java - 尝试修改 Activity 的后退按钮

Question

我正在尝试修改特定 Activity 的后退按钮导航，但遇到错误

UNCAUGHT EXCEPTION CURRENT ACTIVITY : BookmarksActivity java.lang.NullPointerException: Attempt to invoke virtual method 'void android.os.Bundle.unparcel()' on a null object reference at android.os.Bundle.putAll(Bundle.java:250) at android.content.Intent.putExtras(Intent.java:8597) at usb.terminal.view.fragment.BookmarksFragment$2.onItemClick(BookmarksFragment.java:162)

我尝试了两种方法，我修改了 ActionBarFragment 中的后退按钮功能。我的第二种方法的问题是，它按预期进入所需的 Activity ，但当我单击列表中的某个项目时，它会不断崩溃并出现上面指定的错误。

private void initListeners() {
    btnBackListener = new View.OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent event) {
            if (event.getAction() == MotionEvent.ACTION_DOWN) {

                Log.d("Back Button", "Back button pressed");

                int flag = BookmarksFragment.getFlag();
                Log.d("Flag Number", String.valueOf(flag));

                if (flag == 1){
                    BookmarksFragment class2 = new BookmarksFragment();
                    class2.fetchBookmarkCategories();
                }

                else {
                    if(getActivity()!=null) {
                        getActivity().finish();
                    }
                }

            }
            return true;
        }
    };

其次，我没有调用另一个类的函数，而是尝试使用以下方法重新加载 Activity :

BookmarksFragment class2 = new BookmarksFragment();
                    class2.fetchBookmarkCategories();

这是我的书签 Activity ，我正在尝试获得我想要的功能。

public class BookmarksActivity extends EmptyActivity {


    public BookmarksActivity() {
        super(new BookmarksFragment());
    }

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


    @Override
    protected void onStart() {
        super.onStart();
        ((ActionBarFragment) actionBarFragment).updateTitle(R.string.bookmark_activity_title);
    }

}

这是我的 BookmarkFragment(仅部分代码):

public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        this.userId = PreferencesHelper.getPrefsUserId(ctx);
        categoriesListView = (NonScrollListView) view.findViewById(R.id.bookmark_categories_list);
        recipesListView = (NonScrollListView) view.findViewById(R.id.bookmark_recipes_list);
        noResultLayout = (LinearLayout)this.getView().findViewById(R.id.bookmark_recipes_empty_panel);

        scrollButton = (CardView) this.getView().findViewById(R.id.load_more_button);
        scrollAction = (LinearLayout) this.getView().findViewById(R.id.load_more_action_layout);
        scrollLoading = (LinearLayout) this.getView().findViewById(R.id.load_more_loading_layout);
        scrollLoadingImage = (ImageView) this.getView().findViewById(R.id.load_more_loading_icon);

        recipesAdapter = new RecipesAdapter(ctx, recipesLinkedList);

        categoriesListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Category category = categoriesLinkedList.get(position);
                fetchBookmarksFromCategory(category.getId());
            }
        });

        recipesListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

                Intent intent = new Intent(ctx, RecipePagerActivity.class);
                Bundle extras = activity.getIntent().getExtras();
                intent.putExtra("Check_Status", 1);
                intent.putExtras(extras);
                int recipeId = recipesLinkedList.get(position).getId();
                int recipeCount = recipesLinkedList.get(position).getNbFavorite();
                boolean recipeStatus = recipesLinkedList.get(position).isFavorite();
                intent.putExtra("Recipe Status", recipeStatus);
                intent.putExtra("Recipe_Count", recipeCount);
                intent.putExtra(RecipesManager.KEY_ID_RECIPE, recipeId);

            }
        });

        setSpinner(view);

        fetchBookmarkLists();
    }

这两种方法都给我带来了相同的错误。有人可以帮忙解决这个问题吗？

Answer 1

您的 activity.getIntent().getExtras() 似乎返回 null 值。

请在使用extras之前尝试进行空检查，并在需要时分配new Bundle()，例如...

                int recipeId = recipesLinkedList.get(position).getId();
                int recipeCount = recipesLinkedList.get(position).getNbFavorite();
                boolean recipeStatus = recipesLinkedList.get(position).isFavorite();

                Intent intent = new Intent(ctx, RecipePagerActivity.class);
                Bundle extras = activity.getIntent().getExtras();
                if (extras == null) extras = new Bundle();  //solution

                extras.putInt("Check_Status", 1);
                extras.putInt(RecipesManager.KEY_ID_RECIPE, recipeId);
                extras.putInt("Recipe_Count", recipeCount);
                extras.putBoolean("Recipe Status", recipeStatus);
                intent.putExtras(extras);