How to clear image(s) cache on back pressed in a Fragment ?

Question

I've a fragment which is called from the MainActivity. And this Fragment fetches a JSON file of image URL's and displays images on the screen. I've used Fresco library to download these images and then pop as a image list view. The images are automatically cached by the Fresco Library.

I want to remove all cached images when I perform a back press from the Fragment. The images are immediately uncached as the user scrolls down the list and I want to uncache all images when user performs a backPress in the Fragment

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    View view  = inflater.inflate(R.layout.fragment_gallery, container, false);
    private List<gallery_adapter> gallery_adapterList = new ArrayList<>();
    ListView list = (ListView) view.findViewById(R.id.galleryList);

    gallery_adapterList.clear();
    if(isNetworkConnected()){
        new galleryImages().execute("http://www.myurl.json");
    }else
        Toast.makeText(context,"No Internet Connection!",Toast.LENGTH_SHORT).show();

    return view;
}






public class galleryImages extends AsyncTask<String, String, String> {

    HttpURLConnection connection;
    BufferedReader reader;

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected String doInBackground(String... params) {
        try {
            URL url = new URL(params[0]);
            connection = (HttpURLConnection) url.openConnection();
            InputStream stream = connection.getInputStream();
            reader = new BufferedReader(new InputStreamReader(stream));
            StringBuilder builder = new StringBuilder();
            String line;
            while ((line = reader.readLine()) != null) {
                builder.append(line);
            }
            String str = builder.toString();
            return str;
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(String s) {
        super.onPostExecute(s);
        if(s!=null){


            try {
                JSONObject parent = new JSONObject(s);
                JSONArray images = parent.getJSONArray("images");

                if(images!=null){

                    for(int i=0; i<images.length();i++){
                        JSONObject child = images.getJSONObject(i);
                        gallery_adapterList.add(new gallery_adapter(child.getString("url"),child.getString("text")));
                    }
                    displayList();

                }else
                    Toast.makeText(context,"error",Toast.LENGTH_SHORT).show();

            } catch (JSONException e) {
                Toast.makeText(context, "Images not yet added. Try later",Toast.LENGTH_SHORT).show();
            }


        }else
            Toast.makeText(context, "Images not yet added. Try later",Toast.LENGTH_SHORT).show();
    }
}

Display list method

private void displayList() {
    ArrayAdapter<gallery_adapter> adapter = new galleryAdapterList();
    list.setAdapter(adapter);
}

public class galleryAdapterList extends ArrayAdapter<gallery_adapter> {

    galleryAdapterList() {
        super(context, R.layout.gallery_item, gallery_adapterList);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        if (convertView == null) {
            LayoutInflater inflater = LayoutInflater.from(context);
            convertView = inflater.inflate(R.layout.gallery_item, parent, false);
        }

        gallery_adapter current = gallery_adapterList.get(position);


        TextView mText=(TextView) convertView.findViewById(R.id.galleryText);
        mText.setText(current.getText());


        uri = Uri.parse(current.getUrl());
//code to remove images from cache
        ImagePipeline imagePipeline = Fresco.getImagePipeline();
        imagePipeline.evictFromCache(uri);     
//code ends here


        SimpleDraweeView mImage = (SimpleDraweeView) convertView.findViewById(R.id.galleryImage);
        mImage.setImageURI(uri);


        return convertView;
    }

}

score 1 · Answer 1 · answered Mar 21 '17 at 10:44

1

I think what you was it's this however if I may why do you want to clear the cache? Because the next time the user opens the activity he needs to wait for the json response again

answered Mar 21 '17 at 10:44

alb

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score 0 · Answer 2 · edited May 23 '17 at 12:25

0

Below are option that you can do so:

1.You can cache backpress event in Fragment and call your function to clear cache images ,Handle Back Press.

2.Track Fragment by it's onAttach(Context) , Mean while you need to write FragmentManager.addOnBackStackChangedListener(); it will be called if you have added your fragment with addtoBackStack .

edited May 23 '17 at 12:25

Community

1
1

answered Mar 21 '17 at 10:46

Herry

7,037
7
50
80

This method will be called in the MainActivity right ? So how will I get the list of URL's in the MainActivity so that they can be Uncached – Avinash_ks Mar 21 '17 at 12:29
You may use Application class to fetch list of URL or may be declare interface to communicate with Fragment to Activity – Herry Mar 21 '17 at 12:31
Thanks @Herry. Used the Application class to fetch the details and then sent it to the Fragment for displaying images – Avinash_ks Mar 22 '17 at 03:48
if my answer help you to resolved you can accept it @Avinash_ks – Herry Mar 22 '17 at 05:21

How to clear image(s) cache on back pressed in a Fragment ?

2 Answers2