今天開始呢，我們就開始用Qt做兩個比較實用的東西，這一篇我們主要探究下文本編輯器的實現。
首先我們來看下我們的大致框架：
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow();
protected:
void closeEvent(QCloseEvent *event);
對於所有定義的信號和槽的類，在類定義開始處的O_OBJECT宏都是必需的。
private slots:
void newFile();
void open();
bool save();
bool saveAs();
void about();
void documentWasModified();
私有槽中包含了創建新文件、打開文件、保存文件以及about。當然了我們還有一個在程序中最重要的函數documentWasModified()，實現的共ing功能是判斷是否文件被修改。
private:
void createActions();
void createMenus();
void createToolBars();
void createStatusBar();
void readSettings();
void writeSettings();
bool maybeSave();
void loadFile(const QString &fileName);
bool saveFile(const QString &fileName);
void setCurrentFile(const QString &fileName);
QString strippedName(const QString &fullFileName);
QTextEdit *textEdit;
QString curFile;
QMenu *fileMenu;
QMenu *editMenu;
QMenu *formMenu;
QMenu *helpMenu;
QToolBar *fileToolBar;
QToolBar *editToolBar;
QAction *newAct;
QAction *openAct;
QAction *saveAct;
QAction *saveAsAct;
QAction *exitAct;
QAction *automaticAct;
QAction *typefaceAct;
QAction *cutAct;
QAction *copyAct;
QAction *pasteAct;
QAction *aboutAct;
QAction *aboutQtAct;
};
在這裡面定義了在程序中用到的所有類的實例，createActions();createMenus(); createToolBars();createStatusBar();用於創建用戶接口。readSetting()用於恢復用戶以前的設置。下面我們就來一一看看具體實現：
MainWindow::MainWindow()
{
textEdit = new QTextEdit;
setCentralWidget(textEdit);
createActions();
createMenus();
createToolBars();
createStatusBar();
readSettings();
connect(textEdit->document(), SIGNAL(contentsChanged()), this, SLOT(documentWasModified));
setCurrentFile("");
}
我們的構造函數首先創建一個文本框實例，而後設置中心窗體，再者調用用戶接口即可完成。
void MainWindow::closeEvent(QCloseEvent *event)
{
if(maybeSave())
{
writeSettings();
event->accept();
}
else
{
event->ignore();
}
}
closeEvent()函數實現功能：在用戶嘗試退出時警告用戶關於未保存的修改信息。
void MainWindow::newFile()
{
if(maybeSave())
{
textEdit->clear();
setCurrentFile("");
}
}
newFile函數實現功能：首先判斷當前文件是否已保存，如果未保存先保存而後創建新文件。
void MainWindow::open()
{
if(maybeSave())
{
QString fileName = QFileDialog::getOpenFileName(this);
if(!fileName.isEmpty())
loadFile(fileName);
}
}
open()函數實現功能：首先判斷當前文件是否已保存，如果未保存則先保存，而後通過QFileDialog的靜態函數getOpenFileName()獲取文件目錄，打開。
bool MainWindow::save()
{
if(curFile.isEmpty())
{
return saveAs();
}
else
{
return saveFile(curFile);
}
}
bool MainWindow::saveAs()
{
QString fileName = QFileDialog::getSaveFileName(this);
if(fileName.isEmpty())
return false;
return saveFile(fileName);
}
save() slot在用戶點擊File|Save菜單項時被調用。如果用戶還沒為文件提供一個名字，則調用saveAs()，否則調用saveFile()來保存文件。
void MainWindow::about()
{
QMessageBox::about(this, tr("About Application"),
tr("The <b>Application</b> example created by <b>Yzs</b> "));
}
about()函數對話框通過QMessageBox::about()靜態函數實現
void MainWindow::documentWasModified()
{
setWindowModified(textEdit->document()->isModified());
}
documentWasModified() slot在QTextEdit中的文本被改變時被調用。我們調用QWidget::setWindowModified()來是標題欄顯示文件已被修改（顯示個*號）。
void MainWindow::createActions()
{
newAct = new QAction(QIcon(":/images/new.png"), tr("&New"), this);
newAct->setShortcut(tr("Ctrl+N"));
newAct->setStatusTip(tr("Create a new file"));
connect(newAct, SIGNAL(triggered()), this, SLOT(newFile()));
openAct = new QAction(QIcon(":/images/open.png"), tr("&Open..."), this);
openAct->setShortcut(tr("Ctrl+O"));
openAct->setStatusTip(tr("Open an existing file"));
connect(openAct, SIGNAL(triggered()), this, SLOT(open()));
saveAct = new QAction(QIcon(":/images/save.png"), tr("&Save"), this);
saveAct->setShortcut(tr("Ctrl+S"));
saveAct->setStatusTip(tr("Save a file"));
connect(saveAct, SIGNAL(triggered()), this, SLOT(save()));
saveAsAct = new QAction(tr("Save &As..."), this);
saveAsAct->setStatusTip(tr("Save the file under a new name"));
connect(saveAsAct, SIGNAL(triggered()), this, SLOT(saveAs()));
exitAct = new QAction(tr("E&xit"), this);
exitAct->setShortcut(tr("Ctrl+Q"));
exitAct->setStatusTip(tr("Exit the application"));
connect(exitAct, SIGNAL(triggered()), this, SLOT(close()));
automaticAct = new QAction(tr("&Automatic"), this);
automaticAct->setChecked(false);
automaticAct->setStatusTip(tr("Automatic the file"));
connect(automaticAct, SIGNAL(triggered()), this, SLOT(automatic()));
typefaceAct = new QAction(tr("&Typeface"), this);
typefaceAct->setStatusTip(tr("typefaceAct"));
connect(typefaceAct, SIGNAL(triggered()), this, SLOT(typeface()));
cutAct = new QAction(QIcon(":/images/cut.png"), tr("Cu&t"), this);
cutAct->setShortcut(tr("Ctrl+X"));
cutAct->setStatusTip(tr("Cut the current selection's contents to the clipboard"));
connect(cutAct, SIGNAL(triggered()), this, SLOT(cut()));
copyAct = new QAction(QIcon(":/images/copy.png"), tr("&Copy"), this);
copyAct->setShortcut(tr("Ctrl+C"));
copyAct->setStatusTip(tr("Copy the current selection's contents to clipboard"));
connect(copyAct, SIGNAL(triggered()), this, SLOT(copy()));
pasteAct = new QAction(QIcon(":/images/paste.png"), tr("&Paste"), this);
pasteAct->setShortcut(tr("Ctrl+V"));
pasteAct->setStatusTip(tr("Paste the current selection's contents to clipboard"));
connect(pasteAct, SIGNAL(triggered()), this, SLOT(paste()));
aboutAct = new QAction(tr("&About"), this);
aboutAct->setStatusTip(tr("Show the application's About box"));
connect(aboutAct, SIGNAL(triggered()), this, SLOT(about()));
aboutQtAct = new QAction(tr("About &Qt"), this);
aboutQtAct->setStatusTip(tr("Show the Qt library's About box"));
connect(aboutQtAct, SIGNAL(triggered()), qApp, SLOT(aboutQt()));
cutAct->setEnabled(false);
copyAct->setEnabled(false);
connect(textEdit, SIGNAL(copyAvailable(bool)),
cutAct, SLOT(setEnabled(bool)));
connect(textEdit, SIGNAL(copyAvailable(bool)),
copyAct, SLOT(setEnabled(bool)));
}
QAction是一個代表用戶行為的對象，例如，保存文件或彈出對話框。一個action可以被放入QMenu或QToolBar中，也可以被放入其它重載了QWidget::actionEvent()的widget中。一個action有一個用於描述它作用的文本，當用戶觸發這個action時，它發出triggered()信號。我們將這個信號連接到一個slot上以實現真正的功能。Edit|Cut和Edit|Copy action必須在QTextEdit包含已選擇的文本時才有效。在默認情況下我們將它們禁用並將QTextEdit::copyAvailable()信號連接到QAction::setEnabled() slot上，以確保在文本編輯器中沒有選擇文本時著兩個行為無效。
本文出自 “驿落黃昏” 博客，請務必保留此出處http://yiluohuanghun.blog.51cto.com/3407300/959827
