进度对话框不出现

Question

我有一个片段，按下按钮时应显示进度对话框并执行包含 AsyncTask 的方法，但是当我按下按钮时，进度对话框不会出现在屏幕上，但会执行异步任务。这是片段的代码

public class ParcheggiaFragment extends Fragment {

private Button button;
ProgressDialog progressDialog1;
SharedPreferences prefs;
HttpGetNoleggio httpGetNoleggio;

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

    final View layout = inflater.inflate(R.layout.fragment_parcheggia, container, false);

    button = (Button) layout.findViewById(R.id.button);
    prefs = this.getActivity().getSharedPreferences(Keys.SHARED_PREFERENCES, Context.MODE_PRIVATE);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {


            progressDialog1.show();

            int a = checkNoleggioCompletato();

            FragmentTransaction fragmentTransaction = getActivity().getSupportFragmentManager().beginTransaction();
            fragmentTransaction.replace(R.id.frame_principale, new ResultFragment());
            fragmentTransaction.commit();

        }
    });

    return layout;
}

private int checkNoleggioCompletato() {

    final int id = prefs.getInt(Keys.ID_UTENTE, -1);

    Integer[] noleggio;
    int idNoleggio = -1;
    try {
        String str = "here i put the url that i have to use" + id; 
        URL url = new URL(str);

        noleggio = httpGetNoleggio.execute(url).get();
        idNoleggio = noleggio[0];
        int idBici = noleggio[1];
        int noleggioResult = idNoleggio;
    } catch (MalformedURLException | ExecutionException | InterruptedException e) {
        e.printStackTrace();
    }
    return idNoleggio;
}

@Override
public void onStart() {

    progressDialog1 = new ProgressDialog(this.getActivity());
    progressDialog1.setIndeterminate(true);

    super.onStart();
}

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    httpGetNoleggio = new HttpGetNoleggio(this.getActivity());

}

@Override
public void onResume() {
    super.onResume();
}

}

代码似乎正确，但我不明白为什么没有出现 ProgressDialog。 HttpNoleggio 是另一个扩展 AsyncTask 并实现 doInBackground 方法的类

Answer 1

根据您的代码，您在 ParcheggiaFragment 中显示进度条，然后用 ResultFragment 替换此片段。由于 ResultFragment 替换了 ParcheggiaFragment ，因此进度条不显示。只需注释以下代码：

FragmentTransaction fragmentTransaction = getActivity().getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.frame_principale, new ResultFragment());
fragmentTransaction.commit();

然后，进度条将可见。