java - AsyncTask 中通过代码旋转屏幕崩溃

Question

我想通过 AsynTask 代码更改屏幕方向，但我注意到如果我放置，我的应用程序就会崩溃

getActivity().setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);

在 public String doInBackground(String... params) 或 public void onPostExecute(String s)

相反，此方法适用于例如 TabbedActivity 类或 Fragment 类。为什么这个方法在AsynTask中不起作用？我真的需要使用它!

这是日志猫

01-01 18:03:40.953 3646-3783/com.example.utente.progettigscorsipa E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1
                                                                                Process: com.example.utente.progettigscorsipa, PID: 3646
                                                                                java.lang.RuntimeException: An error occurred while executing doInBackground()
                                                                                    at android.os.AsyncTask$3.done(AsyncTask.java:318)
                                                                                    at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:354)
                                                                                    at java.util.concurrent.FutureTask.setException(FutureTask.java:223)
                                                                                    at java.util.concurrent.FutureTask.run(FutureTask.java:242)
                                                                                    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:243)
                                                                                    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
                                                                                    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
                                                                                    at java.lang.Thread.run(Thread.java:761)
                                                                                 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.app.FragmentActivity.setRequestedOrientation(int)' on a null object reference
                                                                                    at com.example.utente.progettigscorsipa.FotoCuboActivity$PlaceholderFragment$MultiplyTask.doInBackground(FotoCuboActivity.java:165)
                                                                                    at com.example.utente.progettigscorsipa.FotoCuboActivity$PlaceholderFragment$MultiplyTask.doInBackground(FotoCuboActivity.java:142)
                                                                                    at android.os.AsyncTask$2.call(AsyncTask.java:304)
                                                                                    at java.util.concurrent.FutureTask.run(FutureTask.java:237)
                                                                                    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:243) 
                                                                                    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133) 
                                                                                    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607) 
                                                                                    at java.lang.Thread.run(Thread.java:761) 

01-01 18:03:41.340 3646-3682/com.example.utente.progettigscorsipa E/EGL_emulation:tid 3682:eglSurfaceAttrib(1146):错误 0x3009 (EGL_BAD_MATCH)01-01 18:03:41.340 3646-3682/com.example.utente.progettigscorsipa W/OpenGLRenderer:无法在表面0x9637ab60上设置EGL_SWAP_BEHAVIOR，错误=EGL_BAD_MATCH

public static class PlaceholderFragment extends Fragment {
    /**
     * The fragment argument representing the section number for this
     * fragment.
     */
    private static final String ARG_SECTION_NUMBER = "section_number";
    private boolean ciclo=true;
    private Activity activity;

    public PlaceholderFragment() {
    }

    /**
     * Returns a new instance of this fragment for the given section
     * number.
     */
    public static PlaceholderFragment newInstance(int sectionNumber) {
        PlaceholderFragment fragment = new PlaceholderFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_SECTION_NUMBER, sectionNumber);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState)
    {
        switch (getArguments().getInt(ARG_SECTION_NUMBER))
        {
            case 1:
                SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getContext());
                SharedPreferences.Editor editor = prefs.edit();
                editor.putInt("i",0);
                editor.commit();
                new MultiplyTask().execute();
                View rootView = inflater.inflate(R.layout.fragment_foto_cubo, container, false);
                return rootView;

            case 2:
                View rootView2 = inflater.inflate(R.layout.fragment_foto_cubo4, container, false);
                return rootView2;

            case 3:
                View rootView3 = inflater.inflate(R.layout.fragment_foto_cubo5, container, false);
                return rootView3;

            case 4:
                View rootView4 = inflater.inflate(R.layout.fragment_foto_cubo6, container, false);
                return rootView4;

            case 5:
                View rootView5 = inflater.inflate(R.layout.fragment_foto_cubo7, container, false);
                return rootView5;

            case 6:
                View rootView6 = inflater.inflate(R.layout.fragment_foto_cubo8, container, false);
                return rootView6;

            case 7:
                View rootView7 = inflater.inflate(R.layout.fragment_foto_cubo2, container, false);
                return rootView7;

            case 8:
                prefs = PreferenceManager.getDefaultSharedPreferences(getContext());
                editor = prefs.edit();
                editor.putInt("i",7);
                editor.commit();
                new MultiplyTask().execute();
                View rootView8 = inflater.inflate(R.layout.fragment_foto_cubo3, container, false);
                return rootView8;

            default:
                View rootView0 = inflater.inflate(R.layout.fragment_foto_cubo, container, false);
                return rootView0;
        }
    }

    @Override
    public void onAttach(Activity activity1)
    {
        super.onAttach(activity1);
        activity = activity1;

    }

    public class MultiplyTask extends AsyncTask<String,String,String>
    {
        @Override
        public void onPreExecute()
        {
            super.onPreExecute();
            Toast.makeText(getActivity(),"Sto eseguendo",Toast.LENGTH_LONG).show();
        }

        @Override
        public void onPostExecute(String s)
        {
            super.onPostExecute(s);
        }

        @Override
        public String doInBackground(String... params)
        {
            SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getContext());
            while(ciclo)
            {
                if(prefs.getInt("i",0)==7)
                    activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
                else
                    activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
            }
            return null;
        }


    }
}

Answer 1

在使用 AsyncTask 时，我将屏幕锁定在当前方向比强制方向(就像您对横向所做的那样)更成功。

//lock screen orientation
private void lockScreenOrientation() {
    int currentOrientation = getResources().getConfiguration().orientation;
    if (currentOrientation == Configuration.ORIENTATION_PORTRAIT) setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
    else setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
}