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Java Direct Manipulation

Java Direct Manipulation. Chris North cs3724: HCI. Java Review. Java Swing components, Layout managers Events Graphics JDBC, MVC. Hit Testing. Mouse click, mouse over Which dot did user click on? Using components: Make each dot a simple component, like a JButton

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Java Direct Manipulation

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  1. Java Direct Manipulation Chris North cs3724: HCI

  2. Java Review • Java • Swing components, Layout managers • Events • Graphics • JDBC, MVC

  3. Hit Testing • Mouse click, mouse over • Which dot did user click on? • Using components: • Make each dot a simple component, like a JButton • Hit testing automatic, each component is a subwindow • Listen to each component • Receive event, check event source • rectangular items, scalability, customize JComponent • Using custom graphics: • Get click event x,y from JPanel • Iterate through data structure, test for hit • Or, shape.contains(x,y) • Data structure for fast lookup?

  4. Manipulation • Dragging, stretching, … • MouseDrag, MouseMove events • Using components: • mousePressed store x,y click in component • mouseDragged • Calculate delta • Move component by delta • Using graphics: • (need to erase it, repaint other graphics, repaint new item) • Calculate delta, calculate new item location, store • Call repaint( ) • Draw new graphics in paintComponent( )

  5. Problem • Dynamic manipulation on top of other graphics • Need to preserve (redraw) other graphics • Examples: MacDraw, powerpoint • Simple solution: • Call repaint( ) while dragging • paintComponent( ) restores other graphics • But: lots of graphics, too slow!

  6. Solutions • Minimize repaint rectangle: • mypanel.repaint(rect) where rect is area of manipulation • paintComponent( ) process only graphics in rect • Modified double buffering: • maintain buffer for background graphics • Paint buffer to screen, then paint manip graphics • XOR painting: • Draw manipulations by inverting pixel colors • drawing with XOR twice returns to original look • graphics.setXORMode(color) • graphics.setPaintMode( ) for normal painting

  7. In JBuilder

  8. Drag-n-Drop • Drag and Drop API • Data transfer

  9. Problem: Flashing • Ugly flashing when repaint: • Paint background • Redraw shapes

  10. Solution: Double buffering

  11. Solution: Double buffering • Double buffered repaint: • Draw all graphics in temporary off-screen image • Paint background color • Paint shapes • Then paint image to JPanel • Bonus: Swing does this for you! • Draw graphics on JPanel • JPanel maintains off-screen image

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