// Category Adapter which open the second fragment containing the blank recyclerview(which should ideally contain intial data.)
public class MyCategoryAdapter extends RecyclerView.Adapter<MyCategoryHolder> {
private Context context;
private ArrayList<Categories> categories;
private Context context1;
public MyCategoryAdapter(Context context, ArrayList<Categories> categories) {
this.context = context;
this.categories = categories;
}
@Override
public MyCategoryHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.category_model, parent, false);
context1 = parent.getContext();
return new MyCategoryHolder(v);
}
@Override
public void onBindViewHolder(MyCategoryHolder holder, final int position) {
Categories c = categories.get(position);
holder.categoryText.setText(c.getName());
holder.categoryIdText.setText(c.getId());
//item click
holder.setItemClickListener(new ItemClickListener() {
@Override
public void onItemClick(int pos) {
Toast.makeText(context.getApplicationContext(), Integer.toString(pos), Toast.LENGTH_SHORT).show();
openActivity();
}
});
}
@Override
public int getItemCount() {
return categories.size();
}
private void openActivity()
{
FragmentActivity fragment = ((FragmentActivity)context1);
fragment.getSupportFragmentManager().beginTransaction().addToBackStack(null).replace(R.id.fragment_container, new SubCategoryFragment()).setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN).commit();
}
}
我制作了一个包含2个Recyclerviews的Android应用程序。两者都有各自的Realm数据库。 First Recyclerview显示类别。当我点击任何项目时，它会为我打开第二个Recyclerview（包含子类别）。我能够为Categories recyclerview加载初始数据，但当我点击其中的任何项目时，它会打开一个空白的recyclerview（理想情况下应显示SubCategories初始数据Realm数据库中的内容）
//Realm for SubCategories
public class SubCategories extends RealmObject{
private String name;
private String id;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
}
//Categories intial data
public class CategoriesInitialData implements Realm.Transaction {
@Override
public void execute(Realm realm) {
Categories categories = new Categories();
categories.setName("Animals");
categories.setId("0");
realm.insertOrUpdate(categories);
categories.setName("Birds");
categories.setId("1");
realm.insertOrUpdate(categories);
categories.setName("Mountains");
categories.setId("2");
realm.insertOrUpdate(categories);
categories.setName("Instagram");
categories.setId("3");
realm.insertOrUpdate(categories);
categories.setName("Facebook");
categories.setId("4");
realm.insertOrUpdate(categories);
categories.setName("Twitter");
categories.setId("5");
realm.insertOrUpdate(categories);
categories.setName("OnePlus");
categories.setId("6");
realm.insertOrUpdate(categories);
categories.setName("Apple");
categories.setId("7");
realm.insertOrUpdate(categories);
categories.setName("Samsung");
categories.setId("8");
realm.insertOrUpdate(categories);
categories.setName("Laptops");
categories.setId("9");
realm.insertOrUpdate(categories);
categories.setName("Food");
categories.setId("10");
realm.insertOrUpdate(categories);
categories.setName("Lifestyle");
categories.setId("11");
realm.insertOrUpdate(categories);
}
@Override
public int hashCode() {
return CategoriesInitialData.class.hashCode();
}
@Override
public boolean equals(Object obj) {
return obj != null && obj instanceof CategoriesInitialData;
}
}
// SubCategories Initial Data
public class SubCategoriesInitialData implements Realm.Transaction {
@Override
public void execute(Realm realm) {
SubCategories subCategories = new SubCategories();
subCategories.setName("Animals1");
subCategories.setId("0");
realm.insertOrUpdate(subCategories);
subCategories.setName("Animals2");
subCategories.setId("0");
realm.insertOrUpdate(subCategories);
subCategories.setName("Animals3");
subCategories.setId("0");
realm.insertOrUpdate(subCategories);
subCategories.setName("Birds1");
subCategories.setId("1");
realm.insertOrUpdate(subCategories);
subCategories.setName("Birds2");
subCategories.setId("1");
realm.insertOrUpdate(subCategories);
subCategories.setName("Birds3");
subCategories.setId("1");
realm.insertOrUpdate(subCategories);
}
@Override
public int hashCode() {
return SubCategoriesInitialData.class.hashCode();
}
@Override
public boolean equals(Object obj) {
return obj != null && obj instanceof SubCategoriesInitialData;
}
}
// Category Fragment
public class CategoryFragment extends Fragment {
Realm realm;
MyCategoryAdapter myCategoryAdapter;
RealmChangeListener realmChangeListener;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View myView = inflater.inflate(R.layout.fragment_categories,container,false);
final RecyclerView rv = (RecyclerView) myView.findViewById(R.id.categoryRV);
rv.setLayoutManager(new LinearLayoutManager(this.getActivity()));
//Realm configuration
Realm.init(getContext());
RealmConfiguration configuration = new RealmConfiguration.Builder().initialData(new CategoriesInitialData()).deleteRealmIfMigrationNeeded().build();
realm = Realm.getInstance(configuration);
//Save
final CategoriesRealmHelper helper = new CategoriesRealmHelper(realm);
//Categories categories = new Categories();
//categories.setName("Last Category");
//helper.save(categories);
//retrieve
helper.retrieveCategories();
//setup adapter
myCategoryAdapter = new MyCategoryAdapter(getContext(), helper.refreshCategories());
rv.setAdapter(myCategoryAdapter);
//data change
realmChangeListener = new RealmChangeListener() {
@Override
public void onChange(Object element) {
//refresh
myCategoryAdapter = new MyCategoryAdapter(getContext(), helper.refreshCategories());
rv.setAdapter(myCategoryAdapter);
}
};
//add changes to realm
realm.addChangeListener(realmChangeListener);
return myView;
}
@Override
public void onDestroyView() {
super.onDestroyView();
realm.removeChangeListener(realmChangeListener);
realm.close();
}
@Override
public void onStop() {
super.onStop();
}
}
// SubCategories Fragment
public class SubCategoryFragment extends Fragment {
Realm realm;
MySubCategoryAdapter mySubCategoryAdapter;
RealmChangeListener realmChangeListener;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View myView = inflater.inflate(R.layout.fragment_subcategories, container, false);
final RecyclerView rv = (RecyclerView) myView.findViewById(R.id.subcategoryRV);
rv.setLayoutManager(new LinearLayoutManager(this.getActivity()));
//Realm configuration
Realm.init(getContext());
RealmConfiguration configuration = new RealmConfiguration.Builder().initialData(new SubCategoriesInitialData()).deleteRealmIfMigrationNeeded().build();
realm = Realm.getInstance(configuration);
//Save
final SubCategoriesRealmHelper helper = new SubCategoriesRealmHelper(realm);
//SubCategories subCategories = new SubCategories();
//subCategories.setName("Hello");
//helper.save(subCategories);
//retrieve
helper.retrieveSubCategories();
//setting up adapter
mySubCategoryAdapter = new MySubCategoryAdapter(getContext(), helper.refreshSubCategories());
rv.setAdapter(mySubCategoryAdapter);
//data change
realmChangeListener = new RealmChangeListener() {
@Override
public void onChange(Object element) {
//refresh
mySubCategoryAdapter = new MySubCategoryAdapter(getContext(), helper.refreshSubCategories());
rv.setAdapter(mySubCategoryAdapter);
}
};
//add changes to realm
realm.addChangeListener(realmChangeListener);
return myView;
}
@Override
public void onDestroyView() {
super.onDestroyView();
realm.removeChangeListener(realmChangeListener);
realm.close();
}
@Override
public void onStop() {
super.onStop();
}
}
// Realm Helper class. I also have a CategoriesRealmHelper class having similar methods
public class SubCategoriesRealmHelper {
Realm realm;
boolean saved;
RealmResults<SubCategories> subCategories;
public SubCategoriesRealmHelper(Realm realm) {
this.realm = realm;
}
//Writing data to subcategories database
public boolean save(final SubCategories subCategories)
{
if(subCategories == null)
{
saved = false;
}
else
{
realm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
try{
realm.copyToRealm(subCategories);
saved = true;
}catch (RealmException e)
{
e.printStackTrace();
saved = false;
}
}
});
}
return saved;
}
//reading data from subcategories database
public void retrieveSubCategories()
{
subCategories = realm.where(SubCategories.class).findAll();
}
//refreshing subcategories data
public ArrayList<SubCategories> refreshSubCategories()
{
ArrayList<SubCategories> latest = new ArrayList<>();
for (SubCategories s : subCategories) {
latest.add(s);
}
return latest;
}
}
//Main Acitivity
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
openFragment();
}
void openFragment(){
getSupportFragmentManager().beginTransaction().add(R.id.fragment_container, new CategoryFragment()).commit();
}
}
//Realm for Categories
public class Categories extends RealmObject {
private String name;
private String id;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
}