Android 小技巧总结

JNI技巧

char*转jbyteArray

jbyteArray getByteArray(JNIEnv *env,const char* buf, int len){

    jbyteArray byteArray = env->NewByteArray(len);
    jbyte* bytes = ( jbyte* )buf;

    env->SetByteArrayRegion(byteArray, 0, len, bytes);
    free((void *)buf);
    return byteArray;
}

jstring转string

string getString(JNIEnv *env, jstring javaString){
    const char *str = env->GetStringUTFChars(javaString, JNI_FALSE);
    string ret = string(str);
    env->ReleaseStringUTFChars(javaString, str);
    return ret;
}

char*, string转jstring

jstring Tools::getJString(JNIEnv *env, string str){
    return getJString(env, str.c_str(), str.length());
}

jstring Tools::getJString(JNIEnv *env, const char *buf, int len){
    return env->NewStringUTF(buf);
}

Java技巧

byte[]转16进制字符串

public static String toHex(byte[] buf) {
        if (buf == null)
            return "";
        StringBuffer result = new StringBuffer(2*buf.length);
        for (int i = 0; i < buf.length; i++) {
            appendHex(result, buf[i]);
        }
        return result.toString();
}

private final static String HEX = "0123456789ABCDEF";
private static void appendHex(StringBuffer sb, byte b) {
    sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));
}

16进制字符串转byte[]

public static byte[] toByte(String hexString) {
    int len = hexString.length()/2;
    byte[] result = new byte[len];
    for (int i = 0; i < len; i++)
        result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue();
    return result;
}