Get the frequency of an audio file in every 1/4 seconds in android

I have a sound file (.3gp) and its about ~1 min. I would like to get the frequency of this sound file in every 1/4 seconds. My idea is to receive samples in every 1/4 seconds from the audio file and using FFT I might get the frequency values. Is there any way to do this?

Actually I would split the sound file into 1/4sec samples sound files (alwyas overwriting the preveious one), then using FFT algorithm and detect the frequency where the magintude is the bigggest. But there might be easier solutions however I dont have a clue how to do this either.

***UPDATE 2 - new code

I use this code so far:

public class RecordAudio extends AsyncTask<Void, double[], Void> {

    @Override
    protected Void doInBackground(Void... arg0) {

        try {
             int bufferSize = AudioRecord.getMinBufferSize(frequency,
             AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT);


            //int bufferSize = AudioRecord.getMinBufferSize(frequency, 
                  //  channelConfiguration, audioEncoding); 

            AudioRecord audioRecord = new AudioRecord( 
                    MediaRecorder.AudioSource.MIC, frequency, 
                    channelConfiguration, audioEncoding, bufferSize); 

            short[] buffer = new short[blockSize];
            //double[] toTransform = new double[blockSize];


            audioRecord.startRecording();


            // started = true; hopes this should true before calling
            // following while loop

            while (started) {
               sampling++;

               double[] re = new double[blockSize];
               double[] im = new double[blockSize];

               double[] newArray = new double[blockSize*2];
               double[] magns = new double[blockSize];

               double MaxMagn=0;
               double pitch = 0;

               int bufferReadResult = audioRecord.read(buffer, 0,
                        blockSize);


               for (int i = 0; i < blockSize && i < bufferReadResult; i++) {
                   re[i] = (double) buffer[i] / 32768.0; // signed   16bit
                   im[i] = 0;
               }    

               newArray = FFTbase.fft(re, im,true);

               for (int i = 0; i < newArray.length; i+=2) {

                   re[i/2]=newArray[i];
                   im[i/2]=newArray[i+1];
                   magns[i/2] = Math.sqrt(re[i/2]*re[i/2]+im[i/2]*im[i/2]);
               }

              // I only need the first half      

              for (int i = 0; i < (magns.length)/2; i++) {
                   if (magns[i]>MaxMagn)
                   {
                       MaxMagn = magns[i];
                       pitch=i;
                   }
               }                                           
                 if (sampling > 50) {
                   Log.i("pitch and magnitude", "" + MaxMagn + "   " + pitch*15.625f);
                   sampling=0;
                   MaxMagn=0;pitch=0;
                   }                   


            }

            audioRecord.stop();

        } catch (Throwable t) {
            t.printStackTrace();
            Log.e("AudioRecord", "Recording Failed");
        }
        return null;
    }

I use this: http://www.wikijava.org/wiki/The_Fast_Fourier_Transform_in_Java_%28part_1%29

Guitar strings seem correct, but my own sound is not good because of this:

The magnitude of the two peaks change most of the time and I always find the biggest to get the fundamental frequency.