或者你可以使用getSupportFragmentManager().getBackStackEntryCount()来检查要做什么:

@Override
    public void onBackPressed() {

        logger.d("@@@@@@ back stack entry count : " + getSupportFragmentManager().getBackStackEntryCount());

        if (getSupportFragmentManager().getBackStackEntryCount() != 0) {

            // only show dialog while there's back stack entry
            dialog.show(getSupportFragmentManager(), "ConfirmDialogFragment");

        } else if (getSupportFragmentManager().getBackStackEntryCount() == 0) {

            // or just go back to main activity
            super.onBackPressed();
        }
    }

如果你重写了片段视图的onKey方法，你需要:

    view.setFocusableInTouchMode(true);
    view.requestFocus();
    view.setOnKeyListener(new View.OnKeyListener() {
            @Override
            public boolean onKey(View v, int keyCode, KeyEvent event) {
                Log.i(tag, "keyCode: " + keyCode);
                if( keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_UP) {
                    Log.i(tag, "onKey Back listener is working!!!");
                    getFragmentManager().popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);
                    return true;
                } 
                return false;
            }
        });

如果你正在使用FragmentActivity。然后像这样做

首先在你的碎片中调用这个。

public void callParentMethod(){
    getActivity().onBackPressed();
}

然后调用你的父类FragmentActivity中的onBackPressed方法。

@Override
public void onBackPressed() {
  //super.onBackPressed();
  //create a dialog to ask yes no question whether or not the user wants to exit
  ...
}

我正在与SlidingMenu和Fragment一起工作，在这里展示我的案例，希望能帮助到别人。

按[后退]键时的逻辑:

When SlidingMenu shows, close it, no more things to do. Or when 2nd(or more) Fragment showing, slide back to previous Fragment, and no more things to do. SlidingMenu not shows, current Fragment is #0, do the original [Back] key does. public class Main extends SherlockFragmentActivity { private SlidingMenu menu=null; Constants.VP=new ViewPager(this); //Some stuff... @Override public void onBackPressed() { if(menu.isMenuShowing()) { menu.showContent(true); //Close SlidingMenu when menu showing return; } else { int page=Constants.VP.getCurrentItem(); if(page>0) { Constants.VP.setCurrentItem(page-1, true); //Show previous fragment until Fragment#0 return; } else {super.onBackPressed();} //If SlidingMenu is not showing and current Fragment is #0, do the original [Back] key does. In my case is exit from APP } } }

检查后台工作完美

@Override
public boolean onKeyDown(int keyCode, KeyEvent event)
{
    if (keyCode == KeyEvent.KEYCODE_BACK)
    {
        if (getFragmentManager().getBackStackEntryCount() == 1)
        {
            // DO something here since there is only one fragment left
            // Popping a dialog asking to quit the application
            return false;
        }
    }
    return super.onKeyDown(keyCode, event);
}

在fragment类中，为back event放以下代码:

 rootView.setFocusableInTouchMode(true);
        rootView.requestFocus();
        rootView.setOnKeyListener( new OnKeyListener()
        {
            @Override
            public boolean onKey( View v, int keyCode, KeyEvent event )
            {
                if( keyCode == KeyEvent.KEYCODE_BACK )
                {
                    FragmentManager fragmentManager = getFragmentManager();
                    fragmentManager.beginTransaction()
                            .replace(R.id.frame_container, new Book_service_provider()).commit();

                    return true;
                }
                return false;
            }
        } );