在EditText中仅允许基于正则表达式的选定字符

import android.text.InputFilter;
import android.text.Spanned;
import java.util.regex.Pattern;

public class RegexInputFilter implements InputFilter {
    private Pattern mPattern;

    public RegexInputFilter(String regex) {
        mPattern = Pattern.compile(regex);
    }

    @Override
    public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
        StringBuilder filteredStringBuilder = new StringBuilder();
        for (int i = start; i < end; i++) {
            char character = source.charAt(i);
            if (mPattern.matcher(String.valueOf(character)).matches()) {
                filteredStringBuilder.append(character);
            }
        }
        return filteredStringBuilder.toString();
    }
}

EditText editText = findViewById(R.id.editText);
editText.setFilters(new InputFilter[]{new RegexInputFilter("[a-zA-Z0-9]")});