在方向变化上处理碎片的愚蠢方式

Question

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，左侧的菜单以及其右侧的内容。默认情况下，选择了第一个菜单，其内容显示在右侧。显示内容的片段如下：

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 );
        }
    }

octerivityCreativity和onCreateview被称为两次。有很多示例使用片段。由于我是这个主题的初学者，因此我无法将示例与我的问题联系起来。我需要一种傻瓜证明方法来处理定向更改。我尚未在清单文件中声明android:configChanges。我需要活动破坏并重新创建，以便我可以在景观模式下使用不同的布局。

Answer 1

您每次转动活动onCreate();中的屏幕时都会创建一个新片段，但您还使用super.onCreate(savedInstanceState);维护旧片段。因此，也许设置标签并找到该片段（如果存在），或将null Bundle传递到Super。

这花了我一段时间来学习，当您与ViewPager之类的东西一起工作时，这确实很痛苦。

我建议您在涵盖此确切的主题时阅读有关片段的额外时间。

这是如何处理常规方向上片段的一个示例：

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");
        }
    }
}

fragment ：

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);
    }
}

Answer 2

可以在Android指南中找到有关如何在方向变化和活动娱乐之间保留数据的良好指南。

摘要：

1. 使您的片段保留：

   setRetainInstance(true);
   

2. 仅在必要时创建一个新片段（或至少从中获取数据）

   dataFragment = (DataFragment) fm.findFragmentByTag("data");
   // create the fragment and data the first time
   if (dataFragment == null) {