【发布时间】：2022-06-11 09:43:54
【问题描述】：
我完全被这个错误迷失了，代码：
适配器：
package com.example.bookapp;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageButton;
import android.widget.TextView;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import com.example.bookapp.databinding.RowCategoryBinding;
import java.util.ArrayList;
public class AdapterCategory extends RecyclerView.Adapter<AdapterCategory.HolderCategory>{
private final Context context;
private final ArrayList<ModelCategory> categoryArrayList;
//view binding
private RowCategoryBinding binding;
public AdapterCategory(Context context, ArrayList<ModelCategory> categoryArrayList) {
this.context = context;
this.categoryArrayList = categoryArrayList;
}
@NonNull
@Override
public HolderCategory onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
binding = RowCategoryBinding.inflate(LayoutInflater.from(context), parent,false);
return new HolderCategory(binding.getRoot());
}
@Override
public void onBindViewHolder(@NonNull HolderCategory holder, int position) {
//get data
ModelCategory model = categoryArrayList.get(position);
String id = model.getId();
String category = model.getCategory();
String uid = model.getUid();
long timestamp = model.getTimestamp();
//set data
holder.categoryTv.setText(category);
//handle click, delete category
holder.deleteBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Toast.makeText(context, ""+category, Toast.LENGTH_SHORT).show();
}
});
}
@Override
public int getItemCount() {
return categoryArrayList.size();
}
/*View holder class to hold UI views for row_category.xml*/
class HolderCategory extends RecyclerView.ViewHolder{
//ui views of row_category
TextView categoryTv;
ImageButton deleteBtn;
public HolderCategory(View v){
super(v);
//init ui views
categoryTv = binding.categoryTv;
deleteBtn = binding.deleteBtn;
}
}
}
行类别：
<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
xmlns:app="http://schemas.android.com/apk/res-auto"
app:contentPadding="10dp"
app:cardUseCompatPadding="true"
app:cardBackgroundColor="@color/white"
>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_vertical"
android:orientation="horizontal">
<TextView
android:id="@+id/categoryTv"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:text="@string/category_title"
android:layout_weight="1"
android:textColor="@color/black"/>
<ImageButton
android:id="@+id/deleteBtn"
android:layout_width="40dp"
android:layout_height="40dp"
android:src="@drawable/ic_baseline_delete_forever_24"
android:background="@drawable/shape_button03"
/>
</LinearLayout>
</androidx.cardview.widget.CardView>
模型类别： 包 com.example.bookapp;
public class ModelCategory {
String id, category, uid;
long timestamp;
//constructor empty req for firebase
public ModelCategory(){
}
//parametrized constructor
public ModelCategory(String id, String category, String uid, long timestamp) {
this.id = id;
this.category = category;
this.uid = uid;
this.timestamp = timestamp;
}
/*----Getter/Setters----*/
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getCategory() {
return category;
}
public void setCategory(String category) {
this.category = category;
}
public String getUid() {
return uid;
}
public void setUid(String uid) {
this.uid = uid;
}
public long getTimestamp() {
return timestamp;
}
public void setTimestamp(long timestamp) {
this.timestamp = timestamp;
}
}
DashboardAdminActivity：
package com.example.bookapp;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.WindowManager;
import android.widget.Toast;
import com.example.bookapp.databinding.ActivityDasboardBinding;
import com.example.bookapp.databinding.ActivityDashboardAdminBinding;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import java.util.ArrayList;
import java.util.Objects;
public class DashboardAdminActivity extends AppCompatActivity {
//view binding
private ActivityDashboardAdminBinding binding;
//firebase auth
private FirebaseAuth firebaseAuth;
//arraylist to store category
private ArrayList<ModelCategory> categoryArrayList;
//adapter
private AdapterCategory adapterCategory;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
binding = ActivityDashboardAdminBinding.inflate(getLayoutInflater());
setContentView(binding.getRoot());
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
//init firebase auth
firebaseAuth = FirebaseAuth.getInstance();
checkUser();
//handle click, logout
binding.logOutBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
firebaseAuth.signOut();
checkUser();
loadCategories();
}
});
//handle click, go to add category
binding.addCategoryBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
startActivity(new Intent(DashboardAdminActivity.this,CategoryAddActivity.class));
}
});
}
private void loadCategories() {
//init arraylist
categoryArrayList = new ArrayList<>();
//get all categories from firebase > Categories
DatabaseReference ref = FirebaseDatabase.getInstance().getReference("Categories");
ref.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
//clear arraylist before adding data info it
categoryArrayList.clear();
for (DataSnapshot ds: snapshot.getChildren()){
//get data
ModelCategory model = ds.getValue(ModelCategory.class);
//add to arraylist
categoryArrayList.add(model);
}
//setup adapter
adapterCategory = new AdapterCategory(DashboardAdminActivity.this, categoryArrayList);
//set adapter tp recyclerView
binding.categoriesRv.setAdapter(adapterCategory);
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
}
});
}
private void checkUser() {
//get current user
FirebaseUser firebaseUser = firebaseAuth.getCurrentUser();
if(firebaseUser==null){
//not logged inm go to main screen
startActivity(new Intent(this,LoginActivity.class));
finish();
}
else{
//logged in, user info
String email = firebaseUser.getEmail();
//set in textview of toolbar
binding.subTitleTv.setText(email);
}
}
}
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"
android:background="@drawable/back01"
tools:context=".DashboardAdminActivity">
<!--Toolbar-->
<RelativeLayout
android:id="@+id/toolbarRl"
android:layout_width="match_parent"
android:layout_height="?actionBarSize"
android:background="@drawable/shape_toolbar02">
<TextView
android:id="@+id/titleTv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:layout_centerHorizontal="true"
android:text="Dashboard Admin"
android:textStyle="bold"
android:textColor="@color/white"/>
<TextView
android:id="@+id/subTitleTv"
android:layout_width="wrap_content"
android:layout_below="@+id/titleTv"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:text="abx@example.com"
android:textColor="@color/white"/>
<ImageButton
android:id="@+id/logOutBtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:src="@drawable/ic_baseline_power_settings_new_24"
android:layout_alignParentEnd="true"
android:layout_marginEnd="10dp"
android:background="@android:color/transparent"/>
</RelativeLayout>
<!--Categories-->
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/categoriesRv"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_above="@+id/bottomLl"
android:layout_below="@id/toolbarRl"
android:layout_margin="5dp"
android:layout_marginStart="5dp"
android:layout_marginTop="5dp"
android:layout_marginEnd="5dp"
android:layout_marginBottom="5dp"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
tools:listitem="@layout/row_category" />
<LinearLayout
android:id="@+id/bottomLl"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_marginStart="10dp"
android:layout_marginEnd="10dp"
android:layout_marginBottom="10dp"
android:orientation="horizontal">
<!--Add Category-->
<Button
android:id="@+id/addCategoryBtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Add Category"
android:layout_weight="1"
android:layout_marginEnd="10dp"
android:background="@drawable/shape_button"
android:minHeight="50dp"
android:textAllCaps="false"
android:textColor="@color/white"/>
<!--Add PDF-->
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="@+id/addPdfFab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ic_baseline_picture_as_pdf_24"
android:tint="@color/white"
app:fabCustomSize="50dp"
android:backgroundTint="@color/yellow"/>
</LinearLayout>
</RelativeLayout>
使用 Firebase 制作电子书应用。 数据不显示。 知道有什么问题吗？ 我已经阅读了与同一问题相关的其他问题，但没有一个有帮助。
【问题讨论】：
-
No layout manager attached; Skipping layout已经作为问题存在，添加Android Studio & Java :以便发布您的问题并不意味着它与之前提出的问题不同 - 为什么要在 onDataChange 内重复创建适配器？创建并分配一次，在 onDataChange 中更改该适配器的数据 -
@Gardener 据我所知已经在 xml 上设置了，所以也不需要在活动中添加它
-
如果您遇到问题，最好在发布问题时创建MCVE。您为此问题发布了近 400（四百）行代码。人们需要解析和尝试在线调试的内容很多。请编辑您的问题并隔离问题，这样可以增加获得帮助的机会。