what's the difference between Qmainwindow and Qwidget and Qdialog?

Question

whats the difference between Qmainwindow and Qwidget and Qdialog in Qt programming. Are they similar with java awt and java swing?

Answer 1

A QWidget is the base class for all drawable classes in Qt. Any QWidget-based class can be shown as a window by showing it when it has no parent.

A QDialog is based on QWidget, but designed to be shown as a window. It will always appear in a window, and has functions to make it work well with common buttons on dialogs (accept, reject, etc.).

QMainWindow is designed around common needs for a main window to have. It has predefined places for a menu bar, a status bar, and other widgets. It does not have any built-in allowances for buttons like QDialog does.