AndroidBottomNavigationView与Fragment重建与重叠问题解决方法探索
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() {
binding.navView.setSelectedItemId(R.id.navigation_member);
}
}, 250);//3秒后执行Runnable中的run方法
}
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