java-util-observer

Observable - Disjoint UI updates for complex objects

This library exists to combine together two objectives in updating UI objects: 1) Be able to 'remotely' notify UI objects about updates without having to iterate through the entire component tree. 2) Allow editting of a shared resource from multiple potential call sites without needing a controller object that holds references to every single interested view.

This is a useful construct in the situation where you have a large number of fixed GUI components in a program (for example, rendering the various statistics of a Dungeons and Dragons (c) character), because the connections are made anonymously.

Requirements

• Java 7
• org.leumasjaffe.event
• Google Guava

Installation

Steps

1. Download or clone this repository.
2. Open a console window in the directory
3. mvn install
4. Add the below block to your pom.xml

Maven Artifact

<dependency>
  <groupId>org.leumasjaffe</groupId>
  <artifactId>observable</artifactId>
</dependency>

Example Code Snippets

ObservableListener

    class SpellBook extends Observable {
      int spellSlotsRemaining, maxSpellSlots;
      List<List<Spell>> spellsAtLevel;
    }

    class SpellBookUI extends JPanel {
      ObservableListener<JTextField, SpellBook> listener;
      SpellBookUI(SpellBook model) {
        JTextField spellsRemaining = new JTextField();
        add(spellsRemaining);
        
        // Set up a listener to anonymously update when model changes
        listener = new ObservableListener<>(spellsRemaining, (text, book) -> {
          text.setText(book.getSpellSlotsRemaining());
        });
        
        // Automatically invokes callback, setting the text field
        listener.setObserved(model);
      }
    }

    class CastSpellCommand {
      SpellBook book;
      void cast(Spell spell) {
        // ...
        --book.spellSlotsRemaining;
        // Will automatically invoke the code in the ObservableListener above
        ObserverDispatch.notifySubscribers(book);
      }
    }