Qt项目中的常见用法

1.QWidget设置为类似如右键菜单setWindowFlags(Qt::FramelessWindowHint | Qt::Popup | Qt::NoDropShadowWindowHint);2.QTreeWidget创建parent item刷新问题ui->treeRoom->resizeColumnToContents(0);3.setWindowFlags(Qt::FramelessWindowHint | Qt::Popup | Qt::NoDropShadowWindowHint);setAttribute(Qt::WA_NoSystemBackground, true);setAttribute(Qt::WA_TranslucentBackground, true);setAttribute(Qt::WA_DeleteOnClose);bool eventFilter(QObject *obj, QEvent *e){if(obj == this){if(QEvent::WindowDeactivate == e->type()){close();e->accept();return true;}}return QWidget::eventFilter(obj, e);}4.QTextCursor insertImage相同图片只显示一个，解决：QTextImageFormat imageFormat;imageFormat.setName(imagePath);this->textCursor().insertImage(imageFormat, QTextFrameFormat::InFlow);5.设置背景色QPalette palette = this->palette();palette.setBrush(QPalette::Background, QBrush(QColor(0, 123, 122)));this->setPalette(palette);this->setAutoFillBackground(true);paintEvent：QPainter painter(this);painter.setBrush(QColor("#1e1e21"));painter.setPen(Qt::NoPen);painter.drawRect(this->rect());6.设置QTextEdit可输入个数：void MyWidget::slotTextChanged(){if (0 == m_count) {return;}QString curText = this->toPlainText();int len = curText.count();if (len > m_count) {int pos = this->textCursor().position();QTextCursor textCursor = this->textCursor();curText.remove(pos - (len - m_count), len - m_count);this->setText(curText);textCursor.setPosition(pos - (len - m_count));this->setTextCursor(textCursor);}}7.QLineEdit设置搜索图标和清除按钮searchAction = new QAction(QIcon(qutil::skin("icon_search")), "", this);m_lineEdit->addAction(searchAction, QLineEdit::LeadingPosition);m_lineEdit->setClearButtonEnabled(true);QAction *clearAction = m_lineEdit->findChild<QAction*>(QLatin1String("_q_qlineeditclearaction"));if (clearAction) {clearAction->setIcon(QIcon(":/xyz");connect(clearAction, &QAction::triggered, [this] () {emit sigClear();});}8.水平线QFrame *line = new QFrame(this);line->setMaximumSize(QSize(16777215, 1));line->setStyleSheet(QStringLiteral("background:rgb(68, 70, 73);"));line->setFrameShape(QFrame::HLine);line->setFrameShadow(QFrame::Sunken);9.使用全局热键QxtGlobalShortcutif (!m_gsCaptureScreen->setShortcut(QKeySequence(Qt::CTRL + Qt::ALT + Qt::Key_A))) {/////////////}10.改变showNormal之后的大小setGeometry11.无title窗口拉伸（windows环境）bool MyWindow::nativeEvent(const QByteArray & eventType, void * message, long * result){Q_UNUSED(eventType);if (this->isMaximized()) {return false;}const int HIT_BORDER = 5;const MSG *msg=static_cast<MSG*>(message);if(msg->message == WM_NCHITTEST) {int xPos = ((int)(short)LOWORD(msg->lParam)) - this->frameGeometry().x();int yPos = ((int)(short)HIWORD(msg->lParam)) - this->frameGeometry().y();if(this->childAt(xPos,yPos) == 0) {*result = HTCAPTION;} else {return false;}if(xPos > 0 && xPos < HIT_BORDER) {*result = HTLEFT;}if(xPos > (this->width() - HIT_BORDER) && xPos < (this->width() - 0)) {*result = HTRIGHT;}if(yPos > 0 && yPos < HIT_BORDER) {*result = HTTOP;}if(yPos > (this->height() - HIT_BORDER) && yPos < (this->height() - 0)) {*result = HTBOTTOM;}if(xPos > 0 && xPos < HIT_BORDER && yPos > 0 && yPos < HIT_BORDER) {*result = HTTOPLEFT;}if(xPos > (this->width() - HIT_BORDER) && xPos < (this->width() - 0) && yPos > 0 && yPos < HIT_BORDER) {*result = HTTOPRIGHT;}if(xPos > 0 && xPos < HIT_BORDER && yPos > (this->height() - HIT_BORDER) && yPos < (this->height() - 0)) {*result = HTBOTTOMLEFT;}if(xPos > (this->width() - HIT_BORDER) && xPos < (this->width() - 0) && yPos > (this->height() - HIT_BORDER) && yPos < (this->height() - 0)) {*result = HTBOTTOMRIGHT;}return true;}return false;}12.安装全局事件过滤器class GlobalEventFilter : public QObject{Q_OBJECTpublic:GlobalEventFilter(QObject *parent);protected:bool eventFilter(QObject *, QEvent *);};GlobalEventFilter *globalEventFilter = new GlobalEventFilter(this);qApp->installEventFilter(globalEventFilter);13.QTreeWidget遍历QTreeWidget *myTree;QTreeWidgetItemIterator iter(myTree);while (*iter) {++iter;}14.这里需要特别注意一点，如果QWidget直接show出来，是有背景色的，但是如果它作为一个父QWidget的子窗口时就没有背景了！此时需要添加如下代码：this->setAutoFillBackground(true);QPalette palette = this->palette();palette.setColor(QPalette::Background, QColor("#36383D"));this->setPalette(palette);15.模态对话框QEventLoop eventLoop;myWidget->setAttribute(Qt::WA_ShowModal, true);myWidget->show();connect(myWidget, &QObject::destroyed,  &eventLoop, &QEventLoop::quit, Qt::DirectConnection);eventLoop.exec();16.QTreeWidget删除itemQTreeWidgetItemIterator iter(ui->treeRoom);while (*iter) {delete item;}17.窗口抖动void Shake::start(QWidget *targetWidget, int number, int range){Q_ASSERT(NULL != targetWidget);m_widget = targetWidget;m_number = number;m_range = range;m_start = 0;m_point = m_widget->pos();m_widget->raise();m_widget->activateWindow();bool isMaximized = m_widget->isMaximized();if (NULL == m_timer){m_timer = new QTimer(this);QObject::connect(m_timer, &QTimer::timeout, [this, isMaximized] {if (m_start < m_number * 4){++m_start;switch (m_start % 4){case 1:{QPoint newPos(m_point.x(), m_point.y() - m_range);m_widget->move(newPos);}break;case 2:{QPoint newPos(m_point.x() - m_range, m_point.y() - m_range);m_widget->move(newPos);}break;case 3:{QPoint newPos(m_point.x() - m_range, m_point.y());m_widget->move(newPos);}break;default:m_widget->move(m_point);break;}} else {m_timer->stop();}});}m_timer->start(40);}

18.如果刷新有问题可以调用：Widget->style()->polish(this);

19. QComboBox 对齐
 // First : Set the combobox the editable (this allows us to use the lineEdit)
  mComboBox->setEditable(true);
  // Second : Put the lineEdit in read-only mode
  mComboBox->lineEdit()->setReadOnly(true);
  // Third  : Align the lineEdit to right
  mComboBox->lineEdit()->setAlignment(Qt::AlignRight);  
  // Fourth : Align each item in the combo to the right
  for(int i = 0; i < mComboBox->count(); i++)
    mComboBox->setItemData(i, Qt::AlignRight, Qt::TextAlignmentRole);

20.// 去掉输入法输入时的虚线，但是会导致输入法输入框位置不正确
void TextEdit::inputMethodEvent(QInputMethodEvent *e)
{
    if (e->commitString().isEmpty() && !e->preeditString().isEmpty()) {
        return;
    }
    QTextEdit::inputMethodEvent(e);
}