Question

我的RecycleView上的布局上有更改视图的问题。我有列表的梦想。这个视图包含两个状态myDreamEmptyLayout女巫显示文字＆＃34;现在你没有梦想。 \ n添加梦想！＆＃34;当myDreamList为空且size等于0.但当myDreamList大小超过1时显示列表梦。问题是当myDream在列表中并删除时，所有人都无法显示我的视图myDreamEmptyLayout。什么问题？

这是我的fragment_my_dream.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
             android:layout_width="match_parent"
             android:layout_height="match_parent"
             android:background="@color/colorBackground"
    >

    <LinearLayout
        android:id="@+id/myDreamEmptyLayout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <TextView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:gravity="center"
            android:text="@string/for_now_you_don_t_have_dream_n_add_dream"
            android:textColor="@color/colorWhite"/>

    </LinearLayout>


    <android.support.v7.widget.RecyclerView
        android:id="@+id/myDreamRecyclerView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:visibility="gone"/>
</FrameLayout>

这是我的片段类

   public class MyDreamFragment extends Fragment {

        public static final int REQUEST_CODE_CREATE = 1;


        @BindView(R.id.myDreamRecyclerView)
        RecyclerView myDreamRecyclerView;
        @BindView(R.id.myDreamEmptyLayout)
        LinearLayout myDreamEmptyLayout;

        private MyDreamAdapter myDreamAdapter;
        private List<MyDream> myDreamList;
        String idUserString;
        private DbHelper dbHelper;
        private Unbinder unbinder;
        private Dao<MyDream, Integer> myDreamDao;
        private Dao<User, Integer> myUserDao;

        @Override

        public void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setHasOptionsMenu(true);
        }

        @Nullable
        @Override
        public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_my_dream, container, false);
            unbinder = ButterKnife.bind(this, rootView);
            TextView title = (TextView) getActivity().findViewById(R.id.toolbarTextView);
            title.setText(R.string.title_my_dreams);
            return rootView;
        }

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

            Application application = (Application) getApplicationContext();
            idUserString = application.getFirebaseId();

            dbHelper = new DbHelper(getActivity());

            try {
                myDreamDao = dbHelper.getDao(MyDream.class);
            } catch (SQLException e) {
                e.printStackTrace();
            }

            try {
                myUserDao = dbHelper.getDao(User.class);
            } catch (SQLException e) {
                e.printStackTrace();
            }

            QueryBuilder<User, Integer> userQa = myUserDao.queryBuilder();

            try {
                userQa.where().eq(User.Columns.FIREBASE_ID, idUserString);
            } catch (SQLException e) {
                e.printStackTrace();
            }

            QueryBuilder<MyDream, Integer> myDreamQa = myDreamDao.queryBuilder();


            try {
                myDreamList = myDreamQa.join(userQa).query();
            } catch (SQLException e) {
                e.printStackTrace();
            }

            if (myDreamList != null && myDreamList.size() > 0) {
                myDreamRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
                myDreamAdapter = new MyDreamAdapter(myDreamList, getActivity());
                myDreamRecyclerView.setAdapter(myDreamAdapter);
            }

        }

        @Override
        public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
            super.onCreateOptionsMenu(menu, inflater);
            inflater.inflate(R.menu.menu_add, menu);
        }

        @Override
        public void onResume() {
            super.onResume();

            if (myDreamList.size() == 0) {

                myDreamEmptyLayout.setVisibility(View.VISIBLE);
                myDreamRecyclerView.setVisibility(View.GONE);

            } else {

                myDreamEmptyLayout.setVisibility(View.GONE);
                myDreamRecyclerView.setVisibility(View.VISIBLE);

            }
        }

        @Override
        public boolean onOptionsItemSelected(MenuItem item) {

            switch (item.getItemId()) {
                case R.id.action_addream:
                    Intent intent = new Intent(getActivity(), AddEditDreamActivity.class);
                    startActivityForResult(intent, REQUEST_CODE_CREATE);
                    return true;
            }

            return super.onOptionsItemSelected(item);
        }


        @Override
        public void onActivityResult(int requestCode, int resultCode, Intent data) {
            super.onActivityResult(requestCode, resultCode, data);

            if (resultCode == AddEditDreamActivity.RESULT_OK) {
                if (requestCode == REQUEST_CODE_CREATE) {
                    if (data != null) {
                        MyDream myDream = data.getParcelableExtra("dream");
                        myDreamAdapter.addMyDream(myDream);
                        Toast.makeText(getActivity(), "Dream was added", Toast.LENGTH_SHORT).show();
                    }
                }
            }

        }

        @Override
        public void onDestroyView() {
            super.onDestroyView();
            unbinder.unbind();
        }
    }

Answer 1

您的myDreamList不会对待处理的更改作出反应，因此myDreamEmptyLayout不会获知新信息（例如大小已达零）可用。要反驳这一情况，请查看this ObservableArrayList及其OnListChangedCallback。将myDreamList更改为ObservableArrayList移动onResume代码（当然没有super）更改为OnListChangedCallback并通过addOnListChangedCallback添加此回调。这样，对列表所做的更改将根据需要反映在布局上。

代码：

//this goes to onCreate. DISCLAIMER : code written without testing, please confirm that it works.
myDreamList.addOnListChangedCallback(new ObservableList.OnListChangedCallback() {

/*snipped useless methods*/

     @Override 
     public void onChanged(ObservableList<T> sender) {
            if (sender.size() == 0) {

                myDreamEmptyLayout.setVisibility(View.VISIBLE);
                myDreamRecyclerView.setVisibility(View.GONE);

            } else {

                myDreamEmptyLayout.setVisibility(View.GONE);
                myDreamRecyclerView.setVisibility(View.VISIBLE);

            }
        }
}

无法根据列表的大小更改视图

1 个答案: