QT日常代码二

最新推荐文章于 2024-05-03 14:25:55 发布

翻译最新推荐文章于 2024-05-03 14:25:55 发布 · 388 阅读

本文介绍如何使用Qt创建带有文件操作功能的窗口，并详细解释了文件对话框的使用方法，包括打开和保存文件的功能实现。此外，还探讨了Qt中的事件处理机制，如鼠标事件的响应和自定义事件处理。

1、文件对话框

first step：创建一个带有文本编辑功能的窗口

openAction= newQAction(QIcon(":/images/file-open"),tr("&Open..."),this);

openAction->setShortcuts(QKeySequence::Open);

openAction->setStatusTip(tr("Open an existing file"));

saveAction= newQAction(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= newQTextEdit(this);

setCentralWidget(textEdit);

second step：菜单和工具栏添加了两个动作：打开和保存

connect(openAction,&QAction::triggered,this,&MainWindow::openFile);

connect(saveAction,&QAction::triggered,this,&MainWindow::saveFile);

last step：openFile()和saveFile()这两个函数的实现

voidMainWindow::openFile()

{

QStringpath =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."));

}

voidMainWindow::saveFile()

{

QStringpath =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."));

}

2、事件

class EventLabel : public QLabel

{

protected:

void mouseMoveEvent(QMouseEvent *event);

void mousePressEvent(QMouseEvent *event);

void mouseReleaseEvent(QMouseEvent *event);

};

void EventLabel::mouseMoveEvent(QMouseEvent *event)

{

this->setText(QString("<center><h1>Move: (%1, %2)</h1></center>")

.arg(QString::number(event->x()), QString::number(event->y())));

}

void EventLabel::mousePressEvent(QMouseEvent *event)

{

this->setText(QString("<center><h1>Press: (%1, %2)</h1></center>")

.arg(QString::number(event->x()), QString::number(event->y())));

}

void EventLabel::mouseReleaseEvent(QMouseEvent *event)

{

QString msg;

msg.sprintf("<center><h1>Release: (%d, %d)</h1></center>",

event->x(), event->y());

this->setText(msg);

}

int main(int argc, char *argv[])

{

QApplication a(argc, argv);

EventLabel *label = new EventLabel;

label->setWindowTitle("MouseEvent Demo");

label->resize(300, 200);

label->show();

return a.exec();

}

运行上面的代码，当我们点击了一下鼠标之后，label 上将显示鼠标当前坐标值。

3、事件的接受与忽略

示例代码：

// ---------- custombutton.h ---------- //

class CustomButton : public QPushButton

{

Q_OBJECT

public:

CustomButton(QWidget *parent = 0);

private:

void onButtonCliecked();

};

// ---------- custombutton.cpp ---------- //

CustomButton::CustomButton(QWidget *parent) :

QPushButton(parent)

{

connect(this, &CustomButton::clicked,

this, &CustomButton::onButtonCliecked);

}

void CustomButton::onButtonCliecked()

{

qDebug() << "You clicked this!";

}

// ---------- main.cpp ---------- //

int main(int argc, char *argv[])

{

QApplication a(argc, argv);

CustomButton btn;

btn.setText("This is a Button!");

btn.show();

return a.exec();

}

点击按钮，会在控制台打印出“You clicked this!”字符串，下面，我们向CustomButton类添加一个事件函数：

// CustomButton

...

protected:

void mousePressEvent(QMouseEvent *event);

...

// ---------- custombutton.cpp ---------- //

...

void CustomButton::mousePressEvent(QMouseEvent *event)

{

if (event->button() == Qt::LeftButton) {

qDebug() << "left";

} else {

QPushButton::mousePressEvent(event);

}

我们重写了CustomButton的mousePressEvent()函数，也就是鼠标按下。在这个函数中，我们判断如果鼠标按下的是左键，则打印出来“left”字符串，否则，调用父类的同名函数。编译运行这段代码，当我们点击按钮时，“You clicked this!”字符串不再出现，只有一个“left”。

再来看一个例子：

class CustomButton : public QPushButton

{

Q_OBJECT

public:

CustomButton(QWidget *parent) : QPushButton(parent)

{

}

protected:

void mousePressEvent(QMouseEvent *event)

{

qDebug() << "CustomButton";

}