对话框Dialog

[b]QMainWindow[/b]

QMainWindow

是 Qt 框架带来的一个预定义好的主窗口类。

主窗口，就是一个普通意义上的应用程序（不是指游戏之类的那种）最顶层的窗口。通常是由一个标题栏，一个菜单栏，若干工具栏和一个任务栏。在这些子组件之间则是我们的工作区。

通过添加动作来添加菜单和工具栏等，比如添加一个打开菜单和工具

QAction *openaction;
openaction = new QAction(QIcon(":/img/open"),tr("&Open"),this);
openaction->setShortcut(QKeySequence::Open);    //给菜单指定快捷键
openaction->setStatusTip(tr("open an existing file"));  //提示

//加入菜单栏的File中
QMenu *file = menuBar()->addMenu(tr("&File"));
file->addAction(openaction);

//加入工具栏
QToolBar *toolBar = addToolBar(tr("&File"));
toolBar->addAction(openaction);

#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."));
}
}

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