Is there any possibility to get userDataHeader from android SmsMessage?

Question

Interested in getting few fields (msgCount, refNumber and seqNumber) from userDataHeader in android SmsMessage object. Does anyone know if it's possible?

object structure tree

Answer 1

Those fields are about three levels deep in private/hidden classes. You can get them with reflection, but do you really need to? msgCount will be equal to the length of the PDU array. The PDUs are ordered, so figuring seqNumber for each is trivial. And I can't think of any reason you'd need refNumber, which is used by the internals and the backend to track submission success/failure and to issue status reports.

In any case, the following is a reflective method you can use to confirm this. Note that these values are only relevant to multipart messages. The data header will be null for single-part messages.

private void listMessageConcatRef(SmsMessage msg) {
    try {
        Field msgBaseField = SmsMessage.class.getDeclaredField("mWrappedSmsMessage"); 
        Object msgBase = msgBaseField.get(msg);

        Class<?> msgBaseCls = Class.forName(
            "com.android.internal.telephony.SmsMessageBase");
        Field dataHeaderField = msgBaseCls.getDeclaredField("mUserDataHeader");
        dataHeaderField.setAccessible(true);
        Object dataHeader = dataHeaderField.get(msgBase);

        if (dataHeader == null) {
            Log.d("SmsMessage", "null data header");
            return;
        }

        Class<?> headerCls = Class.forName(
            "com.android.internal.telephony.SmsHeader");
        Field concatRefField = headerCls.getDeclaredField("concatRef");
        Object concatRef = concatRefField.get(dataHeader);

        Class<?> concatRefCls = Class.forName(
            "com.android.internal.telephony.SmsHeader$ConcatRef");
        Field msgCountField = concatRefCls.getDeclaredField("msgCount");
        Field refNumberField = concatRefCls.getDeclaredField("refNumber");
        Field seqNumberField = concatRefCls.getDeclaredField("seqNumber");
        Field isEightBitsField = concatRefCls.getDeclaredField("isEightBits");

        int msgCount = msgCountField.get(concatRef);
        int refNumber = refNumberField.get(concatRef);
        int seqNumber = seqNumberField.get(concatRef);
        boolean isEightBits = isEightBitsField.get(concatRef);

        Log.d("ConcatRef", "msgCount = " + msgCount);
        Log.d("ConcatRef", "refNumber = " + refNumber);
        Log.d("ConcatRef", "seqNumber = " + seqNumber);
        Log.d("ConcatRef", "isEightBits = " + isEightBits);
    }
    catch (ClassNotFoundException | NoSuchFieldException | IllegalAccessException e) {
        e.printStackTrace();
    }
}