Listview不显示数据，而是显示要显示值的空白位置

Question

我正在解析JSON，并用它来夸大listview。第一个列表视图显示正确的值，但是当我从“贡献者”按钮打开另一个活动时，第二个listview没有显示任何值，而是在空白处显示文本。

这是我的代码...

主要活动

package com.example.pc.jbossoutreachapp;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.view.View;


public class MainActivity extends AppCompatActivity {


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




    public void getStarted(View view)
    {
        Intent intent = new Intent(this, repositories.class);
        startActivity(intent);
    }

}

布局活动。主要

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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/background"
    tools:context=".MainActivity">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="358dp"
        android:layout_height="251dp"
        android:contentDescription="@string/ContentDescipt"
        app:layout_constraintBottom_toTopOf="@+id/textView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@drawable/logo" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="0dp"
        android:layout_height="31dp"
        android:layout_marginBottom="1dp"
        android:gravity="center"
        android:text="@string/JBoss"
        android:textColor="@android:color/holo_red_dark"
        android:textSize="@dimen/size"
        android:textStyle="bold"
        app:fontFamily="sans-serif-smallcaps"
        app:layout_constraintBottom_toTopOf="@+id/textView3"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/imageView" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="0dp"
        android:layout_height="25dp"
        android:gravity="center"
        android:text="@string/JBoss_intro"
        android:textSize="18sp"
        app:layout_constraintBottom_toTopOf="@+id/button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <Button
        android:id="@+id/button"
        android:layout_width="114dp"
        android:layout_height="48dp"
        android:background="#f0e68c"
        android:onClick="getStarted"
        android:text="@string/Button"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView3" />

</android.support.constraint.ConstraintLayout>

存储库类

  

这里的代码工作正常，项目显示在列表视图中

HttpHandler类进行服务调用并返回Json String。

package com.example.pc.jbossoutreachapp;

import android.app.ProgressDialog;
import android.content.Intent;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;

public class repositories extends AppCompatActivity {

    private String TAG = MainActivity.class.getSimpleName();

    private ProgressDialog ProgDialog;
    private ListView listview;

    private static String url = "https://api.github.com/orgs/JBossOutreach/repos";

    ArrayList<HashMap<String,String>> RepoDetails;


    public void link(View view)
    {
        TextView text = findViewById(R.id.Repolink);
        String url = text.getText().toString();

        Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
        startActivity(browserIntent);

    }



    public void Contributors(View view)
    {
        listview = findViewById(R.id.list);
        TextView name = findViewById(R.id.RepositoryName);
        String n = name.getText().toString();
        String url1 = "https://api.github.com/repos/JBossOutreach/"+n+"/contributors";
        Intent intent = new Intent(this, contributors.class);
        Bundle bundle = new Bundle();
        bundle.putString("url", url1);
        intent.putExtras(bundle);
        startActivity(intent);
    }

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

        RepoDetails = new ArrayList<>();

        listview = (ListView)findViewById(R.id.list);

        new GetContacts().execute();
    }


    private class GetContacts extends AsyncTask<Void, Void, Void>
    {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();

            ProgDialog = new ProgressDialog(repositories.this);
            ProgDialog.setMessage("Please wait...");
            ProgDialog.setCancelable(false);
            ProgDialog.show();
        }

        @Override
        protected Void doInBackground(Void... voids) {

            HttpHandler sh = new HttpHandler();

            String Json_String = sh.makeServiceCall(url);

            Log.e(TAG, "Response from url: " + Json_String);

            if(Json_String != null)
            {
                try
                {
                  JSONArray array = new JSONArray(Json_String);
                    for(int i = 0; i < array.length(); i++)
                    {
                        JSONObject ob = array.getJSONObject(i);

                        String name = ob.getString("name");

                        JSONObject owner = ob.getJSONObject("owner");
                        String link = owner.getString("html_url");

                        HashMap<String, String> contact = new HashMap<>();

                        contact.put("name", name);
                        contact.put("link", link+"/"+name);

                        RepoDetails.add(contact);
                    }
                }
                catch(final JSONException e)
                {
                    Log.e(TAG, "Json parsing error: " + e.getMessage());
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            Toast.makeText(getApplicationContext(),
                                    "Json Parsing error: " + e.getMessage(), Toast.LENGTH_LONG).show();                        }
                    });
                }
            }

            else
            {
                Log.e(TAG, "Couldn't get Json from server");
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Toast.makeText(getApplicationContext(),
                                "Couldn't get json from server ", Toast.LENGTH_LONG).show();
                    }
                });
            }

            return null;
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            super.onPostExecute(aVoid);
            if(ProgDialog.isShowing())
            {
                ProgDialog.dismiss();
            }

            ListAdapter adapter = new SimpleAdapter(
                    repositories.this, RepoDetails, R.layout.repo_list_item, new String[]
                    {"name", "link"}, new int[]{R.id.RepositoryName, R.id.Repolink});

            listview.setAdapter(adapter);
        }

    }

}

repositories.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/background">

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginStart="109dp"
        android:layout_marginLeft="109dp"
        android:layout_marginTop="0dp"
        android:text="@string/Heading1"
        android:textSize="24sp"
        android:textStyle="bold" />

    <ListView
        android:id="@+id/list"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:layout_marginStart="0dp"
        android:layout_marginTop="0dp" />

</RelativeLayout>

repo_list_itmen.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android = "http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="5dp">

    <TextView
        android:id="@+id/RepositoryName"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:paddingTop="15dp"
        android:paddingBottom="8dp"
        android:textColor="@color/NameRepo" />

    <TextView
        android:id="@+id/Repolink"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:onClick="link"
        android:paddingBottom="8dp"
        android:textColor="@color/colorAccent" />

    <Button
        android:id="@+id/button2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="Contributors"
        android:text="@string/Contributors" />


</LinearLayout>

贡献者类

  

问题从这里开始，不显示任何项目，但仅显示项目的空白。

package com.example.pc.jbossoutreachapp;

import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.Toast;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;

public class contributors extends AppCompatActivity {


    private String TAG = contributors.class.getSimpleName();
    ArrayList<HashMap<String, String>> names;
    ListView lv;
    private ProgressDialog progressDialog;
    static String url;


    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.contributors);
        names = new ArrayList<>();
        lv = findViewById(R.id.list2);

        Bundle bundle = getIntent().getExtras();
        System.out.print(url);
        url = bundle.getString("url");

        new contributors.getcontrib().execute();
    }


    private class getcontrib extends AsyncTask<Void, Void, Void> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();

            progressDialog = new ProgressDialog(contributors.this);
            progressDialog.setMessage("Please wait...");
            progressDialog.setCancelable(false);
            progressDialog.show();
        }

        @Override
        protected Void doInBackground(Void... voids) {

            HttpHandler hd = new HttpHandler();
            String Json_result = hd.makeServiceCall(url);
            Log.e(TAG, "Response from url: " + Json_result);

            if (Json_result != null) {
                try {
                    JSONArray array = new JSONArray(Json_result);
                    for (int i = 0; i < array.length(); i++) {
                        JSONObject obj = array.getJSONObject(i);
                        String contributor_name = obj.getString("login");

                        HashMap<String, String> hashMap = new HashMap<>();
                        hashMap.put("name", contributor_name);


                        names.add(hashMap);
                    }
                } catch (final JSONException e) {
                    Log.e(TAG, "Json parsing error: " + e.getMessage());
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            Toast.makeText(getApplicationContext(),
                                    "Json Parsing error: " + e.getMessage(), Toast.LENGTH_LONG).show();
                        }
                    });
                }
            }


            return null;
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            super.onPostExecute(aVoid);
            if (progressDialog.isShowing()) {
                progressDialog.dismiss();
            }

            ListAdapter adapter = new SimpleAdapter(
                    contributors.this, names, R.layout.contributor_list_items, new String[]
                    {"contributors"}, new int[]{R.id.ContributorsName});
            ((SimpleAdapter) adapter).notifyDataSetChanged();
            lv.setAdapter(adapter);
        }

    }

}

contributors.xml

 <?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@drawable/background">

        <TextView
            android:id="@+id/textView2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentStart="true"
            android:layout_alignParentLeft="true"
            android:layout_alignParentTop="true"
            android:layout_marginStart="109dp"
            android:layout_marginLeft="109dp"
            android:layout_marginTop="0dp"
            android:text="@string/Heading2"
            android:textSize="24sp"
            android:textStyle="bold" />

        <ListView
            android:id="@+id/list2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentStart="true"
            android:layout_alignParentTop="true"
            android:layout_marginStart="0dp"
            android:layout_marginTop="0dp" />

    </RelativeLayout>

contributors_list_items.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android = "http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="5dp">

    <TextView
        android:id="@+id/ContributorsName"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:paddingTop="15dp"
        android:paddingBottom="8dp"
        android:textColor="@color/colorPrimaryDark" />

</LinearLayout>

Answer 1

从更改您的AsyncTask调用

new contributors.getcontrib().execute();

到

new getcontrib().execute();

编辑：

另外，从以下位置更改适配器初始化代码：

ListAdapter adapter = new SimpleAdapter(
                    contributors.this, names, R.layout.contributor_list_items, new String[]
                    {"contributors"}, new int[]{R.id.ContributorsName});

到

ListAdapter adapter = new SimpleAdapter(
                    contributors.this, names, R.layout.contributor_list_items, new String[]
                    {"name"}, new int[]{R.id.ContributorsName});

注意：您已在“名称”键而不是“贡献者”键中添加了贡献者名称

Answer 2

首先检查Ur响应。

          String url1 = "https://api.github.com/repos/JBossOutreach/"+n+"/contributors";

Ur Json Respo

          {
         "message": "Not Found",
          "documentation_url": "https://developer.github.com/v3/repos/#list-contributors"
        }