Question

I used following method to write data to a file in one android application

 private void writeFileToInternalStorage() {

    String eol = System.getProperty("line.separator");
    BufferedWriter writer = null;

 try{
    writer = new BufferedWriter(new OutputStreamWriter(openFileOutput("myFile.txt", MODE_WORLD_WRITEABLE|MODE_WORLD_READABLE)));
      writer.write("Hello world!");
    } 
    catch (Exception e) 
    {
        e.printStackTrace();
    } 
    finally 
    {
      if (writer != null) 
      {
        try 
        {
            writer.close();
        } 
        catch (IOException e) 
        {
            e.printStackTrace();
        }
      }
    }
}

Then I tried to read that file from another android application using this method

 private void readFileFromInternalStorage(){
    String eol = System.getProperty("line.separator");
    BufferedReader input = null;
    try 
    {
        input = new BufferedReader(new InputStreamReader(openFileInput("myFile1.txt")));
         String line;
        StringBuffer buffer = new StringBuffer();
        while ((line = input.readLine()) != null) 
        {
            buffer.append(line + eol);


        }

       TextView tv = (TextView) findViewById(R.id.textView);  
        tv.setText(buffer.toString().trim());

    } 
    catch (Exception e) 
    {
        e.printStackTrace();
    } 
    finally 
    {
        if (input != null) 
        {
            try 
            {
                input.close();
            } 
            catch (IOException e) 
            {
                e.printStackTrace();
            }
        }
    }
}

Second method can’t read the file. I added read write permissions also, but it shows only blank screen. What can be the error and how can I correct that ??. I’m new to Android programming and need your help.

Thanks!

Answer 1

The problem is

openFileOutput("myFile.txt", MODE_WORLD_WRITEABLE|MODE_WORLD_READABLE))

The documentation says:

This file is written to a path relative to your app within the

So the case is you are writing file in path relative to application 1 and trying to read it from
path relative to application 2.

You should be able to call Environment.getExternalStorageDirectory() to get the root path to the SD card and use that to create a FileOutputStream. From there, just use the standard java.io routines.

Look below snippet to write file to SD card.

private void writeToSDCard() {


try
        {
            File file = new File(Environment.getExternalStorageDirectory(),
                    "filename");
            BufferedWriter writer = new BufferedWriter(new FileWriter(file));
            writer.write("Hello World");
            writer.close();
        } catch (IOException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
}

Look below snippet to read file saved on SD card.

private void readFileFromSDCard() {
    File directory = Environment.getExternalStorageDirectory();
    // Assumes that a file article.rss is available on the SD card
    File file = new File(directory + "/article.rss");
    if (!file.exists()) {
        throw new RuntimeException("File not found");
    }
    Log.e("Testing", "Starting to read");
    BufferedReader reader = null;
    try {
        reader = new BufferedReader(new FileReader(file));
        StringBuilder builder = new StringBuilder();
        String line;
        while ((line = reader.readLine()) != null) {
            builder.append(line);
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        if (reader != null) {
            try {
                reader.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}