How to Cache Parsed JSON for Offline usage

Question

I have parsed JSON successfully but now i want to Cache it for offline usage, even internet is not available, and if any new entry comes i want to cache that as well.

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Answer 1

Why not just save it to cache folder of your app using something like this:

String path = Environment.getExternalStorageDirectory() + File.separator + "cache" + File.separator;
File dir = new File(path);
if (!dir.exists()) {
    dir.mkdirs();
}
path += "data";
File data = new File(path);
if (!data.createNewFile()) {
    data.delete();
    data.createNewFile();
}
ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(data));
objectOutputStream.writeObject(actorsList);
objectOutputStream.close();

And after, you can read it in any time using:

List<?> list = null;
File data = new File(path);
try {
    if(data.exists()) {
        ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream(data));
        list = (List<Object>) objectInputStream.readObject();
        objectInputStream.close();
    }
} catch (IOException e) {
    e.printStackTrace();
} catch (ClassNotFoundException e) {
    e.printStackTrace();
}

UPDATE: Okay, make class named ObjectToFileUtil, paste this code to created class

package <yourpackagehere>;

import android.os.Environment;

import java.io.*;

public class ObjectToFileUtil {

    public static String objectToFile(Object object) throws IOException {
        String path = Environment.getExternalStorageDirectory() + File.separator + "cache" + File.separator;
        File dir = new File(path);
        if (!dir.exists()) {
            dir.mkdirs();
        }
        path += "data";
        File data = new File(path);
        if (!data.createNewFile()) {
            data.delete();
            data.createNewFile();
        }
        ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream(data));
        objectOutputStream.writeObject(object);
        objectOutputStream.close();
        return path;
    }

    public static Object objectFromFile(String path) throws IOException, ClassNotFoundException {
        Object object = null;
        File data = new File(path);
        if(data.exists()) {
            ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream(data));
            object = objectInputStream.readObject();
            objectInputStream.close();
        }
        return object;
    }
}

Change < yourpackagehere > to your package name and don't forget to add WRITE_EXTERNAL_STORAGE permission to AndroidManifest.xml. In your MainActivity add field

private String dataPath;

and replace your onPostExecute method of JSONAsyncTask class to

protected void onPostExecute(Boolean result) {
    dialog.cancel();
    adapter.notifyDataSetChanged();
    if(result) {
        try {
            dataPath = objectToFile(arrayList);
        } catch (IOException e) {
            e.printStackTrace();
        }
    } else {
        Toast.makeText(getApplicationContext(), "Unable to fetch data from server", Toast.LENGTH_LONG).show();
    }
}

Now you can access get actorsList from File anytime when you want, by using

try {
    actorsList = (ArrayList<Actors>)objectFromFile(dataPath);
} catch (IOException e) {
    e.printStackTrace();
} catch (ClassNotFoundException e) {
    e.printStackTrace();
}

If you want to save path of file after closing application you must save dataPath string (and load on application start), for example, using SharedPreferences.

Answer 2

And what would be the best option to cache data ? SharedPreferences or SQLite database

Which is purely based on the data you received.

1. If the data is Small,Unstructured data then use Shared Pref.
2. If the data is Large,Structured data then use SQLite.

But for store the full data better you can use file concept. Store the string data in your code String data = EntityUtils.toString(entity); the data you have to save to the file.If any changes in the data from the server add that to file.And retrieve the data if internet not present. Get the example code for file operations from the above link.