[ fromfile: formlayout.xml id: formlayout ]

Sometimes, you need to create your own dialogs with custom input fields. The dialog shown in Figure 9.10 shows a QFormLayout inside a QVBoxLayout. It gets a QString, QDate, and QColor from the user. You can use objects of type QLayout to organize widgets into grids, nested rows or columns, or forms.

Figure 9.10.  QFormLayout Example

The QFormLayout class is meant to simplify the creation of forms, manually or from Designer. It creates two columns, one for fixed-size labels and the other for variable-size input widgets. Following is the class definition for InputForm.

#ifndef INPUTFORM_H
#define INPUTFORM_H

#include <QDialog>
class QLineEdit;
class QDateEdit;
class QPushButton;
class QDialogButtonBox;

class InputForm : public QDialog {
    Q_OBJECT
public:
    explicit InputForm(QWidget* parent = 0);
    void updateUi();
protected slots:
    void accept();
    void chooseColor();
private:
    QColor m_color;
    QLineEdit* m_name;
    QDateEdit* m_birthday;
    QPushButton* m_colorButton;
    QDialogButtonBox* m_buttons;
};

#endif // INPUTFORM_H

Example 9.3 displays some lines from the InputForm constructor. Each call to addRow() adds an input widget and its corresponding QLabel to the layout in one line of code. It is not necessary to explicitly construct the QLabels.

[ . . . . ]

    m_name = new QLineEdit;
    m_birthday = new QDateEdit;
    m_birthday->setDisplayFormat("dd/MM/yyyy");
    m_colorButton = new QPushButton(tr("Choose"));
    m_colorButton->setAutoFillBackground(true);

    m_buttons = new QDialogButtonBox(QDialogButtonBox::Ok |
                                     QDialogButtonBox::Cancel);

    QVBoxLayout* vbox = new QVBoxLayout;
    QFormLayout* layout = new QFormLayout;

    layout->addRow(tr("Name"), m_name);     
    layout->addRow(tr("Birthdate"), m_birthday);
    layout->addRow(tr("Favorite Color"), m_colorButton);

    vbox->addLayout(layout);                
    vbox->addWidget(m_buttons);

    Q_ASSERT(vbox->parent() == 0);
    Q_ASSERT(m_birthday->parent() == 0);
    setLayout(vbox);                        
    Q_ASSERT(vbox->parent() == this);
    Q_ASSERT(m_birthday->parent() == this);
    

You can use a QDialogButtonBox for presenting the standard buttons to a user. This guarantees that they show up in the same order every time. It also makes it possible for the dialogs to show up in different places on different platforms, depending on the style and dimensions of the screen.

It was not necessary to set the parents of the various widgets in the form. They were all added to various layouts that form a component tree with vbox as the root. The call setLayout(vbox) sets the parent of vbox to the host InputForm object. It also reparents all QWidgets that were added to the various sublayouts of vbox to the parent of vbox (once again, the host InputForm). The Q_ASSERTs above and below that statement verify this.