简介

在BottomNavigationView+多个Fragment框架下，进行Fragment切换时，会导致Fragment重建，也会出现同级Fragment未hide，导致重叠

解决方法

第一步

初始化一个默认需要显示的Fragment页面

public void InitFragment(Bundle savedInstanceState) {
        //判断activity是否重建，如果不是，则不需要重新建立fragment.
        if (savedInstanceState == null) {
            fragmentManager = getSupportFragmentManager();
            fragmentTransaction = fragmentManager.beginTransaction();
            if (mMovie == null) {
                mMovie = new HomeFragment();
            }
            CurrentFragment = mMovie;
            fragmentTransaction.replace(R.id.nav_host_fragment_activity_main, mMovie).commit();//fragment parent layout id
        }
    }
1
2
3
4
5
6
7
8
9
10
11
12

第二步

监听BottomNavigationView切换事件

 binding.navView.setOnNavigationItemSelectedListener(listener);
1

对同级每一个Fragment进行监听，当进行切换的时候，对其状态进行show或者hide

private BottomNavigationView.OnNavigationItemSelectedListener listener = new BottomNavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull @NotNull MenuItem item) {
            switch (item.getItemId()) {
                case R.id.navigation_home:
                    if (mMovie == null) {
                        mMovie = new HomeFragment();
                    }
                    switchContent(CurrentFragment, mMovie);
                    return true;
                case R.id.navigation_dashboard:
                    if (mExplore == null) {
                        mExplore = new ExploreFragment();
                    }
                    switchContent(CurrentFragment, mExplore);
                    return true;
                case R.id.navigation_notifications:
                    if (mLibrary == null) {
                        mLibrary = new LibraryFragment();
                    }
                    switchContent(CurrentFragment, mLibrary);
                    return true;
                case R.id.navigation_member:
                    if (mMember == null) {
                        mMember = new MemberFragment();
                    }
                    switchContent(CurrentFragment, mMember);
                    return true;
            }
            return false;
        }
    };
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32

第三步

此为对原Fragment进行隐藏,对要跳转的Fragment进行show，防止页面重叠

public void switchContent(Fragment from, Fragment to) {
        if (from == null || to == null) return;

        if (CurrentFragment != to) {
            CurrentFragment = to;
            fragmentManager = getSupportFragmentManager();
            fragmentTransaction = fragmentManager.beginTransaction();
            if (!to.isAdded()) {  
                //fragment parent layout id
                fragmentTransaction.hide(from).add(R.id.nav_host_fragment_activity_main, to).commit(); 
            } else {
                fragmentTransaction.hide(from).show(to).commit(); 
            }
        }
    }
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

使用

    private FragmentManager fragmentManager;
    private FragmentTransaction fragmentTransaction;
    private HomeFragment mMovie = null;
    private ExploreFragment mExplore = null;
    private LibraryFragment mLibrary = null;
    private MemberFragment mMember = null;
    private Fragment CurrentFragment = null;
1
2
3
4
5
6
7

  InitFragment(savedInstanceState);
 binding.navView.setOnNavigationItemSelectedListener(listener);
1
2

同级Fragment跳转

当BottomNavigationView中的同级Fragment需要进行跳转时，可使用EventBus进行跨进程通信实现，然后拿到BottomNavigationView实例进行切换即可，此id为需要跳转的Fragment 页面ID

 @Subscribe(threadMode = ThreadMode.MAIN, sticky = true)
    public void OnEvent(ChangeFragBean bean) {
        binding.navView.setSelectedItemId(R.id.navigation_dashboard);
    }
1
2
3
4

Activity跳转到Fragment

同样使用EventBus,从一个Activity跳转到BottomNavigationView的某个Fragment时，需要加一个延迟执行，因为Activity可能未销毁，延迟时间，根据具体手机性能决定，大致在300-500毫秒即可

 @Subscribe(threadMode = ThreadMode.MAIN, sticky = true)
    public void OnEvent(MermberBean bean) {
        Handler handler = new Handler();
        handler.postDelayed(new Runnable() {
            @Override
            public void run() {
                /**
                 *要执行的操作
                 */
                binding.navView.setSelectedItemId(R.id.navigation_member);
            }
        }, 250);//3秒后执行Runnable中的run方法
    }
1
2
3
4
5
6
7
8
9
10
11
12
13