为什么我从音频记录的输出中得到的只有零？

我想使用AudioTrack播放声音，并同时使用AudioRecord进行录制。但是我什么也得不到，除了零。为什么？

我试图从byte[]缓冲区读取数据，但得到的全部为零。这是我的代码：

import java.io.BufferedOutputStream;
import java.io.DataOutputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.sql.Time;
import java.util.Timer;
import java.util.TimerTask;

import android.media.AudioFormat;
import android.media.AudioRecord;
import android.media.MediaRecorder;

public class RecordThread implements Runnable {

private static final int Encording = AudioFormat.ENCODING_PCM_16BIT; //Data size for each frame = 16 bytes
private static final int Sample_rate = 8000;                         //Sample rate = 8000 HZ
private static final int Channel = AudioFormat.CHANNEL_IN_MONO;      //Set as single track
public static final int Buffersize = AudioRecord.getMinBufferSize(Sample_rate, Channel, Encording); //Buffer size
@Override
public void run() {
    // TODO Auto-generated method stub

    AudioRecord audioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC,Sample_rate, Channel, Encording, Buffersize);
    while(MessageUsed.RecordPermit){
    try {
        FileOutputStream ops = new FileOutputStream(TestoOFDMMain.file2);
        BufferedOutputStream bos = new BufferedOutputStream(ops);
        DataOutputStream dos = new DataOutputStream(bos);

        byte[] buffer = new byte[Buffersize]; 


            audioRecord.startRecording();   //Start Recording
            int bufferReadResult = audioRecord.read(buffer, 0, buffer.length);  //Read Array size
            MessageUsed.RecordStop = false;
            /*Write Data to file*/
            for(int i=0;i<bufferReadResult;i++){
                dos.write(buffer[i]);
            System.out.println(buffer[i]);  
                if(MessageUsed.ProcessPermit == true){
                        break;
                    }
                }

        audioRecord.stop();
        dos.close();
        MessageUsed.RecordStop = true;
        Thread.sleep(300);
        MessageUsed.ProcessStart = true;

        Thread.sleep(900);

    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    }
}
}