Android AsyncTask -

Question

我有一個線程循環顯示進度對話框，直到一切都完成。

在這個線程我試圖運行一個類'MapInteractor'，它繪製到谷歌地圖的多邊形。但是，我收到了一個錯誤，'不在主線程中'。所以我讀了一下，人們似乎建議使用AsyncTask。 我試過這個，但是我仍然得到一個錯誤。下面顯示縮短的代碼以及錯誤。 如果任何人有任何想法如何解決這個問題，將不勝感激。 我一直把我的頭髮撕掉幾個小時！

mapInteractor = new MapInteractor(this); 
    fileReader = new FileReader(this); 

    try { 
     progress = ProgressDialog.show(this, progressText, "Loading..", 
      true); 


     new Thread(new Runnable() { 
      public void run() { 

       //does stuff 

      for (CountryData c : countryData){ 
       try { 
       c.setLatAndLong(fileReader.getlatlong(c.getCountryName())); 
       } catch (IOException e) { 
        e.printStackTrace(); 
       } 
       mapInteractor.execute(c.getLatAndLong()); 
      } 

      runOnUiThread(new Runnable() {    
      @Override 
      public void run() { 
       progress.dismiss(); 
       } 
      }); 
      } 
     }).start(); 


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

    } 

我的地圖交互器類：

public class MapInteractor extends AsyncTask<double[],Integer,Boolean>{ 

// Google Map 
    private static GoogleMap googleMap; 
    private int j = 1; 
    static int count = 0; 
    private FragmentActivity fragmentActivity = null; 

    public MapInteractor(FragmentActivity fragmentActivity) { 
     this.fragmentActivity = fragmentActivity; 
    } 


@Override 
protected Boolean doInBackground(double[]... latLongs) { 
    boolean complete = false; 
    count++; 
    System.out.println(count); 
    if (googleMap == null) { 
     googleMap = ((SupportMapFragment) fragmentActivity.getSupportFragmentManager().findFragmentById(R.id.map)).getMap(); 
    } 

    PolygonOptions polygonOptions = new PolygonOptions(); 
    System.out.println("length of array = " + latLongs[0].length); 
    for(int i =0;i < latLongs[0].length-1;i++){   
     if(i == 0){ 
      polygonOptions.add(new LatLng(latLongs[0][j], latLongs[0][i])); 
     }else{ 
      try{ 
       if(((i*2)+1) <= latLongs.length){ 
        polygonOptions.add(new LatLng(latLongs[0][(i*2)+1], latLongs[0][i*2])); 
       } 

      }catch(Exception e){ 
       e.printStackTrace(); 
      };    
     }  
    } 
    if(latLongs.length != 0){ 
     Polygon polygon = googleMap.addPolygon(polygonOptions.strokeColor(Color.TRANSPARENT).fillColor(Color.RED)); 
     complete = true; 
    } 
    return complete; 
} 

我碰到下面的堆棧跟蹤：

04-02 10:48:46.320: E/AndroidRuntime(1704): FATAL EXCEPTION: AsyncTask #1 
    04-02 10:48:46.320: E/AndroidRuntime(1704): java.lang.RuntimeException: An error occured while executing doInBackground() 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at android.os.AsyncTask$3.done(AsyncTask.java:200) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:274) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at java.util.concurrent.FutureTask.setException(FutureTask.java:125) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:308) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at java.util.concurrent.FutureTask.run(FutureTask.java:138) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at java.lang.Thread.run(Thread.java:1019) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): Caused by: java.lang.IllegalStateException: Not on the main thread 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at maps.k.o.b(Unknown Source) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at maps.i.g.b(Unknown Source) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at maps.e.al.a(Unknown Source) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at etl.onTransact(SourceFile:152) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at android.os.Binder.transact(Binder.java:279) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at com.google.android.gms.maps.internal.IGoogleMapDelegate$a$a.addPolygon(Unknown Source) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at com.google.android.gms.maps.GoogleMap.addPolygon(Unknown Source) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at test.threatlevelsystemproject.MapInteractor.doInBackground(MapInteractor.java:60) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at test.threatlevelsystemproject.MapInteractor.doInBackground(MapInteractor.java:1) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at android.os.AsyncTask$2.call(AsyncTask.java:185) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306) 
    04-02 10:48:46.320: E/AndroidRuntime(1704): ... 4 more 

感謝。

Answer 1

doInBackgroundAsyncTask類中的方法，在其他線程中執行，並且您不能在此方法中執行任何UI更改，您可以在onPostExecute方法中執行UI更改。

PolygonOptions polygonOptions; 

@Override 
protected void onPreExecute() { 
    if (googleMap == null) { 
     googleMap = ((SupportMapFragment) fragmentActivity.getSupportFragmentManager().findFragmentById(R.id.map)).getMap(); 
    } 
} 

.... 

@Override 
protected void onPostExecute() { 
    Polygon polygon = googleMap.addPolygon(polygonOptions.strokeColor(Color.TRANSPARENT).fillColor(Color.RED)); 
} 

，或者如果你願意，你可以在你的活動創建一個處理程序，並在doInBackground後運行的，這一個你必須聲明AsyncTask作爲內部類，你的活動或片段