QDockWidget causes qt to crash

问题

I Have the version of Qt that is built into ubuntu 11.10. And am trying to use a QDockWidget that cannot actually dock (basically, I just want a window that floats. I don't want to just make the view be a top level view because then I would have the OS window bar up there, which I don't want, and if I were to hide it, then the window won't be movable).

So, I basically make a new Qt Gui project, and don't change any of the files, except for the mainwindow.cpp file, which I change to:

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QDockWidget>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    QDockWidget *dockWidget = new QDockWidget(this);
    // Without window management and attached to mainwindow (central widget)
    dockWidget->setFloating( true );
    // resize by frame only - not positional moveable
    dockWidget->setFeatures( QDockWidget::DockWidgetMovable );
    // never dock in mainwindow
    dockWidget->setAllowedAreas( Qt::NoDockWidgetArea );
    // title
    dockWidget->setWindowTitle( "Dock Widget" );
    // add contents. etc etc....
    dockWidget->show();
}

MainWindow::~MainWindow()
{
    delete ui;
}

The problem is that when I go to move the widget, the whole program crashes. I want to know if I am doing something very wrong, or if there is just a bug in qt.

回答1:

You made the widget floating but not floatable.

dockWidget->setFeatures( QDockWidget::DockWidgetMovable | 
    QDockWidget::DockWidgetFloatable );

And you can also have a movable frameless window, by handling the mouse dragging yourself through mousePressEvent, mouseReleaseEvent and mouseMoveEvent.

How to hide the now useless float button

Based on QDockWidget source code, the "float button" is not shown if there is a title bar widget:

 dockWidget->setTitleBarWidget(new QLabel("Dock Widget", dockWidget));

Or since it has a name (which isn't documented), you can hide it explicitly:

 QAbstractButton * floatButton = 
   dockWidget->findChild<QAbstractButton*>("qt_dockwidget_floatbutton");
 if(floatButton) 
     floatButton->hide();

来源：https://stackoverflow.com/questions/9559666/qdockwidget-causes-qt-to-crash

标签

c++

qt4

qdockwidget