A Quick and Dirty Guide to Events

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A Quick and Dirty Guide to Events
What's happenin'?

• CS 102-02
• Lecture 4-3

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That Which Must Be Done

• What's an event?
• Why are events important?
• How do we deal with events in Java?

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Events According to Webster's
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The Computer Definition of Events

• Events are things that happen in the world that
  objects notice
• Bill Gates dancing across the Quad in a hot pink
  tutu might be an event to some people, but not to
  most Java objects
• Mouse clicks, double clicks, mouse movements

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User-Centric Programs

• Ancient history
• Programs led users by the nose
• Type in this number
• Type in that number
• Get the printout
• Today's enlightened programs
• Users are in control
• Need to track what a user is doing...

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What to Track?

• Need to know
• Where's the mouse pointer which component and
  where is it within the component?
• Who's got the focus?
• Focus is the program's center of attention
• If the cursor is blinking in a TextField, that's
  because the TextField has focus

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More to Know

• Mouse clicks
• Single, double, triple (Or maybe how far apart
  and how long are successive clicks)
• Which mouse button (1 for Mac, 2 for Windows, 3
  for X Windows)?
• Keyboard
• Which key?
• Was it modified (Ctrl, Shift, Alt)?
• What about function keys?

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Some Java Events

• ActionEvent
• AdjustmentEvent
• ComponentAdapter
• ComponentEvent
• ContainerAdapter
• ContainerEvent
• FocusAdapter
• FocusEvent
• InputEvent

• ItemEvent
• KeyAdapter
• KeyEvent
• MouseAdapter
• MouseEvent
• MouseMotionAdapter
• PaintEvent
• TextEvent
• WindowAdapter
• WindowEvent

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Mouse Events

• MOUSE_CLICKED
• The mouse clicked event type.
• MOUSE_DRAGGED
• The mouse dragged event type.
• MOUSE_ENTERED
• The mouse entered event type.

MOUSE_EXITED The mouse exited event type.
MOUSE_MOVED The mouse moved event type.
MOUSE_PRESSED The mouse pressed event type.
MOUSE_RELEASED The mouse released event type.
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