Android非英文邮箱验证问题：俄文邮箱匹配返回false求助

Got it, let's figure out why your Russian email validation is failing with Android's default EMAIL_ADDRESS pattern and how to fix it.

Android's android.util.Patterns.EMAIL_ADDRESS uses a regex that only supports ASCII characters for both the local part (before the @) and domain part (after the @). Russian emails (like иван@пример.рф) contain Unicode Cyrillic characters, which fall outside the ASCII range—so the matcher returns false by design.

1. Use a Custom Unicode-Aware Regex #

The most comprehensive fix is to define your own regex pattern that supports Unicode letters and numbers, aligning with modern email standards (RFC 6531, which explicitly allows internationalized email addresses).

Here's a ready-to-use implementation:

import java.util.regex.Pattern;

public class EmailValidator {
    // Regex that supports Unicode letters, numbers, and valid email symbols
    private static final Pattern UNICODE_EMAIL_PATTERN = Pattern.compile(
        "^[\\p{L}\\p{N}_+.-]+@[\\p{L}\\p{N}-]+(\\.[\\p{L}\\p{N}-]+)*$",
        Pattern.CASE_INSENSITIVE
    );

    public static boolean isValidEmail(String email) {
        if (email == null || email.trim().isEmpty()) {
            return false;
        }
        return UNICODE_EMAIL_PATTERN.matcher(email).matches();
    }
}

Quick Regex Breakdown: #

• \p{L}: Matches any Unicode letter (including Cyrillic, Latin, Arabic, etc.)
• \p{N}: Matches any Unicode digit
• _+.-: Allows standard email symbols in the local part (before @)
• The domain section supports Unicode letters/numbers, hyphens, and nested subdomains

Test this with your Russian email (e.g., иван@пример.рф)—it should return true immediately.

2. Handle Internationalized Domain Names (IDNs) (Optional) #

If you only need to fix domain parts like .рф but want to keep using the default pattern for the local part, you can convert the domain to its punycode representation first. Note: This won't help if your local part has Cyrillic characters.

Example code:

import android.webkit.URLUtil;

public static boolean isValidEmailWithIDN(String email) {
    if (email == null || !email.contains("@")) {
        return false;
    }
    String[] emailParts = email.split("@", 2);
    String localPart = emailParts[0];
    String domain = emailParts[1];
    
    // Convert international domain to punycode (ASCII-compatible format)
    String punycodeDomain = URLUtil.toPunycode(domain);
    String asciiConvertedEmail = localPart + "@" + punycodeDomain;
    
    // Use default pattern on the ASCII-converted email
    return android.util.Patterns.EMAIL_ADDRESS.matcher(asciiConvertedEmail).matches();
}

• The custom regex approach is preferred because it handles both Unicode local parts and domains in one go.
• The default EMAIL_ADDRESS pattern is great for ASCII-only emails, but it's outdated for supporting global users.

内容的提问来源于stack exchange，提问作者rabit