为什么我在 listView 中得到最后一个标题？ [关闭]

Question

public class MainActivity extends AppCompatActivity{

     ListView aboutNews;

     ArrayList<String> newscontent;

    public  void DisplayNews(String title)

    {
        aboutNews = findViewById(R.id.aboutNews);
        newscontent = new ArrayList<String>();

        newscontent.add(title);
        ArrayAdapter<String> myArrayAdapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,newscontent);
        aboutNews.setAdapter(myArrayAdapter);



    }
    public class downloadTask extends AsyncTask<String , Void , String>
    {

        @Override
        protected String doInBackground(String... urls) {
            String result = "";
            URL url;
            HttpURLConnection urlConnection = null;
            try {
                url = new URL(urls[0]);
                urlConnection = (HttpURLConnection) url.openConnection();
                InputStream in = urlConnection.getInputStream();
                InputStreamReader reader = new InputStreamReader(in);
                int data = reader.read();
                while(data!=-1)
                {
                    char current = (char) data;
                    result += current;
                    data = reader.read();
                }
                return result;
            }
            catch (Exception e)
            {
                e.printStackTrace();
                return null;
            }

        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            try {
                JSONObject jsonObject = new JSONObject(s);
                String news = jsonObject.getString("articles");
                JSONArray arr = new JSONArray(news);
                for(int i = 0;i<arr.length();i++)
                {
                    JSONObject jsonPart = arr.getJSONObject(i);
                    // Log.i("title",jsonPart.getString("title"));
                    //Log.i("description",jsonPart.getString("description"));
                    // Log.i("Image_url",jsonPart.getString("urlToImage"));
                    // Log.i("published at",jsonPart.getString("publishedAt"));
                    // Log.i("content",jsonPart.getString("content"));
                    String title = jsonPart.getString("title");
                    String description = jsonPart.getString("description");
                    String urlToImage = jsonPart.getString("urlToImage");
                    String publish = jsonPart.getString("publishedAt");
                    String content = jsonPart.getString("content");
                    Log.i("title",title);
                    

                    DisplayNews(title);

                }


            }catch (Exception e)
            {
                e.printStackTrace();

            }


        }
    }

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

        downloadTask task = new downloadTask();
        try
        {
        task.execute("https://newsapi.org/v2/top-headlines?country=in&apiKey=065e210edf9d43469ed4614ec90c07f7");
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }



    }



}
    

Answer 1

因为您每次调用 DisplayNews() 函数时都会重新初始化 ArrayList。

newscontent = new ArrayList<String>();

从 DisplayNews 函数中删除此行并将其添加到 onCreate 方法或其他仅初始化一次的位置。