Qt橡皮筋选择矩形透明

Question

如何使橡皮筋选择透明？我想这个代码，但它不工作：

void RubberBand::mousePressEvent(QMouseEvent* event) { 
    if (event->buttons() != Qt::LeftButton) return; 
    if (rubberBand.isVisible()) { 
     rubberBand.hide(); 
     return; 
    } 
    auto posItem = RelativeClippedCoordinates(event->globalPos()); 
    origin = CoordinatesItemToGlobal(pixmapItem, posItem); 
    selectionRect.setTopLeft(posItem); 
    rubberBand.setGeometry(QRect(origin, QSize())); 
    rubberBand.setStyleSheet("background-color:trasparent;"); 
    rubberBand.show(); 
} 

Answer 1

为了执行这个任务，我们必须覆盖paintEvent方法并激活Qt::WA_TranslucentBackground属性。

customrubberband.h

#ifndef CUSTOMRUBBERBAND_H 
#define CUSTOMRUBBERBAND_H 

#include <QRubberBand> 

class CustomRubberBand : public QRubberBand 
{ 
public: 
    CustomRubberBand(Shape s, QWidget * p = 0); 

protected: 
    void paintEvent(QPaintEvent *); 
}; 

#endif // CUSTOMRUBBERBAND_H 

customrubberband.cpp

#include "customrubberband.h" 

#include <QPainter> 

CustomRubberBand::CustomRubberBand(Shape s, QWidget *p): QRubberBand(s, p) 
{ 
    setAttribute(Qt::WA_TranslucentBackground, true); 
} 

void CustomRubberBand::paintEvent(QPaintEvent *) 
{ 

    if(isVisible()){ 
     QPainter painter(this); 
     painter.setPen(Qt::blue); 
     painter.setBrush(QBrush(QColor(85, 142, 253, 100))); 
     painter.drawRect(rect()); 
    } 
} 

在你的情况，你必须改变：

RubberBand.h

#include <QRubberBand> 
[...] 
QRubberBand rubberBand; 

到

#include "customrubberband.h" 
[...] 
CustomRubberBand rubberBand; 

完整代码：https://github.com/eyllanesc/stackoverflow/tree/master/qimvi