如何将带有ArrayList的捆绑包从片段传递到活动

Question

I have a ListFragment that implements a click listener to pass clicked object to IngredientActivity. When I retrieve the object in the IngredientActivity, the objects's variables are null.

public class ListFragment extends Fragment implements ListRecipeAdapter.ListItemClickListener {
....
@Override
    public void onListItemClick(Recipe selectedRecipe) {
        Bundle bundle = new Bundle();
        ArrayList<Recipe> selectedRecipeArray = new ArrayList<>();
        selectedRecipeArray.add(selectedRecipe);
        bundle.putParcelableArrayList("recipe",selectedRecipeArray);
        Intent intent = new Intent(getActivity(), IngredientActivity.class);
        intent.putExtras(bundle);
        startActivity(intent);
    }
}

I retrieve the bundle and extract the Arraylist of object as:

public class IngredientActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        ....
        Bundle bundle = getIntent().getExtras();
        ArrayList<Recipe> recipes = bundle.getParcelableArrayList("recipe");
        recipe = recipes.get(0);

    }
}

The listener is interface:

public interface ListItemClickListener {
        void onListItemClick(Recipe recipeId);
    }

Recipe is defined as a Parcelable:

public class Recipe implements Parcelable {
...
}

When I print this in logcat:

Recipe in Fragment:

com.example.android.bakingapp.Models.Recipe@5d8b71e

ArrayList in Fragment:

[com.example.android.bakingapp.Models.Recipe@5d8b71e]

Bundle in Fragment:

Bundle[{selected_recipe=[com.example.android.bakingapp.Models.Recipe@5d8b71e]}]

The retrieved object looks different:

Bundle in Activity:

Bundle[mParcelledData.dataSize=6784]

ArrayList in Activity:

[com.example.android.bakingapp.Models.Recipe@1abf1e8]

Recipe in Activity:

com.example.android.bakingapp.Models.Recipe@1abf1e8

Answer 1

Did you implement the Parcelable object correctly?

After parceled, you can have different address object because object are recreated with that data.

Check out the Parcelable implementation of the Recipe object.

Answer 2

It looks like you have issue in your parcelable object. Make sure all fields are serialized right.

Another option - your parcelable object is too large. There is size limitation on Parcelable that is attached to intent - something about 1 mb.

Answer 3

I have a ListFragment that implements a click listener to pass clicked object to IngredientActivity. When I retrieve the object in the IngredientActivity, the objects' variables are null.

I would like you to rethink the structure, what you are doing is passing the ArrayList object via Bundle from Fragment relevant Activity , which is the not the proper way to go.

Solution: You may want to use interface which would be going to pass the clicked object via callback method to activity(Here I am assuming you will need to set the interface once fragment is created)

Make like

        public class ListFragment extends Fragment {
        ....

        private ListItemClickListener mListener;

        public void setListClickListner(ListItemClickListener listener){
        this.mListener=listener;
        }

/**Note : you will need to call      
mListener.onListItemClick(selectedRecipe);
in the relavent click event of ListView/RecyclerView with instance of 
receipe. */

}

and in Activity:

public class IngredientActivity extends AppCompatActivity  implements ListRecipeAdapter.ListItemClickListener{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        ....
        Bundle bundle = getIntent().getExtras();
        ArrayList<Recipe> recipes = bundle.getParcelableArrayList("recipe");
        recipe = recipes.get(0);

    }

    // Callback method
   @Override
    public void onListItemClick(Recipe selectedRecipe) {
        // Whatever thing you want to do goes here...
        mListener.onListItemClick(selectedRecipe);
    }

}

I hope it makes sense.

Answer 4

You can use Android Parcelable or Java Serializable interface. Both will work. With performance level, parcelable is faster than serializable.