How to create a negative NumberPicker

Question

Does anyone know of an easy way to allow negative numbers with Android's default numberpicker? I understand that it's the InputFilter that disallows this, but is there any easy way to override without rewriting the whole widget?

Answer 1

A more generic and elegant solution is to use NumberPicker.Formatter and use only positive numbers in the NumberPicker.

Example if I want to select a number in [-50, 50]:

final int minValue = -50
final int maxValue = 50
NumberPicker numberPicker = new NumberPicker(myActivity);
numberPicker.setMinValue(0);
numberPicker.setMaxValue(maxValue - minValue);
numberPicker.setValue(myCurrentValue - minValue);
numberPicker.setFormatter(new NumberPicker.Formatter() {
    @Override
    public String format(int index) {
        return Integer.toString(index + minValue);
    }
});

then to get back the selected value:

int myNewValue = numberPicker.getValue() + minValue

Answer 2

Use:

String[] nums {"-1","-2","-3","-4"};
numberpicker.setDisplayedValues(nums);

or

String[] nums = new String[4];
for(int i=0; i<nums.length; i++)
nums[i] = "-" + Integer.toString(i);
numberpicker.setDisplayedValues(nums);

Either of those will let you use any set of Strings for your NumberPicker. What you are doing is you are specifying a set of strings which you the pass to the NumberPicker. Then it will display your values instead of the default ones.