問題描述

我需要在我的應用程序中實現一個加載..."窗口，但我更喜歡用上面有文本的深色透明層覆蓋整個 QMainWindow.有人知道怎么做嗎?我不確定如何在 Qt 中重疊小部件/布局.任何幫助將不勝感激.

這個答案是在我與疊加層相關的一系列答案中:

//https://github.com/KubaO/stackoverflown/tree/master/questions/overlay-widget-19362455#include #if QT_VERSION >= QT_VERSION_CHECK(5,0,0)#include #萬一類 OverlayWidget : 公共 QWidget{void newParent() {如果 (!parent()) 返回；parent()->installEventFilter(this);增加();}民眾:顯式 OverlayWidget(QWidget * parent = {}) : QWidget{parent} {setAttribute(Qt::WA_NoSystemBackground);setAttribute(Qt::WA_TransparentForMouseEvents);newParent();}受保護://!從父小部件捕獲調整大小和子事件bool eventFilter(QObject * obj, QEvent * ev) 覆蓋 {如果(對象==父()){if (ev->type() == QEvent::Resize)resize(static_cast(ev)->size());else if (ev->type() == QEvent::ChildAdded)增加();}返回 QWidget::eventFilter(obj, ev);}//!跟蹤父小部件更改布爾事件(QEvent* ev)覆蓋{if (ev->type() == QEvent::ParentAboutToChange) {if (parent()) parent()->removeEventFilter(this);}else if (ev->type() == QEvent::ParentChange)newParent();返回 QWidget::event(ev);}};類 LoadingOverlay : 公共 OverlayWidget{民眾:LoadingOverlay(QWidget * parent = {}) : OverlayWidget{parent} {setAttribute(Qt::WA_TranslucentBackground);}受保護:無效paintEvent(QPaintEvent *)覆蓋{QPainter p{this};p.fillRect(rect(), {100, 100, 100, 128});p.setPen({200, 200, 255});p.setFont({"arial,helvetica", 48});p.drawText(rect(), "Loading...", Qt::AlignHCenter | Qt::AlignVCenter);}};int main(int argc, char * argv[]){QApplication a{argc, argv};QMainWindow 窗口；QLabel 中央{"你好"};central.setAlignment(Qt::AlignHCenter | Qt::AlignTop);central.setMinimumSize(400, 300);LoadingOverlay 疊加{&central};QTimer::singleShot(5000, &overlay, SLOT(hide()));window.setCentralWidget(&central);window.show();返回 a.exec();}

I need to implement a "Loading..." window in my application but I do prefer to cover the whole QMainWindow with a dark transparent layer with a text above. Does anybody know how to do that? I am not sure how to overlap widgets/layouts in Qt. Any help will be appreciated.

This answer is in a series of my overlay-related answers: first, second, third.

The most trivial solution is to simply add a child transparent widget to QMainWindow. That widget must merely track the size of its parent window. It is important to properly handle changes of widget parentage, and the z-order with siblings. Below is a correct example of how to do it.

If you want to stack overlays, subsequent overlays should be the children of OverlayWidget, in the z-order. If they were to be siblings of the OverlayWidget, their stacking order is undefined.

This solution has the benefit of providing minimal coupling to other code. It doesn't require any knowledge from the widget you apply the overlay to. You can apply the overlay to a QMainWindow or any other widget, the widget can also be in a layout.

Reimplementing QMainWindow's paint event would not be considered the best design. It makes it tied to a particular class. If you really think that a QWidget instance is too much overhead, you better had measurements to show that being the case.

It is possible, of course, to make the overlay merely a QObject and to put the painting code into an event filter. That'd be an alternative solution. It's harder to do since you have to also properly deal with the parent widget's Qt::WA_StaticContents attribute, and with the widget potentially calling its scroll() method. Dealing with a separate widget is the simplest.

// https://github.com/KubaO/stackoverflown/tree/master/questions/overlay-widget-19362455
#include <QtGui>
#if QT_VERSION >= QT_VERSION_CHECK(5,0,0)
#include <QtWidgets>
#endif

class OverlayWidget : public QWidget
{
   void newParent() {
      if (!parent()) return;
      parent()->installEventFilter(this);
      raise();
   }
public:
   explicit OverlayWidget(QWidget * parent = {}) : QWidget{parent} {
      setAttribute(Qt::WA_NoSystemBackground);
      setAttribute(Qt::WA_TransparentForMouseEvents);
      newParent();
   }
protected:
   //! Catches resize and child events from the parent widget
   bool eventFilter(QObject * obj, QEvent * ev) override {
      if (obj == parent()) {
         if (ev->type() == QEvent::Resize)
            resize(static_cast<QResizeEvent*>(ev)->size());
         else if (ev->type() == QEvent::ChildAdded)
            raise();
      }
      return QWidget::eventFilter(obj, ev);
   }
   //! Tracks parent widget changes
   bool event(QEvent* ev) override {
      if (ev->type() == QEvent::ParentAboutToChange) {
         if (parent()) parent()->removeEventFilter(this);
      }
      else if (ev->type() == QEvent::ParentChange)
         newParent();
      return QWidget::event(ev);
   }
};

class LoadingOverlay : public OverlayWidget
{
public:
   LoadingOverlay(QWidget * parent = {}) : OverlayWidget{parent} {
      setAttribute(Qt::WA_TranslucentBackground);
   }
protected:
   void paintEvent(QPaintEvent *) override {
      QPainter p{this};
      p.fillRect(rect(), {100, 100, 100, 128});
      p.setPen({200, 200, 255});
      p.setFont({"arial,helvetica", 48});
      p.drawText(rect(), "Loading...", Qt::AlignHCenter | Qt::AlignVCenter);
   }
};

int main(int argc, char * argv[])
{
   QApplication a{argc, argv};
   QMainWindow window;
   QLabel central{"Hello"};
   central.setAlignment(Qt::AlignHCenter | Qt::AlignTop);
   central.setMinimumSize(400, 300);
   LoadingOverlay overlay{&central};
   QTimer::singleShot(5000, &overlay, SLOT(hide()));
   window.setCentralWidget(&central);
   window.show();
   return a.exec();
}

這篇關于Qt 中 QMainWindow 上的深色透明層的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！