一.Qt中的字符串类

QString  vs  string：

QString在Qt库中几乎是无所不在的

所有的Qt图形用户组件都依赖于QString

实验1 ：QString 初体验

#include <QDebug>
void Sample_1()
{
    QString s = "add";
    s.append(" ");    // "add "
    s.append("Qt");   // "add Qt"
    s.prepend(" ");   // " add Qt"
    s.prepend("C++"); // "C++ add Qt"
    qDebug() << s;
    s.replace("add", "&"); // "C++ & Qt"
    qDebug() << s;
}
void Sample_2()
{
    QString s = "";
    int index = 0;
    s.sprintf("%d. I'm %s, thank you!", 1, "Delphi Tang"); // "1. I'm Delphi Tang, thank you!"
    qDebug() << s;
    index = s.indexOf(",");
    s = s.mid(0, index);   // "1. I'm Delphi Tang"
    qDebug() << s;
    index = s.indexOf(".");
    s = s.mid(index + 1, s.length()); // " I'm Delphi Tang"
    s = s.trimmed();                  // "I'm Delphi Tang"
    qDebug() << s;
    index = s.indexOf(" ");
    s = s.mid(index + 1, s.length()); // "Delphi Tang"
    qDebug() << s;
}
void Sample_3(QString* a, int len)
{
    for(int i=0; i<len; i++)
    {
        for(int j=i+1; j<len; j++)
        {
            if( a[j] < a[i] )
            {
                QString tmp = a[i];
                a[i] = a[j];
                a[j] = tmp;
            }
        }
    }
}
int main()
{
    qDebug() << "Sample_1:";
    Sample_1();
    qDebug() << endl;
    qDebug() << "Sample_2:";
    Sample_2();
    qDebug() << endl;
    qDebug() << "Sample_3:";
    QString company[5] =
    {
        QString("Oracle"),
        QString("Borland"),
        QString("Microsoft"),
        QString("IBM"),
        QString("D.T.Software")
    };
    Sample_3(company, 5);
    for(int i=0; i<5; i++)
    {
        qDebug() << company[i];
    }
    return 0;
}

运行结果：

实验2：为计算器实例添加消息响应–获取按键输入回显到QLineEdit 文本框

目录：

QCalculatorUI.h：

#ifndef _QCALCULATORUI_H_
#define _QCALCULATORUI_H_

#include <QWidget>
#include <QLineEdit>
#include <QPushButton>

class QCalculatorUI : public QWidget
{
    Q_OBJECT
private:
    QLineEdit* m_edit;
    QPushButton* m_buttons[20];

    QCalculatorUI();
    bool construct();
private slots:
    void onButtonClicked();
public:
    static QCalculatorUI* NewInstance();
    void show();
    ~QCalculatorUI();
};

#endif

QCalculatorUI.cpp：

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

QCalculatorUI::QCalculatorUI() : QWidget(NULL, Qt::WindowCloseButtonHint)
{

}

bool QCalculatorUI::construct()
{
    bool ret = true;
    const char* btnText[20] =
    {
        "7", "8", "9", "+", "(",
        "4", "5", "6", "-", ")",
        "1", "2", "3", "*", "<-",
        "0", ".", "=", "/", "C",
    };

    m_edit = new QLineEdit(this);

    if( m_edit != NULL )
    {
        m_edit->move(10, 10);
        m_edit->resize(240, 30);
        m_edit->setReadOnly(true);
        m_edit->setAlignment(Qt::AlignRight);
    }
    else
    {
        ret = false;
    }

    for(int i=0; (i<4) && ret; i++)
    {
        for(int j=0; (j<5) && ret; j++)
        {
            m_buttons[i*5 + j] = new QPushButton(this);

            if( m_buttons[i*5 + j] != NULL )
            {
                m_buttons[i*5 + j]->resize(40, 40);
                m_buttons[i*5 + j]->move(10 + (10 + 40)*j, 50 + (10 + 40)*i);
                m_buttons[i*5 + j]->setText(btnText[i*5 + j]);

                connect(m_buttons[i*5 + j], SIGNAL(clicked()), this, SLOT(onButtonClicked()));
            }
            else
            {
                ret = false;
            }
        }
    }

    return ret;
}

QCalculatorUI* QCalculatorUI::NewInstance()
{
    QCalculatorUI* ret = new QCalculatorUI();

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

    return ret;
}

void QCalculatorUI::show()
{
    QWidget::show();

    setFixedSize(width(), height());
}

void QCalculatorUI::onButtonClicked()
{
    QPushButton* btn = (QPushButton*)sender();
    QString clickText = btn->text();

    if( clickText == "<-" )
    {
        QString text = m_edit->text();

        if( text.length() > 0 )
        {
            text.remove(text.length()-1, 1);

            m_edit->setText(text);
        }
    }
    else if( clickText == "C" )
    {
        m_edit->setText("");
    }
    else if( clickText == "=" )
    {

    }
    else
    {
        m_edit->setText(m_edit->text() + clickText);
    }
}

QCalculatorUI::~QCalculatorUI()
{

}

main.cpp：

#include <QApplication>
#include "QCalculatorUI.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QCalculatorUI* cal = QCalculatorUI::NewInstance();
    int ret = -1;

    if( cal != NULL )
    {
        cal->show();

        ret = a.exec();

        delete cal;
    }

    return ret;
}