如何从 AsyncTask 获取并显示一个值？

Question

我想获取并显示通过 Asynctask 获得的值，但我对它不是很熟悉...

我的异步任务：

private class loadDetails extends AsyncTask<Void,Void,Void>() {

        @Override
        protected void doInBackground(Void... voids) {

            final Movie details = (Movie) getIntent().getExtras().getSerializable("MOVIE_DETAILS");
            int idMovie = details.getId();

            OkHttpClient client = new OkHttpClient();

            Request request = new Request.Builder()
                    .url("https://api.themoviedb.org/3/movie/" + idMovie + "?api_key=" + API_KEY + "&language=en-US")
                    .build();

            Response response = client.newCall(request).execute();
            JSONObject root = new JSONObject(response.body().string());

            int runtime = root.getInt("runtime");
            Log.i("test", runtime + " min");

            return null;
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            //?
        }
    }

我的完整 activity 代码：

public class MovieDetailActivity extends AppCompatActivity {

    private ImageView backdrop_image, poster;
    private TextView overview, releaseDate, genresList;
    private RatingBar rating;
    private static final String TAG = "MovieDetails";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.activity_movie_detail);
        new loadDetails().execute();

        final Movie details = (Movie) getIntent().getExtras().getSerializable("MOVIE_DETAILS");

        ActionBar actionBar = getSupportActionBar();
        actionBar.setDisplayHomeAsUpEnabled(true);
        actionBar.setTitle(details.getTitle());

        backdrop_image = findViewById(R.id.movie_backdrop_image);
        poster = findViewById(R.id.movie_poster);
        title = findViewById(R.id.movie_title);
        releaseDate = findViewById(R.id.movie_release_date);
        rating = (RatingBar) findViewById(R.id.movie_rating_bar);
        overview = findViewById(R.id.movie_overview);
        genresList = findViewById(R.id.movie_genres);

        if (details != null){

            Glide.with(this)
                    .load(IMAGE_BASE_URL + details.getBackdropPath())
                    .apply(RequestOptions.placeholderOf(R.color.colorPrimary))
                    .into(backdrop_image);
            Glide.with(this)
                    .load(IMAGE_BASE_URL + details.getPosterPath())
                    .apply(RequestOptions.placeholderOf(R.color.colorPrimary))
                    .into(poster);

            title.setText(details.getTitle());
            releaseDate.setText(details.getReleaseDate());
            overview.setText(details.getOverview());
            double d = details.getTMDBRating();
            float f = (float) d;
            rating.setRating(f/2);

        }
    }

    private class loadDetails extends AsyncTask<Void,Void,Void>() {

        @Override
        protected void doInBackground(Void... voids) {

            final Movie details = (Movie) getIntent().getExtras().getSerializable("MOVIE_DETAILS");
            int idMovie = details.getId();

            OkHttpClient client = new OkHttpClient();

            Request request = new Request.Builder()
                    .url("https://api.themoviedb.org/3/movie/" + idMovie + "?api_key=" + API_KEY + "&language=en-US")
                    .build();

            Response response = client.newCall(request).execute();
            JSONObject root = new JSONObject(response.body().string());

            int runtime = root.getInt("runtime");
            Log.i("test", runtime + " min");

            return null;
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            //?
        }
    }

    @Override
    public boolean onSupportNavigateUp(){
        finish();
        return true;
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.save_menu, menu);
        return true;
    }
}

我想在 TextView 中显示 runtime。

Answer 1

您可以尝试以下方法：

//create a method to set the value to the textview
private void setTextViewValue(int runtime)
{
     textView.setText(String.valueOf(runtime))
}
//change the last parameter to Integer
private class loadDetails extends AsyncTask<Void,Void,Integer>() {

        @Override
        protected Integer doInBackground(Void... voids) {

            final Movie details = (Movie) getIntent().getExtras().getSerializable("MOVIE_DETAILS");
            int idMovie = details.getId();

            OkHttpClient client = new OkHttpClient();

            Request request = new Request.Builder()
                    .url("https://api.themoviedb.org/3/movie/" + idMovie + "?api_key=" + API_KEY + "&language=en-US")
                    .build();

            Response response = client.newCall(request).execute();
            JSONObject root = new JSONObject(response.body().string());

            int runtime = root.getInt("runtime");
            Log.i("test", runtime + " min");

            return runtime;
        }

        @Override
        protected void onPostExecute(Integer runtime) {
            //call the method to set the runtime value
            setTextViewValue(runtime);
        }
    }

简单说明一下AsyncTask的参数如下：

第一个参数 - 传递给 execute() 函数并由 doInBackground() 接收的值的数据类型
第二个参数 - 传递给 onProgressUpdate() 的值的数据类型
第三个参数是 doInBackground 返回的值的数据类型，并在调用时传递给 onPostExecute()

OnPostExecute 随后将调用您的自定义函数以将文本设置为 textview。

Answer 2

private class loadDetails extends AsyncTask<Void,Void,Integer>() {

    @Override
    protected Integer doInBackground(Void... voids) {

        final Movie details = (Movie) getIntent().getExtras().getSerializable("MOVIE_DETAILS");
        int idMovie = details.getId();

        OkHttpClient client = new OkHttpClient();

        Request request = new Request.Builder()
                .url("https://api.themoviedb.org/3/movie/" + idMovie + "?api_key=" + API_KEY + "&language=en-US")
                .build();

        Response response = client.newCall(request).execute();
        JSONObject root = new JSONObject(response.body().string());

        int runtime = root.getInt("runtime");
        Log.i("test", runtime + " min");

        return runtime;
    }

    @Override
    protected void onPostExecute(Integer anInt) {
        yourTextView.setText("yourInt = " + anInt);
    }
}

应该可以解决问题。我没有编译它，但通常异步任务的第三个泛型参数是 return 类型，从 doInBackround() 到 onPostExecute() 并且那里你可以触摸你的观点。

Answer 3

AsyncTask 不了解生命周期，这意味着如果用户更改配置，您的应用程序将泄漏内存；它甚至可能崩溃。因此，您需要使用 Livedata and ViewModel，它只会在 activity 处于活动状态时更新您的 activity。如果您的应用程序崩溃，您将失去客户，这在业界被认为是糟糕的编程习惯。

如何从 AsyncTask 获取并显示一个值？

How to get and show a value from an AsyncTask?

java

android

android-asynctask