Android 使用“后退”按钮时不总是替换碎片

我使用actionbar选项卡是因为我需要导航元素出现在每个页面上。我使用ActionBarSherlock实现向后兼容性（最低API 8，目标API 17）。我的主要活动扩展了SherlockFragmentActivity。在我的

onCreate（）

中，我有

ActionBar actionBar = getSupportActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

actionBar.setDisplayShowTitleEnabled(true);

Tab tab1 = actionBar.newTab().setText("My Pages")
    .setTabListener(new MyPagesFragment());

Tab tab2 = actionBar.newTab().setText("Search")
    .setTabListener(new SearchFragment());

Tab tab3 = actionBar.newTab().setText("About")
    .setTabListener(new AboutFragment());

// Start with the second tab selected.
actionBar.addTab(tab1, 0, false);
actionBar.addTab(tab2, 1, true);
actionBar.addTab(tab3, 2, false);

所有选项卡片段都是SherlockListFragments，它们实现了

ActionBar.TabListener

，并执行此操作

@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
    ft.replace(android.R.id.content, this, "mypages");
}

@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
    ft.remove(this);
}

@Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
    // Force a complete reload.
    onTabSelected(tab, ft);
}

搜索页面有一个EditText，并在调用之前在AsyncTask中使用其值从API获取数据并将其添加到SQLite数据库

((MainActivity) getActivity()).showDetailView(responseCode);

显示详细信息，这是我的主要活动中的一种方法，如下所示：

protected void showDetailView(long codeID) {
    SherlockFragment detailFragment = new DetailFragment();
    Bundle args = new Bundle();
    args.putLong("codeID", codeID);
    detailFragment.setArguments(args);

    FragmentManager manager = getSupportFragmentManager();
    FragmentTransaction ft = manager.beginTransaction();
    ft.replace(android.R.id.content, detailFragment);
    ft.addToBackStack(null);
    ft.commit();
}

DetailFragment是一个SherlockFragment，它使用

getArguments（）

检索代码ID--

--并从数据库中读取匹配数据以显示它。所述数据通常包含指向更多详细信息的链接，单击该链接会导致使用新的代码ID再次调用showDetailView

MyPages是所有缓存详细信息页面的列表，它也调用showDetailView：

@Override
public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
  ((MainActivity) getActivity()).showDetailView(pages[position].codeId);
}

搜索现在可见。搜索项目以打开详细视图-

07-20 23:34:52.123: D/NAVIGATION_TRACE(7425): SEARCH - handleResponseCode
07-20 23:34:52.123: D/NAVIGATION_TRACE(7425): MAIN - showDetailView - 31

细节现在可见；搜索消失了。单击我的页面选项卡-

07-20 23:35:37.787: D/NAVIGATION_TRACE(7425): SEARCH - onTabUnselected
07-20 23:35:37.787: D/NAVIGATION_TRACE(7425): MYPAGES - onTabSelected
07-20 23:35:37.826: D/NAVIGATION_TRACE(7425): MYPAGES - onCreateView
07-20 23:35:37.873: D/NAVIGATION_TRACE(7425): MYPAGES - onActivityCreated

MyPages现在可见；细节消失了。单击后退按钮-

07-20 23:36:12.130: D/NAVIGATION_TRACE(7425): SEARCH - onCreateView
07-20 23:36:12.201: D/NAVIGATION_TRACE(7425): SEARCH - onActivityCreated

搜索和MyPages现在都显示出来了

---

主要活动：

public class MainActivity extends SherlockFragmentActivity 
{

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {   
        super.onCreate(savedInstanceState);
        Log.d("NAVIGATION_TRACE", "MAIN - onCreate");

        ActionBar actionBar = getSupportActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        actionBar.setDisplayShowTitleEnabled(true);

        Tab tab1 = actionBar.newTab().setText("My Pages")
            .setTabListener(new TabListener<MyPagesFragment>(
            this, "mypages", MyPagesFragment.class));

        Tab tab2 = actionBar.newTab().setText("Search")
            .setTabListener(new TabListener<SearchFragment>(
            this, "search", SearchFragment.class));

        Tab tab3 = actionBar.newTab().setText("About")
            .setTabListener(new TabListener<AboutFragment>(
            this, "about", AboutFragment.class));

        // Start with the second tab selected.
        actionBar.addTab(tab1, 0, false);
        actionBar.addTab(tab2, 1, true);
        actionBar.addTab(tab3, 2, false);
    }

    @Override
    public void onBackPressed()
    {
        FragmentManager fm = getSupportFragmentManager();
        if (0 < fm.getBackStackEntryCount())
        {
            super.onBackPressed();
        } else {
            // prompt to quit
            AlertDialog.Builder alertErrorResponse = new AlertDialog.Builder(this);
            alertErrorResponse.setMessage("Close app?");
            alertErrorResponse.setNegativeButton("Cancel", null);
            alertErrorResponse.setPositiveButton("OK", new DialogInterface.OnClickListener()
            {
            @Override
            public void onClick(DialogInterface dialog, int which)
            {
                finish();
            }
            });
            alertErrorResponse.show();
        }
    }

    public void showDetailView(long codeID) {
        Log.d("NAVIGATION_TRACE", "MAIN - showDetailView - "+String.valueOf(codeID));
        lastShownCode = codeID;
        FragmentManager manager = getSupportFragmentManager();
        FragmentTransaction ft = manager.beginTransaction();
        SherlockFragment detailFragment = new DetailFragment();
        Bundle args = new Bundle();
        args.putLong("codeID", codeID);
        detailFragment.setArguments(args);
        ft.replace(android.R.id.content, detailFragment, "details");
        ft.addToBackStack(null);
        ft.commit();
    }

    public class TabListener<T extends SherlockListFragment> implements ActionBar.TabListener
    {
        private final SherlockFragmentActivity mActivity;
        private final String mTag;
        private final Class<T> mClass;
        private SherlockListFragment mFragment;

        public TabListener (SherlockFragmentActivity activity, String tag, Class<T> clz) 
        {
            Log.d("NAVIGATION_TRACE", "TabListener - "+tag+" - "+clz.getCanonicalName());
            mActivity = activity;
            mTag = tag;
            mClass = clz;

            FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
            mFragment = (SherlockListFragment) mActivity.getSupportFragmentManager().findFragmentByTag(mTag);
            if (mFragment != null && !mFragment.isDetached()) 
            {
                Log.d("NAVIGATION_TRACE", "DETACH - "+mTag);
                removeDetail(ft);
                ft.detach(mFragment);
            }
            ft.commit();
        }

        public void clearBackStack()
        {
            Log.d("NAVIGATION_TRACE", "clearBackStack - "+mTag);
            FragmentManager fm = mActivity.getSupportFragmentManager();
            if (null != fm && 0 < fm.getBackStackEntryCount())
            {
            fm.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
            }
        }

        @Override
        public void onTabSelected(Tab tab, FragmentTransaction ft) 
        {
            Log.d("NAVIGATION_TRACE", "onTabSelected - "+mTag);

            clearBackStack();

            ft = mActivity.getSupportFragmentManager().beginTransaction();

            if (mFragment == null) 
            {
                Log.d("NAVIGATION_TRACE", "ADD/SHOW - "+mClass.getName());
                removeDetail(ft);
                mFragment = (SherlockListFragment) SherlockListFragment.instantiate(mActivity, mClass.getName());
                ft.add(android.R.id.content, mFragment, mTag);
                ft.commit();
            } 
            else 
            {
                Log.d("NAVIGATION_TRACE", "ATTACH/SHOW - "+mClass.getName());
                removeDetail(ft);
                ft.attach(mFragment);
                ft.show(mFragment);
                ft.commit();
            }

        }

        @Override
        public void onTabUnselected(Tab tab, FragmentTransaction ft) 
        {        
            Log.d("NAVIGATION_TRACE", "onTabUnselected - "+mTag);
            ft = mActivity.getSupportFragmentManager().beginTransaction();

            if (null != mFragment) 
            {
                Log.d("NAVIGATION_TRACE", "HIDE/DETACH - "+mTag);
                removeDetail(ft);
                ft.hide(mFragment);
                ft.detach(mFragment);
                ft.commitAllowingStateLoss();
            }
        }

        @Override
        public void onTabReselected(Tab tab, FragmentTransaction ft) {
        }

        public void removeDetail(FragmentTransaction ft) {
            SherlockFragment detailFragment = (SherlockFragment) mActivity.getSupportFragmentManager().findFragmentByTag("details");
            if (null != detailFragment && !detailFragment.isDetached()) {
            Log.d("NAVIGATION_TRACE", "DETACH - details");
            ft.detach(detailFragment);
            }
        }
    }   
}

公共类MainActivity扩展了SherlockFragmentActivity
{
@凌驾
创建时受保护的void（Bundle savedInstanceState）
{   
super.onCreate（savedInstanceState）；
Log.d（“导航跟踪”，“主-创建”）；
ActionBar ActionBar=getSupportActionBar（）；
actionBar.setNavigationMode（actionBar.NAVIGATION\u MODE\u选项卡）；
actionBar.setDisplayShowTitleEnabled（true）；
Tab tab1=actionBar.newTab（）.setText（“我的页面”）
.setTabListener（新的TabListener(
这是“mypages”，MyPagesFragment.class）；
Tab tab2=actionBar.newTab（）.setText（“搜索”）
.setTabListener（新的TabListener(
这个“search”，SearchFragment.class）；
Tab tab3=actionBar.newTab（）.setText（“关于”）
.setTabListener（新的TabListener(
这个“关于”，关于fragment.class）；
//从选择第二个选项卡开始。
actionBar.addTab（tab1，0，false）；
actionBar.addTab（tab2，1，true）；
actionBar.addTab（tab3，2，false）；
}
@凌驾
public void onBackPressed（）
{
FragmentManager fm=getSupportFragmentManager（）；
if（007-20 23:36:12.130: D/NAVIGATION_TRACE(7425): SEARCH - onCreateView
07-20 23:36:12.201: D/NAVIGATION_TRACE(7425): SEARCH - onActivityCreated

public class MainActivity extends SherlockFragmentActivity 
{

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {   
        super.onCreate(savedInstanceState);
        Log.d("NAVIGATION_TRACE", "MAIN - onCreate");

        ActionBar actionBar = getSupportActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        actionBar.setDisplayShowTitleEnabled(true);

        Tab tab1 = actionBar.newTab().setText("My Pages")
            .setTabListener(new TabListener<MyPagesFragment>(
            this, "mypages", MyPagesFragment.class));

        Tab tab2 = actionBar.newTab().setText("Search")
            .setTabListener(new TabListener<SearchFragment>(
            this, "search", SearchFragment.class));

        Tab tab3 = actionBar.newTab().setText("About")
            .setTabListener(new TabListener<AboutFragment>(
            this, "about", AboutFragment.class));

        // Start with the second tab selected.
        actionBar.addTab(tab1, 0, false);
        actionBar.addTab(tab2, 1, true);
        actionBar.addTab(tab3, 2, false);
    }

    @Override
    public void onBackPressed()
    {
        FragmentManager fm = getSupportFragmentManager();
        if (0 < fm.getBackStackEntryCount())
        {
            super.onBackPressed();
        } else {
            // prompt to quit
            AlertDialog.Builder alertErrorResponse = new AlertDialog.Builder(this);
            alertErrorResponse.setMessage("Close app?");
            alertErrorResponse.setNegativeButton("Cancel", null);
            alertErrorResponse.setPositiveButton("OK", new DialogInterface.OnClickListener()
            {
            @Override
            public void onClick(DialogInterface dialog, int which)
            {
                finish();
            }
            });
            alertErrorResponse.show();
        }
    }

    public void showDetailView(long codeID) {
        Log.d("NAVIGATION_TRACE", "MAIN - showDetailView - "+String.valueOf(codeID));
        lastShownCode = codeID;
        FragmentManager manager = getSupportFragmentManager();
        FragmentTransaction ft = manager.beginTransaction();
        SherlockFragment detailFragment = new DetailFragment();
        Bundle args = new Bundle();
        args.putLong("codeID", codeID);
        detailFragment.setArguments(args);
        ft.replace(android.R.id.content, detailFragment, "details");
        ft.addToBackStack(null);
        ft.commit();
    }

    public class TabListener<T extends SherlockListFragment> implements ActionBar.TabListener
    {
        private final SherlockFragmentActivity mActivity;
        private final String mTag;
        private final Class<T> mClass;
        private SherlockListFragment mFragment;

        public TabListener (SherlockFragmentActivity activity, String tag, Class<T> clz) 
        {
            Log.d("NAVIGATION_TRACE", "TabListener - "+tag+" - "+clz.getCanonicalName());
            mActivity = activity;
            mTag = tag;
            mClass = clz;

            FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
            mFragment = (SherlockListFragment) mActivity.getSupportFragmentManager().findFragmentByTag(mTag);
            if (mFragment != null && !mFragment.isDetached()) 
            {
                Log.d("NAVIGATION_TRACE", "DETACH - "+mTag);
                removeDetail(ft);
                ft.detach(mFragment);
            }
            ft.commit();
        }

        public void clearBackStack()
        {
            Log.d("NAVIGATION_TRACE", "clearBackStack - "+mTag);
            FragmentManager fm = mActivity.getSupportFragmentManager();
            if (null != fm && 0 < fm.getBackStackEntryCount())
            {
            fm.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
            }
        }

        @Override
        public void onTabSelected(Tab tab, FragmentTransaction ft) 
        {
            Log.d("NAVIGATION_TRACE", "onTabSelected - "+mTag);

            clearBackStack();

            ft = mActivity.getSupportFragmentManager().beginTransaction();

            if (mFragment == null) 
            {
                Log.d("NAVIGATION_TRACE", "ADD/SHOW - "+mClass.getName());
                removeDetail(ft);
                mFragment = (SherlockListFragment) SherlockListFragment.instantiate(mActivity, mClass.getName());
                ft.add(android.R.id.content, mFragment, mTag);
                ft.commit();
            } 
            else 
            {
                Log.d("NAVIGATION_TRACE", "ATTACH/SHOW - "+mClass.getName());
                removeDetail(ft);
                ft.attach(mFragment);
                ft.show(mFragment);
                ft.commit();
            }

        }

        @Override
        public void onTabUnselected(Tab tab, FragmentTransaction ft) 
        {        
            Log.d("NAVIGATION_TRACE", "onTabUnselected - "+mTag);
            ft = mActivity.getSupportFragmentManager().beginTransaction();

            if (null != mFragment) 
            {
                Log.d("NAVIGATION_TRACE", "HIDE/DETACH - "+mTag);
                removeDetail(ft);
                ft.hide(mFragment);
                ft.detach(mFragment);
                ft.commitAllowingStateLoss();
            }
        }

        @Override
        public void onTabReselected(Tab tab, FragmentTransaction ft) {
        }

        public void removeDetail(FragmentTransaction ft) {
            SherlockFragment detailFragment = (SherlockFragment) mActivity.getSupportFragmentManager().findFragmentByTag("details");
            if (null != detailFragment && !detailFragment.isDetached()) {
            Log.d("NAVIGATION_TRACE", "DETACH - details");
            ft.detach(detailFragment);
            }
        }
    }   
}

public class MyPagesFragment extends SherlockListFragment implements
        OnItemClickListener
    {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState)
    {
        Log.d("NAVIGATION_TRACE", "MYPAGES - onCreateView");
        View view = inflater.inflate(R.layout.mypages, null);

        // code to set up list adapter here
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        Log.d("NAVIGATION_TRACE", "MYPAGES - onActivityCreated");
        getListView().setOnItemClickListener(this);
    }

    @Override
    public void onItemClick(AdapterView<?> parent, View v, int position, long id)
    {
        Log.d("NAVIGATION_TRACE", "MYPAGES - onItemClick");
        ((MainActivity) getActivity()).showDetailView(pages[position].codeId);
    }
}

public class DetailFragment extends SherlockFragment implements
        OnItemClickListener
{

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

        // bunch of display / list set up code goes here

        return view;
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);    
        lvLinks.setOnItemClickListener(this);   
    }

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id)
    {
        // Details page can open other details pages:
        ((MainActivity) getActivity()).showDetailView(pages[position].id);
    }

}

    FragmentManager manager = getSupportFragmentManager();
    if (manager.getBackStackEntryCount() > 0)
        getSupportFragmentManager().popBackStack();
    else
        finish();