how can i refresh fragment when back button is pressed?

Question

How can I refresh the view of a fragment, when the back button is pressed?

I have tried this in the onResume method of the fragment but it doesn't work.

OK, here is the code

@SuppressWarnings("unused")
public class RestaurantMenuFragment extends Fragment {

    private static final String TAG = "MenuItemsFragment";
    private static final String CATEGORIES_KEY = "categories";
    private static final String SELECTED_CATEGORY_ID_KEY = "category";
    private static final String RESTAURANT_KEY = "restaurant123";
    private static final String RESTAURANT_KCITY = "city";
    private Spinner mCategoriesSpinner;
    private ArrayAdapter<CategoriesResponse.Category> mCategoriesAdapter;
    private ListView mListView;
    private List<MenuItem> mItems;
    private MenuItemsAdapter mItemsAdapter;
    private EmptyLayout mEmptyLayout;
    private Restaurant mRestaurant;
    private int mCategoryId;
    private List<CategoriesResponse.Category> mCategories;
    private RestaurantActivity mActivity;
    private MainApplication mApplication;
    private CategoriesResponse mCategoriesResponse;
    private ActionBar mActionBar;
    private Gson mGson;
    int categ;
    private ObjectGetter mObjectGetter;

    public static RestaurantMenuFragment newInstance(Restaurant restaurant) {
        RestaurantMenuFragment fragment = new RestaurantMenuFragment();
        Bundle args = new Bundle();
        args.putString(RESTAURANT_KEY, new Gson().toJson(restaurant));
         String dd=restaurant.city;

         Log.i("dd12", dd);
        fragment.setArguments(args);

        return fragment;
    }

    public RestaurantMenuFragment() {
    }

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

        mActivity = (RestaurantActivity) getActivity();
        mApplication = (MainApplication) mActivity.getApplication();
        mActionBar = mActivity.getSupportActionBar();

        mGson = new Gson();

        mObjectGetter = new ObjectGetter();
        mCategories = new ArrayList<CategoriesResponse.Category>();
        Log.i("mCategories",""+mCategories);
        mItems = new ArrayList<MenuItem>();
        Log.i("12345",""+mItems);
        mItemsAdapter = new MenuItemsAdapter(getActivity(), mItems);    

        Bundle args = getArguments();
        if (args != null) {
            mRestaurant = mGson.fromJson(args.getString(RESTAURANT_KEY),
                    Restaurant.class);
        }

        if (savedInstanceState != null) {
            mRestaurant = mGson.fromJson(
                    savedInstanceState.getString(RESTAURANT_KEY),
                    Restaurant.class);
            mCategoryId = savedInstanceState.getInt(SELECTED_CATEGORY_ID_KEY);
            mCategoriesResponse = mGson.fromJson(
                    savedInstanceState.getString(CATEGORIES_KEY),
                    CategoriesResponse.class);
        }

        assert mRestaurant != null;    
        updateCart();
    }

    public void updateCart() {
        View view = mActionBar.getCustomView();
        Button cartButton = (Button) view.findViewById(R.id.cartButton);

        int nOfItems = 0;
        if (mApplication.isCartCreated()) {
            nOfItems = mApplication.getCart().getNOfAllItems();
        }
        cartButton.setText(String.format("%d", nOfItems));
        if (nOfItems > 0) {
            cartButton.setEnabled(true);
        } else {
            cartButton.setEnabled(false);
        }
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        Gson gson = new Gson();

        outState.putString(RESTAURANT_KEY, gson.toJson(mRestaurant));
        outState.putInt(SELECTED_CATEGORY_ID_KEY, mCategoryId);
        outState.putString(CATEGORIES_KEY, gson.toJson(mCategoriesResponse));
    }   

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        // TODO Auto-generated method stub    
        super.onViewCreated(view, savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
       View view = inflater.inflate(R.layout.spinner_list, container, false);
       RestaurantActivity activity = (RestaurantActivity) getActivity();
       String myDataFromActivity = activity.getMyData();
       String myDataFromActivity1 = activity.getMyData1();
       Log.i("myDataFromActivity",myDataFromActivity);
       Log.i("myDataFromActivity1",myDataFromActivity1);

       categ=Integer.parseInt(myDataFromActivity1);

        mListView = (ListView) view.findViewById(R.id.list122334);
        mListView.setAdapter(mItemsAdapter);

        Log.d(TAG,"Querying items url "
                + Urls.menuItemsQuery(mRestaurant.id,categ));       

        mEmptyLayout = EmptyLayout.with(getActivity()).to(mListView)
                .setEmptyMessage(R.string.categories_empty_message)
                .showLoading();                 

        loadItems();
        return view;
    }

    private void loadItems() {
        mEmptyLayout.showLoading();
        mItems.clear();
        mObjectGetter.getJsonObjectOrDialog(mActivity,
                Urls.menuItemsQuery(mRestaurant.id, categ),
                ItemsResponse.class,
                new ObjectGetter.OnFinishedListener<ItemsResponse>() {
                    @Override
                    public void onFinishedLoadingObject(
                            ItemsResponse itemsResponse) {
                        mEmptyLayout.showEmpty();

                        if (itemsResponse != null
                                && itemsResponse.items != null) {
                            mItems.addAll(itemsResponse.items);
                        }
                        mItemsAdapter.notifyDataSetChanged();

                    }
                });
        }


    private class MenuItemsAdapter extends ArrayAdapter<MenuItem> {

        private static final String TAG = "MenuItemsAdapter";

        public MenuItemsAdapter(Context context, List<MenuItem> menuItems) {
            super(context, 0, menuItems);
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            final MenuItem menuItem = getItem(position);                

            View view = convertView;
            final ViewHolder viewHolder;
            LayoutInflater inflater;
            if (convertView == null) {
                inflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                view = inflater.inflate(R.layout.menu_item, parent, false);
                viewHolder = new ViewHolder();

                viewHolder.name = (TextView) view.findViewById(R.id.name);
                viewHolder.description = (TextView) view.findViewById(R.id.description);
                viewHolder.price = (TextView) view.findViewById(R.id.price);
                viewHolder.add = (Button) view.findViewById(R.id.add);
                viewHolder.selectedView = view.findViewById(R.id.selectedView);
                viewHolder.remove = (Button) view.findViewById(R.id.remove);
                viewHolder.total = (TextView) view.findViewById(R.id.itemTotal);
                viewHolder.quantity = (TextView) view.findViewById(R.id.quantity);

                view.setTag(viewHolder);
            } else {
                viewHolder = (ViewHolder) convertView.getTag();
            }

            try
            {               
                viewHolder.name.setText(menuItem.name);
                viewHolder.description.setText(menuItem.description);

                viewHolder.price.setText(String.valueOf(menuItem.price));

            }catch(NullPointerException e){
                 e.printStackTrace();
            }

            viewHolder.add.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {                   

                    mApplication.createNewCartIfPossibleAndAskIfNot(
                            getActivity(), mRestaurant,
                            new MainApplication.OnCreateCartListener() {
                                @Override
                                public void onCreateCart(Cart cart) {
                                    cart.addOne(menuItem);
                                    updateItemFromCart(menuItem, viewHolder);
                                    updateCart();
                                }
                            });
                }
            });

            viewHolder.remove.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {

                    if (!mApplication.isCartCreated()) {
                        return;
                    }
                    mApplication.getCart().removeOne(menuItem);
                    updateItemFromCart(menuItem, viewHolder);
                    updateCart();
                }
            });   

            return view;
        }

        private void updateItemFromCart(MenuItem menuItem, ViewHolder viewHolder) {    
            if (!mApplication.isCartCreated()) {
                return;
            }
            int quantity = mApplication.getCart().getNOfItemsOfType(menuItem);
            if (quantity > 0) {
                viewHolder.selectedView.setVisibility(View.VISIBLE);
            } else {
                viewHolder.selectedView.setVisibility(View.GONE);
            }
            viewHolder.quantity.setText(String.valueOf(quantity));

            viewHolder.total.setText(String.valueOf(quantity
                    * menuItem.price));
        }

        class ViewHolder {
            TextView name;
            TextView description;
            TextView price;
            Button add;
            View selectedView;
            Button remove;
            TextView total;
            TextView quantity;              
        }    
    }

    @Override
    public void onResume() {
        super.onResume();

        updateCart();
        mItems.clear();
        if (mItemsAdapter != null) {

            mItemsAdapter.notifyDataSetChanged();               
        }   
    }

    @Override
    public void onDestroy() {
        if (mObjectGetter != null) {
            mObjectGetter.stopRequests();
        }
        super.onDestroy();      
    }
}

Now, i want to update the listvieww data when the user pressed the back button. I set the new loadItems() method in the onResume() Method of the Fragment. This Method is called but the old listview data appears and new data also appears...

Answer 1

Back button should be handled from Activity. You can override onBackPressed in Activity and call a function on corresponding fragment to reloadItems().

Here are your 3 options I could think of.

1. Get reference to Fragment and call function to reLoadItems and its better to define an interface for this communication which fragment implements.

2. Better solution than first one. Add a LocalBroadcast which Activity broadcasts and your fragment listens and updates data on receiving broadcast.

Example for this : http://luboganev.github.io/blog/messaging-with-localbroadcastmanager/

3. Otto event bus where both activity and fragment classes are connected to the event bus and they activity publishes event and fragment subscribes to it. This is what I am using for something similar in my application. (But I have pretty frequent asynchronous events that come along. SO I am using this. 2nd option might be sufficient in your case).

Example for this : http://www.vogella.com/tutorials/JavaLibrary-EventBusOtto/article.html

Answer 2

As ramesh already mentioned, back button handling happens in your activity class that holds the fragments. Here is a simple example, how you can handle these back button events for your fragment.

Activity Code:

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
  boolean returnSuperKeyDown = true;

  if(keyCode == KeyEvent.KEYCODE_BACK){
    Fragment fragment = getYourCurrentFragment();

    if (fragment instanceof YourFragment) {
      returnSuperKeyDown = ((YourFragment) fragment).onFragmentKeyDown();
    }
  }

  if (returnSuperKeyDown) {
    return super.onKeyDown(keyCode, event);
  } else {
    return true;
  }
}

YourFragment Method:

public boolean onFragmentKeyDown() {
  updateYourFragment();
  return false;
}

Answer 3

@Rithe, @sunder sharma

As per me there is simple to refresh the fragment when come back from other fragment,

We just have to override the onActivityCreated Method for refresh fragment.

Like as

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
   //your code which you want to refresh
    loadItems();
}

Answer 4

You can also update/refresh the fragment using onStart() method.

public void onStart(){


 super.onStart();
    //update your fragment
}

This worked fine for me.

Answer 5

调用您的loadItem（）方法onHiddenChanged（布尔隐藏）方法.onHiddenChanged被重写的方法