[英]onChanged LiveData not called, RecyclerView remains empty
當我使用 Retrofit 和 LiveData 發出 GET 請求時,我的 onChanged function 永遠不會被調用,並且我的 RecyclerView 永遠不會更新(它仍然為空)? GET 請求完美運行! 誰能幫我? 非常感謝!
這是我的 function:
public void getProductsByBarcode(RecyclerView recyclerView, ProductListAdapter adapter){
String accessToken = getIntent().getExtras().getString("accessToken");
EditText insertBarcode = findViewById(R.id.barcodeNumber);
String barcode = insertBarcode.getText().toString();
addViewModel = ViewModelProvider.AndroidViewModelFactory.getInstance(
this.getApplication()).create(ProductsViewModel.class);
addViewModel.setData(barcode, accessToken);
addViewModel.getProductsList().observe(this, new Observer<Product>() {
@Override
public void onChanged(Product prods) {
adapter.submitList(addViewModel.getListFood());
Log.d("lista", "c'è qualcosa nella lista");
Log.d("lista", prods.getFood().toString());
}
});
}
這是我的視圖模型
public class ProductsViewModel extends AndroidViewModel {
private ProductRepository repository;
private LiveData<Product> productsList;
private String barcode;
private String accessToken;
public ProductsViewModel(Application application) {
super(application);
barcode="";
accessToken="";
repository = new ProductRepository(application, barcode, accessToken);
productsList = null;
}
public LiveData<Product> getProductsList(){
if(productsList==null){
productsList = new LiveData<Product>() {
@Override
public void observe(@NonNull LifecycleOwner owner, @NonNull Observer<? super Product> observer) {
super.observe(owner, observer);
}
};
}
return productsList;
}
public List<Food> getListFood(){
return this.repository.listResponse;
}
public void setData(String bar, String tok){
this.accessToken = tok;
this.barcode = bar;
repository.setData(bar, tok);
productsList = repository.getProductsList();
}
public String getSessionToken(){
return this.repository.sessionToken;
}
/*public void insertProduct(Product product){
this.repository.insert(product);
}*/
}
這是我的存儲庫:
public class ProductRepository {
private ProductDao prodDao;
private MutableLiveData<Product> productsList;
private String baseURL = "/products?barcode=";
private String barcode;
private String accessToken;
public String sessionToken;
public List<Food> listResponse;
ProductRepository (Application app, String iBarcode, String rToken){
ProductRoomDatabase db = ProductRoomDatabase.getDatabase(app);
prodDao = db.productDao();
barcode = iBarcode;
accessToken = rToken;
productsList = null;
}
MutableLiveData<Product> getProductsList(){
GetProductService service = RetrofitClientInstance.getRetrofitInstance().create(GetProductService.class);
Call<Product> call = service.getAllProducts("Bearer " + accessToken, baseURL+barcode);
call.enqueue(new Callback<Product>(){
@Override
public void onResponse(Call<Product> call, Response<Product> response) {
if(response.isSuccessful()) {
Log.d("response1", response.toString());
Log.d("response2", response.body().toString());
sessionToken = response.body().getToken();
Log.d("tokenDaGet", sessionToken);
listResponse = response.body().getFood();
if(listResponse.size()==0){
Log.d("listaProdotti", "nulla");
}else{
Log.d("listaProdotti", listResponse.toString());
Log.d("barcode0", listResponse.get(0).getBarcode());
}
insertAll(listResponse);
productsList.setValue(response.body());
}
}
@Override
public void onFailure(Call<Product> call, Throwable t) {
Log.e("ERR", call.toString());
Log.e("tERR", t.getMessage());
Log.e("t2ERR", t.toString());
Log.e("RETROFIT", "Richiesta Retrofit fallita, ma è ancora attiva.");
}
});
return productsList;
}
public void setData(String barcode, String tok) {
this.accessToken = tok;
this.barcode = barcode;
prodDao.getProductsList();
}
void insert(Food food){
ProductRoomDatabase.databaseWriteExecutor.execute(() -> {
prodDao.insert(food);
});
}
void insertAll(List<Food> products){
ProductRoomDatabase.databaseWriteExecutor.execute(() -> {
prodDao.insertAll(products);
});
}
}
這是我的適配器:
public class ProductListAdapter extends ListAdapter<Food, ProductViewHolder> {
protected ProductListAdapter(@NonNull FoodDiff diffCallback) {
super(diffCallback);
}
@NonNull
@Override
public ProductViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
return ProductViewHolder.create(parent);
}
@Override
public void onBindViewHolder(@NonNull ProductViewHolder holder, int position) {
Food current = getItem(position);
holder.bind(current.getBarcode());
}
static class FoodDiff extends DiffUtil.ItemCallback<Food> {
@Override
public boolean areItemsTheSame(@NonNull Food oldItem, @NonNull Food newItem) {
return oldItem == newItem;
}
@Override
public boolean areContentsTheSame(@NonNull Food oldItem, @NonNull Food newItem) {
return oldItem.getBarcode().equals(newItem.getBarcode());
}
}
}
這是我的 ViewHolder:
public class ProductViewHolder extends RecyclerView.ViewHolder {
private TextView prodItemView;
public ProductViewHolder(@NonNull View itemView) {
super(itemView);
prodItemView = itemView.findViewById(R.id.productId);
}
public void bind(String text){
prodItemView.setText(text);
}
static ProductViewHolder create(ViewGroup parent) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.product_item, parent, false);
return new ProductViewHolder(view);
}
}
編輯:現在,我已從 LiveData 更改為 MutableLiveData,並且添加了 'productsList.setValue(response.body());' 但我有 null object 參考的錯誤。
java.lang.NullPointerException:嘗試在 null ZA8CFDE633191119EB2AC96F8 上調用虛擬方法 'void androidx.lifecycle.MutableLiveData.setValue(java.lang.Object)'
您無法在 onResponce() 之外獲得響應。您可以使用 mutableLiveData。
public void getProductsList(){
GetProductService service = RetrofitClientInstance.getRetrofitInstance().create(GetProductService.class);
Call<Product> call = service.getAllProducts("Bearer " + accessToken, baseURL+barcode);
call.enqueue(new Callback<Product>(){
@Override
public void onResponse(Call<Product> call, Response<Product> response) {
if(response.isSuccessful()) {
Log.d("response1", response.toString());
Log.d("response2", response.body().toString());
sessionToken = response.body().getToken();
Log.d("tokenDaGet", sessionToken);
listResponse = response.body().getFood();
if(listResponse.size()==0){
Log.d("listaProdotti", "nulla");
}else{
Log.d("listaProdotti", listResponse.toString());
Log.d("barcode0", listResponse.get(0).getBarcode());
}
insertAll(listResponse);
//here set value for mutableliveData,observe this from your activity
// because return statement will invoked first before get response from
// server.
productsList.setValue(yourData);
}
}
@Override
public void onFailure(Call<Product> call, Throwable t) {
Log.e("ERR", call.toString());
Log.e("tERR", t.getMessage());
Log.e("t2ERR", t.toString());
Log.e("RETROFIT", "Richiesta Retrofit fallita, ma è ancora attiva.");
}
});
}
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