Android Action Bar 选项卡 - 内部片段事务问题

我已经使用 Google 自己的以下示例成功在操作栏中设置了选项卡：http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/app/FragmentTabs.html http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/app/FragmentTabs.html作为基地。我的代码看起来像这样：

public class Main extends SherlockFragmentActivity {

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);        

    getSupportActionBar().setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

    ActionBar.Tab tab1 = getSupportActionBar().newTab();
    tab1.setIcon(R.drawable.ic_tab_example_selected);
    tab1.setTabListener(new TabListener<Tab1>(this, "A", Tab1.class));
    getSupportActionBar().addTab(tab1);

    ActionBar.Tab tab2 = getSupportActionBar().newTab();
    tab2.setIcon(R.drawable.ic_tab_example_selected);
    tab2.setTabListener(new TabListener<Tab2>(this, "B", Tab2.class));
    getSupportActionBar().addTab(tab2);

    ActionBar.Tab tab3 = getSupportActionBar().newTab();
    tab3.setIcon(R.drawable.ic_tab_example_selected);
    tab3.setTabListener(new TabListener<Tab3>(this, "C", Tab3.class));
    getSupportActionBar().addTab(tab3);

    ActionBar.Tab tab4 = getSupportActionBar().newTab();
    tab4.setIcon(R.drawable.ic_tab_example_selected);
    tab4.setTabListener(new TabListener<Tab4>(this, "D", Tab4.class));
    getSupportActionBar().addTab(tab4);     
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getSupportMenuInflater();
    inflater.inflate(R.menu.menu, menu);
    return true;
}

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

    /** Constructor used each time a new tab is created.
      * @param activity  The host Activity, used to instantiate the fragment
      * @param tag  The identifier tag for the fragment
      * @param clz  The fragment's Class, used to instantiate the fragment
      */
    public TabListener(SherlockFragmentActivity activity, String tag, Class<T> clz) {
        mActivity = activity;
        mTag = tag;
        mClass = clz;
    }       

    /* The following are each of the ActionBar.TabListener callbacks */

    public void onTabSelected(Tab tab, FragmentTransaction ft) {

        // Check if the fragment is already initialized
        if (mFragment == null) {
            // If not, instantiate and add it to the activity
            mFragment = Fragment.instantiate(mActivity, mClass.getName());
            ft.add(android.R.id.content, mFragment, mTag);
        } else {
            // If it exists, simply attach it in order to show it
            ft.attach(mFragment);
        }
    }

    public void onTabUnselected(Tab tab, FragmentTransaction ft) {

        if (mFragment != null) {
            // Detach the fragment, because another one is being attached
            ft.detach(mFragment);
        }
    }

    public void onTabReselected(Tab tab, FragmentTransaction ft) {
        // User selected the already selected tab. Usually do nothing.
    }
}
}

这样，我就有了多个选项卡，可以在每个选项卡中的不同片段之间切换。但是，当我在选项卡中并从选项卡中更改片段时，我的问题就开始了。这就是问题：

当我在Tab 1，我将选项卡中加载的初始片段替换为新片段。然后我去Tab 2这显示了它的初始片段。然而，片段的视图交换到Tab 1仍然显示在后面Tab 2分段：

这是我目前用来从内部更改片段的代码Tab 1:

// Create new fragment and transaction
    FragmentTransaction transaction = ctx.getFragmentManager().beginTransaction();
    transaction.setCustomAnimations(R.anim.slide_in_left, R.anim.slide_out_right);

    // Replace whatever is in the fragment_container view with this fragment,
    // and add the transaction to the back stack
    transaction.replace(container, fragment, tag);

    if(addToBackStack)
        transaction.addToBackStack(tag);

    // Commit the transaction
    transaction.commit();

所有这一切都是通过 ActionBar Sherlock 和 Google v4 支持库来完成的。

好的，所以这个答案假设您希望在每次交换选项卡时擦除每个选项卡的历史记录。我的意思是，选项卡 1 从片段 1 开始，然后单击并将其更改为片段 2。如果选择选项卡 2，您将撤消选项卡 1 的历史记录，下次单击选项卡 1 时，您将返回到碎片 1.

话虽如此，这就是解决方案：将 onTabUnselected 替换为以下内容

public void onTabUnselected(Tab tab, FragmentTransaction ft) {
        if (mFragment != null) {
            //this segment removes the back history of everything in the tab you are leaving so when you click on the tab again you go back to a fresh start
            FragmentManager man = mActivity.getFragmentManager();
            if(man.getBackStackEntryCount()>0) //this check is required to prevent null point exceptions when clicking off of a tab with no history
                man.popBackStack(man.getBackStackEntryAt(0).getName(), FragmentManager.POP_BACK_STACK_INCLUSIVE); //this pops the stack back to index 0 so you can then detach and then later attach your initial fragment
            //also it should be noted that if you do popbackstackimmediate here instead of just popbackstack you will see a flash as the gui changes back to the first fragment when the code executes
            //end
            ft.detach(mFragment);
        }
    }