quantiom / EventHandler

A simple event handler system written in Java.

EventHandler

A simple and lightweight event handler system made in Java.

Features

• Scalable and fast
• Custom event support
• Cancellable events
• Event priorities
• Event inheritence support (ex: TestEvent extends TestSuperEvent, TestEvent gets called from the handler and then TestSuperEvent will also be called)

Event Implementation

public class TestEvent extends Event implements EventCancellable {
    private boolean isCancelled;
    private String data;

    // can be whatever
    public TestEvent(String data) {
        this.data = data;
    }

    public String getData() {
        return data;
    }

    @Override
    public boolean isCancelled() {
        return this.isCancelled;
    }

    @Override
    public void setCancelled(boolean cancelled) {
        this.isCancelled = cancelled;
    }
}

Listener Class Example

public class SomeListener implements EventListener {
    // will be invoked
    @HandleEvent
    public void onTestEvent(TestEvent event) {
        System.out.println("Data: " + event.getData());
    }
    
    // will not be invoked
    public void onNotInvokedTestEvent(TestEvent event) {
        System.out.println("Data: " + event.getData());
    }
}

Usage

// create the handler and listener instances
EventHandler handler = new EventHandler();
ListenerTest testListener = new ListenerTest();

// register the listener
handler.registerEvents(testListener);

// make sure data is not overridden yet
Assert.assertEquals("None", testListener.getData());
Assert.assertEquals(0, testListener.getTimesRan());

// call the test event
handler.callEvent(new TestEvent("New data"));

// data should now be what was passed into the TestEvent constructor
Assert.assertNotEquals("None", testListener.getData());
Assert.assertEquals("New data", testListener.getData());
Assert.assertEquals(1, testListener.getTimesRan());

// unregister the listener
handler.unregisterEvents(testListener);

// call the test event, this should not change the data now
handler.callEvent(new TestEvent("Different data"));
Assert.assertNotEquals("Different data", testListener.getData());
Assert.assertEquals(1, testListener.getTimesRan());

See tests for more.