Java 集成新闻源不显示（ANDROID KITKAT）

因此，我正在为爱狗者创建一个应用程序（大学项目），我正在尝试创建一个集成的新闻提要，显示与狗有关的新闻，点击后会将用户带到网站。我做了一个虚拟应用程序来测试系统，它工作得非常好。当我把它切换到我目前的狗应用程序，它完全停止工作。问题是，我用来显示文章列表的活动完全没有显示任何内容

这里有两个活动，一个链接活动和一个新闻项目活动。“链接”活动是页面使用的主要活动，并以某种方式在页面上显示文本。newsItem活动充当getter，通过JSON文件查找数组中的某些单词，并将它们解析回应用程序。我还使用localHost来托管JSON文件

如果你们能帮我，那太不可思议了！我撞到了一堵完整的砖墙

Links\u活动类连接到Activity\u Links.xml文件

newsItem类连接到Article.xml文件

链接\u活动类

   package uk.ac.napier.doggo;

import android.content.Intent;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;


import com.android.volley.DefaultRetryPolicy;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonObjectRequest;
import com.android.volley.toolbox.Volley;
import com.squareup.picasso.Picasso;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.ArrayList;
import java.util.List;

public class Links_Activity extends AppCompatActivity {

    private List<newsItem> newsFeed = new ArrayList<>();

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

        engine();
        addClickListener();

    }

    private void engine() {
        RequestQueue queue = Volley.newRequestQueue(this);

        JsonObjectRequest myReq = new JsonObjectRequest(Request.Method.GET,
                "http://10.0.2.2/news.json",
                null,
                new Response.Listener<JSONObject>() {
                    @Override
                    public void onResponse(JSONObject response) {
                        try {
                            JSONArray newsItems = response.getJSONArray("newsItems");

                            for (int i = 0; i < newsItems.length(); i++) {
                                JSONObject temp = newsItems.getJSONObject(i);

                                String image = temp.getString("image");
                                String title = temp.getString("title");
                                String time = temp.getString("time");
                                String date = temp.getString("date");
                                String content = temp.getString("content");
                                String link = temp.getString("link");


                                newsFeed.add(new newsItem(title, content, date, time, link, image));

                            }
                        } catch(JSONException e){
                            Log.i("myTag", e.toString());
                        }
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        Log.i("myTag", error.toString());
                    }
                });



        myReq.setRetryPolicy(new DefaultRetryPolicy(
                30*1000,
                DefaultRetryPolicy.DEFAULT_MAX_RETRIES,
                DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));
        queue.add(myReq);



        ArrayAdapter<newsItem> adapter = new customAdapter();

        ListView  newsItems = (ListView) (findViewById(R.id.newsItems));
        newsItems.setAdapter(adapter);

    }

    private void addClickListener() {
        ListView newsItems = (ListView) (findViewById(R.id.newsItems));
        newsItems.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                newsItem currentItem = newsFeed.get(position);
                Intent i = new Intent (Intent.ACTION_VIEW);
                i.setData(Uri.parse(currentItem.getUrl()));
                startActivity(i);
            }
        });
    }



        private class customAdapter extends ArrayAdapter<newsItem> {
                public customAdapter() {
            super(Links_Activity.this, R.layout.article, newsFeed);
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

            if(convertView == null) {
                convertView = getLayoutInflater().inflate(R.layout.article, parent, false);
            }

            newsItem currentItem = newsFeed.get(position);

            ImageView newsImage = (ImageView) convertView.findViewById(R.id.leftIco);
            TextView heading = (TextView) convertView.findViewById(R.id.heading);
            TextView desc = (TextView) convertView.findViewById(R.id.desc);

            heading.setText(currentItem.getNewsHeading());
            desc.setText(currentItem.getNewsDesc());

            Picasso.with(Links_Activity.this).load(currentItem.getImageURL()).into(newsImage);


            return convertView;
        }

    }

    public void Back(View view) {
        Intent startBackActivity = new Intent(this, Menu_Activity.class);
        startActivity(startBackActivity);
    }
}

package uk.ac.napier.doggo;

import java.util.PriorityQueue;

/**
 * Created by MarkB on 10/03/2017.
 */

public class newsItem {

    private String newsHeading;
    private String newsDesc;
    private String newsDescSmall;
    private String time;
    private String date;
    private String url;
    private String imageURL;

    public newsItem(String newsHeading, String newsDesc, String date,  String time, String url, String imageURL) {
        this.newsHeading = newsHeading;
        this.newsDesc = newsDesc;
        this.time = time;
        this.date = date;
        this.url = url;
        this.imageURL = imageURL;

        this.newsDescSmall = this.newsDesc.substring(0, 50) + "...";
    }

    public String getNewsHeading() {
        return newsHeading;
    }

    public String getNewsDesc() {
        return newsDesc;
    }

    public String getTime() {
        return time;
    }

    public String getDate() {
        return date;
    }

    public String getUrl() {
        return url;
    }

    public String getImageURL() {
        return imageURL;
    }
}

article.xml

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

<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="News Feed"
    android:textSize="25sp"
    android:textAlignment="center"
    android:id="@+id/logo"
    android:layout_alignParentRight="true"
    android:layout_alignParentEnd="true"/>

<TextView
    android:text="Articles Courtesy of Dogster.com"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/textView"
    android:layout_alignParentBottom="true"
    android:layout_alignParentStart="true" />

<ListView
    android:layout_width="wrap_content"
    android:layout_height="400dp"
    android:id="@+id/newsItems"
    android:layout_centerVertical="true"
    android:layout_alignParentStart="true" />

</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="10dp">

<ImageView
    android:layout_width="80dp"
    android:layout_height="100dp"
    android:id="@+id/leftIco"
    android:src="@mipmap/ic_launcher"
    android:maxHeight="100dp"
    android:maxWidth="100dp"
    android:adjustViewBounds="true"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"/>

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textSize="16sp"
    android:text="Heading Text"
    android:id="@+id/heading"
    android:scrollHorizontally="false"
    android:maxLines="100"
    android:ellipsize="none"
    android:layout_alignParentTop="true"
    android:layout_toRightOf="@+id/leftIco"
    android:layout_toEndOf="@+id/leftIco"
    android:layout_marginLeft="24dp"
    android:layout_marginStart="24dp"/>

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Description"
    android:id="@+id/desc"
    android:lineSpacingExtra="-3dp"
    android:layout_marginBottom="26dp"
    android:layout_alignBottom="@+id/leftIco"
    android:layout_alignLeft="@+id/heading"
    android:layout_alignStart="@+id/heading"/>




</RelativeLayout>

试试这个：

将数组项传递给适配器：

customAdapter adapter = new customAdapter(this, newsFeed);
ListView  newsItems = (ListView) (findViewById(R.id.newsItems));
newsItems.setAdapter(adapter);

现在在适配器类中使用：

private List<newsItem> newsFeed_list ;

   public customAdapter(Context context, ArrayList<newsItem> items) {
        super(context, items);
        this.newsFeed_list = items;
    }

---

您从未调用过适配器。notifyDataSetChanged（）

但是，您有一个ArrayAdapter，因此只需添加到其中，而不是Arraylist，您就不需要通知了

        // See here
        adapter.add(new newsItem(title, content, date, time, link, image));
    }  // end loop
} catch(JSONException e){
    Log.i("myTag", e.toString());
}

---

对代码的一些重新安排应该是可行的

public class LinksActivity extends AppCompatActivity 
  implements AdapterView.OnItemClickListener, Response.ErrorListener {

    private List<NewsItem> newsFeed = new ArrayList<>();
    private ArrayAdapter<NewsItem>  adapter;

    // Moved the Volley response to top-level
    private Response.Listener<JSONObject>  newsListener = new Response.Listener<JSONObject>()  {        

        @Override
        public void onResponse(JSONObject response) {
            try {
                JSONArray newsItems = response.getJSONArray("newsItems");

                for (int i = 0; i < newsItems.length(); i++) {
                    JSONObject temp = newsItems.getJSONObject(i);

                    String image = temp.getString("image");
                    String title = temp.getString("title");
                    String time = temp.getString("time");
                    String date = temp.getString("date");
                    String content = temp.getString("content");
                    String link = temp.getString("link");


                    newsFeed.add(new newsItem(title, content, date, time, link, image));
                }

                // Important!
                adapter.notifyDataSetChanged();

            } catch(JSONException e){
                Log.i("myTag", e.toString());
            }
        }
    };

    // This is Volley's error listener over the entire Activity
    @Override
    public void onErrorResponse(VolleyError error) {
        Log.i("myTag", error.toString());
    }

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

        // Set and define the List and Adapter here
        ListView  newsItems = (ListView) findViewById(R.id.newsItems);
        newsItems.setOnItemClickListener(this);

        adapter = new CustomAdapter();
        newsItems.setAdapter(adapter);

        engine();
    }

    private void engine() {
        RequestQueue queue = Volley.newRequestQueue(this);

        // Now this method is much 'cleaner'
        JsonObjectRequest myReq = new JsonObjectRequest(Request.Method.GET,
                "http://10.0.2.2/news.json",
                null, 
                newsListener, this);

        myReq.setRetryPolicy(new DefaultRetryPolicy(
                30*1000,
                DefaultRetryPolicy.DEFAULT_MAX_RETRIES,
                DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));
        queue.add(myReq);
    }

    // The Activity itself handles the clicking
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        NewsItem currentItem = newsFeed.get(position);
        Intent i = new Intent (Intent.ACTION_VIEW);
        i.setData(Uri.parse(currentItem.getUrl()));
        startActivity(i);
    }
}

公共类链接活动扩展了AppCompative活动
实现AdapterView.OnItemClickListener、Response.ErrorListener{
private List newsFeed=new ArrayList（）；
专用阵列适配器；
//将截击反应移动到最高级别
private Response.Listener newsListener=新的Response.Listener（）{
@凌驾
公共void onResponse（JSONObject响应）{
试一试{
JSONArray新闻项=response.getJSONArray（“新闻项”）；
对于（int i=0；i

是否存在任何有用的错误？此代码是否生成？

customAdapter

方法看起来可疑。代码生成很好，但没有显示任何相关错误。我认为这可能与本地主机和JSON对象请求有关。为什么不在您的

onResponse

中打印所述JSON来确保它与JSON有关？查明问题是什么将是调试问题的良好的第一步。我是否做了与catch异常类似的事情来进行调试？我仍然是Android的一个noob你能告诉我在Links_活动中会去哪里吗？我不完全明白我到底把这些信息放在哪里了，以及如何处理这些信息。我对安卓开发非常陌生，它不是安卓专用的。它只是java。您已经有了

新闻源。添加
。我知道这很令人沮丧，但你必须明白我是一个彻头彻尾的笨蛋。你能给我看看代码和它的位置吗？比如说写代码，因为我不理解术语或者这些方法是如何工作的。基本上，你成功地添加到了一个列表中，是的。但是Android不会更新ArrayAdapter，除非你明确告诉它。因此，
adapter.notifyDataSetChanged（）
需要位于
onResponse
中的
循环的
之后。你可以看到我对相关部分的回答
newsItem currentItem = newsFeed_list.get(position);

        newsFeed.add(new newsItem(title, content, date, time, link, image));
    }  // end loop
    // notify the adapter to display the new data 
    adapter.notifyDataSetChanged()
} catch(JSONException e){
    Log.i("myTag", e.toString());
}

        // See here
        adapter.add(new newsItem(title, content, date, time, link, image));
    }  // end loop
} catch(JSONException e){
    Log.i("myTag", e.toString());
}

public class LinksActivity extends AppCompatActivity 
  implements AdapterView.OnItemClickListener, Response.ErrorListener {

    private List<NewsItem> newsFeed = new ArrayList<>();
    private ArrayAdapter<NewsItem>  adapter;

    // Moved the Volley response to top-level
    private Response.Listener<JSONObject>  newsListener = new Response.Listener<JSONObject>()  {        

        @Override
        public void onResponse(JSONObject response) {
            try {
                JSONArray newsItems = response.getJSONArray("newsItems");

                for (int i = 0; i < newsItems.length(); i++) {
                    JSONObject temp = newsItems.getJSONObject(i);

                    String image = temp.getString("image");
                    String title = temp.getString("title");
                    String time = temp.getString("time");
                    String date = temp.getString("date");
                    String content = temp.getString("content");
                    String link = temp.getString("link");


                    newsFeed.add(new newsItem(title, content, date, time, link, image));
                }

                // Important!
                adapter.notifyDataSetChanged();

            } catch(JSONException e){
                Log.i("myTag", e.toString());
            }
        }
    };

    // This is Volley's error listener over the entire Activity
    @Override
    public void onErrorResponse(VolleyError error) {
        Log.i("myTag", error.toString());
    }

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

        // Set and define the List and Adapter here
        ListView  newsItems = (ListView) findViewById(R.id.newsItems);
        newsItems.setOnItemClickListener(this);

        adapter = new CustomAdapter();
        newsItems.setAdapter(adapter);

        engine();
    }

    private void engine() {
        RequestQueue queue = Volley.newRequestQueue(this);

        // Now this method is much 'cleaner'
        JsonObjectRequest myReq = new JsonObjectRequest(Request.Method.GET,
                "http://10.0.2.2/news.json",
                null, 
                newsListener, this);

        myReq.setRetryPolicy(new DefaultRetryPolicy(
                30*1000,
                DefaultRetryPolicy.DEFAULT_MAX_RETRIES,
                DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));
        queue.add(myReq);
    }

    // The Activity itself handles the clicking
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        NewsItem currentItem = newsFeed.get(position);
        Intent i = new Intent (Intent.ACTION_VIEW);
        i.setData(Uri.parse(currentItem.getUrl()));
        startActivity(i);
    }
}