Change the step size of a NumberPicker

Question

Is it possible to do that in a more convenient way than handling it in the OnScrollListener event? Pity it doesn't have a step size attribute...

Answer 1

The NumberPicker in Android has a method called setDisplayedValues. You can use this one to show custom values (it takes an array of Strings) and then map them when you need the value. So if you need steps of 5 in an minute picker, for example, you can create an array like this:

String[] minuteValues = new String[12];

for (int i = 0; i < minuteValues.length; i++) {
    String number = Integer.toString(i*5);
    minuteValues[i] = number.length() < 2 ? "0" + number : number;
}

minutePicker.setDisplayedValues(minuteValues);

And then when you get the value in the OnValueChangeListener, you just need to cast it back to an integer:

Integer.parseInt(minuteValues[newVal]);

Answer 2

To set a step count of '5' for example, use the NumberPicker.Formatter:

    NumberPicker.Formatter formatter = new NumberPicker.Formatter() {
        @Override
        public String format(int value) {
            int temp = value * 5;
            return "" + temp;
        }
    };
    numberPicker.setFormatter(formatter);

Answer 3

Why not just add an OnValueChangeListener Something like:

numberPicker.setOnValueChangedListener(new NumberPicker.OnValueChangeListener() {

     @Override
     public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
         picker.setValue((newVal < oldVal)?oldVal-5:oldVal+5);
     }

});

Answer 4

The NumberPicker in Android has a method called setDisplayedValues. You can use this one to show custom values (it takes an array of Strings) and then map them when you need the value.

For example, you can create a function like this:

public String[] getArrayWithSteps (int iMinValue, int iMaxValue, int iStep)
{ 
   int iStepsArray = (iMaxValue-iMinValue) / iStep+1; //get the lenght array that will return

   String[] arrayValues= new String[iStepsArray]; //Create array with length of iStepsArray 

   for(int i = 0; i < iStepsArray; i++)
   {
     arrayValues[i] = String.valueOf(iMinValue + (i * iStep));
   }

   return arrayValues;
}

So, you should call the method> NumberPicker.setDisplayedValues, for example:

int min = 5;
int max = 180;
int step = 10;

String[] myValues = getArrayWithSteps(min, max, step); //get the values with steps... Normally 

//Setting the NumberPick (myNumberPick)
myNumberPick.setMinValue(0);
myNumberPick.setMaxValue((max-step) / min + 1); //Like iStepsArray in the function
//Because the Min and Max Value should be the range that will show. 
//For example, Min = 0 and Max = 2, so the NumberPick will display the first three strings in the array String (myValues); 
myNumberPick.setDisplayedValues(myValues);//put on NumberPicker 

For get the Value in the NumberPick:

String sValue = String.valueOf(10+(myNumberPick.getValue()*5)); //->> (iMinValue + (myNumberPick.getValue()*iStep))

Answer 5

When using methods described above, one needs to be aware that the picker allows user not only to select a value by scrolling, but also by entering it with keyboard.

By default, the input type of the input field is set to TYPE_CLASS_NUMBER, and therefore user is presented with numerical keyboard. It seems that when you use setDisplayedValues the picker changes the type to TYPE_CLASS_TEXT, however, when you use setFormatter the input type is not changed.

Therefore using formatter in this case may lead to unexpected behavior. Let's say you want the user to be able to pick only the values "0" or "5". You may have code like this:

NumberPicker numberPicker = (NumberPicker) findViewById(R.id.my_number_picker);
numberPicker.setMinValue(0);
numberPicker.setMaxValue(1);
numberPicker.setFormatter(v -> v == 0 ? "0" : "5");

However, in this scenario the user is presented with the numerical keyboard, but is able only to enter only "0" or "1".

If you use instead:

numberPicker.setDisplayedValues(new String[] { "0", "5" });

the user will see the text keyboard, but will be able to enter "0" or "5" as expected.

If you are bothered with the text keyboard you can use reflection to access the private field and set the input type back to number (which is of course not recommended unless really necessary). The field is called "mInputText", or "mText" if you target oldies goldies like Gingerbread.

    try {
        Field inputField = NumberPicker.class.getDeclaredField("mInputText");
        inputField.setAccessible(true);

        EditText inputText = (EditText) inputField.get(numberPicker);
        inputText.setRawInputType(InputType.TYPE_CLASS_NUMBER);
    } catch (ClassCastException e) {
        // Just ignore this exception and do nothing.
    } catch (IllegalAccessException e) {
        // Just ignore this exception and do nothing.
    } catch (NoSuchFieldException e) {
        // Just ignore this exception and do nothing.
    }

Answer 6

This is better approach for ajpolt solution

with any predefined step size, it support for custom value set via keyboard.

 final NumberPicker np = (NumberPicker) dialogView.findViewById(R.id.numberPicker1);
    np.setMaxValue(1000); // max value 1000
    np.setMinValue(0);   // min value 0
    np.setValue(defValue);
    np.setWrapSelectorWheel(false);
    final int m_oldFocus = np.getDescendantFocusability();
    np.setDescendantFocusability(NumberPicker.FOCUS_BLOCK_DESCENDANTS);
    np.setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch(View view, MotionEvent motionEvent) {
            np.setDescendantFocusability(m_oldFocus);
            return false;
        }
    });

    np.setOnValueChangedListener(new NumberPicker.OnValueChangeListener() {
        @Override
        public void onValueChange(NumberPicker numberPicker, int oldVal, int newVal) {
            int stepSize = 10;
            if(newVal%stepSize !=0){
                if(newVal < oldVal){
                    numberPicker.setValue(((int)(newVal/stepSize)) *stepSize);
                }else{
                    numberPicker.setValue((((int)(newVal/stepSize)) *stepSize ) +stepSize );
                }

            }else{
                numberPicker.setValue(newVal);
            }

        }
    });

*I know this is 5 years old Question, but might be useful for somebody