Question

First, I have researched this question a lot. I learned how to read from my text file in the assets folder. The problem is that I don’t want to end up with a string because the file is actually an arraylist written using json and inside that arraylist are objects. I need to access one object only. Here’s what I mean:

I have a Book class, which has an int called chapter, an int called title, and an int called pageNum. I created several Book objects and added them to an ArrayList. Then I used the following code to write my ArrayList to a text file (in a regular java project):

ArrayList<Book> aList = new ArrayList<Book>();
aList.add(book1);
//etc...add more Book objects here...

File aFile = new File("books.txt");
FileOutputStream aFileStream = new FileOutputStream(aFile);
JSONOutputStream jsonOut = new JSONOutputStream(aFileStream);
jsonOut.writeObject(aList);
jsonOut.close();

That code creates a text file which I then put into the /assets folder in my Android project because I want it included with the app. In a non-Android java project I could simply use the following code to repopulate an ArrayList so that I could parse Book obects from specific indexes:

File bFile = new File("books.txt");
FileInputStream bFileStream = new FileInputStream(bFile);
JSONInputStream jsonIn = new JSONInputStream(bFileStream);
Arraylist<Book> bList = (ArrayList<Book>) jsonIn.readObject();
Book aBook = bList.get(253); //some arbitrary index

The json code I’m using comes from quickconnectfamily.org. You have to add a file called qc_json.jar to the build path of your project. http://www.quickconnectfamily.org/qcjson/more.html

The problem in Android is when I read the file using InputStream, I can only get the entire file into a string, the code above doesn’t work in Android. I can’t wrap JSONInputStreams around an InputStream, only around a FileInputStream. But it seems I am unable to use
FileInputStream.

So what I need is a way to create an ArrayList rather than a string in my Android app.
Without giving away too much about my app, the app basically generates a random number and creates a Book object from that index in the ArrayList. Then the user is quizzed with info from that specific book. Sounds silly, but the real app is much cooler.

I’m open to solutions, alternative methods of storing objects in a text file, etc. Please don’t simply post criticism about my grammar, syntax, or application idea. I’m pretty new to app development and I couldn’t care less about personal opinions. If anyone wants to see
more code I can upload it, but it doesn’t seem necessary at this point. Thanks.

Answer 1

I figured out the solution. I connected my Evo 4G and tested the app and it worked. Here’s what I did:

I used the following method to read from the file, which is what I was doing before:

InputStream is = appContext.getAssets().open("books.txt");
int size = is.available();
buffer = new byte[size];
is.read(buffer);
is.close();
String bufferString = new String(buffer);

When you do this, you end up with a String of the entire file. This is what I was able to do before, but what I wanted was a way to convert the String to an ArrayList of Book objects. Here’s how I accomplished this:

//convert string to JSONArray
jsonArray = new JSONArray(bufferString);
//parse an Object from a random index in the JSONArray
JSONObject anObject = jsonArray.getJSONObject(randomNum); 

Book aBook = new Book();
aBook.setTitle((String) anObject.get("title"));
//you can continue to set the different attributes of the Book object using key/value pairs from the Book class (e.g. setPageNum, setChapter, etc).

I don’t know, maybe that was obvious to some people, but I really couldn’t find any examples that did this. In a different question someone mentioned using the json library native to Android org.json and so I tried that and it worked.