Question

任何人都可以帮我从节点＆＃34;食物＆＃34;并把它放在RecyclerView。这些是我一直在处理的文件，但事实证明这是一个空列表。我在互联网上查看了一个教程，但大多数都是使用较旧版本的Firebase。最近，Firebase用户界面已更新，数据绑定过程已更改为新的FirebaseRecyclerAdapter结构

这是我的数据库结构：

"foods" : {
"AntipastoSalad" : {
  "duration" : "30",
  "img" : "https://firebasestorage.googleapis.com/v0/b/mealplanner-ec8ca.appspot.com/o/res%2Fsalad.jpg?alt=media&token=257d4392-8a1f-4fb7-84b5-b63abb4643f4",
  "name" : "Antipasto salad",
  "type" : "Salad"
},

这是我的活动：

    private RecyclerView mRecycleView;
    private Query query;
    private FirebaseRecyclerOptions<Meal> options;
    private DatabaseReference mDatabase;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_food_list_row);

        mDatabase = FirebaseDatabase.getInstance().getReference().child("foods");

        //Recycle View
        mRecycleView = (RecyclerView) findViewById(R.id.meal_items);
        mRecycleView.setHasFixedSize(true);
        mRecycleView.setLayoutManager(new LinearLayoutManager(this));
    }


    @Override
    protected void onStart() {
        super.onStart();

        query = FirebaseDatabase.getInstance().getReferenceFromUrl("https://mealplanner-ec8ca.firebaseio.com/foods/AntipastoSalad");

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

        FirebaseRecyclerAdapter<Meal, FoodListRowActivity.MealRowHolder> firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<Meal, FoodListRowActivity.MealRowHolder>(
                options) {
            @Override
            public FoodListRowActivity.MealRowHolder onCreateViewHolder(ViewGroup parent, int viewType) {
                View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.food_row, parent, false);
                return new FoodListRowActivity.MealRowHolder(v);
            }

            @Override
            protected void onBindViewHolder(FoodListRowActivity.MealRowHolder holder, int position, Meal current) {
                holder.setTitle(current.getName());
                String duration = current.getDuration() + "min";
                holder.setDuration(duration);
            }
        };

        //Populate Item into Adapter
        mRecycleView.setAdapter(firebaseRecyclerAdapter);

        mRecycleView.addOnItemTouchListener(new RecycleViewItemClickListener(this, mRecycleView, new RecycleViewItemClickListener.OnItemClickListener() {
            @Override
            public void onItemClick(View view, int position) {
                Intent viewMeal = new Intent(FoodListRowActivity.this, CookingInstructionActivity.class);
                startActivity(viewMeal);
            }

            @Override
            public void onLongItemClick(View view, int position) {
                //TODO: DELETE
            }
        }));
    }

    public static class MealRowHolder extends RecyclerView.ViewHolder {

        View mView;

        public MealRowHolder(View itemView) {
            super(itemView);
            mView = itemView;

        }

        public void setTitle(String title) {
            TextView foodTitle = (TextView) mView.findViewById(R.id.list_item_foodList_name);
            foodTitle.setText(title);
        }


        public void setDuration(String title) {
            TextView foodDuration = (TextView) mView.findViewById(R.id.list_item_foodList_calories);
            foodDuration.setText(title);
        }
    }
}

和班级结构：

public class Meal{

private String img;
private String duration;
private String name;
private String instruction;

public Meal(){

}

public Meal (String img, String duration, String name, String instruction){
    this.img = img;
    this.name = name;
    this.duration = duration;
    this.instruction = instruction;
}

public void update(String duration, String name, String instruction)
{
    this.name = name;
    this.duration = duration;
    this.instruction = instruction;
}
public String getName(){
    return name;
}

public String getDuration() {
    return duration;
}

public String getInstruction() {
    return instruction;
}

public String getImg(){return img;}

Answer 1

query方法中指定的setQuery()应该是您要在RecyclerView中显示的列表根目录的引用，如下所示：

query = FirebaseDatabase.getInstance().getReference().child("foods");

您还需要在适配器上调用startListening()以指示它开始从数据库中检索数据。

来自FirebaseRecyclerAdapter lifecycle documentation：

FirebaseRecyclerAdapter使用事件监听器来监控Firebase查询的更改。要开始侦听数据，请调用startListening()方法。您可能希望在onStart()方法中调用此方法。确保在调用startListening()之前已完成读取数据所需的任何身份验证，否则您的查询将失败。
@Override protected void onStart() {
    super.onStart();
    adapter.startListening();
}
同样，stopListening()调用会删除事件侦听器和适配器中的所有数据。当包含Activity或Fragment时，请调用此方法：
@Override protected void onStop() {
    super.onStop();
    adapter.stopListening();
 }

Answer 2

这就是我使用Firebase用户界面在recyclerview中检索我的数据的方式：

 private FirebaseRecyclerAdapter<TaskPOJO, TaskViewHolder> adapter;
 private void loadTasks() {


        database = FirebaseDatabase.getInstance();
        tasks = database.getReference("Tasks");
        adapter = new FirebaseRecyclerAdapter<TaskPOJO, TaskViewHolder>(TaskPOJO.class, R.layout.task_item, TaskViewHolder.class, tasks) {
            @Override
            protected void populateViewHolder(TaskViewHolder viewHolder, final TaskPOJO model, int position) {


                Log.wtf("valueTEst", "populateViewHolder: "+model.toString() );
                Log.wtf("TEstScript1", "populateViewHolder: "+model.getTitle() );
                viewHolder.title.setText(model.getTitle());
                viewHolder.desc.setText(model.getDescripttion()+"\n");
                viewHolder.remaining.setText(model.getRemaining()+"/"+model.getPoint());
                viewHolder.points.setText("Points "+model.getRemaining());
                Glide.with(viewHolder.title.getContext())
                        .load(model.getImage())
                        .into(viewHolder.image);


                viewHolder.setClickListener(new ItemClickListener() {
                    @Override
                    public void onClick(View view, int position, boolean isLongClick) {
                        Toast.makeText(getActivity(), "" /*+ model.getTitle()*/, Toast.LENGTH_SHORT).show();

                        Intent TaskPOJODetail = new Intent(getActivity(), Main.class);
                        TaskPOJODetail.putExtra("value","detail");
                        TaskPOJODetail.putExtra("taskId",adapter.getRef(position).getKey());
                        startActivity(TaskPOJODetail);
                    }
                });
            }
        };
        progressBar.setVisibility(View.GONE);
        recyclerViewTasks.setAdapter(adapter);
    }

这是我的firebase结构：

希望这会对你有所帮助。

Answer 3

请覆盖getItemCount()的{{1}}方法。

FirebaseRecyclerAdapter

Reference.

Firebase UI 3.0.0：检索数据以回收视图

3 个答案: