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);
}

最理想的方法如下: 片段:当按下后退按钮并自定义时调用的回调

public class MyActivity extends Activity
{
    //...
    //Defined in Activity class, so override
    @Override
    public void onBackPressed()
    {
        super.onBackPressed();
        myFragment.onBackPressed();
    }
}

public class MyFragment extends Fragment
{
    //Your created method
    public static void onBackPressed()
    {
        //Pop Fragments off backstack and do your other checks
    }
}

 @Override
    public void onResume() {

        super.onResume();

        getView().setFocusableInTouchMode(true);
        getView().requestFocus();
        getView().setOnKeyListener(new View.OnKeyListener() {
            @Override
            public boolean onKey(View v, int keyCode, KeyEvent event) {

                if (event.getAction() == KeyEvent.ACTION_UP && keyCode == KeyEvent.KEYCODE_BACK){

                    if (mDrawerLayout.isDrawerOpen(GravityCompat.START)){
                        mDrawerLayout.closeDrawer(GravityCompat.START);
                    }
                    return true;
                }

                return false;
            }
        });
    }

            rootView.setFocusableInTouchMode(true);
            rootView.requestFocus();
            rootView.setOnKeyListener(new View.OnKeyListener() {
            @Override
            public boolean onKey(View v, int keyCode, KeyEvent event)   {
            if (keyCode == KeyEvent.KEYCODE_BACK) {


                Fragment NameofFragment = new NameofFragment;

                FragmentTransaction  transaction=getFragmentManager().beginTransaction();
                transaction.replace(R.id.frame_container,NameofFragment);

                transaction.commit();

                return true;
            }
            return false;
        }
    });

    return rootView;

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
  ...
}

我宁愿这样做:

private final static String TAG_FRAGMENT = "TAG_FRAGMENT";

private void showFragment() {
    final Myfragment fragment = new MyFragment();
    final FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
    transaction.replace(R.id.fragment, fragment, TAG_FRAGMENT);
    transaction.addToBackStack(null);
    transaction.commit();
}

@Override
public void onBackPressed() {
    final Myfragment fragment = (Myfragment) getSupportFragmentManager().findFragmentByTag(TAG_FRAGMENT);

    if (fragment.allowBackPressed()) { // and then you define a method allowBackPressed with the logic to allow back pressed or not
        super.onBackPressed();
    }
}