App Refactoring - Our 'Edit' Option (Part 3)

As we're using (and replacing) Fragments instead of switching between Activities, we have two options when trying to implement event handling. We can

• Implement the event handling and listeners 'in house' and manage everything inside the Fragment - but this can get a bit tricky when we want to handle more than one event (like our situation)

or

• we implement a callback listener to the parent activity (in our case 'Home'), which ties in with the particular navigation pattern we're trying to adhere to - so this is what we'll do.

If you recall, Android Studio generated a lot of boilerplate code for us, including some template callback listeners - which we needed to implement, to get a version of our app running. We'll now revisit this code (and the whole EditFragment) and complete our 'Edit' feature.

First, familarise yourself with the particular listener we need to implement

public interface OnFragmentInteractionListener 
{    
// TODO: Update argument type and name    
void onFragmentInteraction(Uri uri);
}

and the default methods to 'hook up', attach\/detach to the UI event

// TODO: Rename method, update argument and hook method into UI event

public void onButtonPressed(Uri uri) 
{    
if (mListener != null) {        
    mListener.onFragmentInteraction(uri);    
    }
}

@Override
public void onAttach(Context context) 
{    
    super.onAttach(context);    
        if (context instanceof OnFragmentInteractionListener) {        
            mListener = (OnFragmentInteractionListener) context;    
            } 
            else {        
                    throw new RuntimeException(context.toString()                
                            + " must implement OnFragmentInteractionListener");    
            }
}

@Override
public void onDetach() 
{    
    super.onDetach();    
    mListener = null;
}

Next, bring in the existing methods from the Edit activity ('toggle' and 'update') and fix any errors.

Note: Seeing as we need to bind to the widgets both for displaying and updating it's probably best to use class-wide widget variables (like we did for our 'Add') so before you proceed, make sure your onCreateView() and update() methods look something like this

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

    View v = inflater.inflate(R.layout.fragment_edit, container, false); 

    ((TextView)v.findViewById(R.id.coffeeNameTextView)).setText(aCoffee.name); 
    ((TextView)v.findViewById(R.id.coffeeShopTextView)).setText(aCoffee.shop); 

    name = (EditText)v.findViewById(R.id.nameEditText); name.setText(aCoffee.name); 
    shop = (EditText)v.findViewById(R.id.shopEditText); shop.setText(aCoffee.shop); 
    price = (EditText)v.findViewById(R.id.priceEditText); price.setText(""+aCoffee.price); 
    ratingBar = (RatingBar) v.findViewById(R.id.coffeeRatingBar); ratingBar.setRating((float)aCoffee.rating); 

    favouriteImage = (ImageView) v.findViewById(R.id.favouriteImageView); 
        if (aCoffee.favourite == true) { 
            favouriteImage.setImageResource(R.drawable.ic_favourite_on); 
            isFavourite = true; 
        } else { 
            favouriteImage.setImageResource(R.drawable.ic_favourite_off); 
            isFavourite = false; 
        } 
    return v;
}

public void update(View v) {    
        if (mListener != null) {        
                String coffeeName = name.getText().toString();        
                String coffeeShop = shop.getText().toString();        
                String coffeePriceStr = price.getText().toString();        
                double ratingValue = ratingBar.getRating();        

                double coffeePrice;        
                        try {            
                        coffeePrice = Double.parseDouble(coffeePriceStr);        
                        } catch (NumberFormatException e) 
                        {            coffeePrice = 0.0;        }        

                if ((coffeeName.length() > 0) && (coffeeShop.length() > 0) && (coffeePriceStr.length() > 0)) {            
                        aCoffee.name = coffeeName;            
                        aCoffee.shop = coffeeShop;            
                        aCoffee.price = coffeePrice;            
                        aCoffee.rating = ratingValue;           
                     }        
                } else            
                Toast.makeText(getActivity(), "You must Enter Something for Name and Shop", Toast.LENGTH_SHORT).show();    
                }
        }

The last thing we need to do is refactor our Listener interface to reflect the events we want to handle so replace the existing interface with this one

public interface OnFragmentInteractionListener {    
    void toggle(View v);    
    void update(View v);
}

And use the Android Studio Tools to implement these new methods back in our 'Home' activity (and fix any residual errors).

Here's the implementation for the 'toggle'

@Override
public void toggle(View v) {    
    EditFragment editFrag = (EditFragment) getFragmentManager().findFragmentById(R.id.homeFrame);    
        if (editFrag != null) {        
                editFrag.toggle(v);    
        }
    }

so have a go at implementing the 'update'.