在方向改变时,片段被第一个替换

Question

我有一个问题 - 当我改变方向时,我的第二个片段(此时处于活动状态)将替换为第一个片段.我从来没有这样的行为,怎么能修复呢？

主要活动:

public class MainActivity extends SherlockFragmentActivity implements onDialogClickListener, ITaskLoaderListener {

FragmentManager fm;
public ActionBar actionBar;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.pager_layout);

    fm = getSupportFragmentManager();

    actionBar = getSupportActionBar();
    actionBar.setHomeButtonEnabled(false);
    actionBar.setDisplayUseLogoEnabled(true);
    actionBar.setDisplayShowTitleEnabled(false);

    FragmentTransaction ft = fm.beginTransaction();

    ft.add(android.R.id.content, new FirstActivity.FirstFragment(), "loan").commit();

    }
}

FirstFragment:

public class FirstActivity extends SherlockFragmentActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Log.d(TAG, "here");
    final ActionBar actionBar = getSupportActionBar();
    actionBar.setDisplayUseLogoEnabled(true);
    actionBar.setDisplayShowTitleEnabled(false);
    FragmentManager fm = getSupportFragmentManager();

    if (fm.findFragmentById(android.R.id.content) == null) {
        FirstFragment first = new FirstFragment();
        fm.beginTransaction().add(android.R.id.content, first).commit();
    }
}

public static class FirstFragment extends SherlockFragment implements OnClickListener, OnItemClickListener {

    private static final String TAG = "LoanFragment";

    private View rootView;
    private Button bExtend;
    private FragmentManager fm;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        if (session.hasLoan()) {
            rootView = inflater.inflate(R.layout.fragment_loan, container, false);
            bExtend = (Button) rootView.findViewById(R.id.b1);

            return rootView;
        }
    }

    @Override
    public void onClick(View v) {
        FragmentTransaction ft = fm.beginTransaction();
        switch (v.getId()) {
        case R.id.b1:
            ft.add(android.R.id.content, new SecondActivity.SecondFragment(), "second").addToBackStack(null).commit();
            break;
        }

第二片段:

public class SecondActivity extends SherlockFragmentActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    final ActionBar actionBar = getSupportActionBar();
    actionBar.setDisplayUseLogoEnabled(true);
    actionBar.setDisplayShowTitleEnabled(false);
    FragmentManager fm = getSupportFragmentManager();

    if (fm.findFragmentById(android.R.id.content) == null) {
        SecondFragment second = new secondFragment();
        fm.beginTransaction().add(android.R.id.content, second).commit();
    }
}

public static class SecondFragment extends SherlockFragment {

    private View rootView;

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

那就是当我在第二个片段并尝试改变方向时,我的第二个片段将替换为第一个片段.为什么？怎么解决？

Answer 1

onCreate将调用方向更改,然后在那里添加第一个片段.您可以保存要显示的片段onSaveInstanceState,然后使用实例状态onCreate添加正确的片段.

编辑:

您需要维护一个变量currentFragmentIndex并将其保存为onSaveInstanceState:

protected void onSaveInstanceState(Bundle bundle) {
    super.onSaveInstanceState(bundle);
    bundle.putInt("currentFragment", currentFragment);
}

然后检索它onCreate并相应地初始化片段:

public void onCreate(Bundle bundle) {
    if (bundle!= null){
        currentFragmentIndex= bundle.getInt("currentFragment");
    } else {
        currentFragmentIndex = 0;
    }
    switch(currentFragmentIndex) {
        case 0: 
            // TODO: Add first fragment
            break;
        case 1: 
            // TODO: Add second fragment
            break;
    }
}

切换到第二个片段时不要忘记更改currentFragmentIndex为1.