在android中使用firebase数据填充ListView

Question

我又回到了这个问题，虽然我很接近：我有以下代码，我试图在列表视图中显示 firebase 值。

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_mystatement);
        listview = (ListView) findViewById(R.id.listview);
        textView4 = (TextView) findViewById(R.id.textView4);
        adapter = new ArrayAdapter<String>(this, android.R.layout.simple_dropdown_item_1line, list);
        listview.setAdapter(adapter);
        dref = FirebaseDatabase.getInstance().getReference();


        DatabaseReference dref = FirebaseDatabase.getInstance().getReference();
        dref= dref.child("Expenditure");

        dref.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot snapshot) {
                for (DataSnapshot postSnapshot : snapshot.getChildren()) {
                    //Getting the data from snapshot
                    DogExpenditure dogExpenditure = postSnapshot.getValue(DogExpenditure.class);

                    //Adding it to a string
                    String expenses = "Amount: "+dogExpenditure.getAmount()+"\nReason for Use: "+dogExpenditure.getItem()+"\n\n";

                    String amount = dogExpenditure.getAmount();
                    String item = dogExpenditure.getItem();

                    System.out.println(expenses);


                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }


            public void onCancelled(FirebaseError firebaseError) {
                System.out.println("The read failed: " + firebaseError.getMessage());
            }
        });

当我在我的 android studio 控制台中运行此代码时，我会看到以下输出。这正是我想要的。但是，它没有显示在应用程序的布局视图中，而是显示一个空白屏幕。

**03-07 15:15:05.777 32332-32332/com.example.moses.farm I/System.out: Amount: dd
03-07 15:15:05.779 32332-32332/com.example.moses.farm I/System.out: Reason for Use: dddd
03-07 15:15:05.782 32332-32332/com.example.moses.farm I/System.out: Amount: kwaraaaa
03-07 15:15:05.782 32332-32332/com.example.moses.farm I/System.out: Reason for Use: ayeeeee**

谁能告诉我如何在我的应用程序中显示该输出，因为目前它没有显示任何内容，但在调试控制台中我可以看到它

Answer 1

您可以使用FirebaseUI.

使用 firebase 数据填充 listView 非常简单。

然后添加依赖项：

1. 连接到 Firebase
2. 创建自定义 FirebaseListAdapter 子类

类似：

  listview = (ListView) findViewById(R.id.listview);
    DatabaseReference dref = FirebaseDatabase.getInstance().getReference();
    mAdapter = new FirebaseListAdapter<DogExpenditure>(this, DogExpenditure.class, R.layout.yourLayout, ref) {
            @Override
            protected void populateView(View view, DogExpenditure myObj, int position) {
               //populate your view
               String amount = dogExpenditure.getAmount()
               //Put the value in your layout.
            }
        };
listview.setAdapter(mAdapter);

更多info here.

Answer 2

//Just above onCreate
List<String> expenseList = new ArrayList<>();
ArrayAdapter<String> adapter;

//In value event listener
expenseList.add(expense)

if(expensList.size() == 1)
{
  adapter = new ArrayAdapter<>(getApplicationContext(),android.R.layout.simple_list_item_1,expensList);
  listView.setAdapter(adapter)
}
else if(expenseList.size() > 1)
{
  adapter.notifyDatasetChanged();
}

Answer 3

创建一个 dref 的单例对象。

并且列表尚未初始化。

Answer 4

您应该将您的费用添加到您的清单中，并使用
通知更改 adapter.notifyDataSetChanged().

list.add(费用)

adapter.notifyDataSetChanged()

Answer 5

首先创建一个适配器，因为您已经有了模型类。 MyAdapter.java

 public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {

private Context context;
private List<DogExpenditure> uploads;

public MyAdapter(Context context, List<DogExpenditure> uploads) {
    this.uploads = uploads;
    this.context = context;
}

@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View v = LayoutInflater.from(parent.getContext())
            .inflate(R.layout.layout_firebase_images, parent, false);
    ViewHolder viewHolder = new ViewHolder(v);
    return viewHolder;
}

@Override
public void onBindViewHolder(ViewHolder holder, int position) {
    DogExpenditure upload = uploads.get(position);

    holder.textViewName.setText(upload.getAmount());
    holder.textView1.setText(upload.getYourData());

}

@Override
public int getItemCount() {

    return uploads.size();
}

class ViewHolder extends RecyclerView.ViewHolder {

    public TextView textViewName;
    public ImageView imageView;

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

        textViewName = (TextView) itemView.findViewById(R.id.textViewName);
        textview1 = (TextView) itemView.findViewById(R.id.your_id);
    }
}
 }

现在在你的活动中

private List<DogExpenditure> uploads;
MyAdapter adapter;
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_mystatement);
    listview = (ListView) findViewById(R.id.listview);
    textView4 = (TextView) findViewById(R.id.textView4);
    adapter = new ArrayAdapter<String>(this, android.R.layout.simple_dropdown_item_1line, list);
    listview.setAdapter(adapter);
    dref = FirebaseDatabase.getInstance().getReference();
    uploads = new ArrayList<>();

    DatabaseReference dref = FirebaseDatabase.getInstance().getReference();
    dref= dref.child("Expenditure");

    dref.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot snapshot) {
            for (DataSnapshot postSnapshot : snapshot.getChildren()) {
                //Getting the data from snapshot
                DogExpenditure dogExpenditure = postSnapshot.getValue(DogExpenditure.class);
                uploads.add(dogExpenditure);
            }
            adapter = new MyAdapter(getApplicationContext(), uploads);
            recyclerView.setAdapter(adapter);
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }


        public void onCancelled(FirebaseError firebaseError) {
            System.out.println("The read failed: " + firebaseError.getMessage());
        }
    });