dos.writeを使用したNullPointerException

Question

このコードは、ファイルを記録し、オーディオファイルから一連の値を返すように記述されているため、信号処理を行うことができます。 私は底部に向かって、この行にnullポインタ例外を取得しておいてください。

dos.write(buffer, 0, bufferSize); 

誰かが間違っているかを説明することができ、私は変更すべきか？

package com.example.wesle.noisemachine; 

import android.content.Intent; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.view.View; 
import android.widget.Button; 
import android.media.MediaPlayer; 
import android.media.MediaRecorder; 
import android.os.Environment; 
import android.widget.Toast; 

import java.io.DataOutputStream; 
import java.io.File; 
import java.io.FileInputStream; 
import java.io.FileNotFoundException; 
import java.io.IOException; 

public class ReceiveScreen extends AppCompatActivity { 

    private Button buttonStart, buttonStop, buttonPlay, buttonDecode; 
    private MediaRecorder mediaRecorder = new MediaRecorder(); 
    private String outputFile; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_receive_screen); 

     buttonStart = (Button) findViewById(R.id.buttonStart); 
     buttonStop = (Button) findViewById(R.id.buttonStop); 
     buttonPlay = (Button) findViewById(R.id.buttonPlay); 
     buttonDecode = (Button) findViewById(R.id.buttonDecode); 
     buttonStop.setEnabled(false); 
     buttonPlay.setEnabled(false); 
     outputFile = Environment.getExternalStorageDirectory().getAbsolutePath() + "/recording.3gp"; 
     mediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC); 
     mediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP); 
     mediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB); 
     mediaRecorder.setOutputFile(outputFile); 

     buttonStart.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       try { 
        mediaRecorder.prepare(); 
        mediaRecorder.start(); 
       } catch (IllegalStateException ise) { 
        System.out.println("ISE Catch"); 
       } catch (IOException ioe) { 
        System.out.println("IO Catch"); 

       } 
       buttonStart.setEnabled(false); 
       buttonStop.setEnabled(true); 


       Toast.makeText(getApplicationContext(), "Recording started", Toast.LENGTH_LONG).show(); 


      } 
     }); 

     buttonStop.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 

       mediaRecorder.stop(); 
       mediaRecorder.release(); 

       buttonStop.setEnabled(false); 
       buttonPlay.setEnabled(true); 
       buttonStart.setEnabled(true); 

       Toast.makeText(getApplicationContext(), "Recording Completed", Toast.LENGTH_LONG).show(); 
      } 
     }); 

     buttonPlay.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       MediaPlayer mediaPlayer = new MediaPlayer(); 

       try { 
        mediaPlayer.setDataSource(outputFile); 
        mediaPlayer.prepare(); 
        mediaPlayer.start(); 
       } catch (Exception e) { 
        System.out.println("E Catch"); 
       } 
       Toast.makeText(getApplicationContext(), "Recording Playing", Toast.LENGTH_LONG).show(); 
      } 
     }); 

     buttonDecode.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       //System.out.println(readFile("recording.3gp")); 
       Toast.makeText(getApplicationContext(), "Decoding", Toast.LENGTH_LONG).show(); 


       //initializes variables 
       File file = new File(outputFile); 
       FileInputStream fileInputStream = null; 
       try { 
        fileInputStream = new FileInputStream(file); 
       } catch (FileNotFoundException e) { 
        e.printStackTrace(); 
       } 
       int bytesRead = 0; 
       int bufferSize = 0; 
       int bytesAvailable = 0; 
       byte[] buffer; 
       int maxBufferSize = 1*1024*1024; 
       DataOutputStream dos = null; 


       // create a buffer of maximum size 
       try { 
        bytesAvailable = fileInputStream.available(); 
       } catch (IOException e) { 
        e.printStackTrace(); 
       } 
       bufferSize = Math.min(bytesAvailable, maxBufferSize); 
       buffer = new byte[bufferSize]; 

       // read file and write it into form... 
       try { 
        bytesRead = fileInputStream.read(buffer, 0, bufferSize); 
       } catch (IOException e) { 
        e.printStackTrace(); 
       } 
       try{ 
        while (bytesRead > 0){ 
        dos.write(buffer, 0, bufferSize); //<<<<<<<HERE 
        bytesAvailable = fileInputStream.available(); 
        bufferSize = Math.min(bytesAvailable, maxBufferSize); 
        try { 
         bytesRead = fileInputStream.read(buffer, 0, bufferSize); 
        } catch (IOException e) { 
         e.printStackTrace(); 
        } 
        } 
       fileInputStream.close(); 
       } catch (IOException e) { 
        e.printStackTrace(); 
       } 

      } 
     }); 

     //Code for the back button 
     Button backbuttonR = (Button) findViewById(R.id.backbuttonR); 
     backbuttonR.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       startActivity(new Intent(ReceiveScreen.this, MainActivity.class)); 
      } 
     }); 
    } 
} 

Answer 1

あなたDataOutputStream dosは

buttonDecode.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 

方法で初期化されることはありません。 NullPointerExceptionを避けるために、この変数を初期化してください。