Android BottomNavigationView与Fragment重建与重叠问题解决方法探索

这篇文章主要介绍了Android BottomNavigationView与Fragment重建与重叠问题解决，总的来说这并不是一道难题，那为什么要拿出这道题介绍？拿出这道题真正想要传达的是解题的思路，以及不断优化探寻最优解的过程。希望通过这道题能给你带来一种解题优化的思路

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 } }

第二步

监听BottomNavigationView切换事件

 binding.navView.setOnNavigationItemSelectedListener(listener);

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; } };

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(); } } }

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); }

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 }

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