How to Limit Decimal Places in Android EditText for Currency Input

How can I limit the number of decimal places in an Android EditText for currency values?

"android:inputType="numberDecimal"

To limit the decimal places in an Android EditText, you can use a combination of input filters and text change listeners. This ensures that only a maximum of two decimal digits are allowed following the decimal separator, which is crucial for handling currency inputs properly.

import android.text.InputFilter;
import android.text.Spanned;
import android.text.TextWatcher;
import android.text.Editable;

// InputFilter to restrict decimal places
InputFilter decimalFilter = new InputFilter() {
    @Override
    public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
        String input = dest.toString().substring(0, dstart) + source + dest.toString().substring(dend);
        if (input.matches("^\d+(\.\d{0,2})?$")) {
            return null; // Input is valid
        }
        return ""; // Input is invalid
    }
};

editText.setFilters(new InputFilter[]{decimalFilter});

// Optionally add a TextWatcher to manage user input more interactively
editText.addTextChangedListener(new TextWatcher() {
    @Override
    public void afterTextChanged(Editable s) {}

    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {}

    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
        // Further input management can be done here if required
    }
});

Causes

• Users may inadvertently input invalid amounts such as 123.123 instead of 123.12 for money values.
• The default behavior of EditText allows for any number of decimal places unless explicitly restricted.

Solutions

• Use an InputFilter to control the maximum number of digits after the decimal point.
• Implement a TextWatcher to validate the input in real-time.

Mistake: Not checking for negative inputs or invalid characters like letters or symbols.

Solution: Implement input validation to only allow numeric entries.

Mistake: Directly changing the EditText text without notifying the user can cause confusion.

Solution: Use a TextWatcher to provide immediate feedback on input changes.