我无法解释为什么onPostExecute没有在我的代码中被调用。我以前已经成功使用几乎这个确切的代码与不同的应用程序。它打印'onPreExecute'和从doInBackground获取JSON的成功结果,只是在return result;
之前,但onPostExecute不打印任何东西 - 使用超级调用或不使用 - 而且不会将我的字符串返回到UI线程。有任何想法吗?onPostExecute没有被ASyncTask调用execute()
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:如果已经张贴了这个原本,我把它作为CustomActivity内部类是这样的:
@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.
}
使用'AsyncTask'类来执行异步操作并仍然阻塞主线程调用'.get()'方法。另外,您遇到的问题总是会发生,或者只是在加载时旋转屏幕? – rciovati
总是发生,与旋转无关。我必须阻止主线程,以便在调用将方法加载到本地数据库的方法之前获得JSON结果,或者使用空指针失败。 –
网络请求完成后,你不能在'AsyncTask'中执行数据库加载吗?我不确定这是否是问题(可能是),但肯定您目前的方法会导致您遇到其他问题(例如ANR)。 – rciovati