Firebase Android ListView 未显示
Posted
技术标签:
【中文标题】Firebase Android ListView 未显示【英文标题】：Firebase Android ListView not being displayed 【发布时间】：2019-06-01 20:00:35 【问题描述】：一旦用户登录，我正在尝试在主菜单屏幕的列表视图中显示来自 firebase 实时数据库的数据。该应用正在运行，但不显示数据。
这是我数据库中的数据
现在是代码。
MainMenu.java 这个函数在 OnCreate() 上调用。
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);
CustomListAdapter.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;
AdapterItem.java
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.xml
<?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_
android:layout_
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:showIn="@layout/app_bar_main_menu">
<ListView
android:id="@+id/listView"
android:layout_
android:layout_
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:layout_marginStart="0dp"
android:layout_marginTop="0dp" />
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"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_
android:layout_
app:layout_behavior="@string/appbar_scrolling_view_behavior"
xmlns:app="http://schemas.android.com/apk/res-auto">
<android.support.constraint.ConstraintLayout
android:layout_
android:layout_
android:layout_marginStart="8dp"
android:layout_marginTop="16dp"
android:layout_marginEnd="8dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<TextView
android:id="@+id/amount"
android:layout_
android:layout_
android:layout_marginEnd="8dp"
android:layout_marginBottom="8dp"
android:text="TextView"
android:textSize="20sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent" />
<TextView
android:id="@+id/serialNo"
android:layout_
android:layout_
android:layout_marginStart="10dp"
android:layout_marginTop="8dp"
android:layout_marginBottom="8dp"
android:text="TextView"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/supplierName"
android:layout_
android:layout_
android:layout_marginTop="8dp"
android:text="TextView"
app:layout_constraintTop_toBottomOf="@+id/serialNo" />
<TextView
android:id="@+id/name"
android:layout_
android:layout_
android:layout_marginBottom="8dp"
android:text="Medium Text"
android:textAppearance="?android:attr/textAppearanceMedium"
android:textColor="#0171B0"
app:layout_constraintBottom_toTopOf="@+id/serialNo" />
</android.support.constraint.ConstraintLayout>
</android.support.constraint.ConstraintLayout>
【问题讨论】：
***.com/questions/40891268/… 【参考方案1】：代码中的问题在于，您在 CustomListAdapter 类中有一个名为 ItemName 的字段，但您使用的是名为 getItemName() 的 getter，这是不正确的，因为 Firebase 正在数据库中查找一个名为 itemName 而不是 ItemName 的字段。看到小写字母i 与大写字母I？
有两种方法可以解决这个问题。第一个是通过根据Java Naming Conventions 重命名字段来更改您的模型类。所以你的模型类应该是这样的：
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;
看这个例子，有private 字段和公共getter。还有一个更简单的解决方案，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并使用正确的名称再次添加即可。此解决方案仅在您处于测试阶段时才有效。
还有第二种方法，就是使用annotations。所以如果你更喜欢使用私有字段和公共getter，你应该只在getter前面使用PropertyName注解。所以你的CustomListAdapter 类应该是这样的：
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;
【讨论】：
以上是关于Firebase Android ListView 未显示的主要内容，如果未能解决你的问题，请参考以下文章
在Android中更新firebase数据库时ListView值重复值
如何使用 Firebase 查询的结果最终在 Android Studio 中填充 ListView