用以实现一个读取文件进度条的功能

1.新建一个无ui界面的工程，其基类为dialog对话框类

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2.代码实现

dialog.h

#ifndef DIALOG_H
#define DIALOG_H

#include <QDialog>
#include <QLabel>
#include <QProgressBar>
#include <QPushButton>

class Dialog : public QDialog
{
    Q_OBJECT

public:
    Dialog(QWidget *parent = 0);
    ~Dialog();

private slots:
    void startProgress();           //定义一个槽函数


private:
    QLabel * fileNum;               //控件声明
    QProgressBar * progressBar;     //控件声明
    QPushButton  * startBtn;        //控件声明
};


#endif // DIALOG_H

dialog.cpp

#include "dialog.h"

Dialog::Dialog(QWidget *parent)
    : QDialog(parent)
{
    this->setWindowTitle(tr("进度条"));
    fileNum = new QLabel(this);
    fileNum->setText(tr("复制文件数目:0"));
    fileNum->setGeometry(20,10,200,18);
    progressBar = new QProgressBar(this);
    progressBar->setGeometry(20,35,200,10);
    startBtn = new QPushButton(this);
    startBtn->setText(tr("开始"));
    startBtn->setGeometry(20,55,80,30);

    //连接信号与槽
    connect(startBtn,SIGNAL(clicked()),this,SLOT(startProgress()));
}

Dialog::~Dialog()
{

}

//槽函数实现
void Dialog::startProgress()
{
    progressBar->setRange(0,100000);      //设置进度条的范围
    for(int i = 1; i <= 100000; i++)
    {
        progressBar->setValue(i);
        QString str = QString("%1").arg(i);
        str = "复制文件数目: "  +str;
        fileNum->setText(str);

    }
}

3.效果展示

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4.不足与需改进之处

1.进程过快。效果不宜呈现，可以将进度条的值调大一点

2.后面可以引入QTimer定时器功能，以实现文件复制

5.改进之后

progressbar.h

#ifndef PROGRESSBAR_H
#define PROGRESSBAR_H

#include <QMainWindow>
#include <QProgressBar>

class ProgressBar : public QMainWindow
{
    Q_OBJECT

public:
    ProgressBar(QWidget *parent = 0);
    ~ProgressBar();
};

//新建类
class QString;
class Progressbar : public QProgressBar
{
    Q_OBJECT
public:
    Progressbar(QWidget *parent = 0):QProgressBar(parent){}
    QString strText;

public slots:
    void stepOne();
};

#endif // PROGRESSBAR_H

progressbar.cpp

#include "progressbar.h"
#include <QString>

ProgressBar::ProgressBar(QWidget *parent)
    : QMainWindow(parent)
{
}

ProgressBar::~ProgressBar()
{

}

void Progressbar::stepOne()
{
    if(this->value()+1 <= this->maximum())
    {
        this->setValue(this->value() + 1);

        strText = "进度条 : " + this->text();
        this->setWindowTitle(strText);
    }
    else
    {
        this->setValue(this->minimum());
    }
}

main.cpp

#include "progressbar.h"
#include <QApplication>
#include <QTimer>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    ProgressBar w;
    w.show();

    //进度条设置
    Progressbar * progress = new Progressbar;
    progress->setWindowTitle("进度条");
    progress->resize(400,40);
    progress->setMaximum(100);
    progress->setMinimum(0);
    progress->setValue(0);

    //设置一个定时器
    QTimer *timer = new QTimer;
    timer->start(500);
    QObject::connect(timer, SIGNAL(timeout()), progress, SLOT(stepOne()));
    progress->show();

    return a.exec();
}