小例子 练习习作
#ifndef TICKER_H #define TICKER_H #include <QWidget> class Ticker : public QWidget { Q_OBJECT public: Ticker(QWidget *parent = 0); void setText(const QString &newText); QString text() const { return myText; } QSize sizeHint() const; protected: void paintEvent(QPaintEvent *event); void timerEvent(QTimerEvent *event); void showEvent(QShowEvent *event); void hideEvent(QHideEvent *event); private: QString myText; int myTimerId; }; #endif
#include <QtGui> #include "ticker.h" Ticker::Ticker(QWidget *parent) : QWidget(parent) { myTimerId = 0; } void Ticker::setText(const QString &newText) { myText = newText; update(); updateGeometry(); } QSize Ticker::sizeHint() const { return fontMetrics().size(0, text()); } void Ticker::paintEvent(QPaintEvent * /* event */) { QPainter painter(this); static int i = 0; i++; if(i%2) { myText = tr("odd"); }else { myText = tr("even"); } int textWidth = fontMetrics().width(text()); painter.drawText(0, 0, textWidth, height(), Qt::AlignLeft | Qt::AlignVCenter, text()); } void Ticker::showEvent(QShowEvent * /* event */) { myTimerId = startTimer(1000); } void Ticker::timerEvent(QTimerEvent *event) { if (event->timerId() == myTimerId) { update(); updateGeometry(); } else { QWidget::timerEvent(event); } } void Ticker::hideEvent(QHideEvent * /* event */) { killTimer(myTimerId); myTimerId = 0; }
#include <QApplication> #include "ticker.h" int main(int argc, char *argv[]) { QApplication app(argc, argv); Ticker ticker; ticker.setWindowTitle(QObject::tr("Ticker")); ticker.setText(QObject::tr("4")); ticker.show(); return app.exec(); }