QT：制作图片浏览器

widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>

namespace Ui {
class Widget;
}

class Widget : public QWidget
{
    Q_OBJECT

public:
    explicit Widget(QWidget *parent = 0);
    ~Widget();

private slots:

    void on_pb_2_clicked();

    void on_pb_left_clicked();

    void on_pb_3_clicked();

private:
    Ui::Widget *ui;
    static int i;   //索引
    QStringList picfiles;   //存储路径
};

#endif // WIDGET_H

widget.cpp

#include "widget.h"
#include "ui_widget.h"
#include <QFileDialog>  //文件对话框

int Widget::i = 0;  //初始化i为0

Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    setWindowTitle("图片浏览器");
    setFixedSize(530,500);

    ui->setupUi(this);   //ui操作在此下面写
}

Widget::~Widget()
{
    delete ui;
}

void Widget::on_pb_2_clicked()
{
    picfiles = QFileDialog::getOpenFileNames(this,"打开图片"