How to Get Application Data Dir in Android

Question

How can I get the Application Data Dir in Android Fragment or standard Java class (that is not an Activity).

I am doing an assignment that requires using Serialization to perform CRUD operation in Android. So far I have a standard Java Class that performs read and write like so

private void readFile() {
    try{
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(filePath));
        books = (List<Book>)ois.readObject();
        ois.close();
    }catch (Exception e){
        Log.e(TAG, e.getMessage());
    }
}

private void writeFile(){
    try {
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(filePath));
        oos.writeObject(books);
        oos.flush();
        oos.close();
    } catch (Exception e){
        Log.e(TAG, e.getMessage());
    }
}

Problem is that this class contructor requires a String DataDir to be passed like so

public class BookSvcSioImpl implements IBookSvc {

private final String TAG = "BookSvcSioImpl";
private List<Book> books = null;
private String dataDir = null;
private String filePath = dataDir + "/myBooks.sio";    


public BookSvcSioImpl(String appDataDirectory){
    this.dataDir = appDataDirectory;
    readFile();
}

I use this String parameter to construct the file path. My question how can I get the Application Data Directory in a Fragment or in standard Java class that is not an Activity. In an Activity I can get it by calling getApplicationInfo.DataDir like so

  String dataDir = getApplicationInfo().dataDir;
                BookSvcSioImpl sioService = new BookSvcSioImpl(dataDir);
                sioService.create(enteredBook);

I am not able to do this in a Fragment or Java class.

Answer 1

I am not able to do this in a Fragment

Call getActivity() on the Fragment to obtain the Activity that hosts the fragment.

Note that getFilesDir() on the Activity (or other Context ) is a better choice than getApplicationInfo().dataDir , as I do not know if dataDir adjusts to handle multiple accounts on tablets.