HELP! * YELLOW=global GREY=local Global HTML version of Foils prepared 1 February 97

Foil 23 Flickering in Applets and its Solution

From Jan 29 Delivered Lecture for Course CPS616 -- Java Lecture 3 -- Exceptions Through Events CPS616 spring 1997 -- Jan 29 1997. by Nancy McCracken * See also color IMAGE
Secs 103.6
Unless you are careful, dynamic applets will give flickering screens
This is due to cycle
paint(g)
update(g) clearing screen
paint(g) drawing new screen .....
where flicker caused by rapid clear-paint cycle.
There are two ways to solve this problem which involve changing update in different ways
  • 1: Change update() either not to clear screen at all (because you know paint() will write over parts that are to be changed) or to just clear the parts of the screen that are changed
  • or 2:Double Buffering


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