Event Handling H_Func(Event) { } Event Receiver Object Source Object Registration

Source vs. Receiver Source/ReceiverReceiver Source

Mouse Event Handling in Java Event: MouseEvent Interface: MouseListener ( mousePressed, mouseClicked, mouseReleased, mouseEntered, mouseExited) MouseMotionListener ( mouseDragged, mouseMoved) Adaptor Class: MouseAdaptor, MouseMotionAdaptor Registration: addMouseListener, addMouseMotionListener

Event-driven Programming Programming paradigm State representation State presentation : paintComponent in java Event handling and state change Request for presentation to reflect new state: repaint in java

Double Buffering Flicking problem Double buffering –Front buffer for display –Back buffer for composition Triple buffering

Single Buffering Frame Buffer Display Composition

Double Buffering in Computer Graphics Front Composition Display Back Front Display Composition Swap Buffers

Double Buffering in Java Front Composition Draw Back Image Window

Double Buffering in Java Step 1: Create the back buffer and its graphics Image backBuffer = createImage(width, height); Graphics gBackBuffer = backBuffer.getGraphics(); Step 2: Compose the scene in the back buffer gBackBuffer.clearRect(…); gBackBuffer.fillOval(…);.... Step 3: copy the back buffer to the front g.drawImage(backBuffer, 0, 0, null);

An Example Event-driven programming paradigm Class Array/Collection Event Handling Double Buffering