這個控件非常簡單，就是一個圓弧在不停地轉(zhuǎn)圈圈。模仿的是WPS中等待界面的效果。通過這個控件學(xué)習(xí)Qt動畫的基本操作。這個控件在VS2015和Qt5.9上測試通過。下面是效果圖：

上代碼，頭文件：

class MWait : public QWidget { ? ?Q_OBJECTpublic: ? ?MWait(QWidget* parent = 0); ? ?QSize sizeHint() const override;private: ? ?void setFlagPos(int where); ? ?void paintEvent(QPaintEvent *event) override;private: ? ?int atWhere; /* [0, 360) */};

CPP文件：

MWait::MWait(QWidget* parent) { ? ?/* 這里0°和360°邊界有重疊，導(dǎo)致同一個角度連續(xù)播放兩幀 */ ? ?/* 但好在肉眼難以分辨出這個問題 */ ? ?QVariantAnimation* ani = new QVariantAnimation(this); ? ?ani->setStartValue(0); ? ?ani->setEndValue(360); ? ?ani->setLoopCount(-1); ? ?ani->setDuration(800); ? ?connect(ani, &QVariantAnimation::valueChanged, this, ? ? ? ?[this](const QVariant& value) { setFlagPos(value.toInt()); }); ? ?ani->start(); }void MWait::setFlagPos(int where) { ? ?atWhere = where; ? ?update(); }void MWait::paintEvent(QPaintEvent *event) { ? ?QPainter painter(this); ? ?painter.setRenderHint(QPainter::Antialiasing); ? ?int d = qMin(width(), height()); ? ?int xoff = (width() - d) / 2; ? ?int yoff = (height() - d) / 2; ? ?painter.translate(xoff, yoff); ? ?painter.setBrush(Qt::NoBrush); ? ?painter.setPen(QPen(QColor(213, 213, 213), 4)); ? ?QRect rect(2, 2, d - 4, d - 4); ? ?painter.drawEllipse(rect); ? ?painter.setPen(QPen(QColor(0, 160, 243), 4, Qt::SolidLine, Qt::RoundCap)); ? ?painter.drawArc(rect, (90 - atWhere) * 16, -150 * 16); } QSize MWait::sizeHint() const{ ? ?return QSize(36, 36); }

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