Problem pulling server list on Android

Question

Whoa, guys, I’m pulling a list from the server and populating a RecyclerView with that list. But when the list is empty, I want a message like: "There are no entries for that product yet". But not a Toast, and yes a fixed message in a TextView. Can someone help me?

Thanks

public class ProductAdminActivity extends AppCompatActivity {

public static final String APP_NAME = "PanApp";
public static final String URL = "https://panapp-backend.appspot.com/_ah/api";
private RecyclerView rvProductAdmin;
private Button btnNewProduct;
private Long bakeryId;
private Bundle params;
private TextView txtAnswer;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    //getLayoutInflater().inflate(R.layout.activity_product_admin, frameLayout);
    setContentView(R.layout.activity_product_admin);
    setTitle("Meus Produtos");

    Intent it = getIntent();
    params = it.getExtras();
    if (params != null) {
        bakeryId = params.getLong("bakeryId");
    }

    txtAnswer = (TextView) findViewById(R.id.textAnswer);
    rvProductAdmin = (RecyclerView) findViewById(R.id.product_list_admin);
    btnNewProduct = (Button) findViewById(R.id.btn_new_product);
    btnNewProduct.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            params.putLong("bakeryId", bakeryId);
            Intent intentFormProduct = new Intent(ProductAdminActivity.this, FormProductActivity.class);
            intentFormProduct.putExtras(params);
            startActivity(intentFormProduct);
        }
    });
    new ProductListAsyncTask(this).execute();
}

private class ProductListAsyncTask extends AsyncTask<Void, Void, CollectionResponseProduct> {
    ProductAdminActivity context;
    private ProgressDialog pd;

    public ProductListAsyncTask(ProductAdminActivity context) {
        this.context = context;
    }

    protected void onPreExecute(){
        super.onPreExecute();
        pd = new ProgressDialog(context);
        pd.setMessage("Listando Produtos...");
        pd.show();
    }

    protected CollectionResponseProduct doInBackground(Void... unused) {
        CollectionResponseProduct collectionResponseProduct = null;
        try {
            ProductApi.Builder builder = new ProductApi.Builder(AndroidHttp.newCompatibleTransport(),
                    new AndroidJsonFactory(), null).setRootUrl(URL);
            builder.setApplicationName(APP_NAME);
            ProductApi service =  builder.build();
            collectionResponseProduct = service.list().execute();
        } catch (Exception e) {
            Log.d("Erro", e.getMessage(), e);
        }
        return collectionResponseProduct;
    }

    @TargetApi(Build.VERSION_CODES.KITKAT)
    protected void onPostExecute(CollectionResponseProduct collectionResponseProduct) {
        pd.dismiss();
        if(collectionResponseProduct.size() > 0){
            List<Product> list = new ArrayList<>();
            List<Product> _list = collectionResponseProduct.getItems();
            for (Product productAux : _list) {
                Product product = new Product();
                product.setProductName(productAux.getProductName());
                product.setProductPrice(productAux.getProductPrice());
                product.setType(productAux.getType());
                product.setBakeryId(productAux.getBakeryId());
                product.setProductImage(productAux.getProductImage());
                if(Objects.equals(bakeryId, product.getBakeryId())){
                    list.add(product);
                }
            }
            rvProductAdmin.setLayoutManager(new LinearLayoutManager(ProductAdminActivity.this));
            rvProductAdmin.setAdapter(new ProductAdapter(list));
        } else {
            txtAnswer.setText("Não existem produtos cadastrados!");
        }
    }
}

}

Adapter:

public class ProductAdapter extends RecyclerView.Adapter<ProductViewHolder> {

private final List<Product> products;

public ProductAdapter(List<Product> products) {
    this.products = products;
}

@Override
public ProductViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
    final LayoutInflater layoutInflater = LayoutInflater.from(viewGroup.getContext());
    final View v = layoutInflater.inflate(R.layout.card_product, viewGroup, false);
    //final View v = layoutInflater.inflate(R.layout.item_product, viewGroup, false);
    return new ProductViewHolder(v);
}

@Override
public void onBindViewHolder(ProductViewHolder productViewHolder, int i) {
    productViewHolder.tvProductName.setText(products.get(i).getProductName());
    productViewHolder.tvPrice.setText(products.get(i).getProductPrice().toString());
    productViewHolder.tvCategory.setText(products.get(i).getType());
    //productViewHolder.tvItensSale.setText(products.get(i).getItensSale());

    String strBase64 = products.get(i).getProductImage();
    byte[] imgBytes = Base64.decode(strBase64, Base64.DEFAULT);
    Bitmap bitmap = BitmapFactory.decodeByteArray(imgBytes, 0, imgBytes.length);

    productViewHolder.ivProduct.setImageBitmap(bitmap);
}

@Override
public int getItemCount() {
    return products.size();
}
}

Exception:

FATAL EXCEPTION: main
                                                                  Process: com.gregmachado.panapp, PID: 8730
                                                                  java.lang.NullPointerException: Attempt to invoke interface method 'java.util.Iterator java.util.List.iterator()' on a null object reference
                                                                      at com.gregmachado.panapp.activity.ProductAdminActivity$ProductListAsyncTask.onPostExecute(ProductAdminActivity.java:106)
                                                                      at com.gregmachado.panapp.activity.ProductAdminActivity$ProductListAsyncTask.onPostExecute(ProductAdminActivity.java:70)
                                                                      at android.os.AsyncTask.finish(AsyncTask.java:651)
                                                                      at android.os.AsyncTask.-wrap1(AsyncTask.java)
                                                                      at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:668)
                                                                      at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                      at android.os.Looper.loop(Looper.java:148)
                                                                      at android.app.ActivityThread.main(ActivityThread.java:5443)
                                                                      at java.lang.reflect.Method.invoke(Native Method)
                                                                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728)
                                                                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)

Answer 1

Here’s what you’re gonna do activity_product_admin.xml create a Textview

<TextView
        android:id="@+id/textResposta"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Resposta"
        android:textStyle="bold"
        android:textColor="#ff00ff"
       />

In your class ProductAdminActivity you will instantiate your TextView, first declaring a variable of type TextView and then make the connection with the .xml.

private TextView textReposta;

Within your onCreate you do this way:

textResposta= (TextView) findViewById(R.id.textResposta);

There remains only replaces your Toast by the following code:

textResposta.setText("Não existem produtos cadastrados!");

That’s it! Hugs! Good Luck!

Answer 2

Solution:

protected CollectionResponseProduct doInBackground(Void... unused) {
        CollectionResponseProduct collectionResponseProduct = null;
        ProductApi.Builder builder = new ProductApi.Builder(AndroidHttp.newCompatibleTransport(),
                new AndroidJsonFactory(), null).setRootUrl(URL);
        builder.setApplicationName(APP_NAME);
        ProductApi service =  builder.build();
        try {
            collectionResponseProduct = service.list().execute();
        } catch (Exception e) {
            Log.d("Erro", e.getMessage(), e);
        }
        return collectionResponseProduct;
    }

    @TargetApi(Build.VERSION_CODES.KITKAT)
    protected void onPostExecute(CollectionResponseProduct collectionResponseProduct) {
        pd.dismiss();
        List<Product> list = new ArrayList<>();
        List<Product> _list = collectionResponseProduct.getItems(); // fiz o get pro List antes
        if(_list == null){ // e fiz o teste aqui no List ao invés do Collection Response
            txtAnswer.setText("Não existem produtos cadastrados!");
        } else {
            for (Product productAux : _list) {
                Product product = new Product();
                product.setProductName(productAux.getProductName());
                product.setProductPrice(productAux.getProductPrice());
                product.setType(productAux.getType());
                product.setBakeryId(productAux.getBakeryId());
                product.setProductImage(productAux.getProductImage());
                if(Objects.equals(bakeryId, product.getBakeryId())){
                    list.add(product);
                }
            }
            rvProductAdmin.setLayoutManager(new LinearLayoutManager(ProductAdminActivity.this));
            rvProductAdmin.setAdapter(new ProductAdapter(list));
        }
    }