自定義列表視圖適配器是空白沒有textviews是在接口

Question

enter image description here看出這是我LIST_ITEM佈局，我想可能會有一些問題，這種佈局

<?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:orientation="vertical" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
android:padding="15dp"> 

<LinearLayout 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:orientation="vertical"> 

    <TextView 
     android:id="@+id/title" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:layout_weight="1" 
     android:textColor="@color/colorAccent" 
     android:textSize="18sp" 
     tools:text="india china tension" /> 

    <TextView 
     android:id="@+id/summary" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:layout_weight="1" 
     android:textColor="@color/colorPrimaryDark" 
     android:textSize="22sp" 
     tools:text="Modi silent on china issue" /> 
</LinearLayout> 

這是主要活動

package com.example.android.myapplication; 
import android.os.Bundle; 
import android.support.v7.app.AppCompatActivity; 
import android.widget.ListView; 

import java.util.ArrayList; 

public class MainActivity extends AppCompatActivity { 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 

     //Creating fake news reports 
     ArrayList<News> news = QueryWeb.extractNews(); 

     //finding a layout reference{@link ListView}in the layout 
     ListView newsListView = (ListView) findViewById(R.id.list); 


     // Create a new adapter that takes list of earthquakes 
     final NewsAdapter adapter = new NewsAdapter(this, news); 

     // Set the adapter on the {@link ListView} 
     // so the list can be populated in the user interface 
     newsListView.setAdapter(adapter); 

    } 



} 

這是陣列適配器 包com.example.android.myapplication;

import android.content.Context; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.ArrayAdapter; 
import android.widget.TextView; 

import java.util.List; 

/** 
* Created by ammulu on 22-07-2017. 
*/ 

public class NewsAdapter extends ArrayAdapter<News> { 


    /** 
    * Constructs a new {@link NewsAdapter}. 
    * 
    * @param context  of the app 
    * @param news is the list of earthquakes, which is the data source of the adapter 
    */ 
    public NewsAdapter(Context context, List<News> news) { 
     super(context, 0, news); 
    } 

    /** 
    * Returns a list item view that displays information about news at the given position 
    * in the list of news 
    */ 
    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
     // Check if there is an existing list item view (called convertView) that we can reuse, 
     // otherwise, if convertView is null, then inflate a new list item layout. 
     View listItemView = convertView; 
     if (listItemView == null) { 
      listItemView = LayoutInflater.from(getContext()).inflate(
        R.layout.newslist_item, parent, false); 
     } 

     // Find the news at that position 
     News currentNews = getItem(position); 

     // Find the TextView with view ID title 
     TextView titleView = (TextView) listItemView.findViewById(R.id.title); 
     //Display the title 
     titleView.setText(currentNews.getTitle()); 

     // Find the TextView with view ID summary 
     TextView summaryView = (TextView) listItemView.findViewById(R.id.summary); 
     //Display the summary 
     summaryView.setText(currentNews.getSummary()); 

     //Return the list item that is showing the appropriate data 
     return listItemView; 

    } 
} 

JSON解析的代碼，我認爲這個問題是在這裏

package com.example.android.myapplication; 

import android.util.Log; 



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



import java.util.ArrayList; 

public final class QueryWeb { 


     /** 
     * sample json response for news query 
     */ 
     private static final String SAMPLE_JSON_RESPONSE = "{\\\"status\\\":\\\"ok\\\",\\\"source\\\": \\\"techcrunch\\\",\\\"sortBy\\\": \\\"top\\\",\"articles\": [{\\\"author\\\": \\\"Alexandra Ames\\\",\\\"title\\\": \\\"Coverage\\\",\\\"description\\\":\\\"Coverage | Sessions: Robotics - Cambridge, MA - July 17, 2017\\\",\\\"url\\\": \\\"https:\\/\\/techcrunch.com\\/events\\/sessions-robotics\\/coverage\\/\\\",\\\"urlToImage\\\": \\\"https:\\/\\/s0.wp.com\\/wp-content\\/themes\\/vip\\/techcrunch-2013\\/assets\\/images\\/techcrunch.opengraph.default.png\\\",\\\"publishedAt\\\": \\\"2017-07-14T00:02:35Z\\\"},\n" + 

                  "{\\\"author\\\": \\\"Matthew Lynley\\\",\\\"title\\\": \\\"Dropbox CTO Aditya Agarwal is leaving\\\",\\\"description\\\": \\\"Aditya Agarwal, who came to Dropbox via its acquisition of Cove way back in 2012 and was given the CTO role last year, will be leaving the company. Agarwal..\\\",\\\"url\\\": \\\"https:\\/\\/techcrunch.com\\/2017\\/07\\/21\\/dropbox-cto-aditya-agarwal-is-leaving\\/\\\",\\\"urlToImage\\\": \\\"https:\\/\\/tctechcrunch2011.files.wordpress.com\\/2017\\/07\\/dropbox-fb-departure.jpg?w=764&h=400&crop=1\\\",\\\"publishedAt\\\":\\\"2017-07-21T17:18:11Z\\\"}],\n" ; 




     /** 
     * Create a private constructor because no one should ever create a {@link QueryWeb} object. 
     * This class is only meant to hold static variables and methods, which can be accessed 
     * directly from the class name QueryUtils (and an object instance of QueryWeb is not needed). 
     */ 
     private QueryWeb() { 
     } 

     /** 
     * Return a list of {@link News} objects that has been built up from 
     * parsing a JSON response. 
     */ 
     public static ArrayList<News> extractNews() { 

      // Create an empty ArrayList that we can start adding earthquakes to 
      ArrayList<News> newsArray = new ArrayList<>(); 

      // Try to parse the SAMPLE_JSON_RESPONSE. If there's a problem with the way the JSON 
      // is formatted, a JSONException exception object will be thrown. 
      // Catch the exception so the app doesn't crash, and print the error message to the logs. 
      try { 


       // TODO: Parse the response given by the SAMPLE_JSON_RESPONSE string and 
       // build up a list of Earthquake objects with the corresponding data. 
       JSONObject baseJsonResponse = new JSONObject(SAMPLE_JSON_RESPONSE); 
       JSONArray titleArray = baseJsonResponse.getJSONArray("articles"); 

       for(int i=0; i < titleArray.length(); i++){ 
        JSONObject newRead = titleArray.getJSONObject(i); 
        String title = newRead.getString("title"); 
        String summary = newRead.getString("description"); 

        // Create a new {@link News} object with the magnitude, location, time, 
        // and url from the JSON response. 
        News news = new News(title, summary); 
        newsArray.add(news); 


       } 

      } catch (JSONException e) { // If an error is thrown when executing any of the above statements in the "try" block, 
       // catch the exception here, so the app doesn't crash. Print a log message 
       // with the message from the exception. 
       Log.e("QueryWeb", "Problem parsing news JSON results", e); 
      } 

      // Return the list of earthquakes 
      return newsArray; 
     } 
    } 

activty主要XML佈局

<?xml version="1.0" encoding="utf-8"?> 
<!-- Layout for a list of news--> 
<ListView xmlns:android="http://schemas.android.com/apk/res/android" 
android:id="@+id/list" 
android:orientation="vertical" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
android:dividerHeight="1dp"/> 

Answer 1

許多項目是如何通過這個適配器表示的數據集。

public NewsAdapter(Context context, List<News> news) { 
    super(context, 0, news); 
} 

@Override 
    public int getCount() { 
     return news.size(); 
    } 

Answer 2

在某些情況下，LayoutInflater在父項中無法正常工作。因此，改變字符串

listItemView = LayoutInflater.from(getContext()).inflate(R.layout.newslist_item, parent, false); 

到：

listItemView = LayoutInflater.from(getContext()).inflate(R.layout.newslist_item, null); 

Answer 3

好吧，首先你需要創建適配器本地列表。

List<News> news = new ArrayList(); 

然後在構造函數試試這個

public NewsAdapter(Context context, List<News> news) { 
    super(context, 0, news); 
    this.news = news 
} 

然後重寫此

@Override 
public int getCount() { 
    return news.size(); 
} 

這是你如何在模型類設置的值。

News news = new News(title, summary); 
news.setTitle(title); 
news.setSummary(summary); 

然後最後你將它們添加到新聞類型

newsArray.add(news) 

的列表，並終於在適配器

titleView.setText(news.get(position).getTitle)); 
summaryView.setText(news.get(position).getSummary);