Question

用户登录后，我试图在主菜单屏幕的列表视图上显示Firebase实时数据库中的数据。该应用程序正在运行，但未显示数据。

这是我数据库中的数据

现在输入密码。

MainMenu.java在OnCreate（）上调用此函数。

bgs= [];
public lineChartData: Array<any>

ngOnInit(){
    this.lineChartData = []
    . . .
}

getbgs() {
    this.bgsService.getbgss(this.token).subscribe(
        data => {
            this.bgs = data.map(k => k.bgs);    
            this.lineChartData = [
                { data: [this.bgs], label: 'Series A' }
            ]
        }
   );
}

CustomListAdapter.java

 public void makeItem ()
    {
        lv = findViewById(R.id.listView);
        db = FirebaseDatabase.getInstance().getReference();
        helper = new FirebaseHelper(db);
        adapter= new AdapterItem(this,helper.retrive());
        lv.setAdapter(adapter);

    }

AdapterItem.java

public class CustomListAdapter{

    private String ItemName;
    private String Quantity;
    private String SerialNo;
    private String SupplierName;
    private String SupplierEmail;
    private String SupplierPhone;


    public CustomListAdapter(){

    }

    public CustomListAdapter (String ItemName,String Quantity,String SerialNo,String SupplierName,String SupplierEmail,String SupplierPhone)
    {
        this.ItemName = ItemName;
        this.Quantity = Quantity;
        this.SerialNo = SerialNo;
        this.SupplierName = SupplierName;
        this.SupplierEmail = SupplierEmail;
        this.SupplierPhone = SupplierPhone;
    }

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

    public String getItemName ()
    {
        return ItemName;
    }

    public void setQuantity (String Quantity)
    {
        this.Quantity = Quantity;
    }


    public String getQuantity ()
    {
        return Quantity;
    }

    public void setSerialNo (String SerialNo)
    {
        this.SerialNo = SerialNo;
    }


    public String getSerialNo ()
    {
        return SerialNo;
    }

    public void setSupplierName (String SupplierName)
    {
        this.SupplierName = SupplierName;
    }

    public String getSupplierName()
    {
        return SupplierName;
    }

    public void setSupplierEmail (String SupplierEmail)
    {
        this.SupplierEmail = SupplierEmail;
    }

    public String getSupplierEmail() {
        return SupplierEmail;
    }

    public void setSupplierPhone (String SupplierPhone)
    {
        this.SupplierPhone = SupplierPhone;
    }

    public String getSupplierPhone() {
        return SupplierPhone;
    }
}

content_main_menu.xml

public class AdapterItem extends BaseAdapter {
    Context c;
    ArrayList<CustomListAdapter> customListAdapters;

    public AdapterItem(Context c, ArrayList<CustomListAdapter> customListAdapters) {
        this.c = c;
        this.customListAdapters = customListAdapters;
    }

    @Override
    public int getCount() {
        return customListAdapters.size();
    }

    @Override
    public Object getItem(int position) {
        return customListAdapters.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if(convertView==null)
        {
            convertView=LayoutInflater.from(c).inflate(R.layout.content_main_menu_list,parent,false);
        }
        TextView ItemName = convertView.findViewById(R.id.name);
        TextView SerialNo = convertView.findViewById(R.id.serialNo);
        TextView SupplierName = convertView.findViewById(R.id.supplierName);
        TextView amount = convertView.findViewById(R.id.amount);

        final CustomListAdapter CLA = (CustomListAdapter) this.getItem(position);

        ItemName.setText(CLA.getItemName());
        SerialNo.setText(CLA.getSerialNo());
        SupplierName.setText(CLA.getSupplierName());
        amount.setText(CLA.getQuantity());

        convertView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(c,CLA.getItemName(),Toast.LENGTH_SHORT).show();
            }
        });

        return convertView;
    }
}

content_main_menu_list.xml是我为要显示的每个数据集创建的自定义布局。

  <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:showIn="@layout/app_bar_main_menu">

    <ListView
        android:id="@+id/listView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:layout_marginStart="0dp"
        android:layout_marginTop="0dp" />

Answer 1

代码中的问题在于，您的CustomListAdapter类中有一个名为ItemName的字段，但是您使用的是名为getItemName()的吸气剂，自Firebase以来这是不正确的正在数据库中查找名为 itemName 而不是ItemName的字段。看到小写的i与大写的I？

有两种方法可以解决此问题。第一个是通过根据Java Naming Conventions重命名字段来更改模型类。因此，您的模型类应如下所示：

public class CustomListAdapter {
    private String itemName, quantity, serialNo, supplierName, supplierEmail, supplierPhone;

    public CustomListAdapter() {}

    public CustomListAdapter(String itemName, String quantity, String serialNo, String supplierName, String supplierEmail, String supplierPhone) {
        this.itemName = itemName;
        this.quantity = quantity;
        this.serialNo = serialNo;
        this.supplierName = supplierName;
        this.supplierEmail = supplierEmail;
        this.supplierPhone = supplierPhone;
    }

    public String getItemName() { return itemName; }
    public String getQuantity() { return quantity; }
    public String getSerialNo() { return serialNo; }
    public String getSupplierName() { return supplierName; }
    public String getSupplierEmail() { return supplierEmail; }
    public String getSupplierPhone() { return supplierPhone; }
}

在此示例中，有private个字段和公共获取器。还有一个更简单的解决方案，可以直接在公共字段上设置值，如下所示：

public class CustomListAdapter {
    public String itemName, quantity, serialNo, supplierName, supplierEmail, supplierPhone;
}

现在只需删除当前数据，然后使用正确的名称再次添加即可。仅当您处于测试阶段时，此解决方案才有效。

还有第二种方法，即使用annotations。因此，如果您更喜欢使用私有字段和公共getter，则应仅在getter之前使用PropertyName批注。因此，您的CustomListAdapter类应如下所示：

public class CustomListAdapter {
    private String ItemName;
    private String Quantity;
    private String SerialNo;
    private String SupplierName;
    private String SupplierEmail;
    private String SupplierPhone;

    public CustomListAdapter() {}

    public CustomListAdapter(String itemName, String quantity, String serialNo, String supplierName, String supplierEmail, String supplierPhone) {
        ItemName = itemName;
        Quantity = quantity;
        SerialNo = serialNo;
        SupplierName = supplierName;
        SupplierEmail = supplierEmail;
        SupplierPhone = supplierPhone;
    }

    @PropertyName("ItemName")
    public String getItemName() { return ItemName; }
    @PropertyName("Quantity")
    public String getQuantity() { return Quantity; }
    @PropertyName("SerialNo")
    public String getSerialNo() { return SerialNo; }
    @PropertyName("SupplierName")
    public String getSupplierName() { return SupplierName; }
    @PropertyName("SupplierEmail")
    public String getSupplierEmail() { return SupplierEmail; }
    @PropertyName("SupplierPhone")
    public String getSupplierPhone() { return SupplierPhone; }
}

Firebase Android ListView未显示

1 个答案: