Question

我正在编写一个购物清单应用，可以将数据保存到Firebase实时数据库并实时更新屏幕。截至目前，我已经拥有它，以便当您点击＆＃34; + List项目＆＃34;按钮，它将一个ShoppingListItem添加到数据库，名称为＆＃34; test＆＃34;。它正确地做到了，但它没有更新屏幕。我已经仔细检查了方法是否被调用，但是屏幕没有反映更新的数据。我也尝试过使用notifyDataSetChanged（）并且似乎没有帮助。

这是ShoppingListFragment的代码：

    public class ShoppingListFragment extends Fragment {

    private ArrayList<String> listItems = new ArrayList<String>();
    private ListView mListView;
    private TextView addItemButton;
    private LinearLayout ll;
    private RecyclerView rv;
    private FirebaseRecyclerAdapter<ShoppingListItem, ShoppingListHolder> firebaseRecyclerAdapter;
    private DatabaseReference mDatabase;

    public ShoppingListFragment() {
        // Required empty public constructor
    }

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

        mDatabase = FirebaseDatabase.getInstance().getReference();


        //get reference to user
        String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
        Query query = mDatabase.child("users").child(uid).child("shopping");

        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_shopping_list, container, false);
        rv = view.findViewById(R.id.shopping_list);
        rv.setLayoutManager(new LinearLayoutManager(getContext()));

        // find the + List Item button
        final TextView addCheckBox = view.findViewById(R.id.add_check_box);



        addCheckBox.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                addNewCheckBox(container);
            }
        });

        FirebaseRecyclerOptions<ShoppingListItem> options = new FirebaseRecyclerOptions.Builder<ShoppingListItem>()
                .setQuery(query, ShoppingListItem.class)
                .build();

        firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<ShoppingListItem, ShoppingListHolder>(options) {
            @Override
            protected void onBindViewHolder(@NonNull ShoppingListHolder holder, int position, @NonNull ShoppingListItem item) {
                holder.setItem(item);
            }

            @NonNull
            @Override
            public ShoppingListHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
                View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.shopping_list_item, parent, false);

                return new ShoppingListHolder(view);
            }
        };

        return view;
    }

    @Override
    public void onStart() {
        super.onStart();
        firebaseRecyclerAdapter.startListening();
        rv.setAdapter(firebaseRecyclerAdapter);
    }

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

        if (firebaseRecyclerAdapter != null) {
            firebaseRecyclerAdapter.stopListening();
        }
    }

    public void addNewCheckBox(ViewGroup container) {
        String key = mDatabase.child("users").child(getUid()).child("shopping_list").push().getKey();

        ShoppingListItem item = new ShoppingListItem("test");

        mDatabase.child("users").child(getUid()).child("shopping_list").child(key).setValue(item);
        firebaseRecyclerAdapter.notifyDataSetChanged();
    }

    public int convertToPx(int input) {
        DisplayMetrics metrics = getResources().getDisplayMetrics();
        int px = (int) (input * ((float)metrics.densityDpi / DisplayMetrics.DENSITY_DEFAULT));
        return px;
    }

    private class ShoppingListHolder extends RecyclerView.ViewHolder {

        private final EditText itemName;

        public ShoppingListHolder(View itemView) {
            super(itemView);

            itemName = itemView.findViewById(R.id.item_name);
        }

        public void setItem(ShoppingListItem item) {
            itemName.setText(item.getItemName());
        }
    }

    private String getUid() {
        return FirebaseAuth.getInstance().getCurrentUser().getUid();
    }
}

和ShoppingListItem：

    public class ShoppingListItem {
    private String itemName;
    private String type;
    private String unit;
    private int quantity;
    private String location;

    public ShoppingListItem() {

    }

    public ShoppingListItem(String name) {
        this.itemName = name;
    }

    public String getItemName() {
        return itemName;
    }

    public void setItemName(String itemName) {
        this.itemName = itemName;
    }
}

购物清单视图的XML：

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/home_fragment_main_layout"
    android:orientation="vertical"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    tools:context="com.jggdevelopment.wannacook.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Shopping List"
        android:textStyle="bold"
        android:textSize="18sp"
        android:layout_marginStart="16dp"
        android:layout_marginBottom="16dp"/>

    <android.support.v7.widget.RecyclerView
        android:id="@+id/shopping_list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:fitsSystemWindows="true"
        android:clipToPadding="false"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/add_check_box"
        android:text="+ List item"
        android:textSize="16sp"
        android:layout_marginStart="40dp"
        android:layout_marginTop="16dp"/>

</LinearLayout>

和购物清单中每个订单项的XML：

    <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">


    <CheckBox
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <EditText
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:id="@+id/item_name"
        android:layout_weight="1"
        android:layout_marginStart="12dp"
        android:layout_marginEnd="32dp"
        android:inputType="text"
        android:background="@android:color/transparent"
        />

    <ImageView
        android:layout_width="20dp"
        android:layout_height="20dp"
        android:id="@+id/xbutton"
        android:layout_marginEnd="12dp"
        android:src="@drawable/ic_close_white_24dp"
        android:layout_gravity="center_vertical"/>


</LinearLayout>

database structure

Answer 1

这不起作用，因为您忘记在onCreate()方法中设置适配器。要解决此问题，请在返回视图之前添加rv.setAdapter(firebaseRecyclerAdapter);：

rv.setAdapter(firebaseRecyclerAdapter);
return view;

您可以从onStart()方法中删除该行代码，因为那里不需要。

如果您有兴趣，我已经创建了一个教程，我将逐步解释如何使用Shopping List App和Android构建 Cloud Firestore 。

屏幕未反映Android中对Firebase数据库的更改

1 个答案: