我正在尝试在用户登录后在主菜单屏幕的 ListView 中显示来自 firebase 实时数据库的数据。该应用程序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 此函数在 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);
}
自定义列表适配器.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_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" />
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_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
xmlns:app="http://schemas.android.com/apk/res-auto">
<android.support.constraint.ConstraintLayout
android:layout_width="0dp"
android:layout_height="100dp"
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_width="wrap_content"
android:layout_height="wrap_content"
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_width="wrap_content"
android:layout_height="wrap_content"
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_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:text="TextView"
app:layout_constraintTop_toBottomOf="@+id/serialNo" />
<TextView
android:id="@+id/name"
android:layout_width="wrap_content"
android:layout_height="23dp"
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>
最佳答案
您的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 在数据库中查找名为 itemName 而不是 ItemName 的字段。看到小写字母 i 与大写字母 I 了吗？
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public getters。还有一个更简单的解决方案，直接在公共(public)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重新添加。此解决方案仅在您处于测试阶段时才有效。
还有第二种方式，就是使用annotations。因此，如果您更喜欢使用私有(private)字段和公共(public) getter，则应该使用 PropertyName仅在 setter/getter 前面注释。所以您的 CustomListAdapter 类应该如下所示:
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; }
}
关于java - Firebase Android ListView 未显示，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/54125503/