Apps Totally confused. Trying to save / load files in Android

[edzillion]

Hi

I have read through numerous tutorials, which all tell me a little bit but I am lost on the overall picture. So how about I start at the start.

I have a Java app I wrote that saves a string of data as a csv file: data.txt - I want to be able to open this file in my android app, so the first thing I did was use the 'push' option in eclipse to save it onto the device. i could save it and view it on the sdcard, but when trying to dave to the app data folder (data/data/package) it seems to work but I cannot see the file there.

So after reading around I saw this piece of code:

        try { // catches IOException below
            final String TESTSTRING = new String("Hello Android");
            
            // ##### Write a file to the disk #####
            /* We have to use the openFileOutput()-method
            * the ActivityContext provides, to
            * protect your file from others and
            * This is done for security-reasons.
            * We chose MODE_WORLD_READABLE, because
            * we have nothing to hide in our file */
            FileOutputStream fOut = openFileOutput("samplefile.txt",
            MODE_WORLD_READABLE);
            OutputStreamWriter osw = new OutputStreamWriter(fOut);
            
            // Write the string to the file
            osw.write(TESTSTRING);
            /* ensure that everything is
            * really written out and close */
            osw.flush();
            osw.close();
            // ##### Read the file back in #####
            
            /* We have to use the openFileInput()-method
            * the ActivityContext provides.
            * Again for security reasons with
            * openFileInput(...) */
            FileInputStream fIn = openFileInput("samplefile.txt");
            InputStreamReader isr = new InputStreamReader(fIn);
            /* Prepare a char-Array that will
            * hold the chars we read back in. */
            char[] inputBuffer = new char[TESTSTRING.length()];
            // Fill the Buffer with data from the file
            isr.read(inputBuffer);
            // Transform the chars to a String
            String readString = new String(inputBuffer);
            
            // Check if we read back the same chars that we had written out
            boolean isTheSame = TESTSTRING.equals(readString);
            
            // WOHOO lets Celebrate =)
            Log.i("File Reading stuff", "success = " + isTheSame);
            
        } catch (IOException ioe) {
            ioe.printStackTrace();
        }
    }

which works fine, though I cannot seem to see the file (I presume this is because it is located in the data/data/package/ folder and I cannot see that through eclipse DDMS.

>> Aside: I seem to have a lot of trouble accessing the file explorer using eclipse. It seems v. tempermental - sometimes I can see all the files and folders, other times I cannot open any of the folders (though it does list data, sdcard and system), with no discernable reason. I just did a test: loaded up the emulator on its own with wipe data set to 'on' and I can access the data folder but no subfolders of it

Anyway, When I try to use this same code to read my data.txt file from the sdcard I get the error: File sdcard/data.txt contains a path separator (I also tried the path /sdcard/data.txt but got the same error.

I read somewhere that openFileInput will not work with the sdcard.

This is really a kind of kludge just to test the data, since in the finished product the app wont read data from the sdcard. Am I missing something, should I serialise the data as XML? What is the best practice here?

Regards
ed

 

[galt]

If your final app will not need to read the card, why not just create your data in a resource file as a string or array, or whatever form best matches the ultimate data source ?

 

[edzillion]

Good point. I guess I was getting tunnel vision there;

What if, say, an application had episodic content? How would the app be updated? Can a server push an update other than the usual android market updates, or would the user have to initiate an update from a webserver or something ...

 

[khooke]

your app could call a remote web service on your server on startup or some other timed basis to check for available downloadable new content?

 

[eialbur]

I need an answer as well - in fact I am running into a number of developers in this situation.

I do not want to package my 'data' files as a Resource - I want them out on the file system (and I don't want copies of the data files left as a Resource). I want to be able to update and add to the data files without having to reinstall the app.

For example - Mahjongg on Linux. You can change the tile set (or add to the tile sets) just by dropping a specially formated file into a specific directory. I want to do something like that. I want to have different data files the user can choose to 'install' into this directory (different data files should be different items in the Marketplace).

I have found a number of other developers wanting this capability, but I haven't seen any solutions yet. I'm new to Android ... can some give me an answer (or point me in the right direction) ?

P.S. I do not want to set up my own server and write my own data download code.

 

[alostpacket]

I need an answer as well - in fact I am running into a number of developers in this situation.

I do not want to package my 'data' files as a Resource - I want them out on the file system (and I don't want copies of the data files left as a Resource). I want to be able to update and add to the data files without having to reinstall the app.

For example - Mahjongg on Linux. You can change the tile set (or add to the tile sets) just by dropping a specially formated file into a specific directory. I want to do something like that. I want to have different data files the user can choose to 'install' into this directory (different data files should be different items in the Marketplace).

I have found a number of other developers wanting this capability, but I haven't seen any solutions yet. I'm new to Android ... can some give me an answer (or point me in the right direction) ?

P.S. I do not want to set up my own server and write my own data download code.

Lots of apps do this actually...

You could maybe start here:

PackageManager | Android Developers