我有ViewPager TabLayout，该主机托管3个Fragments。每个片段包含ListView和来自Firebase的数据。 FragmentOne和FragmentTwo正常运行，问题出在FragmentThree出现黑屏。但是在我像本视频中一样重新加载FragmentThree 1次后，数据和RecyclerView才出现
MainActivity.java
package com.example.yehezkiel.eclassapp;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.design.widget.NavigationView;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
private Toolbar toolbar;
private TabLayout tabLayout;
private ViewPager viewPager;
private List<MataKuliah> listMatkul = new ArrayList<>();
private ArrayList<String> keys = new ArrayList<>();
private myAdapter myAdapter;
private Button logoutBtn;
private FirebaseAuth mAuth;
private FirebaseAuth.AuthStateListener authListener;
private RecyclerView mRecycleView;
private RecyclerView.Adapter mAdapter;
private RecyclerView.LayoutManager mLayoutManager;
private DrawerLayout mDrawerLayout;
private ActionBarDrawerToggle mToggle;
private Toolbar mToolbar;
private NavigationView mNavigationView;
private TextView mTextName;
private TextView mTextNim;
static {
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
}
DatabaseReference userRef = FirebaseDatabase.getInstance().getReference("users");
FirebaseUser users = FirebaseAuth.getInstance().getCurrentUser();
DatabaseReference mataKuliahRef = FirebaseDatabase.getInstance().getReference("courses");
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
mAuth = FirebaseAuth.getInstance();
//Navbar menu
mToolbar = (Toolbar) findViewById(R.id.navbaraction);
setSupportActionBar(mToolbar);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawabel_main);
mToggle = new ActionBarDrawerToggle(this, mDrawerLayout, R.string.open, R.string.close);
mDrawerLayout.addDrawerListener(mToggle);
mToggle.syncState();
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
mNavigationView = (NavigationView) findViewById(R.id.nav_menu);
View header = mNavigationView.getHeaderView(0);
mTextName = (TextView) header.findViewById(R.id.header_name);
mTextNim = (TextView) header.findViewById(R.id.header_nim);
//Tab Layout
viewPager = (ViewPager) findViewById(R.id.viewpager);
setupViewPager(viewPager);
tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(viewPager);
mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
switch (item.getItemId()) {
case (R.id.tugas):
break;
case (R.id.logout_menu):
signOut();
break;
}
return true;
}
});
userRef.child(users.getUid()).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
String name = (String) dataSnapshot.child("name").getValue().toString();
String nim = (String) dataSnapshot.child("nim").getValue().toString();
mTextNim.setText(nim);
mTextName.setText(name);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
authListener = new FirebaseAuth.AuthStateListener() {
@Override
public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
FirebaseUser user = firebaseAuth.getCurrentUser();
if (user == null) {
startActivity(new Intent(MainActivity.this, LoginActivity.class));
finish();
}
}
};
}
private void setupViewPager(ViewPager viewPager) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFragment(new OneFragment(), "Beranda");
adapter.addFragment(new TwoFragment(), "Tugas");
adapter.addFragment(new ThreeFragment(), "Pengumuman");
viewPager.setAdapter(adapter);
}
class ViewPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public ViewPagerAdapter(FragmentManager manager) {
super(manager);
}
@Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
@Override
public int getCount() {
return mFragmentList.size();
}
public void addFragment(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
@Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position);
}
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if(mToggle.onOptionsItemSelected(item)){
return true;
}
return super.onOptionsItemSelected(item);
}
private void signOut() {
mAuth.signOut();
}
@Override
public void onStart() {
super.onStart();
mAuth.addAuthStateListener(authListener);
}
}
ThreeFragment.java
package com.example.yehezkiel.eclassapp;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
public class ThreeFragment extends Fragment {
View v;
private List<DaftarPengumuman> listPengumuman = new ArrayList<>();
private ArrayList<String> obj3 = new ArrayList<>();
List<ListItem> consolidatedList = new ArrayList<>();
private RecyclerView mRecyclerView;
private RecyclerView.Adapter adapter;
private FirebaseAuth mAuth;
private DatabaseReference userRef;
private FirebaseUser users;
private DatabaseReference mataKuliahRef;
private DatabaseReference daftarPengumumanRef;
public ThreeFragment() {
// Required empty public constructor
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
v = inflater.inflate(R.layout.fragment_three, container, false);
userRef = FirebaseDatabase.getInstance().getReference("users");
users = FirebaseAuth.getInstance().getCurrentUser();
mataKuliahRef = FirebaseDatabase.getInstance().getReference("courses");
daftarPengumumanRef = FirebaseDatabase.getInstance().getReference("pengumuman");
mAuth = FirebaseAuth.getInstance();
mRecyclerView = (RecyclerView) v.findViewById(R.id.PengumumanRView);
mRecyclerView.setHasFixedSize(true);
adapter = new PengumumanAdapter(getActivity().getApplicationContext(), consolidatedList);
LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity().getApplicationContext());
layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
mRecyclerView.setLayoutManager(layoutManager);
mRecyclerView.setAdapter(adapter);
userRef.child(users.getUid()).child("courses").addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(final DataSnapshot dataSnapshot) {
obj3.clear();
if(dataSnapshot.exists()){
long datacount = dataSnapshot.getChildrenCount();
int i = 0;
for(DataSnapshot dataHasil : dataSnapshot.getChildren()){
final String idCourse = dataHasil.getKey();
obj3.add(idCourse);
Log.e("anjay",obj3.toString());
if(datacount-1 == i){
queryObj3();
}
i++;
}
}else {
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
HashMap<String, List<DaftarPengumuman>> groupedHashMap = groupDataIntoHashMap(listPengumuman);
for (String nama_p : groupedHashMap.keySet()) {
PengumumanItem nameItem = new PengumumanItem();
nameItem.setNama_matkul(nama_p);
consolidatedList.add(nameItem);
for (DaftarPengumuman daftarPengumuman : groupedHashMap.get(nama_p)) {
GeneralItem generalItem = new GeneralItem();
generalItem.setDaftarPengumuman(daftarPengumuman);//setBookingDataTabs(bookingDataTabs);
consolidatedList.add(generalItem);
}
}
return v;
}
public void queryObj3(){
for(int j = 0 ; j<obj3.size() ;j++){
mataKuliahRef.child(obj3.get(j)).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(final DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
if (dataSnapshot.hasChild("pengumuman")) {
final String name = (String) dataSnapshot.child("name").getValue();
for (DataSnapshot idKeyPeng : dataSnapshot.child("pengumuman").getChildren()) {
daftarPengumumanRef.child(idKeyPeng.getKey()).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot2) {
DaftarPengumuman pengumuman = new DaftarPengumuman();
pengumuman = dataSnapshot2.getValue(DaftarPengumuman.class);
pengumuman.setNama_p(name);
listPengumuman.add(pengumuman);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
}
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
}
private HashMap<String, List<DaftarPengumuman>> groupDataIntoHashMap(List<DaftarPengumuman> listOfDaftarPengumuman) {
HashMap<String, List<DaftarPengumuman>> groupedHashMap = new HashMap<>();
for (DaftarPengumuman daftarPengumuman : listOfDaftarPengumuman) {
String hashMapKey = daftarPengumuman.getNama_p();
if (groupedHashMap.containsKey(hashMapKey)) {
// The key is already in the HashMap; add the pojo object
// against the existing key.
groupedHashMap.get(hashMapKey).add(daftarPengumuman);
} else {
// The key is not there in the HashMap; create a new key-value pair
List<DaftarPengumuman> list = new ArrayList<>();
list.add(daftarPengumuman);
groupedHashMap.put(hashMapKey, list);
}
}
return groupedHashMap;
}
}
MainActivity.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/drawabel_main"
tools:context="com.example.yehezkiel.eclassapp.MainActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">
<include
layout="@layout/navbar_action"
android:layout_width="match_parent"
android:layout_height="wrap_content"></include>
<android.support.design.widget.TabLayout
android:id="@+id/tabs"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:tabGravity="fill"
app:tabMode="fixed" />
</android.support.design.widget.AppBarLayout>
<android.support.v4.view.ViewPager
android:id="@+id/viewpager"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior" />
</LinearLayout>
<android.support.design.widget.NavigationView
android:layout_width="wrap_content"
android:layout_height="match_parent"
app:menu="@menu/navbar_main"
android:layout_gravity="start"
app:headerLayout="@layout/navbar_header"
android:id="@+id/nav_menu">
</android.support.design.widget.NavigationView>
</android.support.v4.widget.DrawerLayout>