[英]Firebase Android ListView not being displayed
用戶登錄后,我試圖在主菜單屏幕的列表視圖上顯示來自 firebase 實時數據庫的數據。該應用程序正在運行,但未顯示數據。
這是我數據庫中的數據
現在是代碼。
MainMenu.java 該函數在 OnCreate() 上調用。
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);
}
自定義列表適配器.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;
}
}
適配器項.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 是我為要顯示的每個數據集創建的自定義布局。
<?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>
你已經在你的代碼中的謊言在事實問題CustomListAdapter
類一場名為ItemName
,但使用的是一個名為吸氣getItemName()
因為火力地堡是尋找數據庫名為場這是不正確itemName
而不是ItemName
. 看到小寫字母i
與大寫字母I
嗎?
有兩種方法可以解決這個問題。 第一個是通過根據Java 命名約定重命名字段來更改模型類。 所以你的模型類應該是這樣的:
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; }
}
在這個例子中,有private
字段和公共 getter。 還有一個更簡單的解決方案,直接在公共字段上設置值,如下所示:
public class CustomListAdapter {
public String itemName, quantity, serialNo, supplierName, supplierEmail, supplierPhone;
}
現在只需刪除當前數據並使用正確的名稱再次添加它。 此解決方案僅在您處於測試階段時才有效。
還有第二種方法,即使用annotations
。 因此,如果您更喜歡使用私有字段和公共 getter,則應僅在 getter 前使用PropertyName注釋。 所以你的CustomListAdapter
類應該是這樣的:
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; }
}
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