TextView.setText not working inside for loop

Question

public void bytesToHex(byte[] in) {
    final StringBuilder builder = new StringBuilder();
    int count=0;
    final int BATCHSIZE=20;
    sendingData = true;
    Log.d("byteToHex", "sendingData = true, start sending data.");
    sendSerial("w"); //write command
    Log.d("byteToHex", "sending w");
    for(byte b : in) {
        //mBluetoothGatt.setCharacteristicNotification(characteristicRX, enabled);
        //byte[] a = mBluetoothGatt.readCharacteristic(characteristicRX);
        while(!newData){
            if(resendData == true){//resends previously sent string
                sendSerial(sendByte);
                Log.d("byteToHex", "resendData = true, resending: " + sendByte);
                resendData = false; //reset resendData flag
            }
        } //wait for next w from mcu

        builder.append(String.format("%02x", b));

        if(builder.length()== BATCHSIZE ){
            sendByte= builder.toString();


            sendSerial(sendByte);
            newData = false;

            Log.d("byteToHex", "newData = false");

            count+=BATCHSIZE;
            Log.d("byteToHex", "Sent " + count/2 + " bytes");
            textViewFileProgress.setText(count/2 + "/" + fileLength); //<- THIS SETTEXT DOES NOT WORK
            builder.setLength(0); //reset the string builder
        }



    } //for(byte b : in)

    //send remaining bytes
    sendByte= builder.toString();
    sendSerial(sendByte);
    newData = false;
    Log.d("byteToHex", "newData = false");
    count+=builder.length();
    Log.d("byteToHex", "Sent " + count/2 + " byte");
    textViewFileProgress.setText(count/2 + "/" + fileLength);//<- THIS SETTEXT WORKS
    builder.setLength(0); //reset the string builder


    sentTerminator = true; //flag to tell BLE service to check if terminator is received on mcu
    sendSerial("||"); //terminating command, tell teensy last hex has been sent
    while(sentTerminator == true){ //while terminator not yet received
        if(resendTerminator == true){ //
            sendSerial("||");
            Log.d("byteToHex", "resending terminator");
            resendTerminator = false; //Resend complete. reset resendTerminator flag.
        }
    }
    sendingData = false;
    //return builder.toString();
}//public void bytesToHex(byte[] in)

I am trying to set the text to my textview to display the current number of bytes sent.

Somehow, i have 2 of the exact same setText code in my function. textViewFileProgress.setText(count/2 + "/" + fileLength);

one of them is inside a for loop, which does not work.

the other is outside the for loop, which works.

I am sure the program ran that code, as I am able to see the debug messages before it in Android monitor.

Any idea what is the problem?

Answer 1

Try this .

Log.e("TAG",builder.length()+"");
if(builder.length()== BATCHSIZE ){
        sendByte= builder.toString();

        sendSerial(sendByte);
        newData = false;
        Log.d("byteToHex", "newData = false");

        count+=BATCHSIZE;
        Log.d("byteToHex", "Sent " + count/2 + " bytes");
        textViewFileProgress.setText(count/2 + "/" + fileLength); //<- THIS SETTEXT DOES NOT WORK
        builder.setLength(0); //reset the string builder
} else {
        Log.e("TAG","length != 20");
}

And you can see the Logcat info

Answer 2

Consider this simple code. You implement your for loop in another background thread then set the text in main thread using onPostExecute() Note that onPostExecute() run in the main thread while doInBackground() run in the background thread so you cannot set the text in doInBackground()

public void outSideFunction()
{
  //pass a string to doInBackground()
  new TextSetterTask.execute("");


}
//implement an inner class
private class TextSetterTask extends AsyncTask<String,Void,String>
{
   @Override
   protected String doInBackground(String... params)
   {
     //loop
      return //the string you want to set the text
     //if the background thread is done it will call the onPostExecute
   }
   @Override
   protected void onPostExecute(String result)
   {
     //set the text
   }



}