Activity reloads the whole data from server again when coming back from an other activity in Android

Question

Basically, I'm working on a app which has a tab-activity including 4 tabs and also I'm using the actvityGroup to manage the activities and backKey pressed() method.

When my app first starts it sends a request to server and shows the progress bar (using AsyncTask) as shown in below image.

After this, my complete UI appears as

it loads new actvity on click event of button "GO" (code is given below)

btnGo.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
                Intent bookSearchResultActivityIntent = new Intent();
                bookSearchResultActivityIntent
                        .setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                bookSearchResultActivityIntent.setClass(getParent(),
                        BookSearchResultActivity.class);
                bookSearchResultActivityIntent.putExtra("LANG", language);
                bookSearchResultActivityIntent.putExtra("SEARCH_KEYWORDS",
                        edTxt_SearchField.getText().toString());
                MyActivityGroup activityStack = (MyActivityGroup) getParent();
                activityStack.push("BooksSearchActivity",
                        bookSearchResultActivityIntent);

also here is my ActivtyGroup.java code

public class MyActivityGroup extends ActivityGroup {
    private Stack<String> stack;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (stack == null) {
                stack = new Stack<String>();
        }
        push("1stStackActivity", new Intent(this, Home.class));
    }

    @Override
    public void finishFromChild(Activity child) {
        pop();
    }

    @Override
    public void onBackPressed() {
        pop();
    }

    public void push(String id, Intent intent) {
        Window window = getLocalActivityManager().startActivity(id,
                        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP));
        if (window != null) {
            stack.push(id);
            setContentView(window.getDecorView());
        }
    }

    public void pop() {
        if (stack.size() == 1) {
            finish();
        }
        LocalActivityManager manager = getLocalActivityManager();
        manager.destroyActivity(stack.pop(), true);
        if (stack.size() > 0) {
            Intent lastIntent = manager.getActivity(stack.peek()).getIntent()
                            .addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            Window newWindow = manager.startActivity(stack.peek(), lastIntent);
            setContentView(newWindow.getDecorView());
        }
    }
}

ok now my question is that when i press the backKey(); it should come to the previous actvity.

• Yes it comes to the previous activity but it send request to the server again and shows the progress bar again and loads until the server sends response. it wastes my time.
• I only want to load the HomeTab just once (when i play the app). not again and again

• I am also adding the

  setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

while starting the activity

• also added following code in menifest.xml file

  android:configChanges="keyboard|keyboardHidden|orientation"

but not working yet.

and here is the code of my Home tab(which sends the request to server in onCreate method)

public class Home extends Activity {
    /** Called when the activity is first created. */
    static final String URL = "http://www.shiaislamiclibrary.com/requesthandler.ashx";
    static final String KEY_ITEM = "Book"; // parent node
    static final String KEY_BOOKAUTHOR = "BookAuthor";
    static final String KEY_BOOKDATEPUBLISHED = "DatePublished";
    static final String KEY_BOOKTITLE = "BookTitle";
    static final String KEY_BOOKCODE = "BookCode";
    static final String KEY_BOOKIMAGE = "BookImage";

    String searchLang;
    String searchKeywords;
    LayoutInflater inflater = null;

    ArrayList<String> BookTitle = new ArrayList<String>();
    ArrayList<String> BookCoverPhotos = new ArrayList<String>();
    ArrayList<String> BookAuther = new ArrayList<String>();
    ArrayList<String> BookPublishDate = new ArrayList<String>();
    ArrayList<String> ImageByte = new ArrayList<String>();
    ArrayList<Bitmap> bitmapArray = new ArrayList<Bitmap>();

    Context ctx = this;
    Activity act = this;
    Context context = Home.this;
    URL bookImageURL = null;
    Bitmap bitMapImage = null;

    Button btnGo;
    Spinner spnrLanguage;
    Spinner spnrBrowseBy;
    String language;
    EditText edTxt_SearchField;

    GridView gridView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // setContentView(R.layout.home_activity);
        View viewToLoad = LayoutInflater.from(this.getParent()).inflate(
                R.layout.home_activity, null);
        this.setContentView(viewToLoad);

        gridView = (GridView) findViewById(R.id.gridview);
        spnrLanguage = (Spinner) findViewById(R.id.spnrLanguage);
        spnrBrowseBy = (Spinner) findViewById(R.id.spnrBrowseBy);
        edTxt_SearchField = (EditText) findViewById(R.id.EditTxt_Search);
        btnGo = (Button) findViewById(R.id.btn_GO);

        ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        // checking for availbe internet Connection
        if (cm.getActiveNetworkInfo() != null
                && cm.getActiveNetworkInfo().isAvailable()
                && cm.getActiveNetworkInfo().isConnected()) {

            new UIThread().execute(URL, "Imam Ali");
        }

        gridView.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> arg0, View arg1, int pos,
                    long arg3) {

                Toast.makeText(context, BookTitle.get(pos), Toast.LENGTH_SHORT)
                        .show();

                Intent bookSearchResultActivityIntent = new Intent();
                bookSearchResultActivityIntent.setClass(getParent(),
                        BookOverView.class);
                bookSearchResultActivityIntent.putExtra("BITMAP",
                        bitmapArray.get(pos));
                bookSearchResultActivityIntent.putExtra("BOOK_TITLE",
                        BookTitle.get(pos));
                bookSearchResultActivityIntent.putExtra("BOOK_AUTHOR",
                        BookAuther.get(pos));
                bookSearchResultActivityIntent.putExtra("BOOK_PUBLISH_DATE",
                        BookPublishDate.get(pos));

                MyActivityGroup activityStack = (MyActivityGroup) getParent();
                activityStack.push("BookOverViewActivity",
                        bookSearchResultActivityIntent);

            }
        });

        // //////////////////// Spinners handler/////////////////////////
        ArrayAdapter<String> adapterLanguage = new ArrayAdapter<String>(
                context, android.R.layout.simple_spinner_item, getResources()
                        .getStringArray(R.array.spnr_language_array));
        ArrayAdapter<String> adapterBrowseBy = new ArrayAdapter<String>(
                context, android.R.layout.simple_spinner_item, getResources()
                        .getStringArray(R.array.spnr_browse_array));
        spnrLanguage.setAdapter(adapterLanguage);
        spnrBrowseBy.setAdapter(adapterBrowseBy);

        spnrLanguage.setOnItemSelectedListener(new OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> arg0, View arg1, int pos,
                    long arg3) {
                Toast.makeText(getParent(),
                        spnrLanguage.getItemAtPosition(pos) + "",
                        Toast.LENGTH_SHORT).show();
                language = spnrLanguage.getItemAtPosition(pos).toString();
            }

            @Override
            public void onNothingSelected(AdapterView<?> arg0) {

            }
        });

        spnrBrowseBy.setOnItemSelectedListener(new OnItemSelectedListener() {

            @Override
            public void onItemSelected(AdapterView<?> arg0, View arg1, int pos,
                    long arg3) {
                Toast.makeText(context,
                        spnrBrowseBy.getItemAtPosition(pos) + "",
                        Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onNothingSelected(AdapterView<?> arg0) {

            }
        });

        // ////////////////////Search Button Handler/////////////////

        btnGo.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {

                if (!edTxt_SearchField.getText().toString().equals("")) {
                    Intent bookSearchResultActivityIntent = new Intent();
                    bookSearchResultActivityIntent
                            .setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                    bookSearchResultActivityIntent.setClass(getParent(),
                            BookSearchResultActivity.class);
                    bookSearchResultActivityIntent.putExtra("LANG", language);
                    bookSearchResultActivityIntent.putExtra("SEARCH_KEYWORDS",
                            edTxt_SearchField.getText().toString());
                    MyActivityGroup activityStack = (MyActivityGroup) getParent();
                    activityStack.push("BooksSearchActivity",
                            bookSearchResultActivityIntent);

                } else {
                    Toast.makeText(context, "Search Field Empty",
                            Toast.LENGTH_SHORT).show();
                }

            }
        });

    }

    private class UIThread extends AsyncTask<String, Integer, String> {

        ProgressDialog progressDialog;

        @Override
        protected void onPreExecute() {
            // TODO Auto-generated method stub
            super.onPreExecute();
            progressDialog = ProgressDialog.show(getParent(),
                    "Acumlating Books from server...",
                    "This may Take a few seconds.\nPlease Wait...");
        }

        @Override
        protected String doInBackground(String... params) {

            String URL = params[0];
            String searchKeywords = params[1];

            XMLParser parser = new XMLParser();
            String XMLString = parser.getXmlFromUrl(URL, searchKeywords,
                    searchLang);
            // Log.i("XML Response", XMLString);

            Document doc = parser.getDomElement(XMLString);

            NodeList nl = doc.getElementsByTagName(KEY_ITEM);

            // looping through all item nodes <item>
            for (int i = 0; i < nl.getLength(); i++) {
                Element e = (Element) nl.item(i);

                BookTitle.add(parser.getValue(e, KEY_BOOKTITLE));
                BookCoverPhotos.add("http://shiaislamicbooks.com/books_Snaps/"
                        + parser.getValue(e, KEY_BOOKCODE) + "/1_thumb.jpg");
                BookAuther.add(parser.getValue(e, KEY_BOOKAUTHOR));
                BookPublishDate.add(parser.getValue(e, KEY_BOOKDATEPUBLISHED));
                Log.i("URLs", BookCoverPhotos.toString());
            }
            for (int i = 0; i < BookAuther.size(); i++) {

                try {
                    bookImageURL = new URL(BookCoverPhotos.get(i));
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                    Log.i("URL", "ERROR at image position" + i + "");
                }

                try {
                    bitMapImage = BitmapFactory.decodeStream(bookImageURL
                            .openConnection().getInputStream());
                    bitmapArray.add(bitMapImage);
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                    Log.i("BITMAP", "ERROR" + i);
                }
            }
            return null;
        }

        @Override
        protected void onPostExecute(String result) {
            super.onPostExecute(result);

            progressDialog.dismiss();
            ImageAdapter adapter = new ImageAdapter(getBaseContext(), act);
            gridView.setAdapter(adapter);
        }
    }

    public class ImageAdapter extends BaseAdapter {

        public ImageAdapter(Context c) {
            context = c;
        }

        // ---returns the number of images---
        public int getCount() {
            // return imageIDs.length;
            return bitmapArray.size();
            // return 6;
        }

        public ImageAdapter(Context ctx, Activity act) {

            inflater = (LayoutInflater) act
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        }

        // ---returns the ID of an item---
        public Object getItem(int position) {
            return position;
        }

        public long getItemId(int position) {
            return position;
        }

        // ---returns an ImageView view---
        public View getView(int position, View convertView, ViewGroup parent) {

            // ImageView bmImage;

            final ViewHolder holder;
            View vi = convertView;
            if (convertView == null) {
                vi = inflater.inflate(R.layout.grid_style, parent, false);
                holder = new ViewHolder();
                holder.txt_BooksTitle = (TextView) vi
                        .findViewById(R.id.txt_BookTitle);

                holder.img_BookCoverPhoto = (ImageView) vi
                        .findViewById(R.id.imgBookCover);
                vi.setTag(holder);
            } else {

                holder = (ViewHolder) vi.getTag();
            }
            holder.txt_BooksTitle.setText(BookTitle.get(position) + "");
            holder.img_BookCoverPhoto.setImageBitmap(bitmapArray.get(position));
            return vi;
        }
    }

    class ViewHolder {
        TextView txt_BooksTitle;
        ImageView img_BookCoverPhoto;
    }
}

• please have a look on my activity group class and tell what should i do. thanks in advance

Answer 1

When loading your data in the Home Tab activity, put it inside some static arrays.

    ArrayList<String> BookTitle = new ArrayList<String>();
    ArrayList<String> BookCoverPhotos = new ArrayList<String>();
    ArrayList<String> BookAuther = new ArrayList<String>();
    ArrayList<String> BookPublishDate = new ArrayList<String>();
    ArrayList<String> ImageByte = new ArrayList<String>();
    ArrayList<Bitmap> bitmapArray = new ArrayList<Bitmap>();

From a quick glimpse on the code, make them static ArrayList<...> ... = null; and check inside the onCreate() method:

if(BookTitle == null)
{
    //needs init
    BookTitle = new ArrayList<String>();
    //perform connect to server and parse response.
}

When the application activity home tab is stopped then restarted, the data will be in memory already and it will skip the if clause keeping the old data for re-use.

Make sure you will clear the static variables when you really want to kill the app - on a quit button click, call a static method to init them to null again, or if you want them to be valid for let's say 12 hours, memorize the timestamp in a static variable and each time you kill/pause the main activity perform a check on it (wheather is null or has a date, if it has a date, check if 12 hours have passed, if yes, clear the static variable contents)

This is the quick and easy way. Another way is to store them in the application database if you don't want to deal with static variables.

There are a lot of options, the point is you kinda have to mark them as "global persistent" data with static, or store them in a databse / file etc.