SeekBar and media player in android

I have a simple player and recorder. Everything works great but have one problem. I want to add seek bar to see progress in playing record and use this seek bar to set the place from the player should play. I have onProgress but with no effect. This is the code:

package com.example.recorder;

import java.io.IOException;

import android.app.Activity;
import android.media.MediaPlayer;
import android.media.MediaRecorder;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;

public class MainActivity extends Activity implements OnSeekBarChangeListener
{
    private static final String LOG_TAG = "AudioRecordTest";
    private static String mFileName = null;
    private SeekBar seekBar;
    private MediaRecorder mRecorder = null;
    private Button startRecord, startPlaying, stopPlaying;
    private MediaPlayer   mPlayer = null;

    private void onRecord(boolean start) {
        if (start) {
            startRecording();
        } else {
            stopRecording();
        }
    }


    
    private void startPlaying() {
        if(mPlayer != null && mPlayer.isPlaying()){
            mPlayer.pause();
        } else if(mPlayer != null){
            mPlayer.start();
        }else{
        mPlayer = new MediaPlayer();
        try {
            
            mPlayer.setDataSource(mFileName);
            mPlayer.prepare();
            mPlayer.start();
            
        } catch (IOException e) {
            Log.e(LOG_TAG, "prepare() failed");
        }
        }
    
    }

    private void stopPlaying() {
        mPlayer.release();
        mPlayer = null;
        startPlaying.setText("Start playing");
    }

    private void pausePlaying(){
        if(mPlayer.isPlaying()){
            mPlayer.pause();