FragmentA中的 ListView会完美刷新。这是我在fragmentA中非常成功的代码，但是在此之前，这是我将在此之后显示代码的输出：
输出： 来自第一个查询
EAT
DRINK
POOP
来自第二个查询
DONALD TRUMP
BARRACK OBAMA
GEORGE BUSH
当我离开时，会获得高于输出的成功
FragmentA -> 活动->返回 FragmentA
当我这样移动时，
FragmentA -> FragmentB ->返回 FragmentA
ListView显示不必要的升序结果
// wrong
POOP
DRINK
EAT
// true
EAT
DRINK
EAT
，根本没有第二个查询。
非常感谢您的回复。在此之后显示代码之前， 这就是为什么为什么要转到“活动”然后成功刷新 因为我将Fragments放在MainActivity中，所以：
MainActiviy -> 活动->在MainActivity中再次调用Create FragmentA -> FragmentB ->不在MainActivity中调用onCreate
FragmentA内部下面的所有代码。
好，首先查询代码：
// when scroll reach bottom
recyclerSeen.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
// vertical scroll
Boolean reachBottom = !recyclerView.canScrollVertically(-1);
if (reachBottom) {
secondQuery();
}
}
});
Query firstQuery = firebaseFirestore
.collection("Posts")
.orderBy("timestamp", Query.Direction.DESCENDING)
.limit(3);
firstQuery.addSnapshotListener(new EventListener<QuerySnapshot>() {
@Override
public void onEvent(QuerySnapshot documentSnapshots, FirebaseFirestoreException e) {
if (isFirstPageFirstLoad) {
lastVisible = documentSnapshots.getDocuments().get(documentSnapshots.size() - 1);
}
for (DocumentChange doc : documentSnapshots.getDocumentChanges()) {
if (doc.getType() == DocumentChange.Type.ADDED) {
//String postId = doc.getDocument().getId();
ContentProfile contentSeen = doc.getDocument().toObject(ContentProfile.class);
/* how to store multi ArrayList */
if (isFirstPageFirstLoad) {
contentList.add(contentSeen);
} else {
contentList.add(0, contentSeen);
}
adapterSeen.notifyDataSetChanged();
}
}
isFirstPageFirstLoad = false;
}
});
第二个查询代码：
public void loadMorePost() {
Query nextQuery = firebaseFirestore
.orderBy("timestamp", Query.Direction.DESCENDING)
.collection("Posts")
.startAfter(lastVisible)
.limit(3);
nextQuery.addSnapshotListener(new EventListener<QuerySnapshot>() {
@Override
public void onEvent(QuerySnapshot documentSnapshots, FirebaseFirestoreException e) {
if (!documentSnapshots.isEmpty()) {
lastVisible = documentSnapshots.getDocuments().get(documentSnapshots.size() - 1);
for (DocumentChange doc : documentSnapshots.getDocumentChanges()) {
if (doc.getType() == DocumentChange.Type.ADDED) {
//String postId = doc.getDocument().getId();
ContentProfile contentSeen = doc.getDocument().toObject(ContentProfile.class);
contentList.add(contentSeen);
adapterSeen.notifyDataSetChanged();
}
}
}
}
});
}
MainActivity.class
public class MainActivity extends AppCompatActivity {
private HomeFragment homeFragment;
private Search search;
private CenterFragment centerFragment;
private Notification notification;
private ProfileFragment profileFragment;
private BottomNavigationView bottomNavigation;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
homeFragment = new HomeFragment();
search = new Search();
centerFragment = new CenterFragment();
notification = new Notification();
profileFragment = new ProfileFragment();
bottomNavigation = findViewById(R.id.bottom_navigation);
BottomNavigationViewHelper.removeShiftAnimation(bottomNavigation);
//initializeFragment
replaceFragment(homeFragment);
}
@Override
public void onStart() {
super.onStart();
bottomNavigation.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener(){
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item){
switch(item.getItemId()){
case R.id.action_home :
replaceFragment(homeFragment);
return true;
case R.id.action_search :
replaceFragment(search);
return true;
case R.id.action_center :
replaceFragment(centerFragment);
return true;
case R.id.action_notif :
replaceFragment(notification);
return true;
case R.id.action_profile :
replaceFragment(profileFragment);
return true;
default:
return false;
}
}
});
}
private void replaceFragment(Fragment fragment){
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.main_container, fragment);
fragmentTransaction.commit();
}
}
我有一个解决上述问题的解决方案，但是我不知道如何刷新它，或者不手动调用MainActivity onCreate()或remove()片段或whatever干净代码，我要做的就是将replace更改为hide。下面的这段代码就像一个魅力一样工作，我不必刷新列表。
public class MainActivity extends AppCompatActivity {
private HomeFragment homeFragment;
private Search search;
private CenterFragment centerFragment;
private Notification notification;
private ProfileFragment profileFragment;
private BottomNavigationView bottomNavigation;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
homeFragment = new HomeFragment();
search = new Search();
centerFragment = new CenterFragment();
notification = new Notification();
profileFragment = new ProfileFragment();
bottomNavigation = findViewById(R.id.bottom_navigation);
BottomNavigationViewHelper.removeShiftAnimation(bottomNavigation);
initializeFragment();
//replaceFragment(homeFragment);
Toast.makeText(MainActivity.this, "MainActivity : onCreate() ", Toast.LENGTH_SHORT).show();
}
@Override
public void onStart() {
super.onStart();
bottomNavigation.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener(){
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item){
Fragment currentFragment = getSupportFragmentManager().findFragmentById(R.id.main_container);
switch(item.getItemId()){
case R.id.action_home :
replaceFragment(homeFragment, currentFragment);
return true;
case R.id.action_search :
replaceFragment(search, currentFragment);
return true;
case R.id.action_center :
replaceFragment(centerFragment, currentFragment);
return true;
case R.id.action_notif :
replaceFragment(notification, currentFragment);
return true;
case R.id.action_profile :
replaceFragment(profileFragment, currentFragment);
return true;
default:
return false;
}
}
});
}
private void initializeFragment(){
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.add(R.id.main_container, homeFragment);
fragmentTransaction.add(R.id.main_container, search);
fragmentTransaction.add(R.id.main_container, centerFragment);
fragmentTransaction.add(R.id.main_container, notification);
fragmentTransaction.add(R.id.main_container, profileFragment);
fragmentTransaction.hide(search);
fragmentTransaction.hide(centerFragment);
fragmentTransaction.hide(notification);
fragmentTransaction.hide(profileFragment);
fragmentTransaction.commit();
}
// private void replaceFragment(Fragment fragment){
// FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
//
// fragmentTransaction.replace(R.id.main_container, fragment);
// fragmentTransaction.commit();
// }
private void replaceFragment(Fragment fragment, Fragment currentFragment){
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
if(fragment == homeFragment){
fragmentTransaction.hide(search);
fragmentTransaction.hide(centerFragment);
fragmentTransaction.hide(notification);
fragmentTransaction.hide(profileFragment);
}
if(fragment == search){
fragmentTransaction.hide(homeFragment);
fragmentTransaction.hide(centerFragment);
fragmentTransaction.hide(notification);
fragmentTransaction.hide(profileFragment);
}
if(fragment == centerFragment){
fragmentTransaction.hide(search);
fragmentTransaction.hide(homeFragment);
fragmentTransaction.hide(notification);
fragmentTransaction.hide(profileFragment);
}
if(fragment == notification){
fragmentTransaction.hide(search);
fragmentTransaction.hide(centerFragment);
fragmentTransaction.hide(homeFragment);
fragmentTransaction.hide(profileFragment);
}
if(fragment == profileFragment){
fragmentTransaction.hide(search);
fragmentTransaction.hide(centerFragment);
fragmentTransaction.hide(notification);
fragmentTransaction.hide(homeFragment);
}
fragmentTransaction.show(fragment);
//fragmentTransaction.replace(R.id.main_container, fragment);
fragmentTransaction.commit();
}