When a user opens a .htt template I want to get the template's base name (label) within the class AboutUI extends JWebPageUI scope. What I'm trying to do is make a file reference to the .info file so I can map the properties and test for 'contains key'.

The API shows a protected field currentAO, but I have failed to get the AlbumObject. I was hoping it was

class AboutUI extends JWebPageUI {
AboutUI.currentAO; 
//or
AboutUI.this.currentAO;

As the user can rename the file (link) I can't assume it is the same as in the skin directory.

Edited by: RobM on 13 Jun 2022, 21:41
Changed title of first post to reflect what the final code does.

You can for instance do IO.baseName(currentAO.getFile());

Good. You can refer to currentAO either as just currentAO or this.currentAO or super.currenAO, but AboutUI.currentAO is a reference to a static variable and as currentAO is an instance variable, it fails. Furthermore, AboutUI.this.currentAO is only allowed within nested classes as a way to refer to the outer scope.

On "static" and "instance" variables:
Think about the world of classes and instances in the Java world as you baking ginger cookies. For each shape of ginger cookie you have a steel template that can "stamp" any number of cookies into the dough. You might have a human shaped steel template, a heart-shaped steel template and so on. If we transfer this baking to Java, then your steel templates are your classes and your ginger cookies are your instances. The process of "stamping" a cookie out of a piece of dough, thereby creating a cookie is the same as the "new Foo()" call in Java. It's called instantiation.

Now that we have this sorted out, let's introduce variables: They can be likened with properties of either your steel templates or ginger cookies. If it's a property of the steel template, for instance its weight or sharpness, then it's a "static" property/variable. If it's a property of individual cookies, for instance weight or color, then it's an ordinary instance variable. When you wrote "AboutUI.currentAO", you directed Java to look for a "static" "currentAO" variable, belonging to the AboutUI class itself and not to the current instance. You were simply looking in the wrong spot for that variable.

Why the term "static"?
One may argue that it would be more intuitive if the keyword to denote variables that belongs to the class itself was called class-variable or similar. The word "static" was chosen as it also refers to in what type of memory this variable type resides. They are, just like the class definitions and methods themselves, stored in the static memory region (doesn't shrink or grow during program execution), while objects, i.e. instances of classes, are stored in a dynamic memory area.

A "field variable" or "field" IS a variable that belongs to each object, i.e. to each instance of a class. This can be contrasted with local variables or method variables which lives only while a method is being executed.

(I may be "anal" with wordings here, but that's a great start to avoid confusion)

Yes, because "currentAO" isn't set until jAlbum calls the setAlbumObject() method of the JWebPageUI class, but you try to refer to it at construction time. If you want to print the correct value of "currentAO", then override setAlbumObject(AlbumObject ao) and first call super.setAlbumObject(ao); then print the value of currentAO. It should now be non-null.

Rob, please see the API docs . To override setAlbumObject, you write (in your sub class):

public void setAlbumObject​(AlbumObject ao) {
    super.setAlbumObject(ao);
    // Now you can refer to either "ao" or "currentAO"
}

Yes.

I have it working with the template's filename hard coded.

Sorry, no, I need new glasses It’s probably all the thrashing about I was doing and just lost my focus.

I’ll have another go tonight, now I have everything else in place getting this fixed will make it more robust. Sorry for being so slow.