我的 customAdapter 或 Activity.java 有什么问题？运行应用程序时，我的 ListView 不显示它的元素

Question

我正在开发 RecyclerView 并使用 CustomAdapter，我的应用程序运行顺利，但我的 ListView 没有显示它的内容！我的代码有什么缺失或错误？我尝试 return arraylist.size() 并输入 list.setHasFixedSize 但没有成功！

prospectowner_listview.java (Activity class)

public class prospectowner_listview extends AppCompatActivity {

    RecyclerView list;
    ArrayList <com.example.android.e7gzlykora.owner> ownerlist = new ArrayList <>();
    private DatabaseReference mFirebaseDatabase;
    private FirebaseDatabase mFirebaseInstance;
    owner owner;
    customAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.prospectowner_listview);

        list = findViewById(R.id.list);
        LinearLayoutManager manager = new LinearLayoutManager(this);
        list.setLayoutManager(manager);
        list.setHasFixedSize(true);
        manager.setOrientation(LinearLayoutManager.VERTICAL);
        adapter = new customAdapter(prospectowner_listview.this,ownerlist);

        mFirebaseInstance = FirebaseDatabase.getInstance();
        mFirebaseDatabase = mFirebaseInstance.getReference("owners");

        mFirebaseDatabase.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                for (DataSnapshot data: dataSnapshot.getChildren()){
                    owner o = data.getValue(owner.class);
                    ownerlist.add(o);
                }
                list.setAdapter(adapter);
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) { }
        });
    }
}

CustomerAdapter.java

public class customAdapter extends RecyclerView.Adapter<customAdapter.MyViewHolder>{

    private final ArrayList<owner> ownerlist;
    private final Context mContext;

    public customAdapter(Context c , ArrayList<owner> p) {
        this.mContext = c;
        this.ownerlist = new ArrayList <>();
    }

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int 
    viewType) {
        return new MyViewHolder(LayoutInflater.from(mContext).inflate(R.layout.prospectowners,parent,false));
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
        owner owner = ownerlist.get(position);

        holder.name.setText(owner.getName());
        holder.field.setText(owner.getFieldname());
        holder.mobile.setText(owner.getMobile());
        holder.address.setText(owner.getAddress());
        holder.cost.setText(owner.getCost());
    }

    @Override
    public int getItemCount() {
        return ownerlist.size();
    }

    public class MyViewHolder extends RecyclerView.ViewHolder {
        public TextView name;
        public TextView field;
        public TextView mobile;
        public TextView address;
        public TextView cost;

       public MyViewHolder(View itemView) {
            super(itemView);
            this.name = itemView.findViewById(R.id.name);
            this.field =  itemView.findViewById(R.id.fieldName);
            this.mobile =  itemView.findViewById(R.id.mobileowner);
            this.address =  itemView.findViewById(R.id.address);
            this.cost =  itemView.findViewById(R.id.cost);
        }
    }
}

Owner.java

public class owner extends ArrayList <owner> {

    public String name;
    public String mobile;
    public String fieldname;
    public String address;
    public String cost;
    public String zone1;
    public String zone2;
    private Class thisClass;

    public owner(){}

    public owner(String name, String mobile,String fieldname,String address, String cost, String zone1, String zone2) {
        this.name = name;
        this.mobile = mobile;
        this.fieldname = fieldname;
        this.address = address;
        this.cost = cost;
        this.zone1 = zone1;
        this.zone2 = zone2;
    }

    public String getMobile() {
        return mobile;
    }

    public String getName() {
        return name;
    }

     public String getAddress() {
        return address;
     }

    public void setName(String name) {
        this.name = name;
    }

    public void setMobile(String mobile) {
        this.mobile = mobile;
    }

    public void setFieldname(String fieldname) {
        this.fieldname = fieldname;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public void setCost(String cost) {
        this.cost = cost;
    }

    public void setZone1(String zone1) {
        this.zone1 = zone1;
    }

    public void setZone2(String zone2) {
        this.zone2 = zone2;
    }

    public void setThisClass(Class thisClass) {
        this.thisClass = thisClass;
    }

    public String getFieldname() {
        return fieldname;
    }

    public String getCost() {
        return cost;
    }

    public String getZone1() {
        return zone1;
    }

    public String getZone2() {
        return zone2;
    }

}

---------------- prospectowners.xml----------------------------

   <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical">


    <TextView
        android:id="@+id/fieldName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""
        android:textColor="@android:color/black"
        android:textStyle="bold"
         />

    <TextView
        android:id="@+id/nameowner"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/fieldName"
        android:layout_marginStart="50dp"
        android:layout_marginLeft="50dp"
        android:layout_marginTop="10dp"
        android:text=""
        android:textColor="@android:color/black"
        />

    <TextView
        android:id="@+id/mobileowner"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/nameowner"
        android:layout_marginStart="50dp"
        android:layout_marginLeft="50dp"
        android:layout_marginTop="10dp"
        android:textColor="@android:color/black"
         />

    <TextView
        android:id="@+id/address"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/mobileowner"
        android:layout_marginStart="50dp"
        android:layout_marginLeft="50dp"
        android:layout_marginTop="10dp"
        android:textColor="@android:color/black"
         />

    <TextView
        android:id="@+id/cost"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/address"
        android:layout_marginStart="50dp"
        android:layout_marginLeft="50dp"
        android:layout_marginTop="10dp"
        android:textColor="@android:color/black"
         />

    <Button
        android:id="@+id/reserve"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
            android:layout_below="@+id/cost"
        android:onClick="reserve"
            android:layout_marginStart="230dp"
            android:layout_marginLeft="270dp"
            android:layout_marginTop="10dp"
            android:text="E7gzly"
            android:textSize="15dp" />

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingBottom="@dimen/activity_vertical_margin">

    <android.support.v7.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/list"
    android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

Answer 1

试试这个，

在你的activityclass改变

list.setAdapter(adapter)

至

list.setAdapter(new customAdapter(prospectowner_listview.this, ownerlist));

Answer 2

在您的适配器中创建新函数：

public void addData(List<Owner> owners){
 this.ownerList = owners;
 notifyOnDataSetChanged();
}

并在 onDataChange 中调用：

adapter.addData(owners);

Answer 3

我认为问题出在您的适配器上，请像下面这样更改您的适配器代码：

public class customAdapter extends RecyclerView.Adapter<customAdapter.MyViewHolder>{

    private ArrayList<owner> ownerlist;
    private Context mContext;

    public customAdapter(Context c , ArrayList<owner> p) {
        this.mContext = c;
        this.ownerlist = p;
    }

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int 
    viewType) {
        return new MyViewHolder(LayoutInflater.from(mContext).inflate(R.layout.prospectowners,parent,false));
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
        owner owner = ownerlist.get(position);

        holder.name.setText(owner.getName());
        holder.field.setText(owner.getFieldname());
        holder.mobile.setText(owner.getMobile());
        holder.address.setText(owner.getAddress());
        holder.cost.setText(owner.getCost());
    }

    @Override
    public int getItemCount() {
        return ownerlist.size();
    }

    public void addData(ArrayList<owner> newData){
        this.ownerlist.addAll(newData);
        notifyOnDataSetChanged();
    }

    public class MyViewHolder extends RecyclerView.ViewHolder {
        public TextView name;
        public TextView field;
        public TextView mobile;
        public TextView address;
        public TextView cost;

       public MyViewHolder(View itemView) {
            super(itemView);
            this.name = itemView.findViewById(R.id.name);
            this.field =  itemView.findViewById(R.id.fieldName);
            this.mobile =  itemView.findViewById(R.id.mobileowner);
            this.address =  itemView.findViewById(R.id.address);
            this.cost =  itemView.findViewById(R.id.cost);
        }
    }
}

然后像这样调用方法 addData：

@Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                for (DataSnapshot data: dataSnapshot.getChildren()){
                    owner o = data.getValue(owner.class);
                    ownerlist.add(o);
                }
                list.setAdapter(adapter);
                adapter.addData(ownerlist);

            }

顺便说一句，实际上你可以在监听器之外设置适配器

UPDATE（本次更新将adapter值的位置设置为默认为空数据，触发listener时填充）

public class customAdapter extends RecyclerView.Adapter<customAdapter.MyViewHolder>{

    private ArrayList<owner> ownerlist;
    private Context mContext;

    public customAdapter(Context c , ArrayList<owner> p) {
        this.mContext = c;
        this.ownerlist = new Arraylist<>();
    }

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int 
    viewType) {
        return new MyViewHolder(LayoutInflater.from(mContext).inflate(R.layout.prospectowners,parent,false));
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
        owner owner = ownerlist.get(position);

        holder.name.setText(owner.getName());
        holder.field.setText(owner.getFieldname());
        holder.mobile.setText(owner.getMobile());
        holder.address.setText(owner.getAddress());
        holder.cost.setText(owner.getCost());
    }

    @Override
    public int getItemCount() {
        return ownerlist.size();
    }

    public void addData(ArrayList<owner> newData){
        this.ownerlist.addAll(newData);
        notifyOnDataSetChanged();
    }

    public class MyViewHolder extends RecyclerView.ViewHolder {
        public TextView name;
        public TextView field;
        public TextView mobile;
        public TextView address;
        public TextView cost;

       public MyViewHolder(View itemView) {
            super(itemView);
            this.name = itemView.findViewById(R.id.name);
            this.field =  itemView.findViewById(R.id.fieldName);
            this.mobile =  itemView.findViewById(R.id.mobileowner);
            this.address =  itemView.findViewById(R.id.address);
            this.cost =  itemView.findViewById(R.id.cost);
        }
    }
}

public class prospectowner_listview extends AppCompatActivity {

    RecyclerView list;
    ArrayList <com.example.android.e7gzlykora.owner> ownerlist = new ArrayList <>();
    private DatabaseReference mFirebaseDatabase;
    private FirebaseDatabase mFirebaseInstance;
    owner owner;
    customAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.prospectowner_listview);

        list = findViewById(R.id.list);
        LinearLayoutManager manager = new LinearLayoutManager(this);
        list.setLayoutManager(manager);
        list.setHasFixedSize(true);
        manager.setOrientation(LinearLayoutManager.VERTICAL);
        adapter = new customAdapter(prospectowner_listview.this,ownerlist);
        list.setAdapter(adapter);

        mFirebaseInstance = FirebaseDatabase.getInstance();
        mFirebaseDatabase = mFirebaseInstance.getReference("owners");

        mFirebaseDatabase.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                for (DataSnapshot data: dataSnapshot.getChildren()){
                    owner o = data.getValue(owner.class);
                    ownerlist.add(o);
                }
                adapter.addData(ownerlist);
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) { }
        });
    }
}

Answer 4

数组列表始终为空，因为您将适配器构造函数初始化为新列表。请查看

我的 customAdapter 或 Activity.java 有什么问题？运行应用程序时，我的 ListView 不显示它的元素

What is wrong with my customAdapter or Activity.java? my ListView not showing it's element when running the app

java

android

listview

arraylist

custom-adapter

我的 customAdapter 或 Activity.java 有什么问题？ 运行 应用程序时，我的 ListView 不显示它的元素

What is wrong with my customAdapter or Activity.java? my ListView not showing it's element when running the app

java

android

listview

arraylist

custom-adapter

我的 customAdapter 或 Activity.java 有什么问题？运行应用程序时，我的 ListView 不显示它的元素