Android: How to store data on internal memory?

Question

It's perfectly described here how to do it, the only problem: He doesnt know the function openFileOutput();

private void saveSettingsFile() {
          String FILENAME = "settings";
          String string = "hello world!";

          FileOutputStream fos = openFileOutput(FILENAME, Context.MODE_PRIVATE); //openFileOutput underlined red
          try {
            fos.write(string.getBytes());
            fos.close();
          } catch (IOException e) {
            Log.e("Controller", e.getMessage() + e.getLocalizedMessage() + e.getCause());
          }
}

Those are the relevant packages I imported:

import java.io.FileOutputStream;
import java.io.IOException;
import android.content.Context;

Infective

Can you share logcat error output? – Jaffe

I just noticed that "openFileOutput" is underlined red. Eclipse asked me to create a so-named method in my class, which I accidently did. Now I removed this method stub and "openFileOutput" is underlined red again. – Infective

@Konstantin: Its more a logical problem than. So logcat doesnt help yet. Right know I cant even compile it. – Infective

So extend context of the code, can you post whole method? – Jaffe

I extended it above. It's just a method of my classe. For my opionion this should work with just those 5 lines of code (according to the link) – Infective

See ALL comments at the answer below – Infective

Answer 1

Have a look at this example of using a FileOutputStrem from the Examples on dev.android.com. It should give you an idea of how to use it correctly.

Poussin

Thank u. I will look into it. however, I still would prefer to get this 5 lines working. I mean the author of the document I referred to above cant be fundamentally wrong. – Infective

you need to call openFileOutput on a context. Try context.openFileOutput() – Poussin

Ok, good suggestion. However I dont have the variable or object "context". How do I create or get it? – Infective

Your context is your Activity. If this code is in a View then all views are created with a context as an argument. If this code is in another class you'll have to pass in the context as an argument as you would with a View. – Poussin

In which class the method is placed? The openFileOutput should be invoked on Context instance (i.e. activity). – Jaffe

@Konstantin Yup, exactly what I just said. – Poussin

It's a class whose instance can be called from everywhere by its static function Controller.getInstance(). That's the singleton way of providing classes, I guess. This class provides data like the session, user data and so on. These stuff needs to be present in all activities. – Infective

It's like a model for all activities through the lifetime of this app. Shall I pass the context of any Activity in its onCreate()-Method to my Controller? Doesnt that cause nasty Bugs by Threading and so on? – Infective

@Infective Then you need to pass in a context instance in the method and invoke openFileInput on the instance. – Jaffe

Do I have to update this reference in the controller when intenting a new activity? In my case activities dont request directly the controller to load this settings file. Model classes do that. – Infective

Well you can reference application context in the controller, just pass it into getInstance method. To obtain application context you have to invoke getApplicationContext on activity. – Jaffe

One more question: Is it enough to pass "getApplicationContext()" to my Controller only while creating my 1st activity? Is that passed by reference? So, is that just a pointer to the application context? – Infective

Answer 2

Class within which this method is declared, is defined as "Static". thats why it is throwing error. Remove static from the class definition and bingo...

Anissaanita

Answer 3

Just add a "try catch" block and put them in between this.

Like this:

    private void saveSettingsFile(String FILENAME, String data) {

    FileOutputStream fos;
    try {
        fos = openFileOutput(FILENAME, Context.MODE_PRIVATE);
        fos.write(data.getBytes());
        fos.close();
    } catch (FileNotFoundException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    } // openFileOutput underlined red
    catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

When there is red line under the line.. First check that the line is under the full sentense or only right side of the sentense .(i.e after equal sign).

If it covers the whole line, then it has to fix some bugs..

Or if it under only the right side of the sentense ...Then it must wants some exception handling things.

If you don't know what type of exception it may generate...
Dont fear , just write all the code in a try block( try{ } ) and then add a catch and pass a Exception object inside catch .. Now its fine..

Like this :

  try
  {
    ...........your code
    ......
  } 
   catch(Exception e)
  {
   e.printstacktrace();

  }

Now all are fine.

Thank you

Wig

Answer 4

openFileOutput is a method of Context object. And don't forget to add finally clause to close the stream. Bellow is an example (a bit clumsy because of Java 6 because of Android).

String data = "Hello";
FileOutputStream fos = null;
try {
    fos = mContext.openFileOutput(FILENAME, Context.MODE_PRIVATE);
    fos.write(data.getBytes(Charset.defaultCharset()));
} catch (IOException e) {
    e.printStackTrace();
} finally {
    if (fos != null) {
        try {
            fos.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

mContext variable should be defined somewhere above and initialized like mContext = getApplicationContext() if you are inside of an activity

Tephra