title: Displaying a double (frequency) that is updated constantly while recording with Android
body: <p>I am building an android application that displays the Frequency of a sustained note with the FFT algorithm. I am using Jtransform methods. My issue currently is that I can't display the frequency on screen. The following code is the fft freqency calculation and the AsynchTask which should display the frequency in a text box</p>
  
  <pre class="lang-java prettyprint-override"><code>import edu.emory.mathcs.jtransforms.fft.DoubleFFT_1D;
  
  public class Tuning extends Activity implements OnClickListener{
  
      int audioSource = MediaRecorder.AudioSource.MIC;    // Audio source is the device mic
      int channelConfig = AudioFormat.CHANNEL_IN_MONO;    // Recording in mono
      int audioEncoding = AudioFormat.ENCODING_PCM_16BIT; // Records in 16bit
  
  
      private DoubleFFT_1D fft;                           // The fft double array
      int blockSize = 1024;                               // deal with this many samples at a time
      int sampleRate = 44100;                             // Sample rate in Hz
      public double frequency = 0.0;                      // the frequency given
  
      RecordAudio recordTask;                             // Creates a Record Audio command
      TextView tv;                                        // Creates a text view for the frequency
  
  
      // On Start Up
      @Override
      public void onCreate(Bundle savedInstanceState){
          super.onCreate(savedInstanceState);
          setContentView(R.layout.tuning);
  
          tv = (TextView) findViewById(R.id.lbl1);
  
      }
  
  
      // The Record and analysis class
      private class RecordAudio extends AsyncTask&lt;Void, Double, Void&gt;{
      @Override
      protected Void doInBackground(Void... params){      
  
          /*Calculates the fft and frequency of the input*/
          try{
              int bufferSize = AudioRecord.getMinBufferSize(sampleRate, channelConfig, audioEncoding);                // Gets the minimum buffer needed
              AudioRecord audioRecord = new AudioRecord(audioSource, sampleRate, channelConfig, audioEncoding, bufferSize);   // The RAW PCM sample recording
  
              short[] buffer = new short[blockSize];          // Save the raw PCM samples as short bytes
              double[] audioDataDoubles = new double[(blockSize*2)]; // Same values as above, as doubles
  
              double[] re = new double[blockSize];
              double[] im = new double[blockSize];
              double[] magnitude = new double[blockSize];
  
              audioRecord.startRecording();                   // Start working
  
              fft = new DoubleFFT_1D(blockSize);
  
              while(started){
                  /* Reads the data from the microphone. it takes in data 
                   * to the size of the window "blockSize". The data is then
                   * given in to audioRecord. The int returned is the number
                   * of bytes that were read*/
  
                  int bufferReadResult = audioRecord.read(buffer, 0, blockSize);
  
                  // Read in the data from the mic to the array
                  for(int i = 0; i &lt; blockSize &amp;&amp; i &lt; bufferReadResult; i++) {
  
                      /* dividing the short by 32768.0 gives us the 
                       * result in a range -1.0 to 1.0.
                       * Data for the compextForward is given back 
                       * as two numbers in sequence. Therefore audioDataDoubles
                       * needs to be twice as large*/
  
                      audioDataDoubles[2*i] = (double) buffer[i]/32768.0; // signed 16 bit
                      audioDataDoubles[(2*i)+1] = 0.0;
                  }
  
                  //audiodataDoubles now holds data to work with
                  fft.complexForward(audioDataDoubles);
  
                  // Calculate the Real and imaginary and Magnitude.
                  for(int i = 0; i &lt; blockSize; i++){
                      // real is stored in first part of array
                      re[i] = audioDataDoubles[i*2];
                      // imaginary is stored in the sequential part
                      im[i] = audioDataDoubles[(i*2)+1];
                      // magnitude is calculated by the square root of (imaginary^2 + real^2)
                      magnitude[i] = Math.sqrt((re[i] * re[i]) + (im[i]*im[i]));
                  }
  
                  double peak = -1.0;
                  // Get the largest magnitude peak
                  for(int i = 0; i &lt; blockSize; i++){
                      if(peak &lt; magnitude[i])
                          peak = magnitude[i];
                  }
                  // calculated the frequency
                  frequency = (sampleRate * peak)/blockSize;
  
                  /* calls onProgressUpdate
                   * publishes the frequency
                   */
                  publishProgress(frequency);
              }
  
          } catch(Throwable t){
              Log.e("AudioRecord", "Recording Failed");
          }
          return null;
      }
  
  
      // This should display the Frequency
      protected void onProgressUpdate(Double value){
  
          //print the frequency 
          setContentView(R.layout.tuning);
          String info = Double.toString(value);
  
          //TextView doubleView = (TextView) findViewById(R.id.DoubleView);
          tv.setText(info);
      }
  
      // For the click of the button
     public void onClick(View v){
         if(started){
             started = false;
             startStopButton.setText("Start");
             recordTask.cancel(true);
         } else {
             started = true;
             startStopButton.setText("Stop");
             recordTask = new RecordAudio();
             recordTask.execute();
         }
     }
  </code></pre>
  
  <p>I have checked other similar questions and I can't find the fault in my code.</p>
  
  <p><strong>EDIT</strong>: added <code>onClick()</code> to code. I know that the frequency is being calculated, and according to Eclipse, at no point is the <code>onProgressUpdate()</code> being called.</p>