微調不顯示選定的項目，從數組列表加載微調框

Question

我有一個問題，我找不到解決方案。我查看並嘗試了多種不同的解決方案，以瞭解爲什麼微調不顯示選定的項目。在使用硬編碼數組時，它工作正常，但不適用於我在onCreate中加載的ArrayList。微調器已填充，但不會顯示所選項目，微調器的空白區域變寬。

public class MainActivity extends ActionBarActivity { 

String[] test = new String[] {"1", "2", "3"}; 
ArrayList<String> routes = new ArrayList<String>(); 
Spinner sp; 
String[] routesArray; 
ArrayAdapter<String> adapter1; 
final static String routeURL = "http://www.ctabustracker.com/bustime/api/v1/getroutes?key="; 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    adapter1 = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, routes); 
    sp = (Spinner) findViewById(R.id.spnRoute); 
    loadRoutes(); 
    adapter1.notifyDataSetChanged(); 
//  routesArray = routes.toArray(new String[routes.size()]); 
//  sp.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, routesArray)); 
//  routesArray = routes.toArray(new String[routes.size()]); 
//  sp.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, routesArray)); 
//  sp.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, test)); 
} 


public void loadRoutes() { 
    new RequestTask().execute(routeURL); 
//  routesArray = routes.toArray(new String[routes.size()]); 
    adapter1.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); 
    sp.setAdapter(adapter1); 
    adapter1.notifyDataSetChanged(); 
} 

class RequestTask extends AsyncTask<String, String[], Void> { 
    @Override 
    protected Void doInBackground(String... strings) { 
     try { 
      URL routesURL = new URL(strings[0]); 
      BufferedReader in = new BufferedReader(new InputStreamReader(routesURL.openStream())); 
      String line; 
      while((line = in.readLine()) != null) { 
       if(line.contains("<rt>")) { 
        int firstPos = line.indexOf("<rt>"); 
        String tempNum = line.substring(firstPos); 
        tempNum = tempNum.replace("<rt>", ""); 
        int lastPos = tempNum.indexOf("</rt>"); 
        routes.add(tempNum.substring(0, lastPos)); 
       } 
      } 
      in.close(); 
     } 
     catch (MalformedURLException e) { 
      e.printStackTrace(); 
     } 
     catch (IOException e) { 
      e.printStackTrace(); 
     } 
     return null; 
    } 
} 
} 

Answer 1

一種AsyncTask是異步的，這意味着它將運行與其他代碼。因此，執行任務後您的代碼將繼續運行，這意味着您的Adapter尚未填充，因爲routes尚未包含任何數據。

解決方案

將下面的代碼中的onPostExecute()您AsyncTask

adapter1.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); 
sp.setAdapter(adapter1); 
adapter1.notifyDataSetChanged();