SIGNAL(triggered()), this, SLOT(onFileOpen()));
           menu->addAction(action);
        }

        menu->addSeparator();

        //Save
        ret = ret &&  makeAction(action,  menu,"Save(&S)",Qt::CTRL + Qt::Key_S);
        if(ret)
        {
            connect(action, SIGNAL(triggered()), this ,SLOT(onFlieSave()));
            menu->addAction(action);
        }

        menu->addSeparator();

        //Save As
        ret = ret &&  makeAction(action, menu, "Save As(&A)...",0);
        if(ret)
        {
           connect(action, SIGNAL(triggered()), this, SLOT(onFileSaveAs()));
           menu->addAction(action);

        }

        menu->addSeparator();

        //print
        ret = ret &&  makeAction(action, menu, "Print(&P)...",Qt::CTRL + Qt::Key_P);
        if(ret)
        {
           menu->addAction(action);
        }

        menu->addSeparator();

        //Exit
        ret = ret &&  makeAction(action,  menu,"Exit(&X)",0);
        if(ret)
        {
           menu->addAction(action);//将菜单项加入到菜单
        }

    }
    if(ret)
    {
        mb->addMenu(menu);//将菜单加入到菜单栏
    }
    else
    {
        delete mb;
    }
    return ret;
}

/************************************************编辑菜单********************************************************/
bool MainWindow::initEditMenu(QMenuBar* mb)
{
    bool ret = true;

    QMenu* menu = new QMenu("Edit(&E)");
    ret = (menu != NULL);
    if(ret)
    {
        QAction* action = NULL;

        //Undo
        ret = ret &&  makeAction(action,  menu,"Undo(&U)",Qt::CTRL + Qt::Key_Z);
        if(ret)
        {
           menu->addAction(action);
        }

        menu->addSeparator();

        //Redo
        ret = ret &&  makeAction(action,  menu,"Redo(&R)...",Qt::CTRL + Qt::Key_Y);
        if(ret)
        {
           menu->addAction(action);
        }

        menu->addSeparator();

        //Cut
        ret = ret &&  makeAction(action,  menu,"Cut(&T)",Qt::CTRL + Qt::Key_X);
        if(ret)
        {
           menu->addAction(action);
        }

        menu->addSeparator();

        //Copy
        ret = ret &&  makeAction(action,  menu,"Copy(&C)...",Qt::CTRL + Qt::Key_C);
        if(ret)
        {
           menu->addAction(action);
        }

        menu->addSeparator();

        //Pase
        ret = ret &&  makeAction(action,  menu,"Pase(&P)...",Qt::CTRL + Qt::Key_V);
        if(ret)
        {
           menu->addAction(action);
        }

        menu->addSeparator();

        //Delete
        ret = ret &&  makeAction(action, menu, "Delete(&L)",Qt::Key_Delete);
        if(ret)
        {
           menu->addAction(action);
        }

        menu->addSeparator();

        //Find
        ret = ret &&  makeAction(action,  menu,"Find(&F)...",Qt::CTRL + Qt::Key_F);
        if(ret)
        {
           menu->addAction(action);
        }

        menu->addSeparator();

        //Replace
        ret = ret &&  makeAction(action,  menu,"Replace(&R)...",Qt::CTRL + Qt::Key_H);
        if(ret)
        {
           menu->addAction(action);
        }

        menu->addSeparator();

        //Goto
        ret = ret &&  makeAction(action,  menu,"Goto(&G)",Qt::CTRL + Qt::Key_G);
        if(ret)
        {
           menu->addAction(action);
        }

        menu->addSeparator();

        //Select All
        ret = ret &&  makeAction(action, menu, "Select All(&A)",Qt::CTRL + Qt::Key_A);
        if(ret)
        {
           menu->addAction(action);
        }

    }
    if(ret)
    {
        mb->addMenu(menu);
    }
    else
    {
        delete mb;
    }
    return ret;
}

/************************************************格式菜单********************************************************/
bool MainWindow::initFormatMenu(QMenuBar* mb)
{
    bool ret = true;

    QMenu* menu = new QMenu("Format(&O)");
    ret = (menu != NULL);
    if(ret)
    {
        QAction* action = NULL;

        //Auto Wrap
        ret = ret &&  makeAction(action,  menu,"Auto Wrap(&W)",0);
        if(ret)
        {
           menu->addAction(action);
        }

        menu->addSeparator();

        //Font
        ret = ret &&  makeAction(action,  menu,"Font(&F)...",0);
        if(ret)
        {
           menu->addAction(action);
        }

    }
    if(ret)
    {
        mb->addMenu(menu);
    }
    else
    {
        delete mb;
    }
    return ret;
}

/************************************************视图菜单********************************************************/
bool MainWindow::initViewMenu(QMenuBar* mb)
{
    bool ret = true;

    QMenu* menu = new QMenu("View(&V)");
    ret = (menu != NULL);
    if(ret)
    {
        QAction* action = NULL;

        //Tool Bar
        ret = ret &&  makeAction(action, menu,"Tool Bar(&T)",0);
        if(ret)
        {
           menu->addAction(action);
        }

        menu->addSeparator();

        //Status Bar
        ret = ret &&  makeAction(action, menu,"Status Bar(&S)",0);
        if(ret)
        {
           menu->addAction(action);
        }

    }
    if(ret)
    {
        mb->addMenu(menu);
    }
    else
    {
        delete mb;
    }
    return ret;
}

/************************************************帮助菜单********************************************************/
bool MainWindow::initHelpMenu(QMenuBar* mb)
{
    bool ret = true;

    QMenu* menu = new QMenu("Help(&H)");
    ret = (menu != NULL);
    if(ret)
    {
        QAction* action = NULL;

        //User Manual
        ret = ret &&  makeAction(action,  menu,"User Manual",0);
        if(ret)
        {
           menu->addAction(action);
        }

        menu->addSeparator();

        //About NotePad
        ret = ret &&  makeAction(action,  menu,"About NotePad...",0);
        if(ret)
        {
           menu->addAction(action);
        }

    }
    if(ret)
    {
        mb->addMenu(menu);
    }
    else
    {
        delete mb;
    }
    return ret;
}
/*****************************************工具************************************************************/
bool MainWindow::initFileToolItem(QToolBar* tb)
{
    bool ret = true;
    QAction* action = NULL;

    ret = ret && makeAction(action, tb, "New", ":/Res/pic/new.png");
    if(ret)
    {
        connect(action, SIGNAL(triggered()), this, SLOT(onFileNew()));
        tb->addAction(action);

    }

    ret = ret && makeAction(action,  tb,"Open", ":/Res/pic/open.png");
    if(ret)
    {
        connect(action, SIGNAL(triggered()), this, SLOT(onFileOpen()));
        tb->addAction(action);
    }

    ret = ret && makeAction(action,  tb,"Save", ":/Res/pic/save.png");
    if(ret)
    {
        connect(action, SIGNAL(triggered()), this ,SLOT(onFlieSave()));
        tb->addAction(action);
    }

    ret = ret && makeAction(action,  tb,"Save As", ":/Res/pic/saveas.png");
    if(ret)
    {
        connect(action, SIGNAL(triggered()), this, SLOT(onFileSaveAs()));
        tb->addAction(action);
    }
    ret = ret && makeAction(action, tb,"Print",  ":/Res/pic/print.png");
    if(ret)
    {
        tb->addAction(action);
    }
    return ret;

}
bool MainWindow::initEditToolItem(QToolBar* tb)
{
    bool ret = true;
    QAction* action = NULL;

    ret = ret && makeAction(action, tb,"Undo",  ":/Res/pic/undo.png");
    if(ret)
    {
        tb->addAction(action);
    }
    ret = ret && makeAction(action,  tb,"Redo", ":/Res/pic/redo.png");
    if(ret)
    {
        tb->addAction(action);
    }

    ret = ret && makeAction(action, tb, "Cut",  ":/Res/pic/cut.png");
    if(ret)
    {
        tb->addAction(action);
    }

    ret = ret && makeAction(action,  tb,"Copy", ":/Res/pic/copy.png");
    if(ret)
    {
        tb->addAction(action);
    }

    ret = ret && makeAction(action, tb,"Paste",  ":/Res/pic/paste.png");
    if(ret)
    {
        tb->addAction(action);
    }

    ret = ret && makeAction(action, tb,"Find",  ":/Res/pic/find.png");
    if(ret)
    {
        tb->addAction(action);
    }
    ret = ret && makeAction(action, tb,"Replace",  ":以上是关于第三十七课深度解析QMap与QHash的主要内容，如果未能解决你的问题，请参考以下文章 
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