onPostExecute没有被ASyncTask execute()调用

Question

我无法解释为什么onPostExecute在我的代码中没有被调用。我已经成功地使用了几乎相同的代码与不同的应用程序之前。它打印'onPreExecute'和JSON从doInBackground获取成功的结果就在return result;之前，但然后onPostExecute不打印任何东西-与超级调用与否-而且不返回我的字符串到UI线程。什么好主意吗?

public class PrivateLoadFromServer extends AsyncTask<String, Integer, String> {
    InputStream is = null;
    String result = null;
    String error_text="";
    JSONObject j = null;
    String url;
    SQLiteOpenHelper helper;
    CustomActivity activity;
    private Context context;
    private ProgressDialog dialog;
    private int count;
    String employee;
    String text;
    public PrivateLoadFromServer(CustomActivity activity,String employee,String url){
        this.url=url;
        this.employee=employee;
        this.activity=activity;
    }
    @Override
    protected void onPreExecute() {
        system.out.println("onPreExecute");
    }
    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);
        System.out.println("onPostExecute");
        activity.setJSONResult(result);
        /*
        if(result!=null){
            System.out.println("Task reported successful");
            taskHandler.taskSuccessful(this.result);
            activity.setJSONResult(this.result);
        } else {
            taskHandler.taskFailed();
        }
        */
        //return;
    }
    @Override
    protected String doInBackground(String... params) {
        System.out.println("Running aSyncTask");
            // Successful code to get JSON result string from server omitted.
        System.out.println("Raw at doInBackground: " + result);
    return result;

编辑:应该张贴这个最初，我叫它作为一个内部类在CustomActivity像这样:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);
    helper=new DBHelper(this);
    loadBasicData();
}
 private void loadBasicData() {
    // If you can encode all of these into one JSON Object, cool.
    String url="*****" //Omitted URL.
    String employee=null;
    PrivateLoadFromServer syncTask = new PrivateLoadFromServer(this,employee,url);
    syncTask.execute();
    try {
        syncTask.get(15000, TimeUnit.MILLISECONDS);
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (ExecutionException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (TimeoutException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    System.out.println("JSONResult at Activity:"+jsonResult); // jsonResult is null
    }
}
    public void setJSONResult(String result){
    System.out.println("setJSONResult"+result);
    this.jsonResult=result; // jsonResult is a field in the Activity.
}

Answer 1

因为您正在调用get，所以JSON结果也从该方法返回(请参阅AsyncTask.java的源代码)。所以你可以直接在输出上调用你的方法。

try {
    setJSONResult(syncTask.get(15000, TimeUnit.MILLISECONDS));
} catch (InterruptedException e) {
    e.printStackTrace();
} catch (ExecutionException e) {
    e.printStackTrace();
} catch (TimeoutException e) {
    e.printStackTrace();
}

Answer 2

检查您是否在代码中的某个地方显式取消AsyncTask，然后才能postExecute

Answer 3

onPostExecute()在主UI线程上被调用。如果它没有被调用，这意味着你的UI线程被阻塞在做别的事情。