Android：传递自定义 POJO 的 ArrayList，它将 Parcelable 作为 Bundle 从 Activity 扩展到 Fragment

Question

我正在尝试传递一个自定义 POJO，它将 Parcelable 作为 Bundle 从我的 Activity 扩展到我的 Fragment。填充的捆绑对象成功传递给我的 Fragment 的 newInstance 方法。但是，在我的 Fragment 的 onCreate 方法中，当我尝试恢复 POJO 类的这个 ArrayList 时，它会以某种方式被丢弃。

//Activity
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_recipe_detail);

    mRecipe = getIntent().getParcelableExtra("com.wernerraubenheimer.bakingapp.data.RecipeModel");
//This works mRecipe is successfully populated with my custom ArrayList<IngredientModel>
//My class IngredientModel extends Parcelable

    IngredientListFragment ingredientListFragment = IngredientListFragment.newInstance(mRecipe.getIngredients());
//Still good so far....

    getSupportFragmentManager()
            .beginTransaction()
            .add(R.id.first_fragment_container, new IngredientListFragment())
            .commit();
}

//Fragment
public static IngredientListFragment newInstance(ArrayList<IngredientModel> ingredients) {

    IngredientListFragment ingredientListFragment = new IngredientListFragment();
    Bundle bundle = new Bundle();
    bundle.putParcelableArrayList("ingredients", ingredients);
    ingredientListFragment.setArguments(bundle);

    return ingredientListFragment;
}

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
//This is where the ball gets dropped, mIngredientList which I initialized when I declared it just after 
//class declaration: private ArrayList<IngredientModel> mIngredientList = new ArrayList<>();
//is now empty??
//I have also placed the call to super.onCreate after the statement below
    mIngredientList = getArguments().getParcelableArrayList("ingredients");
    //have also used savedInstanceState
}

我想在 Fragment 的 onCreateView 中的 RecyclerView 中使用 ArrayList：

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

    View rootView = inflater.inflate(R.layout.fragment_ingredient_list, container, false);

    rvIngredientList = (RecyclerView)rootView.findViewById(R.id.rv_ingredient_list);
    ingredientLayoutManager = new LinearLayoutManager(getActivity());
    ingredientLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
    rvIngredientList.setLayoutManager(ingredientLayoutManager);

    IngredientListAdapter ingredientListAdapter = new IngredientListAdapter(mIngredientList);
    rvIngredientList.setAdapter(ingredientListAdapter);

    return rootView;
}

Answer 1

请确保您使用的是您创建的对象。

这应该可行。

IngredientListFragment ingredientListFragment = IngredientListFragment.newInstance(mRecipe.getIngredients());

getSupportFragmentManager()
        .beginTransaction()
        .add(R.id.first_fragment_container, ingredientListFragment)
        .commit();

Answer 2

getSupportFragmentManager()
            .beginTransaction()
            .add(R.id.first_fragment_container, new 
             IngredientListFragment())
            .commit();

in this method you are providing new instance of fragment, rather than the one which you created using
IngredientListFragment ingredientListFragment = IngredientListFragment.newInstance(mRecipe.getIngredients());