Read write SD-card List

Question

I´ve been googling, I´ve looked at StackOverflow and see a lot of examples, but I can´t really get a hold of it. I´m new to android and learning how to read/write.

Maybe one of you can help me with some simple code. What I want is to save the score, time left and passed checkpoints in a file, since you can stop and play again days later.

So in my imagination, ideal would be (since it´s only simple data) not to work with SQL lite, but just with a textfile. I couldn´t really find examlpe code of how to work with a list, read, write.

It would be nice if you read an entire list (strings) from the file, this list can change in length. Then you can update the list, let´s say list[5]=200 (was 500) and then write it back to the file. Also you might want to add data to the file (the passed checkpoints).

As a start I came up with this, but I´m stuck with the checkpoints and am not sure if I write to the file the entire file will be rewritten or I´m adding data:

  private static String filename = "currentgamedata.txt";
    private String myDir = Environment.getExternalStorageDirectory() + "/MyDirectory/"; 
    String enter = System.getProperty( "line.separator" );


   public void WriteCurrentGameData(){

     try {
         BufferedWriter writer = new BufferedWriter( new OutputStreamWriter(openFileOutput( myDir+filename , MODE_WORLD_WRITEABLE)));
         String MinutesLeft=Long.toString(GameTimeLeft);
         String SaveScore=Integer.toString(score);

         writer.write(MinutesLeft+enter);
         writer.write(SaveScore+enter);
         //HERE SHOULD COME SOME CODE FOR THE CHECKPOINTS

         writer.close();

     } catch (Exception e) {
         e.printStackTrace();
     }       
    }

    public void ReadCurrentGameData(){ 

     try {
         BufferedReader input = new BufferedReader( new InputStreamReader(
                 openFileInput( myDir+filename )));
         GameTimeLeft=Long.parseLong(input.readLine());
         score=Integer.parseInt(input.readLine());
         Log.d( "Reader" , Long.toString(GameTimeLeft) );
         Log.d( "Reader" , Integer.toString(score) );
         input.close();

     } catch (Exception e) {
         e.printStackTrace();
     }

 }

Sorry, somhow the code doesn´t come out very beautifully. So summarized the questions:

• What kind of method should I use if I want the game data written and read and why? (FE like up here or SQLlite?)
• I´m getting the myDir, is this the best location to store such data, where else and why?
• Is there a way to work with an ArrayList? Does anybody have a simple example for that?

Thanks a lot!

Answer 1

You have several options :

• Shared preferences: store private primitive data in key-value pairs. It's ok to store a small amount of simple data. It could fit your needs depending of the size of the data you need to store.
• Internal Storage : store private data on the device memory. I think it is the best choice because the data is private and can not be accessed by other applications.
• External Storage : store PUBLIC data on the shared external storage. This is what you are trying to do. It will work but I think it is not a good idea because the user could change the file and hack the game.
• SQLite Databases : store structured data in a private database. Probably an overkill in your case, where the data is simple and a relational storage is not really needed.
• Network Connection

In any case, try to use a file format that simplifies further processing, for example you could use a Properties file (easy to write/parse in Java), and store each level checkpoint as a property or something like that (ie level_1_checkpoint=200).