Thread: Using FileOutputStream to save array of bytes

Hi, I am having trouble implementing FileOutputStream to save an array of data. In this code, I implement a loop which counts to 9, stores the counter values in a byte array, then writes the array to a text file on an Android device (4.2.2). The code runs and I am able to save a text file on the Android external storage and open it up on the device to view the contents. However I cannot get it to save as numerical numbers. With the code below, I am seeing two symbols of "?" which are inside of a diamond. Every other way I tried it would return a blank document. I seem to be missing something fundamental about how the "write" function of FileOutputStream saves data. If someone can help me with this data handing I would appreciate it, thank you.

 
package com.example.sdcardsavetest;
 
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.concurrent.TimeUnit;
import com.example.sdcardsavetest.R;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
 
 
public class MainActivity extends Activity {
 
	File myExternalFile;
	private String filename = "MySampleFile.txt";
	private String filepath = "MyFileStorage";
	TextView TextView;
	byte[] array = new byte[100];
	byte x = 1;
 
	 @Override
	 public void onCreate(Bundle savedInstanceState) {
	     super.onCreate(savedInstanceState);
	     setContentView(R.layout.activity_main);
	     TextView = (TextView)findViewById(R.id.TextView);
	     Button startButton = (Button)findViewById(R.id.button);
	     Button saveToExternalStorage = (Button) findViewById(R.id.saveExternalStorage);
 
		 if (!isExternalStorageAvailable() || isExternalStorageReadOnly()) {  
			   saveToExternalStorage.setEnabled(false);
			  } 
			  else {
			   myExternalFile = new File(getExternalFilesDir(filepath), filename);
			  }
 
		 saveToExternalStorage.setOnClickListener(new View.OnClickListener() {
			 @Override
	         public void onClick(View v) {
				 try{
					FileOutputStream fos = new FileOutputStream(myExternalFile);
					System.out.println(array);//debugging
				        fos.write(array);
				        fos.close();
 
				 }
				    catch (IOException ex) { }
				 }
		 	 });	 
 
		 startButton.setOnClickListener(new View.OnClickListener() {
	         @Override
	         public void onClick(View v) {
	             loop();
	         }
	     });
	 }
 
	 private static boolean isExternalStorageReadOnly() {  
		  String extStorageState = Environment.getExternalStorageState();  
		  if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(extStorageState)) {  
		   return true;  
		  }  
		  return false;  
		 }  
 
		 private static boolean isExternalStorageAvailable() {  
		  String extStorageState = Environment.getExternalStorageState();  
		  if (Environment.MEDIA_MOUNTED.equals(extStorageState)) {  
		   return true;  
		  }  
		  return false;  
 		 } 
 
void loop(){
 
	runOnUiThread(new Thread(new Runnable(){
 
     public void run(){
 
    	 for (byte i = 1; i < 10; i++){
    		array [x] = i;
			TextView.setText(String.valueOf(i));
			x++;
 
			try {
          	  TimeUnit.MILLISECONDS.sleep(1000); 
		          	} 	
                   catch (InterruptedException ie) {}
 
			  }
     	   }
       }));
	} 
}

I am seeing two symbols of "?" which are inside of a diamond

It is unclear, at least to me, how you 'see' the file contents. Do you display the file contents elsewhere? How are you reading the file? How do you know this is a writing problem rather than a reading problem?

The data is being saved as binary - try writing in text form (eg convert the byte to a String). As suggested in the API for FileOutputStream:

FileOutputStream is meant for writing streams of raw bytes such as image data. For writing streams of characters, consider using FileWriter.

[B@41449958

That is the String returned by the byte array's toString() method.
To write the contents of the array use: fos.write(array);

FileOutputStream is meant for writing streams of raw bytes

You should use a different class and method to write text.

For testing: write a small simple program that will compile and execute on the desk top and that can be posted here to show what you are trying to do. Testing Android code is too cumbersome.

The Writer classes like FileWriter and OutputStreamWriter might work.

fos.write(array.toString().getBytes());

As norm pointed out, using the toString() method of array will use the default toString() method - see Object (Java Platform SE 7 )
Loop over the array and write each value as a String using the appropriate writer class that is meant for text