how to transfer arraylist data from one activity to another?

Question

I am trying to transfer the data of an ArrayList to another Activity to display some of its content there in a new ArrayList. I will be filtering the data to be displayed in the next Activity. The content of the ArrayList is from mysql database using json.

The line - productList = new ArrayList<myProduct>(); - causes my arraylist to go empty because it creates a new object. I dont know if im doing the proper way of coding but I hope you can provide me some of your idea.

Here are my codes:

Menu.java

public class Menu extends AppCompatActivity implements AdapterView.OnItemClickListener {

    public ArrayList<myProduct> productList;
    Button viewOrder;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_menu);

        String product = "http://10.0.2.2/myDB/product.php";

        StringRequest stringRequestProduct = new StringRequest(Request.Method.GET, product, new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                Log.d(TAG, response);

                productList = new JsonConverter<myProduct>().toArrayList(response, myProduct.class);
                }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Toast.makeText(getApplicationContext(), "Error retrieving data", Toast.LENGTH_SHORT).show();
            }
        });

        MySingleton.getInstance(getApplicationContext()).addToRequestQueue(stringRequestProduct);

        viewOrder = (Button)findViewById(R.id.viewOrder);
        viewOrder.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent i = new Intent(Menu.this, Order.class);
                startActivity(i);

            }
        });
    }
}

myProduct.class

import com.google.gson.annotations.SerializedName;

public class myProduct {

    @SerializedName("productID")
    public int productID;
    @SerializedName("categoryID")
    public int categoryID;
    @SerializedName("productName")
    public String productName;
    @SerializedName("productPrice")
    public int productPrice;

    public int productQuantity = 0;

    public myProduct(int productID, int categoryID, String productName, int productPrice){
        this.productID = productID;
        this.categoryID = categoryID;
        this.productName = productName;
        this.productPrice = productPrice;
    }

    public int getProductID(){
        return productID;
    }

    public int getCategoryID(){
        return categoryID;
    }

    public String getProductName(){
        return productName;
    }

    public int getProductPrice(){
        return productPrice;
    }

}

Order.Java

public class Order extends AppCompatActivity {

    public ListView orderListView;
    public myOrderAdapter orderAdapter;
    public ArrayList<myProduct> productList, filter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_order);

        orderListView = (ListView)findViewById(R.id.orderList);
        productList = new ArrayList<myProduct>();
        filter = new ArrayList<myProduct>();

        for(myProduct item : productList){
            //Condition before adding    
            if(item.productQuantity > 0) {
                Log.d(TAG,item.getProductName());
                filter.add(item);
            }
        }
        orderAdapter = new myOrderAdapter(getApplicationContext(),filter);
        orderListView.setAdapter(orderAdapter);
    }
}

Answer 1

To achieve this , you need to implement Parcelable (Note that, you can also achieve this by Serializable but Parcelable is much faster than Serializable , and it is highly recommended for android )

You have to make your myProduct class Parcelable , you can implement in manually or there is a android studio plugin which make your model class parcelable . You can take a look at this post , to implement parcelable .

After implementing Parcelable , in your Menu class do something like this

 viewOrder.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent i = new Intent(Menu.this, Order.class);
                Bundle bundle = new Bundle();
                bundle.putParcelableArrayList("productList",productList);
                intent.putExtras(bundle);
                startActivity(i);
            }
        });

And in your Order class , receive this in following way .

ArrayList<myProduct> productList=
               (ArayList<myProduct>)bundle.getParcelableArrayList("productList");

EDIT Your myProduct class should be look like this , after implementing parcelable

public class myProduct implements Parcelable {

    public int productID;

    public int categoryID;

    public String productName;

    public int productPrice;

    public int productQuantity = 0;

    public myProduct(int productID, int categoryID, String productName, int productPrice){
        this.productID = productID;
        this.categoryID = categoryID;
        this.productName = productName;
        this.productPrice = productPrice;
    }

    public int getProductID(){
        return productID;
    }

    public int getCategoryID(){
        return categoryID;
    }

    public String getProductName(){
        return productName;
    }

    public int getProductPrice(){
        return productPrice;
    }


    protected myProduct(Parcel in) {
        productID = in.readInt();
        categoryID = in.readInt();
        productName = in.readString();
        productPrice = in.readInt();
        productQuantity = in.readInt();
    }

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeInt(productID);
        dest.writeInt(categoryID);
        dest.writeString(productName);
        dest.writeInt(productPrice);
        dest.writeInt(productQuantity);
    }

    @SuppressWarnings("unused")
    public static final Parcelable.Creator<myProduct> CREATOR = new Parcelable.Creator<myProduct>() {
        @Override
        public myProduct createFromParcel(Parcel in) {
            return new myProduct(in);
        }

        @Override
        public myProduct[] newArray(int size) {
            return new myProduct[size];
        }
    };
}

Hope this helps. Let me know if it works.

Answer 2

implement the Serializable to your model class

import java.io.Serializable; 
public class myProduct implements Serializable{

    @SerializedName("productID")
    public int productID;
    @SerializedName("categoryID")
    public int categoryID;
    @SerializedName("productName")
    public String productName;
    @SerializedName("productPrice")
    public int productPrice;

    public int productQuantity = 0;

    public myProduct(int productID, int categoryID, String productName, int productPrice){
        this.productID = productID;
        this.categoryID = categoryID;
        this.productName = productName;
        this.productPrice = productPrice;
    }

    public int getProductID(){
        return productID;
    }

    public int getCategoryID(){
        return categoryID;
    }

    public String getProductName(){
        return productName;
    }

    public int getProductPrice(){
        return productPrice;
    }

}

and pass it in this way

Bundle bundle = new Bundle();
bundle.putSerializable("productList", productList);
intent.putExtras(bundle);

and get it as-

Intent intent = this.getIntent();
Bundle bundle = intent.getExtras();

List<myProduct> productList=
               (List<myProduct>)bundle.getSerializable("productList");

Answer 3

After creating your intent object add your json string as

intent.putExtra("list",jsonString);

And then start the other activity

At your other activity grab the extras by

String json = getIntent().getExtras().getString("list");

And then you can parse the json and use your list.