I have used of MVVM
and ROOM
and databindig
in my app.According Guide to app architecture ,I want to cash data using room.In the xml
layout of RecyclerView
item, I use CategoryViewModel
variable.I get list of categories from Room
database withLiveData
type. I want to change LiveData<list<CategoryItem>>
type to MutableLiveData<ArrayList<CategoryViewModel>>
type. Because finally my adapter consume ArrayList<CategoryViewModel>
data type.How to get value of LiveData
? When I call getValue()
method, returns null. this is CategoryItem
model:
@Entity(tableName = "category_table")
public class CategoryItem implements Serializable {
@PrimaryKey
private int id;
private String title;
private String imagePath;
@TypeConverters({SubCategoryConverter.class})
private ArrayList<String> subCategory;
@TypeConverters({DateConverter.class})
private Date lastRefresh;
public CategoryItem(int id, String title, String imagePath, ArrayList<String> subCategory, Date lastRefresh) {
this.id = id;
this.title = title;
this.imagePath = imagePath;
this.subCategory = subCategory;
this.lastRefresh=lastRefresh;
}
public CategoryItem(int id, String title, String imagePath) {
this.id = id;
this.title = title;
this.imagePath = imagePath;
}
public CategoryItem() {
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getImagePath() {
return imagePath;
}
public void setImagePath(String imagePath) {
this.imagePath = imagePath;
}
public ArrayList<String> getSubCategory() {
return subCategory;
}
public void setSubCategory(ArrayList<String> subCategory) {
this.subCategory = subCategory;
}
public Date getLastRefresh() {
return lastRefresh;
}
public void setLastRefresh(Date lastRefresh) {
this.lastRefresh = lastRefresh;
}
}
this is CategoryViewModel
class:
public class CategoryViewModel extends AndroidViewModel {
private String title;
private String imagePath;
private MutableLiveData<ArrayList<CategoryViewModel>> allCategories=new MutableLiveData<>();
private CategoryRepository repository;
public CategoryViewModel(@NonNull Application application) {
super(application);
repository=new CategoryRepository(application, Executors.newSingleThreadExecutor());
}
public void init(CategoryItem categoryItem){
this.title=categoryItem.getTitle();
this.imagePath=categoryItem.getImagePath();
}
public MutableLiveData<ArrayList<CategoryViewModel>> getAllCategories(){
allCategories=repository.getCategory();
return allCategories;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getImagePath() {
return imagePath;
}
}
This is CategoryRepository
class:
public class CategoryRepository {
private static final String TAG="CategoryRepository";
private static int FRESH_TIMEOUT_IN_MINUTES = 1;
private final Executor executor;
private APIInterface apiInterface;
public MutableLiveData<ArrayList<CategoryViewModel>> arrayListMutableLiveData=new MutableLiveData<>();
private CategoryDao categoryDao;
private Application application;
public CategoryRepository(Application application,Executor executor) {
this.executor = executor;
this.application = application;
apiInterface= APIClient.getClient().create(APIInterface.class);
LearnDatabase database= LearnDatabase.getInstance(application);
categoryDao=database.categoryDao();
}
public MutableLiveData<ArrayList<CategoryViewModel>> getCategory(){
refreshCategory();
List<CategoryItem> items;
categoryDao.loadCategoryItem();
items=categoryDao.loadCategoryItem().getValue(); // return null
CategoryItem category;
ArrayList<CategoryViewModel> arrayList=new ArrayList<>();
for(int i=0;i<items.size();i++){
category=items.get(i);
CategoryViewModel categoryViewModel=new CategoryViewModel(application);
categoryViewModel.init(category);
arrayList.add(categoryViewModel);
}
arrayListMutableLiveData.setValue(arrayList);
return arrayListMutableLiveData;
}
private void refreshCategory(){
executor.execute(() -> {
String lastRefresh=getMaxRefreshTime(new Date()).toString();
boolean sliderExists =(!(categoryDao.hasCategory(lastRefresh)).isEmpty());
Log.e(TAG,"sliderExist: "+sliderExists);
Log.e(TAG,"lastrefresh: "+lastRefresh);
Log.e(TAG,"hasSlider: "+categoryDao.hasCategory(lastRefresh).toString());
// If user have to be updated
if (!sliderExists) {
Log.e(TAG,"in if");
apiInterface.getCategory().enqueue(new Callback<List<CategoryItem>>() {
@Override
public void onResponse(Call<List<CategoryItem>> call, Response<List<CategoryItem>> response) {
executor.execute(() -> {
List<CategoryItem> categories=response.body();
for (int i=0;i<categories.size();i++){
categories.get(i).setLastRefresh(new Date());
categoryDao.saveCategory(categories.get(i));
}
});
}
@Override
public void onFailure(Call<List<CategoryItem>> call, Throwable t) {
Log.e(TAG,"onFailure "+t.toString());
}
});
}
});
}
private Date getMaxRefreshTime(Date currentDate){
Calendar cal = Calendar.getInstance();
cal.setTime(currentDate);
cal.add(Calendar.MINUTE, -FRESH_TIMEOUT_IN_MINUTES);
return cal.getTime();
}
}
This is xml
layout of item of recyclerView
:
<?xml version="1.0" encoding="utf-8"?>
<layout>
<data class="CategoryDataBinding">
<variable
name="category"
type="com.struct.red.alltolearn.viewmodel.CategoryViewModel"/>
</data>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="200dp"
android:layout_height="150dp"
app:cardCornerRadius="15dp">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="@+id/imgItemCategory"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scaleType="centerCrop"
app:imageUrl="@{category.imagePath}" />
<TextView
android:id="@+id/txtTitleItemCategory"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:text="@{category.title}"
android:textColor="#FFFFFF"
android:textSize="20sp"
android:textStyle="bold" />
</RelativeLayout>
</android.support.v7.widget.CardView>
</layout>
This is CategoryDao
class:
@Dao
public interface CategoryDao {
@Query("SELECT * FROM course_table")
LiveData<List<CategoryItem>> loadCategoryItem();
@Insert(onConflict = OnConflictStrategy.REPLACE)
void saveCategory(CategoryItem category);
@Query("SELECT * FROM category_table WHERE lastRefresh > Date(:lastRefreshMax)")
List<CategoryItem> hasCategory(String lastRefreshMax);
}
And finally I observe MutableLiveData
in my Fragment:
private void setupCategoryRecycler() {
categoryViewModel = ViewModelProviders.of(this).get(CategoryViewModel.class);
categoryViewModel.getAllCategories().observe(this, new Observer<ArrayList<CategoryViewModel>>() {
@Override
public void onChanged(@Nullable ArrayList<CategoryViewModel> categoryViewModels) {
Log.e(TAG, "categoryitem: " + categoryViewModels.toString());
categoryAdapter = new CategoryAdapter(getContext(), categoryViewModels);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getContext(), LinearLayoutManager.HORIZONTAL, true);
linearLayoutManager.setReverseLayout(true);
CategoryRecy.setLayoutManager(linearLayoutManager);
CategoryRecy.setAdapter(categoryAdapter);
}
});
}
from How to get value of LiveData from repository that don't access to lifeCycleOwner for observing it?
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