MonoDroid Set Max Value for EditText

Question

Is there a way to set a maximum value for an edittext created in the activity? For instance, if I didn't want the user to be able to enter a number higher than 8, etc. The edittext is already set up as a numeric field.

et = new EditText(this);
et.InputType = (int)Android.Text.InputTypes.ClassNumber;

Answer 1

You can specify allowed characters for an EditText using the digits attribute:

<EditText
    android:digits="012345678"
    ... />

or from code:

editText.KeyListener = DigitsKeyListener.GetInstance("012345678");

Edit:

It sounds like what you're trying to do is go from an integer max value to the string representation Android needs. You could do something like this:

int maxValue = 8;
string digits = string.Join(string.Empty, Enumerable.Range(0, maxValue + 1));
editText.KeyListener = DigitsKeyListener.GetInstance(digits);

Answer 2

You should create a new class "InputFilterMinMax.java" in the same folder.

Then you should use filter:

textEdit = (TextView)findViewById(R.id.editText1);
textEdit.setFilters(new InputFilter[]{ new InputFilterMinMax("0", "180")});

in your class activity (I've set min as "0" and max as "180").

Code of InputFilterMinMax.java:

import android.text.InputFilter;
import android.text.Spanned;

public class InputFilterMinMax implements InputFilter {

    private int min, max; //paramets that you send to class

    public InputFilterMinMax(int min, int max) {
        this.min = min;
        this.max = max;
    }

    public InputFilterMinMax(String min, String max) {
        this.min = Integer.parseInt(min);
        this.max = Integer.parseInt(max);
    }

    @Override
    public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {   
        try {
            //int input = Integer.parseInt(dest.toString() + source.toString());
            String startString = dest.toString().substring(0, dstart);
            String insert = source.toString();
            String endString = dest.toString().substring(dend);
            String parseThis = startString+insert+endString;
            int input = Integer.parseInt (parseThis);
            if (isInRange(min, max, input))
                return null;
        } catch (NumberFormatException nfe) { }     
        return "";
    }

    private boolean isInRange(int a, int b, int c) {
        return b > a ? c >= a && c <= b : c >= b && c <= a;
    }
}

Source: Android set min max value an edittext accepts

Answer 3

If you want a general use min max range checked EditText, you should do something like the following (this assumes an EditText set for numeric input):

// This handles the minimum value check, this can't be done until AFTER you have given
// the user time to give input (aka not at a character-by-character resolution)
// One easy way to do this is to wait for the user to change focus
final int minimum = 15;
edit_text.setOnFocusChangeListener(
                new View.OnFocusChangeListener() {
                    @Override
                    public void onFocusChange(View _, boolean has_focus) {
                        if (!has_focus && Integer.parseInt(edit_text.getText()) < minimum)
                            edit_text.setText(minimum + "");
                    }
                }
        );
// This handles the maximum value check, because the number increases monotonically with
// the addition of a digit, you can see that the user is inputting a number that is larger
// than the maximum number before the user tells you they are done
final int maximum = 180;
edit_text.setFilters(new InputFilters[] {
    new InputFilter() {
        @Override
        public CharSequence filter(CharSequence source, int source_start, int source_end,
                                   Spanned destination, int destination_start, 
                                   int destination_end) {   
           try {
               String prefix = destination.toString().substring(0, destination_start);
               String insert = source.toString();
               String suffix = destination.toString().substring(destination_end);
               String input_string = prefix + insert + suffix;
               int input = Integer.parseInt(input_string);

               // Leaves input within the bound alone
               if (input <= max)
                   return null;
            } catch (NumberFormatException _) { }
            // Blocks insertions of "source" strings that make the string larger than the maximum     
            return "";
        }
    }
});

You can name these abstract classes if you want to reuse them multiple times.