How to return data from multiple echos between two activities?

Question

I am writing an android app that communicates via UART with a sensor device. The device sends data to the phone based on a 4-character ASCII command formatted like so:

":"[char1][char2][Carriage_return] (For example, ":AB\\r")

I have two activities, CalculationActivity and UartActivity.

CalculationActivity needs to get three different sensor readings from UartActivity and perform certain calculations with them. For example,

CalculationActivity:

protected void onCreate(Bundle savedInstanceState){
    // blah, blah, blah...
    Intent i = new Intent(this, UartActivity.class);
    startActivityForResult(i, DATA_REQUEST);
}

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
     if (requestCode == DATA_REQUEST) {
         if (resultCode == RESULT_OK) {
             string sensor_data_distance = data.getStringExtra("distance");
             //need these also:
             //string sensor_data_heading = data.getStringExtra("heading");
             //string sensor_data_elevation = data.getStringExtra("elevation");
             //...
             //parse the strings and perform calculation
             //...
         }
      }
   }
}

UartActivity sends the commands to the device. Upon receiving them, the device echos back the requested data and my RX echo handler catches it. For example,

UartActivity:

protected void onCreate(Bundle savedInstanceState){
    // setup and initialize UART
    String get_distance_command = ":DI\r"; //command for distance
    String get_heading_command = ":HE\r"; //command for heading
    String get_elevation_command = ":EL\r"; //command for elevation

    uartSendData(get_distance_command); //send command to TX handler

    //want to be able to send these other two:
    //uartSendData(get_heading_command);
    //uartSendData(get_elevation_command); 
}

@Override
public synchronized void onDataAvailable(){ //RX echo handler
    //blah, blah, blah...
    //get received bytes
    final String result_string = bytesToText(bytes);
    Intent i = new Intent();
    i.putExtra("distance", result_string);
    //want to be able to do this for the other two:
    //i.putExtra("heading", result_string);
    //i.putExtra("elevation", result_string);
    setResult(UartActivity.RESULT_OK);
    finish();
}

Hopefully, you can infer from the commented out lines of code what I am trying to accomplish here. Note that I am able to successfully get only one reading (distance, in this case), but not more than that (heading and elevation, in this case).

I considered starting the UartActivity three different times with each command but I don't really like that solution. I would rather only run the activity once, send the three commands, catch all of the echo responses, and pass them back to CalculationActivity. Is this even possible?

Answer 1

You are missing returnIntent in setResult.

Try replacing

setResult(UartActivity.RESULT_OK);

with

setResult(UartActivity.RESULT_OK, i);