java - 如何在 Android ListView 中显示 Firebase 项目？

Question

我正在尝试在 Android ListView 中显示一些 Firebase 记录。目前，当我输入一条新记录时，我的代码正在向 ListView 返回一个单独的 0，但是我的 Firebase 数据库正在完美地显示我想要的信息。

我在这个问题上花了很多时间，但似乎不能完全查明问题所在。

如有任何帮助，我们将不胜感激。

下面是我显示/添加新记录的代码:

    TenantList tenantListAdapter;

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

        mAuth = FirebaseAuth.getInstance();
        FirebaseUser user = mAuth.getCurrentUser();
        String uid = user.getUid();

        //databaseTenantsList = FirebaseDatabase.getInstance().getReference("tenants").child(uid);

        textViewPropertyName = (TextView) findViewById(R.id.textViewPropertyName);
        editTextTenantsName = (EditText) findViewById(R.id.editTextTenantsName);
        seekBarAge = (SeekBar) findViewById(R.id.seekBarAge);

        buttonAddTenant = (Button) findViewById(R.id.buttonAddTenant);

        listViewTenants = (ListView) findViewById(R.id.listViewTenants);
        tenants = new ArrayList<>();
        tenantListAdapter = new TenantList(this, tenants);
        listViewTenants.setAdapter(tenantListAdapter);

        Intent intent = getIntent();

        tenants = new ArrayList<>();

        String id = intent.getStringExtra(PropertyActivity.PROPERTY_ID);
        String name = intent.getStringExtra(PropertyActivity.PROPERTY_NAME);

        textViewPropertyName.setText(name);

        databaseTenants = FirebaseDatabase.getInstance().getReference("tenants").child(uid).child(id).child(uid);

        //databaseTenants = FirebaseDatabase.getInstance().getReference("tenants").child(id);

        buttonAddTenant.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                saveTenant();
            }
        });
    }

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

        databaseTenants.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                tenants.clear();

                for(DataSnapshot tenantSnapshot : dataSnapshot.getChildren()){
                    Tenant tenant = tenantSnapshot.getValue(Tenant.class);

                    tenants.add(tenant);
                }
                tenantListAdapter.notifyDatasetChanged();
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });

    }

    private void saveTenant() {

        String tenantName = editTextTenantsName.getText().toString().trim();
        int age = seekBarAge.getProgress();

        if(!TextUtils.isEmpty(tenantName)){

            String id = databaseTenants.push().getKey();

            Tenant tenant = new Tenant(id, tenantName, age);

            FirebaseUser user = mAuth.getCurrentUser();
            String uid = user.getUid();

            databaseTenants.child(uid).child(id).setValue(tenant);

            Toast.makeText(this, "Tenant saved successfully", Toast.LENGTH_LONG).show();

        } else {

            Toast.makeText(this, "Tenant name should not be empty", Toast.LENGTH_LONG).show();
        }
    }
}

租户列表

    public class TenantList extends ArrayAdapter<Tenant> {

    private Activity context;
    private List<Tenant> tenants;

    public TenantList(Activity context, List<Tenant> tenants) {

        super(context, R.layout.tenant_list_layout, tenants);
        this.context = context;
        this.tenants = tenants;
    }

    @NonNull
    @Override
    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
        LayoutInflater inflater = context.getLayoutInflater();

        View listViewItem = inflater.inflate(R.layout.tenant_list_layout, null, true);

        TextView textViewTenant = (TextView) listViewItem.findViewById(R.id.textViewTenant);
        TextView textViewAge = (TextView) listViewItem.findViewById(R.id.textViewAge);

        Tenant tenant = tenants.get(position);
        textViewTenant.setText(tenant.getTenantName());
        textViewAge.setText(String.valueOf(tenant.getTenantAge()));

        return listViewItem;

    }
}

要添加更多上下文，这是我的数据结构:

Answer 1

据我所见，在到达 tennat 对象之前还有一层。

databaseTenants = FirebaseDatabase.getInstance().getReference("tenants").child(uid).child(id).child(uid);

此外，将您的适配器创建拉取到 onCreate 方法，以便您可以全局访问它:

添加成员变量:

TenantList tenantListAdapter

并在您的 ListView 之后对其进行初始化，将租户拉到适配器实例化之前以便您可以访问它:

listViewTenants = (ListView) findViewById(R.id.listViewTenants);
tenants = new ArrayList<>();
tenantListAdapter = new TenantList(this, tenants);
listViewTenants.setAdapter(tenantListAdapter);

然后，在您的事件监听器中:

databaseTenants.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                tenants.clear();

                for(DataSnapshot tenantSnapshot : dataSnapshot.getChildren()){ 
                    for(DataSnapshot lastSnapshot: tenantSnapshot.getChildren()){ 
                       Tenant tenant = lastSnapshot.getValue(Tenant.class); 
                       tenants.add(tenant); 
                    } 
                 } 
               tenantListAdapter.notifyDataSetChanged();
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });