Qt ：非window子窗体的透明度设置 .

问题的由来

         心血来潮，想利用QTimer 配合 setWindowOpacity()方法来实现一个窗体淡入的效果。

✿实验代码

 粗糙的实验代码：

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1. void Widget::on_pushButton_clicked()  
2. {  
3.    QTimer *timerOpacity = new QTimer(this);  
4.    connect(timerOpacity,SIGNAL(timeout()),this,SLOT(changeOpacity()));  
5.    timerOpacity->start(100);  
6. }  
7.   
8. void Widget::changeOpacity()  
9. {  
10.     if (opalevel > 8) return;  
11.     double opacity[9] =  {0.9,0.8,0.7,0.6,0.5,0.4,0.3,0.2,0.1};  
12.     ui->stackedWidget->setWindowOpacity(opacity[opalevel]);  
13.     ui->widget->setWindowOpacity(opacity[opalevel]);  
14.     this->setWindowOpacity(opacity[opalevel]);  
15.   
16.     qDebug()<<"opalevel = "<< opalevel <<" ui->widget opacity:"<<ui->widget->windowOpacity();  
17.     qDebug()<<"opalevel = "<< opalevel <<" ui->stackedWidget opacity:"<<ui->stackedWidget->windowOpacity();  
18.     qDebug()<<"opalevel = "<< opalevel <<" ui opacity : "<< this->windowOpacity()<<endl;  
19. }  

void Widget::on_pushButton_clicked(){   QTimer *timerOpacity = new QTimer(this);   connect(timerOpacity,SIGNAL(timeout()),this,SLOT(changeOpacity()));   timerOpacity->start(100);}void Widget::changeOpacity(){    if (opalevel > 8) return;    double opacity[9] =  {0.9,0.8,0.7,0.6,0.5,0.4,0.3,0.2,0.1};    ui->stackedWidget->setWindowOpacity(opacity[opalevel]);    ui->widget->setWindowOpacity(opacity[opalevel]);    this->setWindowOpacity(opacity[opalevel]);    qDebug()<<"opalevel = "<< opalevel <<" ui->widget opacity:"<<ui->widget->windowOpacity();    qDebug()<<"opalevel = "<< opalevel <<" ui->stackedWidget opacity:"<<ui->stackedWidget->windowOpacity();    qDebug()<<"opalevel = "<< opalevel <<" ui opacity : "<< this->windowOpacity()<<endl;}

✿实验失败

现象是主窗体的有淡入的效果，即透明度有变化，但是子窗体没有，opacity始终为1 。

Log ：

opalevel =  0  ui->widget opacity: 1 
opalevel =  0  ui->stackedWidget opacity: 1 
opalevel =  0  ui opacity  0.898039 
......

opalevel =  8  ui->widget opacity: 1 
opalevel =  8  ui->stackedWidget opacity: 1 
opalevel =  8  ui opacity  0.0980392 

✿失败原因

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1. void QWidget::setWindowOpacity(qreal opacity)  
2. {  
3.     Q_D(QWidget);  
4.     if (!isWindow())  
5.         return;  
6. //...   
7. }  

void QWidget::setWindowOpacity(qreal opacity){    Q_D(QWidget);    if (!isWindow())        return;//...}

✿解决方案

     QGraphicsOpacityEffect

        

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1. // in the constructor   
2. opacityEffect = new QGraphicsOpacityEffect;  
3. ui->widget->setGraphicsEffect(opacityEffect);  
4. ...  
5. // in changeOpacity()   
6. opacityEffect->setOpacity(opacity[opalevel]);  

// in the constructoropacityEffect = new QGraphicsOpacityEffect;ui->widget->setGraphicsEffect(opacityEffect);...// in changeOpacity()opacityEffect->setOpacity(opacity[opalevel]);

✿效果图