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，左边是菜单，右边是内容，默认选择第一个菜单，右边显示内容。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 );
        }
    }

onActivityCreated和onCreateView被称为两次，有许多使用片段的例子，因此我是这个片段的初学者我无法将这个例子与我的问题联系起来。我需要傻瓜证明的方式来以更好的方式处理方向更改。我没有在清单文件中声明android：configChanges，我需要活动销毁并重新创建，以便我可以在横向模式下使用不同的布局。请帮助解决方法

Answer 1

每次在活动中转动屏幕时，您都会创建一个新片段onCreate();但是您还要使用super.onCreate(savedInstanceState);维护旧片段。所以也许设置标签并找到它存在的片段，或者将空包传递给super。

这花了我一些时间来学习，当你使用像viewpager这样的东西时它真的可以成为一个双关语。

我建议你阅读fragments一个额外的时间，因为这个主题已经涵盖了。

以下是如何在常规方向更改中处理片段的示例：

<强>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");
        }
    }
}

<强>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);
    }
}

Answer 2

有关如何在方向更改和活动重建之间保留数据的良好指导原则in android guidelines。

要点：

使您的片段可以保留：
```
setRetainInstance(true);
```

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) {

在方向改变时处理片段的万无一失的方法

2 个答案: