MediaPlayer配seekbar的問題

小白萌新求救
不知道為什麼seekbar沒有隨著音樂的播放移動,
一直在原地,
懷疑問題出在這句,
可能是因為int progress一直是0

seekbar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
i = progress;
if (fromUser) {
mediaplayer.seekTo(progress);
}
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
});

package com.example.user.lab2_leemingchak;



import android.media.AudioManager;

import android.media.MediaPlayer;

import android.net.Uri;

import android.os.Handler;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.ImageButton;

import android.widget.ProgressBar;

import android.widget.SeekBar;



public class MainActivity extends AppCompatActivity implements MediaPlayer.OnPreparedListener,

        MediaPlayer.OnCompletionListener {

    private MediaPlayer mediaplayer;

    private SeekBar seekbar;

    private Runnable runnable;

    private Handler handble;

    private int i;

    ImageButton playbtn, stopbtn;



    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);



//initialize button UIs

        playbtn = (ImageButton) findViewById(R.id.playBtn);

        stopbtn = (ImageButton) findViewById(R.id.stopBtn);

        seekbar = (SeekBar) findViewById(R.id.seekBar);

//convert String url to Uri format using .parse()

        Uri path = Uri.parse("android.resource://" + //set the music file in res/raw as default

                getPackageName() + "/" + R.raw.enm);

//disable the Play and Stop buttons using .setEnabled()

        playbtn.setEnabled(false);

        stopbtn.setEnabled(false);

//new a MediaPlayer object

        mediaplayer = new MediaPlayer();

//set OnPreparedListener() and OnCompletionListener() to the MediaPlayer object

        mediaplayer.setOnPreparedListener(this);

        mediaplayer.setOnCompletionListener(this);

        seekbar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {

            @Override

            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {

                i = progress;

                if (fromUser) {

                    mediaplayer.seekTo(progress);

                }

            }

            @Override

            public void onStartTrackingTouch(SeekBar seekBar) {

            }

            @Override

            public void onStopTrackingTouch(SeekBar seekBar) {

            }

        });



//prepare and download the audio file, onPrepared() method will be run when ready to play

        try {

            mediaplayer.reset();

            mediaplayer.setDataSource(this, path);

            mediaplayer.setAudioStreamType(AudioManager.STREAM_MUSIC);  //in streaming mode

            mediaplayer.prepareAsync();

        } catch (Exception e) {

            e.printStackTrace();

        }

    }

    // when Play/Pause button is clicked

// check whether the MediaPlayer is playing or not, start playing if not, otherwise, pause the playback

    public void onPlayUrlClick(View view) {

        if (mediaplayer.isPlaying()) {

            mediaplayer.pause();

            playbtn.setEnabled(true);

            stopbtn.setEnabled(true);

            playbtn.setImageResource(R.drawable.play);

        } else {

            mediaplayer.start();

            playbtn.setEnabled(true);

            stopbtn.setEnabled(true);

            playbtn.setImageResource(R.drawable.puase);

        }

    }

    // when Stop button is clicked

    public void onStopClick(View view) {

        mediaplayer.seekTo(0);

        playbtn.setEnabled(true);

        stopbtn.setEnabled(true);

    }

    @Override

    //when the audio file is ready to play

//enable the Play button and disable the Stop button

    public void onPrepared(MediaPlayer mediaplayer) {

        seekbar.setMax(mediaplayer.getDuration());

        changeSeekbar();

        playbtn.setEnabled(true);

        stopbtn.setEnabled(false);

    }



    private void changeSeekbar() {

        seekbar.setProgress(mediaplayer.getCurrentPosition());

        if (mediaplayer.isPlaying()) {

            handble = new Handler();

            runnable = new Runnable() {

                @Override

                public void run() {

                    changeSeekbar();

                }

            };

            handble.postDelayed(runnable, 1000);

        }

    };

    @Override

    //when the audio file plays to the end

    public void onCompletion(MediaPlayer mediaplayer) {

        mediaplayer.seekTo(0);

    }



    public void onbackClick(View view) {

        i = i - 5;

        mediaplayer.seekTo(i);

    }

    public void onskipClick(View view) {

        i = i + 5;

        mediaplayer.seekTo(i);

    }

}