我想知道代码的Firebase数据库的结构。
我已经完成了代码，但是我不知道数据库的结构。
WallpapersActivity.java
public class WallpapersActivity extends AppCompatActivity {
List<Wallpaper> wallpaperList;
List<Wallpaper> favList;
RecyclerView recyclerView;
WallpapersAdapter adapter;
DatabaseReference dbWallpapers, dbFavs;
ProgressBar progressBar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_wallpapers);
Intent intent = getIntent();
final String category = intent.getStringExtra("category");
Toolbar toolbar = findViewById(R.id.toolbar);
toolbar.setTitle(category);
setSupportActionBar(toolbar);
favList = new ArrayList<>();
wallpaperList = new ArrayList<>();
recyclerView = findViewById(R.id.recycler_view);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
adapter = new WallpapersAdapter(this, wallpaperList);
recyclerView.setAdapter(adapter);
progressBar = findViewById(R.id.progressbar);
dbWallpapers = FirebaseDatabase.getInstance().getReference("images")
.child(category);
if (FirebaseAuth.getInstance().getCurrentUser() != null) {
dbFavs = FirebaseDatabase.getInstance().getReference("users")
.child(FirebaseAuth.getInstance().getCurrentUser().getUid())
.child("favourites")
.child(category);
fetchFavWallpapers(category);
} else {
fetchWallpapers(category);
}
}
private void fetchFavWallpapers(final String category) {
progressBar.setVisibility(View.VISIBLE);
dbFavs.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
progressBar.setVisibility(View.GONE);
if (dataSnapshot.exists()) {
for (DataSnapshot wallpaperSnapshot : dataSnapshot.getChildren()) {
String id = wallpaperSnapshot.getKey();
String title = wallpaperSnapshot.child("title").getValue(String.class);
String desc = wallpaperSnapshot.child("desc").getValue(String.class);
String url = wallpaperSnapshot.child("url").getValue(String.class);
Wallpaper w = new Wallpaper(id, title, desc, url, category);
favList.add(w);
}
}
fetchWallpapers(category);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
private void fetchWallpapers(final String category) {
progressBar.setVisibility(View.VISIBLE);
dbWallpapers.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
progressBar.setVisibility(View.GONE);
if (dataSnapshot.exists()) {
for (DataSnapshot wallpaperSnapshot : dataSnapshot.getChildren()) {
String id = wallpaperSnapshot.getKey();
String title = wallpaperSnapshot.child("title").getValue(String.class);
String desc = wallpaperSnapshot.child("desc").getValue(String.class);
String url = wallpaperSnapshot.child("url").getValue(String.class);
Wallpaper w = new Wallpaper(id, title, desc, url, category);
if (isFavourite(w)) {
w.isFavourite = true;
}
wallpaperList.add(w);
}
adapter.notifyDataSetChanged();
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
private boolean isFavourite(Wallpaper w) {
for (Wallpaper f : favList) {
if (f.id.equals(w.id)) {
return true;
}
}
return false;
}
}
Wallpaper.java
public class Wallpaper {
@Exclude
public String id;
public String title, desc, url;
@Exclude
public String category;
@Exclude
public boolean isFavourite = false;
public Wallpaper(String id, String title, String desc, String url, String category) {
this.id = id;
this.title = title;
this.desc = desc;
this.url = url;
this.category = category;
}
}
Category.java
public class Category {
public String name, desc, thumb;
public Category(String name, String desc, String thumb) {
this.name = name;
this.desc = desc;
this.thumb = thumb;
}
}
HomeFragment.java
public class HomeFragment extends Fragment {
private List<Category> categoryList;
private ProgressBar progressBar;
private DatabaseReference dbCategories;
private RecyclerView recyclerView;
private CategoriesAdapter adapter;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_home, container, false);
}
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
progressBar = view.findViewById(R.id.progressbar);
progressBar.setVisibility(View.VISIBLE);
recyclerView = view.findViewById(R.id.recycler_view);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new GridLayoutManager(getActivity(), 2));
categoryList = new ArrayList<>();
adapter = new CategoriesAdapter(getActivity(), categoryList);
recyclerView.setAdapter(adapter);
dbCategories = FirebaseDatabase.getInstance().getReference("categories");
dbCategories.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
progressBar.setVisibility(View.GONE);
for (DataSnapshot ds : dataSnapshot.getChildren()) {
String name = ds.getKey();
String desc = ds.child("desc").getValue(String.class);
String thumb = ds.child("thumbnail").getValue(String.class);
Category c = new Category(name, desc, thumb);
categoryList.add(c);
}
adapter.notifyDataSetChanged();
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
}
答案 0 :(得分：1)
学习与您的代码相对应的JSON结构的最简单方法是将每个Java类的实例写入数据库。
但是从快速扫描中我希望：
"Wallpaper": {
"title": "value of title",
"desc": "value of desc",
"url": "value of url"
}