Qt update（）不工作 [英] Qt update() doesn't work

问题描述

我有一个问题，在 QGraphicsItem 中的update（）函数不工作。我想做的是，当我移动圆，其他 QGraphicsItem （在平均时间roundrect）改变颜色。
这是一个例子，我想做什么：

I have a problem , that update() function in QGraphicsItem doesn't work. What I want to do is , when I move circle , other QGraphicsItem( in the mean time roundrect ) changes color. This is a example, what I want to do:

circle.cpp：

circle.cpp:

void CircleItem::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
    // RoundRect Object
    RectItem->SetBackGround();
    QGraphicsItem::mouseMoveEvent( event );
}

RoundRect.cpp：

RoundRect.cpp:

void RoundRectItem::SetBackGround()
{
    ChangeBackground = true;
    update();
}

void RoundRectItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    QRectF rec = QRectF( QPoint( 0,0 ), boundingRect().size() / 2 );

    roundRect = QRectF(rec.adjusted(-rec.height() / 2, 0, rec.height()/2, 0));

    roundRect.moveTo( boundingRect().center().x() - roundRect.width() / 2,
                      boundingRect().center().y() - roundRect.height() / 2 );

    if( !ChangeBackground )
        painter->setBrush( backBrush );
    else
        painter->setBrush( QBrush( Qt::blue ) );

    painter->setPen( QColor( 255,255,255 ) );

    painter->drawRoundedRect(roundRect, roundRect.height() / 2, roundRect.height() / 2 );
}

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So the question is, how can I make this update() work right.

推荐答案

正在调用QGraphicsItem的update（）方法。你应该调用你正在使用的QGraphicsView的update（）。例如，你可以保持你的QGraphicsView作为你的项目的成员类，如：

You are invoking the update() method of QGraphicsItem. You should call the update() of the QGraphicsView you are working with. For example you can keep your QGraphicsView as a member class of your item like:

QGraphicsView * parent;

当您希望更改发生时调用它的更新方法：

And call it's update method when you want the changes take place like:

void RoundRectItem::SetBackGround()
{
    ChangeBackground = true;
    parent->update();
}

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