Dynamically adding QWidgets to QVBoxLayout

Question

I'm trying to add QWidgets at the top of a QVBoxLayout. But they get inserted at the bottom, growing upwards. In the QVBoxLayout is a vertical spacer to 'push' all widgets to the top (but they are pushed to the bottom). With Ctrl+A the widgets are inserted.

The widget inserted is a simple widget with horizontal layout and two labels.

How do I get these widgets to be inserted/pushed at/to the top?

On every insert there's a small windows window visible without caption or text. It disappears really quickly. Why is this? I don't want it. How do I get rid of this?

Below is a small example.

mainwindow.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>400</width>
    <height>300</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralWidget">
   <layout class="QGridLayout" name="gridLayout">
    <item row="0" column="0">
     <widget class="QWidget" name="widget" native="true">
      <layout class="QVBoxLayout" name="verticalLayout">
       <item>
        <widget class="QLabel" name="label">
         <property name="text">
          <string>First at top</string>
         </property>
        </widget>
       </item>
       <item>
        <spacer name="verticalSpacer">
         <property name="orientation">
          <enum>Qt::Vertical</enum>
         </property>
         <property name="sizeHint" stdset="0">
          <size>
           <width>20</width>
           <height>221</height>
          </size>
         </property>
        </spacer>
       </item>
      </layout>
     </widget>
    </item>
   </layout>
  </widget>
  <widget class="QMenuBar" name="menuBar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>400</width>
     <height>21</height>
    </rect>
   </property>
   <widget class="QMenu" name="menuAdd">
    <property name="title">
     <string>File</string>
    </property>
    <addaction name="actionFile"/>
    <addaction name="separator"/>
    <addaction name="actionE_xit"/>
   </widget>
   <addaction name="menuAdd"/>
  </widget>
  <action name="actionFile">
   <property name="text">
    <string>Add</string>
   </property>
   <property name="shortcut">
    <string>Ctrl+A</string>
   </property>
  </action>
  <action name="actionE_xit">
   <property name="text">
    <string>E&amp;xit</string>
   </property>
   <property name="shortcut">
    <string>Ctrl+X</string>
   </property>
  </action>
 </widget>
 <layoutdefault spacing="6" margin="11"/>
 <resources/>
 <connections/>
</ui>

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
  Q_OBJECT

public:
  explicit MainWindow(QWidget *parent = 0);
  ~MainWindow();

private slots:
  void on_actionFile_triggered();

  void on_actionE_xit_triggered();

private:
  Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

mainwindow.cpp

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

MainWindow::MainWindow(QWidget *parent) :
  QMainWindow(parent),
  ui(new Ui::MainWindow)
{
  ui->setupUi(this);
}

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

void MainWindow::on_actionE_xit_triggered()
{
  QApplication::quit();
}

void MainWindow::on_actionFile_triggered()
{
  int i = ui->verticalLayout->count();

  QHBoxLayout* layout = new QHBoxLayout();
  layout->addWidget(new QLabel(tr("One.%1").arg(i)));
  layout->addWidget(new QLabel(tr("Two.%1").arg(i)));

  QWidget* window = new QWidget;
  window->setLayout(layout);
  window->show();

  ui->verticalLayout->addWidget(window);
}

Answer 1

Adding widgets to the top

Instead of addWidget(), use insertWidget() with an index of 0.

The unwanted, disappearing, little window

About the small, unwanted window: This is probably because you are creating QLabels without specifiying a parent. Thus they are created as toplevel-windows until you add them to the layout. Specify your window as parent (first ctor argument of QLabel).