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Android?BottomNavigationView與Fragment重建與重疊問題解決方法探索_Android

作者：FranzLiszt1847 ? 更新時間： 2023-03-13 編程語言

簡介

在BottomNavigationView+多個Fragment框架下，進行Fragment切換時，會導致Fragment重建，也會出現同級Fragment未hide，導致重疊

解決方法

第一步

初始化一個默認需要顯示的Fragment頁面

public void InitFragment(Bundle savedInstanceState) {
        //判斷activity是否重建，如果不是，則不需要重新建立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
        }
    }

第二步

監聽BottomNavigationView切換事件

 binding.navView.setOnNavigationItemSelectedListener(listener);

對同級每一個Fragment進行監聽，當進行切換的時候，對其狀態進行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;
        }
    };

第三步

此為對原Fragment進行隱藏,對要跳轉的Fragment進行show，防止頁面重疊

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(); 
            }
        }
    }

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;

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

同級Fragment跳轉

當BottomNavigationView中的同級Fragment需要進行跳轉時，可使用EventBus進行跨進程通信實現，然后拿到BottomNavigationView實例進行切換即可，此id為需要跳轉的Fragment 頁面ID

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

Activity跳轉到Fragment

同樣使用EventBus,從一個Activity跳轉到BottomNavigationView的某個Fragment時，需要加一個延遲執行，因為Activity可能未銷毀，延遲時間，根據具體手機性能決定，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() {
                /**
                 *要執行的操作
                 */
                binding.navView.setSelectedItemId(R.id.navigation_member);
            }
        }, 250);//3秒后執行Runnable中的run方法
    }

原文鏈接：https://blog.csdn.net/News53231323/article/details/126015892

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