JavaFX：如何调用和传递控制对象？

Question

This is a method for getting the text of different JavaFx controls.

private String getText(Node item) {
        
    String txt = "";

    if (item instanceof Label) {
        if(!((Label)item).getText().isEmpty()){
            txt = ((Label)item).getText();
        }
    }
    if (item instanceof TextField) {
        if(!((TextField)item).getText().isEmpty()){
            txt = ((TextField)item).getText();
        }
    }
    if (item instanceof CheckBox) {
        if(!((CheckBox)item).getText().isEmpty()){
            txt = ((CheckBox)item).getText();
        }
    }
    return txt;
}

I'm trying to lessen the lines of codes. Instead of defining Label, TextField, CheckBox, etc. Is there an object class that I could call for all other controls and put in beside the Node item so that I don't need to repeat and specify each control? Is there a way to make it like this?

private String getText(Node item, X x) {

    String txt = "";

    if (item instanceof x) {
        if(!((x)item).getText().isEmpty()){
            txt = ((x)item).getText();
        }
    return txt;
}

What should I replace X & x. I don't know what object should I call or replace the Control. Just don't mind about the logic of isEmpty. My main concern is what object should I call or replace the Control. And call the method like this

getText(txtSample, TextField.class) 

or

getText(lblSample, Label.class)

Thank you.

Answer 1

Since the common superclass Control has no method getText() (because not all controls have text), this is not possible.

EDIT: as James_D pointed out, Label and CheckBox do have a common ancestor that has the method getText() , namely Labeled . This saves us another instanceof check.

However, the rest of the similarities can be extracted. Suppose we first write a helper method to extract the text from the control (note the down casting in the same statement as the instanceof :

    private String getRawText( final Node item )
    {
        if( item instanceof Labeled labeled )
            return labeled.getText();
        else if( item instanceof TextField field )
            return field.getText();
        else //this is the default
            return "";
    }

then the original function becomes:

    private String getText( final Node item ) 
    {

        final var  txt = getRawText( item );

        return txt.isEmpty() 
                ? ""
                : txt;
    }

But note that you check text.isEmpty() while the default, with which you initialized the variable txt is itself empty ( "" ). Thus the check for empty is not needed. Did you mean .isBlank() (stripping whitespace only strings)? Or getText() == null ?

Otherwise, it can be removed, and then your left with the function getRawText() only.