Dialog

A Window with a button bar and the handling that belongs to a save button: check the input, move it to the model, save, close.

Dialog dlg = new Dialog(true, false, 460, -1, "Order \"Big Ones\"") {
	@Override protected void createFrame() throws Exception {
		super.createFrame();
		createButtons();                          // A Dialog does not make its buttons by itself
	}

	@Override public void createContent() throws Exception {
		FormBuilder fb = new FormBuilder(this);
		fb.label("Copies").control(copies);
	}

	@Override protected boolean onValidate() throws Exception {
		Integer value = copies.getValueSafe();    // Empty: the control reports that itself
		if(null == value) {
			return false;                         // Refused: the dialog stays open
		}
		return true;
	}

	@Override protected boolean onSave() throws Exception {
		order(copies.getValue());
		return true;
	}
};
dlg.setButtonsOnBottom(true);                     // Before the bar exists, or it throws
add(dlg);

• The buttons
• What the save button does
• How it closed

The buttons

getButtonBar() returns the bar - a ButtonBar2, behind the IButtonBar interface - and creates it in the top area the first time it is asked for. setButtonsOnBottom(true) puts it in the bottom area instead, and has to be called before anything else touches the bar - afterwards it throws IllegalStateException.

What is on the bar is up to the dialog:

• createButtons() makes the usual pair: a save button (labelled with the application's "okay" text) and a cancel button. Nothing calls it for you - the dialog above does it from createFrame(), which is where a subclass is expected to do it.
• getButtonBar().addButton(...) adds buttons of your own, exactly as on any other button bar. A dialog that never calls createButtons() has only these.

The two buttons carry the test ids saveButton and cancelButton.

What the save button does

Every step that returns false leaves the dialog standing, which is how it refuses to be closed. The three that are meant to be overridden divide the work:

A dialog that refuses has to say why: post a message on the control (setMessage), on the dialog (addGlobalMessage) or in a box (MsgBox2.on(this).error(...)) before returning false. The dialog is an error fence, so the first two are shown inside it.

How it closed

dlg.setOnClose(reason -> {
	if(!Dialog.RSN_SAVE.equals(reason)) {
		//-- Cancelled.
	}
});

For a dialog that asks for one single value there is a subclass that writes all of this for you: InputDialog.