Java代码在逐步调试模式下运行良好，而不是在默认运行模式下

Question

我开发了一个Andriod应用程序。我从DB中读取一些字符串，并在ListView中输出它们。我的问题是，如果我使用逐步模式，DB返回的字符串工作得很好。如果我处于运行模式，或者即使我将断点放在接收结果的行之后。字符串变量将为空

 BackgroundWorker backgroundWorker = new BackgroundWorker( this);
 backgroundWorker.execute("Names");
 res = backgroundWorker.FinalRes;
 res = res.replace("[","");
 res = res.replace("]","");
 res = res.replace("\"","");
 ParsedStringsResult = PasrString(res);
 ArrayList<ListNames> NameSs= new ArrayList<ListNames>();
 int size = ParsedStringsResult.length;
 for ( int i=0; i<size;i++ )
 NameSs.add(new ListNames(ParsedStringsResult[i]));

如果我把断点放在res=backgroundWorker.FinalRes;
它运行良好，显示了它的价值 如果我把它放在这一行之后，甚至在默认运行模式下，res将为空

为什么会发生这种情况，我如何解决

我的背景课

public class BackgroundWorker extends AsyncTask<String , Void, String> {

Context context;

public String FinalRes="";
AlertDialog alertDialog;
BackgroundWorker(Context ctx)
{
    context = ctx;
}
@Override
protected String doInBackground(String... params) {
    String type = params[0];

    if (type == "Names") {
        String url_login = "http://192.168.1.2/MyApp/getNames.php";

        try {
            URL url = new URL(url_login);
            HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
            httpURLConnection.setRequestMethod("POST");
            httpURLConnection.setDoOutput(true);
            httpURLConnection.setDoInput(true);


          /*  OutputStream outputStream = httpURLConnection.getOutputStream();
            BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));
            String post_data = URLEncoder.encode("name", "UTF-8") + "=" + URLEncoder.encode(name, "UTF-8");// +"&"+ w nkml tany
            bufferedWriter.write(post_data);
            bufferedWriter.flush();
            bufferedWriter.close();
            outputStream.close();*/


            InputStream inputStream = httpURLConnection.getInputStream();
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream, "iso-8859-1"));
            String result = "";
            String line;
            while ((line = bufferedReader.readLine()) != null) {
                result += line;
            }
            bufferedReader.close();
            inputStream.close();
            httpURLConnection.disconnect();
            FinalRes = result;
            return result;

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
    else
        return null;
}

@Override
protected void onPreExecute(){
   // alertDialog = new AlertDialog.Builder(context).create();
 //   alertDialog.setTitle("Login Status");
}

@Override
protected void onPostExecute(String result){
    //alertDialog.setMessage(result);
    //alertDialog.show();
    //FinalRes = result;
}

}

Answer 1

试一试：

BackgroundWorker backgroundWorker = new BackgroundWorker( this);
backgroundWorker.execute("Names");
while(backgroundWorker.getStatus() != AsyncTask.Status.FINISHED) // While the status is different from "FINISHED" you wait for the task to finished
    Thread.sleep(100)
res = backgroundWorker.FinalRes;

此处还显示了： Android, AsyncTask, check status?

Answer 2

在启动后台工作程序和设置其最终结果之间存在竞争条件

通过设置断点，您只需等待足够长的时间即可完成流程

您只需要通过某种方式等待FinalRes被设置。如果看不到BackgroundWorker类的代码，就不可能说如何最好地做到这一点