Question

我有登录Activity和三个片段即loader，homePage，参加考试。现在我在homePage我希望我的应用程序通过点击后退来退出。我已经成功实现了我的目标但是双重背压也适用于拿出我不想要的考勤片段。在点击后面的考勤片段中，它应该只是前面的片段，但它没有发生。

这是我的代码： -

MainActivity.java

@Override
    public void onBackPressed() {

        //for(int i=0;i<getFragmentManager().getBackStackEntryCount();i++)
        Home_Screen home_screen = (Home_Screen) getFragmentManager().findFragmentByTag
                ("Home_Screen_Teacher");

        if (home_screen != null && home_screen.isVisible()) {

             DrawerLayout navigation_drawer = home_screen.getView().findViewById(R.id.drawer_layout);
            if (navigation_drawer.isDrawerOpen(GravityCompat.START)) {
                navigation_drawer.closeDrawer(Gravity.LEFT);
            }


            else {
                if (backpressedTime + 2000 > System.currentTimeMillis()) {

                    this.finish();
                    System.exit(0);
                    return;
                }
                else {
                    second=(int)(backpressedTime/1000);
                    Snackbar.make(findViewById(R.id.home_screen_teacher),"Detach",Snackbar.LENGTH_LONG).show();
                }
                backpressedTime = System.currentTimeMillis();
                    //super.onBackPressed();
                }

            }
            else{

                super.onBackPressed();
            }


        }

Loader fragment.java

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View loadder_fragment=inflater.inflate(R.layout.fragment_loader_fragment, container, false);

        Loader=(AVLoadingIndicatorView)loadder_fragment.findViewById(R.id.loder_login);
        handler=new Handler();
        runnable=new Runnable() {
            @Override
            public void run() {
                Loader.setVisibility(View.INVISIBLE);
                timer.cancel();

                fragmentManager=getFragmentManager();
                fragmentTransaction=fragmentManager.beginTransaction();
                fragmentTransaction.setCustomAnimations(R.animator.slide_in_left,R.animator
                        .slide_out_left,R.animator.slide_in_right,R.animator.slide_out_right);
                Home_Screen home_screen=new Home_Screen();
                fragmentTransaction.replace(R.id.Home_screen_fragment_3,home_screen,
                        "Home_Screen_Teacher");
                fragmentTransaction.addToBackStack(null);
                fragmentTransaction.commit();

            }


        };

        timer=new Timer();
        timer.schedule(new TimerTask() {
            @Override
            public void run() {
                handler.post(runnable);
            }
        }, 5000,5000);



        return loadder_fragment;
    }

Home_Screen fragmnent.java

 navigation_drawer=(DrawerLayout)Home_screen.findViewById(R.id.drawer_layout);
        navigationView=(NavigationView)Home_screen.findViewById(R.id.Navigation_view_for_teacher);
        home_screen_take_attendance_button=(Button)Home_screen.findViewById(R.id
                .home_screen_take_attendance_button);
        home_screen_take_attendance_button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                getActivity().getFragmentManager().beginTransaction().replace(R.id
                        .fragment_take_attendance,new Take_attendance(),"take_attendence")
                        .addToBackStack(null).commit();

            }
        });

Take_attendance fragment.java

 toolbar.setNavigationOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                fragmentManager=getFragmentManager();
                fragmentTransaction=fragmentManager.beginTransaction();

                fragmentTransaction.setCustomAnimations(R.animator.slide_in_left,R.animator          .slide_out_left,R.animator.slide_in_right,R.animator.slide_out_right);
                Home_Screen home_screen=new Home_Screen();      fragmentTransaction.replace(R.id.Home_screen_fragment1,home_screen,"Home_Screen_Teacher");
                fragmentTransaction.addToBackStack(null);
                fragmentTransaction.commit();
            }
        });
           //Some code

请帮助。过去两天我遇到了这个问题。我已经实现了我的目标，但退出应用程序的双重抑制也在我不想要的考勤片段中工作。

Answer 1

在应用onBackPressed()逻辑之前，请检查背堆上是否有碎片。

示例：

@Override
public void onBackPressed() {

    int backStackCount = getSupportFragmentManager().getBackStackEntryCount();

    if (backStackCount > 0) {
        // returns to previous fragment
        getSupportFragmentManager().popBackStack();

    } else {
        // apply your "double press" logic
        super.onBackPressed();
    }
}

双击以退出应用

1 个答案: