将字节转换为单个int Android

Question

I am implementing a Bluetooth Android application, where Image is sent from one device to another. The bitmap's byte array is sent and successfully reconstructed at the receiver end. However, I need to send a single integer value together with the bitmap as an index(so the receiver knows what to do with the received bitmap). So basically I want to send this in a byte stream:

int|bitmap

Since I need to transfer an int up to 27, that means it fits into a single byte, right? My current code looks like this:

ba[0] = Integer.valueOf(drawableNumber).byteValue(); //drawableNumber value is between 1 and 27
 ByteArrayOutputStream bs = new ByteArrayOutputStream();  //create new output stream
 try {
     bs.write(ba);         //bytes of the integer
     bs.write(bitmapdata); //bytes of the bitmap
     bs.toByteArray()      // put everything into byte array
}

 mChatService.write(bs.toByteArray()); // that is where bytes are sent to another device

And at the receiver end:

 case MESSAGE_READ:
    readBuf = (byte[]) msg.obj;  // readBuf contains ALL the received bytes using .read method

So my question is, how can I reconstruct the integer and the image I have sent(basically a single byte to a single integer)? I manage to reconstruct the bitmap alone, but I need this additional integer value to know what to do with the received image. The integer value will always be between 0 and 27. I have checked all other answers, but could not find a proper solution..

EDIT: Main question is how to separate the integer bytes from the bitmap bytes in the byte array. Because at the receiving end I want to reconstruct the sent integer AND the bitmap separately

Answer 1

When I try this in java, it simply tells me what my mind was thinking when I commented. An integer is represented as a byte (so in your case, it is simply ba[0]). Or it should be based on your code. Any more than that and it would be a long. That means it is also the first byte that will get read out of your buffer (or should be).

import java.io.ByteArrayOutputStream;


public class TestClass {
    public static void main(String args[]){
        byte[] ba = new byte[10];
        int myInt = 13;
        ByteArrayOutputStream bs = new ByteArrayOutputStream();  //create new output stream

        try {
           bs.write(myInt);         //bytes of the integer
           ba = bs.toByteArray();      // put everything into byte array
        } finally{};

        for(int i = 0; i < ba.length; i++){
          System.out.println(i);
          System.out.println(ba[i]);
        }
    }
}

Again I realize this isn't exactly an answer, just too much for a comment.

Answer 2

由于将字节转换为int是一种低估，因此您只需将字节分配给int变量即可。

int myInt = ba[0];