Fix ListBox loop paint bug.

src/components/ListBox.cpp

@@ -13,16 +13,17 @@ ListBox::ListBox(QWidget *parent) : QToolButton(parent) {
 }
 
 void ListBox::paintEvent(QPaintEvent *e) {
-    QString temp = this->text();
-    this->setText("");
-    QToolButton::paintEvent(e);
-    this->setText(temp);
     QStylePainter painter(this);
     QStyleOptionToolButton opt;
     initStyleOption(&opt);
+    //在最后绘制按钮的时候将text清空，避免绘制出左对齐的文字
+    opt.text.clear();
+    painter.drawComplexControl(QStyle::CC_ToolButton, opt);
+    //自行绘制居中对齐的文字
     int x = (size().width() - this->iconSize().width()) / 2 - (this->text().length() * opt.font.pixelSize()) / 4;
     int y = this->iconSize().height() + 2;
     painter.drawText(x,y,this->text());
 }
 
 
+