Question

我正在运行一个查询，以从数据库中收集YouTube ID。 AsyncTask 工作正常，我获得了信息，但无法将其从onPostExecute传递给onCreate。

这是我尝试做的事情。

将youtubeIdCode设为全局变量。
运行查询以从数据库获取ID。
返回doInBackground中的youtubeid。
在onPostExecute中设置youtubeIdCode = doInBackground的结果。

尝试在onCreate中调用youtubeIdCode，以查看onPostExecute的结果是否传递给youtubeIdCode。这是我遇到的问题。它没有从onPostExecute传递到onCreate。如何传递它，因为在onCreate中，我将需要ID来形成YouTube网址。

//Activity needs added to manifest.
public class DetailsActivity extends AppCompatActivity {

//LOG tag for debugging
private static final String TAG = "GalleryActivity";

String youtubeIdCode;

//Override on Create and set contentView to new activity_details layout.
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_details);
    //Log for debugging so we can tell if activity started successfully.
    Log.d(TAG, "onCreate: started.");
    youtubeIdCode = "";

    loadMovieData();
    String test = "The value is" + youtubeIdCode;
    Log.v("youtube code test", test);

    Intent intent = getIntent();
    Movie movie = intent.getParcelableExtra("movie");

    String image = movie.getMoviePoster();
    String title = movie.getTitle();
    String releaseDate = movie.getDate();
    String voteAverage = movie.getVoteAverage();
    String plot = movie.getPlot();

    ImageView poster = findViewById(R.id.details_image);
    Picasso.with(this).load(image).into(poster);

    TextView name = findViewById(R.id.details_title);
    name.setText((getResources().getString(R.string.movie_title)) + " " + title);

    TextView dateRelease = findViewById(R.id.details_release_date);
    dateRelease.setText((getResources().getString(R.string.release_date)) + " " + releaseDate);

    TextView averageVote = findViewById(R.id.details_voter_average);
    averageVote.setText((getResources().getString(R.string.vote_average)) + " " + voteAverage);

    TextView moviePlot = findViewById(R.id.details_plot);
    moviePlot.setText((getResources().getString(R.string.plot)) + " " + plot);

}

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

    @Override
    protected String doInBackground(String... strings) {
        final String YOUTUBE_ID = "id";
        final String RESULTS = "results";
        String youtubeId = " ";

        Intent intent = getIntent();
        Movie movie = intent.getParcelableExtra("movie");
        String id = movie.getID();

        final URL trailerUrl = NetworkUtils.buildUrlTrailer(id);
        Log.v("Built trailer url", trailerUrl.toString());

        try {
            String jsonResponse = NetworkUtils.getReponseFromHttpUrl(trailerUrl);

            JSONObject moviesObject = new JSONObject(jsonResponse);

            JSONArray resultsArray = moviesObject.getJSONArray(RESULTS);

            for(int i = 0; i < resultsArray.length(); i ++){
                JSONObject movieObject = resultsArray.getJSONObject(i);
                youtubeId = movieObject.getString(YOUTUBE_ID);
                Log.v("youtubeid", youtubeId);
            }

        } catch (IOException e) {
            e.printStackTrace();
        } catch (JSONException e) {
            e.printStackTrace();
        }

        return youtubeId;
    }

    @Override
    protected void onPostExecute(String s) {
        youtubeIdCode = s;
        Log.v("onposttest", s);
    }
}

//Tell the new method to get the data based on the search term within the url.
private void loadMovieData() {
    //If there is a network connection, fetch the data.
    ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
    boolean isConnected = activeNetwork != null &&
            activeNetwork.isConnectedOrConnecting();
    if (isConnected) {
        new FetchTrailer().execute();
    } else {
        Toast toast = Toast.makeText(this, getString(R.string.no_internet_toast), Toast.LENGTH_LONG);
        toast.show();
    }
 }
}

Answer 1

我认为您需要重新考虑应用程序的逻辑。使用AsyncTask的主要思想是任务运行时主线程不会阻塞。

这意味着onCreate()不应等待AsyncTask完成以继续执行，这就是您所暗示的应该发生的情况。

应用程序的思考方式是，您要使用youtube id进行URL设置，并在任务完成时通过onPostExecute()触发任何附加处理。

Answer 2

只需要对var进行设置，就需要输入te值，然后onPostExecute只需调用该setter函数并在AsyncTask中传递var的值，然后使用一种方法来获取小部件上的文本（如果您必须在传递值之前将其设置为空。

也尝试在单独的类中执行AsyncTask

AsyncTask OnPostExecute

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="System.ComponentModel.Annotations" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" /> 
        <bindingRedirect oldVersion="0.0.0.0-4.2.1.0" newVersion="4.2.1.0" /> 
      </dependentAssembly>
    </assemblyBinding>
  </runtime>
</configuration>

在您的情况下，setupData看起来与此类似

 @Override
    protected void onPostExecute(List<ListaLineal> superlistItems) {
        super.onPostExecute(superlistItems);


        activity.setSuperListItems(superlistItems); -> this retrieve the value of a list that I was using (I got the value of the list in doInBackground)
        activity.setupData(); -> method for setting up data
    }

Answer 3

在致电asynTask时，您可以这样做，但我不确定它是否可以正常工作。

new FetchTrailer(){
     @Override
     protected void onPostExecute(Object o) {
     super.onPostExecute(o);
  }
}.execute()

将值从onPostExecute传递给onCreate

3 个答案: