Question

I have an application that uses the bluetooth to receive some data (bytes) from other device. everything is going well, but I have a small issue on receiving the bytes all together. After receiving the bytes I show them on a Toast just to test them. When the other device sends 10 bytes together (for example: “ABCDEFGHIJ”), the program will take the first byte “A” only and show it on a Toast, then go to the second iteration and read the other 9 bytes and show “BCDEFGHIJ” on the Toast. Here is my code:

byte[] buffer = new byte[1024]; // Read 1K character at a time.
int bytes = 0; // Number of bytes.

while(true)
{
    try
    {
        // Read from the InputStream.
        bytes = bInStream.read(buffer);

        // Send the obtained bytes to the MainActivity.
        mainActivityHandler.obtainMessage(MainActivity.MESSAGE_READ, bytes, -1, buffer).sendToTarget();
    }
    catch(IOException e)
    {
        connectionLost();
        break;
    }
}

In the MainActivity, I have:

// The Handler that gets information back from the BluetoothManager.
private final Handler handler = new Handler()
{
    @Override
    public void handleMessage(Message msg)
    {
        switch(msg.what)
        {
            case MESSAGE_READ:
                byte[] readBuf = (byte[]) msg.obj;

                // construct a string from the valid bytes in the buffer.
                String readMessage = new String(readBuf, 0, msg.arg1);
                Toast.makeText(MainActivity.this, readMessage, Toast.LENGTH_SHORT).show();
                break;

            // ...
        }
    }
};

How can I receive all the bytes together?!

Answer 1

Mmm most likely the culprit is in the way you’re sending the messages. Your receive has no problems, it will receive as many bytes (up to your 1024) as it is written to.

If you have no control over the way the messages are sent you can probably read one byte at a time and then send a handler message you when you hit a predefined terminator. Ex: “ABCDEFGHIJ#” where # is the terminator.

String msg = "";
byte ch;
while((ch=mInStream.read())!='#') {
    bytes++;
    msg+=ch;
}