UploadingItemAdapter给出LogCat null值，listItem的文本视图在listview的片段中也保持空白

Question

我不知道哪个部分我弄错了。在UploadItemAdapter.class,uploadingDetails.getTitle()和uploadingDetails.getDiscription()，我的日志猫都给了我null。在android listView屏幕textView项目也是空白Screenshot。我的电脑Screen.我的代码如下所述。 UploadItemAdapter.java

package com.example.shiva.gconnection.extendedVersion;

import android.content.Context;
import android.support.v4.app.FragmentActivity;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;

import com.example.shiva.gconnection.R;
import com.example.shiva.gconnection.UploadingDetails;

import java.util.List;

/**
 * Created by shiva on 3/3/18.
 */

public class UploadItemAdapter extends ArrayAdapter<UploadingDetails>{
    public UploadItemAdapter( Context context, int resource, List<UploadingDetails> objects) {
        super(context, resource, objects);
    }

    @Override
    public View getView(int position ,View convertView,ViewGroup parent) {
        if (convertView == null) {
            convertView = ((FragmentActivity) getContext()).getLayoutInflater().inflate(R.layout.uploaded_material_child, parent, false);
        }
        TextView titalTV = (TextView) convertView.findViewById(R.id.title_item_upload_material);
        TextView discriptionTV= (TextView) convertView.findViewById(R.id.discription_item_upload_material);

        UploadingDetails uploadingDetails = getItem(position);
        titalTV.setText(uploadingDetails.getTitle());
        discriptionTV.setText(uploadingDetails.getDiscription());
        Log.v("abcd",uploadingDetails.getTitle() +" "+uploadingDetails.getDiscription());
        return convertView;
    }
}

uploaded_material.xml

<?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:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_margin="10dp"
    android:orientation="vertical">

    <ListView
        android:id="@+id/lv_upload_item"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:transcriptMode="alwaysScroll"
        tools:listitem="@layout/uploaded_material_child" />
</LinearLayout>

Uploaded_material_child.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:orientation="vertical"
    android:layout_height="wrap_content">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Title"
        android:id="@+id/title_item_upload_material"
        android:textSize="20dp"
        android:textColor="@android:color/black"
        android:layout_margin="5dp"/>
    <TextView
        android:layout_margin="5dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Discription"
        android:textColor="@android:color/black"
        android:id="@+id/discription_item_upload_material"
        android:textSize="16dp" />
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="UploadedBy"
        android:id="@+id/uploaded_by"
        android:textSize="16dp"
        android:textColor="@android:color/black"
        android:layout_margin="5dp"/>
</LinearLayout>

fragment last view.Java

package com.example.shiva.gconnection.extendedVersion;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import com.example.shiva.gconnection.R;
import com.example.shiva.gconnection.UploadingDetails;
import com.google.firebase.database.ChildEventListener;
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 java.util.ArrayList;

public class FragmentLastView extends Fragment {
    private FirebaseDatabase mdatabase;
    private DatabaseReference mdbRef;
    private ListView mItemLV;
    private ChildEventListener childEventListener;
    private ArrayAdapter mUploadItemAdapter;

    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view= inflater.inflate(R.layout.uploaded_material,container,false);
        mdatabase = FirebaseDatabase.getInstance();
        mdbRef = mdatabase.getReference("College");
        return view;
    }

    @Override
    public void onViewCreated(View view,Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        final String subjectName = getArguments().getString("SubjectName");
        final String branchname = getArguments().getString("BranchName");
        final String class1Name = getArguments().getString("Class1Name");
        final String className = getArguments().getString("ClassName");

        final ArrayList<UploadingDetails> uploadingDetails = new ArrayList<>();
        mItemLV= (ListView)view.findViewById(R.id.lv_upload_item);

        mUploadItemAdapter = new UploadItemAdapter(view.getContext(),R.layout.uploaded_material_child,uploadingDetails);
        mItemLV.setAdapter(mUploadItemAdapter);

        childEventListener = new ChildEventListener() {
            @Override
            public void onChildAdded(DataSnapshot dataSnapshot, String s) {
                UploadingDetails updetails = dataSnapshot.getValue(UploadingDetails.class);
                uploadingDetails.add(updetails);
                mUploadItemAdapter.notifyDataSetChanged();
            }
            @Override
            public void onChildChanged(DataSnapshot dataSnapshot, String s) {}
            @Override
            public void onChildRemoved(DataSnapshot dataSnapshot) {}
            @Override
            public void onChildMoved(DataSnapshot dataSnapshot, String s) {}
            @Override
            public void onCancelled(DatabaseError databaseError) {}
        };
        mdbRef.child(branchname).child(subjectName).child(className).child(class1Name).addChildEventListener(childEventListener);


    }
}

uploading details.Java

package com.example.shiva.gconnection;

    public class UploadingDetails {
        private String mTitle;
        private String mDiscription;
        private String mArrayUri;

        public UploadingDetails(){
        }

        public UploadingDetails(String title, String discription,String arrayUri){
            this.mTitle= title;
            this.mDiscription=discription;
            this.mArrayUri=arrayUri;

        }

        public String getTitle(){
            return this.mTitle;
        }

        public String getDiscription(){
            return this.mDiscription;
        }

        public String getArrayUri(){return this.mArrayUri;}
    }

Answer 1

模型类中字段的名称必须与要在firebase数据引用节点中检索的数据的名称相同

Answer 2

我不明白它是如何工作的但是当我改变以下代码问题时解决了UploadindDetils.java

package com.example.shiva.gconnection;

public class UploadingDetails {
    private String mTitle;
    private String mDiscription;
    private String mArrayUri;

    public UploadingDetails() {
    }

    public UploadingDetails(String title, String discription, String arrayUri) {
        this.mTitle = title;
        this.mDiscription = discription;
        this.mArrayUri = arrayUri;

    }

    public String getTitle() {
        return this.mTitle;
    }

    public void setTitle(String title) {
        this. mTitle = title;
    }

    public void setDiscription(String discription) {
        this.mDiscription = discription;
    }

    public void setArrayUri(String arrayUri) {
        this.mArrayUri = arrayUri;
    }

    public String getDiscription() {
        return this.mDiscription;
    }

    public String getArrayUri() {
        return this.mArrayUri;
    }
}