Question

我有一个使用以下代码

扩展SampleActivityBase的mainactivity

public class MainActivity extends SampleActivityBase {

 protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    if (savedInstanceState == null) {
        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        SlidingTabsBasicFragment fragment = new SlidingTabsBasicFragment();
        transaction.replace(R.id.sample_content_fragment, fragment);
        transaction.commit();
    }
  }
}

我有另一个班级

public class SlidingTabsBasicFragment extends Fragment {

在这个课程中我有另一个子类

class SamplePagerAdapter extends PagerAdapter {

在覆盖所有必要的功能后，我还有一个功能

public String getJSON(String url) {
        class GetJSON extends AsyncTask<String, Void, String> {
            ProgressDialog loading;
            @Override
            protected void onPreExecute() {
                super.onPreExecute();
                loading = ProgressDialog.show(SlidingTabsBasicFragment.this.getContext(), "Please Wait...", "Checking", true, true);
            }

            @Override
            protected String doInBackground(String... params) {
                Log.d("doInBackground : ", "Function Started");
                String uri = params[0];
                BufferedReader bufferedReader = null;
                try {
                    URL url = new URL(uri);
                    HttpURLConnection con = (HttpURLConnection) url.openConnection();
                    StringBuilder sb = new StringBuilder();
                    bufferedReader = new BufferedReader(new InputStreamReader(con.getInputStream()));
                    String json;

                    while ((json = bufferedReader.readLine()) != null) {
                        sb.append(json + "\n");
                    }
                    jsonString = sb.toString().trim();
                    return sb.toString().trim();

                } catch (Exception e) {
                    return new String("Exception: " + e.getMessage());
                }
            }
            @Override
            protected void onPostExecute(String s) {
               if(loading.isShowing()) {
                    loading.dismiss();
                }

                super.onPostExecute(s);
                jsonString = s;
            }
        }

        GetJSON gj = new GetJSON();
        gj.execute(url);
        return jsonString;

    }

当我在SamplePagerAdapter类中调用此函数时，除了Progress Dialog之外，每件事都可以正常工作。它没有显示......

请告诉我我做错了什么，如何显示进度对话框。选项卡显示来自在线数据库的数据，我希望在数据变胖时启动进度对话框。

Answer 1

保持适配器类的单独尝试.get（）instaed of .execute

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