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我正在构建一个应用程序，我在其中使用 SQLBrite sql 包装器进行所有数据库操作。此外，我正在使用 Auto Value 使用 Google AutoValue 库自动处理我的所有 getter 和 setter。

现在，我的问题是处理设备旋转并处理我的 putParcelable() 方法需要两个参数，其中第一个是 KEY，第二个是 Parcelable 类型的值。正如我之前所说，我的 Recipe 类（下面的代码）是一个 SQLBrite 实现的类，并且没有实现 Parcelable。我需要一些帮助来将其转换为实现 Parcelable 接口。

@AutoValue
public abstract class Recipe {
    public abstract int id();
    public abstract String name();
    public abstract List<Ingredients> ingredients();
    public abstract List<Step> steps();
    public abstract int servings();
    public abstract String image();

    public static Builder builder() {
        return new AutoValue_Recipe.Builder();
    }

    public static TypeAdapter<Recipe> typeAdapter(Gson gson) {
        return new AutoValue_Recipe.GsonTypeAdapter(gson);
    }

    @AutoValue.Builder
    public abstract static class Builder {
        public abstract Builder id(int id);
        public abstract Builder name(String name);
        public abstract Builder ingredients(List<Ingredients> ingredients);
        public abstract Builder steps(List<Step> steps);
        public abstract Builder servings(int servings);
        public abstract Builder image(String image);

        public abstract Recipe build();
    }
}

现在，我尝试转换上面的代码来实现 Parcelable 接口，但是，现在我的代码不起作用。请帮我转换这个类来实现 Parcelable 接口。

@AutoValue
public abstract class Recipe implements Parcelable {
    public static final String ID = "id";
    public static final String NAME = "name";
    public static final String INGREDIENTS = "ingredients";
    public static final String STEPS = "steps";
    public static final String SERVINGS = "servings";
    public static final String IMAGE = "image";

    private int id;
    private String name;
    private List<Ingredients> ingredients;
    private List<Step> steps;
    private int servings;
    private String image;

    public abstract int id();
    public abstract String name();
    public abstract List<Ingredients> ingredients();
    public abstract List<Step> steps();
    public abstract int servings();
    public abstract String image();

    public static Recipe.Builder builder() {
        return new AutoValue_Recipe.Builder();
    }

    public static TypeAdapter<Recipe> typeAdapter(Gson gson) {
        return new AutoValue_Recipe.GsonTypeAdapter(gson);
    }

    public static final class Builder {
        private final ContentValues values = new ContentValues();
        List<Ingredients> ingredient;
        List<Step> step;

        public Recipe.Builder id(int id) {
            values.put(ID, id);
            return this;
        }

        public Builder name(String name) {
            values.put(NAME, name);
            return this;
        }

        public Builder ingredients(List<Ingredients> ingredients) {
        *//*for(int i=0; i<ingredients.size(); i++) {
            values.put(INGREDIENTS, ingredients.get(i).ingredient());
        }*//*
            this.ingredient = ingredients;
            return this;
        }

        public Builder steps(List<Step> steps) {
            *//*for(int i=0; i<steps.size(); i++) {
                values.put(STEPS, steps.get(i));
            }*//*
            this.step = steps;
            return this;
        }

        public Builder servings(int servings) {
            values.put(SERVINGS, servings);
            return this;
        } 

        public Builder image(String image) {
            values.put(IMAGE, image);
            return this;
        }

        public Recipe build() {
            Recipe recipe = null;
            recipe.id = (int) values.get(ID);
            recipe.name = (String) values.get(NAME);
            recipe.ingredients = ingredient;
            recipe.steps = step;
            recipe.servings = (int) values.get(SERVINGS);
            recipe.image = (String) values.get(IMAGE);

            return recipe;
        }
    }

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeInt(id);
        dest.writeString(name);
        dest.writeList(ingredients);
        dest.writeList(steps);
        dest.writeInt(servings);
        dest.writeString(image);
    }
}

编辑：我将使用修改后的类来处理我的设备旋转，以将我的回收器视图的滚动状态保存在片段中。我的 onSaveInstanceState() 方法看起来像这样，

private static final String BUNDLE_RECYCLER_LAYOUT = "BUNDLE_RECYCLER_LAYOUT";
ArrayList<Recipe> mRecipeList = new ArrayList<>(0);

@Override
public void onSaveInstanceState(Bundle bundle) {
    super.onSaveInstanceState(bundle);
   bundle.putParcelable(BUNDLE_RECYCLER_LAYOUT,
   mRecipeListRecyclerView.getLayoutManager().onSaveInstanceState());

   bundle.putParcelableArrayList(BUNDLE_RECYCLER_RECIPE_DATA, mRecipeList);
}

putParcelable 中的第二个参数是 Parcelable 类型。

我的 onCreateView() 方法如图所示：

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

     View view = inflater.inflate(R.layout.fragment_recipe_list, container, false);
    unbinder = ButterKnife.bind(this, view);

    if(savedInstanceState != null) {
        Parcelable savedRecyclerViewState = savedInstanceState.getParcelable(BUNDLE_RECYCLER_LAYOUT);
        mRecipeListRecyclerView.getLayoutManager().onRestoreInstanceState(savedRecyclerViewState);
        mRecipeList = savedInstanceState.getParcelableArrayList(BUNDLE_RECYCLER_RECIPE_DATA);
        mRecipeListAdapter.refreshRecipes(mRecipeList);
    } else {
        mRecipeList = getArguments().getParcelableArrayList(BUNDLE_RECYCLER_RECIPE_DATA);
    }

    mRecipeListAdapter = new RecipeListAdapter(getContext(), mRecipeList, recipeId
            -> mRecipeListPresenter.loadRecipeDetails(recipeId));
    mRecipeListAdapter.setHasStableIds(true);

    gridLayoutManager = new GridLayoutManager(getContext(), mGridColumnCount);
    mRecipeListRecyclerView.setLayoutManager(gridLayoutManager);
    mRecipeListRecyclerView.setHasFixedSize(true);
    mRecipeListRecyclerView.setAdapter(mRecipeListAdapter);

    return view;
}

任何帮助都会很棒，因为我在转换类以实现 Parcelable 接口时被卡住了。

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1 回答 1

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        mRecipeListRecyclerView.getLayoutManager().onRestoreInstanceState(savedRecyclerViewState);

你不需要打电话onRestoreInstanceState()。这已经被安卓系统自动调用了。此外，您不需要ArrayList自己保存和恢复。RecyclerView已经为您处理好这些细节。

至于保存滚动位置，你应该做更多的研究。例如，我发现ListView通过快速搜索跳转到屏幕方向更改的顶部。这个链接有一个清楚的例子，说明如何做你想做的事。

这个答案是关于ScrollView但示例代码与您需要的非常相似。

于 2017-07-06T19:43:05.890 回答