88 
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，左侧是菜单，右侧是其内容。默认情况下，第一个菜单被选中，其内容显示在右侧。显示内容的 Fragment 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 );
        }
    }

onActivityCreated 和 onCreateView 被调用两次。有很多使用片段的例子。由于我是该主题的初学者，因此无法将示例与我的问题联系起来。我需要一种万无一失的方法来处理方向变化。我没有android:configChanges在清单文件中声明。我需要销毁并重新创建活动，以便我可以在横向模式下使用不同的布局。

4

2 回答 2

133

每次在活动中转动屏幕时，您都在创建一个新片段，onCreate();但您也使用super.onCreate(savedInstanceState);. 所以也许设置标签并找到片段（如果存在），或者将空包传递给超级。

这花了我一段时间来学习，当你使用像 viewpager 这样的东西时，这真的很痛苦。

我建议您多花点时间阅读有关Fragments的内容，因为这个主题已经涵盖了。

以下是如何处理常规方向变化的片段的示例：

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");
        }
    }
}

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);
    }
}
于 2012-11-09T10:48:59.423 回答
21

可以在 android 指南中找到有关如何在方向更改和活动重新创建之间保留数据的良好指南。

概括：

  1. 使您的片段可保留：

    setRetainInstance(true);

  2. 仅在必要时创建新片段（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) {
于 2015-10-01T13:33:31.260 回答