Google play商店应用内计费

Question

我意识到每次应用程序运行时都没有必要检查谷歌play商店，尤其是如果购买已经准备好了。如果用户在使用应用程序时没有GPRS/WiFi，这也可能会导致问题！

因此，我在考虑创建一个共享偏好，它将作为检查用户是否购买了应用内购买的条件。

还有其他更安全的方法吗？正如我所读到的，共享首选项可以很容易地改变。

Answer 1

您可以使用ProGuard。

或者，您可以在共享首选项或数据库中使用一些加密文本以安全的方式保存购买状态。所以更难操纵它。

加密示例：

 MCrypt mcrypt = new MCrypt();
 String encrypted = MCrypt.bytesToHex(mcrypt.encrypt("Text to Encrypt"));

MCrypt mcrypt = new MCrypt();
String decrypted = new String(mcrypt.decrypt(encrypted));

public class MCrypt {

    private String iv = "fedcba9876543210";//Dummy iv (CHANGE IT!)
    private IvParameterSpec ivspec;
    private SecretKeySpec keyspec;
    private Cipher cipher;
    private String SecretKey = "0123456789abcdef";//Dummy secretKey (CHANGE IT!)

    public MCrypt() {
        ivspec = new IvParameterSpec(iv.getBytes());

        keyspec = new SecretKeySpec(SecretKey.getBytes(), "AES");

        try {
            cipher = Cipher.getInstance("AES/CBC/NoPadding");
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (NoSuchPaddingException e) {
            e.printStackTrace();
        }
    }

    public byte[] encrypt(String text) throws Exception {
        if (text == null || text.length() == 0) throw new Exception("Empty string");

        byte[] encrypted = null;

        cipher.init(Cipher.ENCRYPT_MODE, keyspec, ivspec);

        encrypted = cipher.doFinal(padString(text).getBytes());
        try { 
            encrypted = android.util.Base64.encode(encrypted, android.util.Base64.NO_PADDING);
        } catch (NoClassDefFoundError e) {
        }

        return encrypted;
    }

    public byte[] decrypt(String code) throws Exception {
        if (code == null || code.length() == 0) throw new Exception("Empty string");

        byte[] decrypted = null;

        cipher.init(Cipher.DECRYPT_MODE, keyspec, ivspec);

        try { 
            decrypted = cipher.doFinal(android.util.Base64.decode(code, android.util.Base64.NO_PADDING));
        } catch (NoClassDefFoundError e) {
        }
        return decrypted;
    }



    private static String padString(String source) {
        char paddingChar = ' ';
        int size = 16;
        int x = source.length() % size;
        int padLength = size - x;

        for (int i = 0; i < padLength; i++) {
            source += paddingChar;
        }

        return source;
    }
}