java - ScrollBar gets stuck when defining Max and Min -

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i trying implement scrollbar eclipse view , have method setup behavior. when run program, no matter how long list<number> data is, thumb big scrollbar , not able move. there doing wrong?

i debugged program , scrollbar maximum set, thumb fills bar. 

private void setupscrollbar(scrollbar scrollbar, list<number> data) {     // set max/minimum     if (data.size() > 0) {         comparator<number> comparator = new comparator<number>() {             @override             public int compare(number o1, number o2) {                 return (int) (o2.doublevalue() - o1.doublevalue());             }         };          double max, min;         data.sort(comparator);         max = data.get(data.size() - 1).doublevalue();         min = data.get(0).doublevalue();          scrollbar.setmax(max);         scrollbar.setmin(min);         scrollbar.setvisibleamount(100 * (max-min));     } else {         scrollbar.setmax(0);         scrollbar.setmin(0);     } }

first of all, custom comparator produces reverse ordered list , pointed out fabian, because of int casting 1 == 1.9 , 1.9 == 2.8 1 != 2.8.

compares 2 arguments order. returns negative integer, zero, or positive integer first argument less than, equal to, or greater second.

to fix this:

  • you can use double comparison data.sort(comparator.comparingdouble(number::doublevalue));.
  • or modify compare method of comparator instance return (int) math.signum(o1.doublevalue() - o2.doublevalue());

the other problem how set visibleamountproperty of scrollbar: (max-min) returns full range of scrollbar, setting property value produces thumb fill 100% available space.

you can fix this, if e.g. set thumb percentage:

final double percentage = 30.0; scrollbar.setvisibleamount((max-min) / 100.0*percentage);

this snippet result in having thumb fill 30% of available space.


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