Question

我对ViewPager中的FragmentActivity和多个片段有疑问。

在FragmentActivity中加载一个对象，并在所有其他片段中使用AsyncTask。我使用了android：configChanges =“orientation | keyboardHidden | keyboard”“hack”来确保对象只加载一次，即使在屏幕旋转期间也是如此。

然而，现在我想在其中一个片段中以横向模式显示更多信息，所以现在黑客不起作用。

我尝试过从Android示例中实现AsyncLoader和FragmentRetainInstanceSupport。但没有一件事有效：

1 - 我无法让FragmentRetainInstanceSupport在ViewPager中工作，当我按照示例代码时，不会在worker-fragment中调用onCreate（）方法 2 - AsyncLoader在屏幕旋转期间崩溃...

这是我（试图）实现AsyncLoader的代码：

public class TeamActivity extends SherlockFragmentActivity implements LoaderManager.LoaderCallbacks<Response<Team>> {
    ViewPager mPager;
    PageIndicator mIndicator;
    FragmentPagerAdapter mAdapter;
    private final int MENU_FOLLOW = Menu.FIRST;
    private final int MENU_UNFOLLOW = Menu.FIRST + 1;
    Team team = null;
    static int team_id;

    public Team getTeam(){
            return team;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            getSupportActionBar().setDisplayHomeAsUpEnabled(true);
            team_id = this.getIntent().getIntExtra("index", 0);
            Log.d("Teamid",""+team_id);
            getSupportLoaderManager().initLoader(0, null, this);//.forceLoad();


            //getSupportLoaderManager().getLoader(0).startLoading();
            //new getTeam().execute();
    }

    @Override
    public boolean onPrepareOptionsMenu(Menu menu) {
            if(team != null) {
                    team.getNaam();
                    SharedPreferences keyValues = this.getSharedPreferences("teams_follow", Context.MODE_PRIVATE);
                    MenuItem menuItem_volg = menu.findItem(MENU_FOLLOW);
                    MenuItem menuItem_delete = menu.findItem(MENU_UNFOLLOW);
                    if(keyValues.contains(String.valueOf(team.getStartnummer()))) {
                            menuItem_volg.setVisible(false);
                            menuItem_delete.setVisible(true);
                    } else {
                            menuItem_volg.setVisible(true);
                            menuItem_delete.setVisible(false);
                    }
            }
            return super.onPrepareOptionsMenu(menu);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
            menu.add(0,MENU_UNFOLLOW,Menu.NONE, R.string.ab_verwijderen)
            .setIcon(R.drawable.ic_action_delete)
            .setVisible(false)
            .setShowAsAction(MenuItem.SHOW_AS_ACTION_ALWAYS);

            menu.add(0,MENU_FOLLOW,Menu.NONE, R.string.ab_volgen)
            .setIcon(R.drawable.ic_action_star)
            .setVisible(false)
            .setShowAsAction(MenuItem.SHOW_AS_ACTION_ALWAYS);

            return super.onCreateOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
            switch (item.getItemId()) {
            case android.R.id.home:
                    Utils.goHome(getApplicationContext());
                    break;
            case MENU_FOLLOW:
                    Utils.addFavoTeam(getApplicationContext(), team);
                    invalidateOptionsMenu();

                    break;
            case MENU_UNFOLLOW:
                    Utils.removeFavoteam(getApplicationContext(), team.getID());
                    invalidateOptionsMenu();
                    break;
            }

            return super.onOptionsItemSelected(item);
    }

    class TeamFragmentAdapter extends FragmentPagerAdapter implements TitleProvider {

            ArrayList<Fragment> fragments = new ArrayList<Fragment>();
            ArrayList<String> titels = new ArrayList<String>();

            public TeamFragmentAdapter(FragmentManager fm) {
                    super(fm);
                    fragments.add(new TeamInformatieFragment());
                    titels.add("Informatie");
                    fragments.add(new TeamLooptijdenFragment());
                    titels.add("Routetijden");
            }



            @Override
            public Fragment getItem(int position) {
                    return fragments.get(position);
            }

            @Override
            public int getCount() {
                    return fragments.size();
            }

            @Override
            public String getTitle(int position) {
                    return titels.get(position);
            }
    }

    private class getTeam extends AsyncTask<Void, Void, Void> {  

            private ProgressDialog progressDialog;
            Response<Team> response;

            protected void onPreExecute() {  
                    progressDialog = ProgressDialog.show(TeamActivity.this,  
                                    "Bezig met laden", "Team wordt opgehaald...", true);
                    progressDialog.setCancelable(true);
                    progressDialog.setOnCancelListener(new OnCancelListener() {
                            public void onCancel(DialogInterface dialog) {
                                    cancel(true);
                                    Utils.goHome(TeamActivity.this);
                            }
                    });
            }

            @Override
            protected Void doInBackground(Void... arg0) {
                    if(!isCancelled())
                            response = api.getTeamByID(team_id);
                    return null;
            }

            @Override  
            protected void onPostExecute(Void result) {
                    if(Utils.checkResponse(TeamActivity.this, response)) {
                            setContentView(R.layout.simple_tabs);
                            team = response.getResponse();
                            mAdapter = new TeamFragmentAdapter(getSupportFragmentManager());

                            mPager = (ViewPager)findViewById(R.id.pager);
                            mPager.setAdapter(mAdapter);

                            mIndicator = (TabPageIndicator)findViewById(R.id.indicator);
                            mIndicator.setViewPager(mPager);
                            invalidateOptionsMenu();
                            progressDialog.dismiss();
                    }

            }
    }

    public static class AppListLoader extends AsyncTaskLoader<Response<Team>> {
            Response<Team> response;
            public AppListLoader(Context context) {
                    super(context);
            }

            @Override public Response<Team> loadInBackground() {
                    response = api.getTeamByID(team_id);
                    return response;
            }

            @Override public void deliverResult(Response<Team> response) {
                    if (isReset()) {
                            return;
                    }

                    this.response = response;
                    super.deliverResult(response);
            }

            @Override protected void onStartLoading() {
                    if (response != null) {
                            deliverResult(response);
                    }
                    if (takeContentChanged() || response == null) {
                            forceLoad();
                    }
            }

            @Override
            protected void onStopLoading() {
                    // Attempt to cancel the current load task if possible.
                    cancelLoad();
            }

            @Override
            protected void onReset() {
                    super.onReset();
                    // Ensure the loader is stopped
                    onStopLoading();
                    response = null;
            }
    }

    private ProgressDialog progressDialog;

    @Override
    public Loader<Response<Team>> onCreateLoader(int arg0, Bundle arg1) {
            progressDialog = ProgressDialog.show(TeamActivity.this,  
                            "Bezig met laden", "Team wordt opgehaald...", true);
            progressDialog.setCancelable(true);
            progressDialog.setOnCancelListener(new OnCancelListener() {
                    public void onCancel(DialogInterface dialog) {
                            finish();
                    }
            });
            return new AppListLoader(this);
    }

    @Override
    public void onLoadFinished(Loader<Response<Team>> loader, Response<Team> response) {
            //Log.d("Loader", "Klaar");
            if(Utils.checkResponse(TeamActivity.this, response)) {
                    team = response.getResponse();
                    setContentView(R.layout.simple_tabs);
                    mAdapter = new TeamFragmentAdapter(getSupportFragmentManager());

                    mPager = (ViewPager)findViewById(R.id.pager);
                    mPager.setAdapter(mAdapter);

                    mIndicator = (TabPageIndicator)findViewById(R.id.indicator);
                    mIndicator.setViewPager(mPager);
                    invalidateOptionsMenu();
                    progressDialog.dismiss();
            }
    }

    @Override
    public void onLoaderReset(Loader<Response<Team>> arg0) {                
            //Utils.goHome(this);
    }

}

片段（示例）：

public class TeamInformatieFragment extends SherlockFragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);


        Team team = ((TeamActivity)this.getActivity()).getTeam();
//ERROR ON NEXT LINE AFTER SCREEN ROTATION:
getSherlockActivity().getSupportActionBar().setTitle(team.getNaam());     
            View view = inflater.inflate(R.layout.team_informatie, container, false);
    return view;
        }

    }

从片段调用该方法（使用getActivity（）。getTeam（））但是在屏幕旋转之后，getTeam（）返回null; 我认为片段在变量团队初始化之前调用getTeam（）太快了（？）

你能帮帮我吗？谢谢！

Answer 1

这可能不是你想听到的，但我建议摆脱

 android:configChanges="orientation|keyboardHidden|keyboard"

这是一个丑陋的黑客攻击，如果你没有正确处理配置更改，许多较新的SDK元素（如Loaders）将会中断。让Android处理配置更改，并围绕它设计代码。

Android AsyncLoader：在fragmentactivity / fragment之间共享对象

1 个答案: