(17）：文件对话框

​​QFileDialog​​​，也就是文件对话框。在本节中，我们将尝试编写一个简单的文本文件编辑器，我们将使用​​QFileDialog​​来打开一个文本文件，并将修改过的文件保存到硬盘。这或许是我们在本系列中所提供的第一个带有实际功能的实例。

首先，我们需要创建一个带有文本编辑功能的窗口

openAction = new QAction(QIcon(":/images/file-open"), tr("&Open..."), this);
openAction->setShortcuts(QKeySequence::Open);
openAction->setStatusTip(tr("Open an existing file"));

saveAction = new QAction(QIcon(":/images/file-save"), tr("&Save..."), this);
saveAction->setShortcuts(QKeySequence::Save);
saveAction->setStatusTip(tr("Save a new file"));

QMenu *file = menuBar()->addMenu(tr("&File"));
file->addAction(openAction);
file->addAction(saveAction);

QToolBar *toolBar = addToolBar(tr("&File"));
toolBar->addAction(openAction);
toolBar->addAction(saveAction);

textEdit = new QTextEdit(this);
setCentralWidget(textEdit);

​​QTextEdit​​​类，这个类用于显示富文本文件。也就是说，它不仅仅用于显示文本，还可以显示图片、表格等等。
 

我们使用​​connect()​​​函数，为这两个​​QAction​​对象添加响应的动作：

/// !!!Qt5
connect(openAction, &QAction::triggered, this, &MainWindow::openFile);
connect(saveAction, &QAction::triggered, this, &MainWindow::saveFile);

下面是最主要的​​openFile()​​​和​​saveFile()​​这两个函数的代码：

void MainWindow::openFile()
{
    QString path = QFileDialog::getOpenFileName(this,
                                                tr("Open File"),
                                                ".",
                                                tr("Text Files(*.txt)"));
    if(!path.isEmpty()) {
        QFile file(path);
        if (!file.open(QIODevice::ReadOnly | QIODevice::Text)) {
            QMessageBox::warning(this, tr("Read File"),
                                 tr("Cannot open file:\n%1").arg(path));
            return;
        }
        QTextStream in(&file);
        textEdit->setText(in.readAll());
        file.close();
    } else {
        QMessageBox::warning(this, tr("Path"),
                             tr("You did not select any file."));
    }
}

void MainWindow::saveFile()
{
    QString path = QFileDialog::getSaveFileName(this,
                                                tr("Open File"),
                                                ".",
                                                tr("Text Files(*.txt)"));
    if(!path.isEmpty()) {
        QFile file(path);
        if (!file.open(QIODevice::WriteOnly | QIODevice::Text)) {
            QMessageBox::warning(this, tr("Write File"),
                                       tr("Cannot open file:\n%1").arg(path));
            return;
        }
        QTextStream out(&file);
        out << textEdit->toPlainText();
        file.close();
    } else {
        QMessageBox::warning(this, tr("Path"),
                             tr("You did not select any file."));
    }
}

完整代码：

mianwindow,h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

class QTextEdit;

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private slots:
    void openFile();
    void saveFile();

private:
    QAction *openAction;
    QAction *saveAction;
    QTextEdit *textEdit;
};

#endif // MAINWINDOW_H

 mainwindow.cpp

#include <QtGui>
#include <QtWidgets>
#include "mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent)
{
    openAction = new QAction(QIcon(":/images/file-open"), tr("&Open..."), this);
    openAction->setShortcuts(QKeySequence::Open);
    openAction->setStatusTip(tr("Open an existing file"));
    connect(openAction, &QAction::triggered, this, &MainWindow::openFile);

    saveAction = new QAction(QIcon(":/images/file-save"), tr("&Save..."), this);
    saveAction->setShortcuts(QKeySequence::Save);
    saveAction->setStatusTip(tr("Save a new file"));
    connect(saveAction, &QAction::triggered, this, &MainWindow::saveFile);

    QMenu *file = menuBar()->addMenu(tr("&File"));
    file->addAction(openAction);
    file->addAction(saveAction);

    QToolBar *toolBar = addToolBar(tr("&File"));
    toolBar->addAction(openAction);
    toolBar->addAction(saveAction);

    textEdit = new QTextEdit(this);
    setCentralWidget(textEdit);
}

MainWindow::~MainWindow()
{
}

void MainWindow::openFile()
{
    QString path = QFileDialog::getOpenFileName(this, tr("Open File"), ".", tr("Text Files(*.txt)"));
    if(!path.isEmpty()) {
        QFile file(path);
        if (!file.open(QIODevice::ReadOnly | QIODevice::Text)) {
            QMessageBox::warning(this, tr("Read File"), tr("Cannot open file:\n%1").arg(path));
            return;
        }
        QTextStream in(&file);
        textEdit->setText(in.readAll());
        file.close();
    } else {
        QMessageBox::warning(this, tr("Path"), tr("You did not select any file."));
    }
}

void MainWindow::saveFile()
{
    QString path = QFileDialog::getSaveFileName(this, tr("Save File"), ".", tr("Text Files(*.txt)"));
    if(!path.isEmpty()) {
        QFile file(path);
        if (!file.open(QIODevice::WriteOnly | QIODevice::Text)) {
            QMessageBox::warning(this, tr("Write File"), tr("Cannot open file:\n%1").arg(path));
            return;
        }
        QTextStream out(&file);
        out << textEdit->toPlainText();
        file.close();
    } else {
        QMessageBox::warning(this, tr("Path"), tr("You did not select any file."));
    }
}