方向变化时处理碎片的万无一失的方法 [英] Fool-proof way to handle Fragment on orientation change

问题描述

public class MainActivity extends Activity implements MainMenuFragment.OnMainMenuItemSelectedListener {

 @Override
 public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    FragmentManager fragmentManager = getFragmentManager();
    FragmentTransaction fragmentTransaction = fragmentManager
            .beginTransaction();

    // add menu fragment
    MainMenuFragment myFragment = new MainMenuFragment();
    fragmentTransaction.add(R.id.menu_fragment, myFragment);

    //add content
    DetailPart1 content1= new DetailPart1 ();
    fragmentTransaction.add(R.id.content_fragment, content1);
    fragmentTransaction.commit();

}
public void onMainMenuSelected(String tag) {
  //next menu is selected replace existing fragment
}

我需要并排显示两个列表视图，菜单在左侧，其内容在右侧.默认情况下，第一个菜单处于选中状态，其内容显示在右侧.显示内容的片段如下:

I have a need to display two list views side by side, menu on left and its content on right side. By default, the first menu is selected and its content is displayed on right side. The Fragment that displays content is as below:

public class DetailPart1 extends Fragment {
  ArrayList<HashMap<String, String>> myList = new ArrayList<HashMap<String, String>>();
  ListAdapter adap;
  ListView listview;

  @Override
  public void onActivityCreated(Bundle savedInstanceState) {
      super.onActivityCreated(savedInstanceState);

       if(savedInstanceState!=null){
        myList = (ArrayList)savedInstanceState.getSerializable("MYLIST_obj");
        adap = new LoadImageFromArrayListAdapter(getActivity(),myList );
        listview.setAdapter(adap);
       }else{
        //get list and load in list view
        getlistTask = new GetALLListTasks().execute();
    }


     @Override
   public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.skyview_fragment, container,false);
           return v;
        }


     @Override
      public void onSaveInstanceState(Bundle outState) {
         super.onSaveInstanceState(outState);
          outState.putSerializable("MYLIST_obj", myList );
        }
    }

onActivityCreated和onCreateView称为两次.有很多使用片段的示例.由于我是该主题的初学者，因此无法将示例与问题联系起来.我需要一种万无一失的方法来处理方向更改.我没有在清单文件中声明android:configChanges.我需要销毁并重新创建活动，以便可以在横向模式下使用不同的布局.

The onActivityCreated and onCreateView are called twice. There are many examples out there using fragments. Since I am beginner in this subject, I am unable relate the example with my problem. I need a fool proof way to handle orientation change. I have NOT declared android:configChanges in manifest file. I need the activity destroy and recreate so that I can use different layout in landscape mode.

推荐答案

每次在活动onCreate();中打开屏幕时，您都在创建一个新的片段，但是您还使用super.onCreate(savedInstanceState);来维护旧片段.因此，也许设置标签并找到该片段是否存在，或者将空束传递给super.

You are creating a new fragment every time you turn the screen in your activity onCreate(); But you are also maintaining the old ones with super.onCreate(savedInstanceState);. So maybe set tag and find the fragment if it exist, or pass null bundle to super.

这花了我一些时间来学习，当您使用诸如viewpager之类的东西时，确实可以说是一个双料.

This took me a while to learn and it can really be a bi**** when you are working with stuff like viewpager.

我建议您多花点时间阅读片段涵盖了确切的主题.

I'd recommend you to read about fragments an extra time as this exact topic is covered.

这是一个如何在规则的方向变化中处理碎片的示例:

Here is an example of how to handle fragments on a regular orientation change:

活动:

public class MainActivity extends FragmentActivity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if (savedInstanceState == null) {
            TestFragment test = new TestFragment();
            test.setArguments(getIntent().getExtras());
            getSupportFragmentManager().beginTransaction().replace(android.R.id.content, test, "your_fragment_tag").commit();
        } else {
            TestFragment test = (TestFragment) getSupportFragmentManager().findFragmentByTag("your_fragment_tag");
        }
    }
}

片段:

public class TestFragment extends Fragment {

    public static final String KEY_ITEM = "unique_key";
    public static final String KEY_INDEX = "index_key";
    private String mTime;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_layout, container, false);

        if (savedInstanceState != null) {
            // Restore last state
            mTime = savedInstanceState.getString("time_key");
        } else {
            mTime = "" + Calendar.getInstance().getTimeInMillis();
        }

        TextView title = (TextView) view.findViewById(R.id.fragment_test);
        title.setText(mTime);

        return view;
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putString("time_key", mTime);
    }
}

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