删除后按下后退按钮更新购物车计数

我有两个活动,一个是UserActivity,另一个是CartActivity我正在展示产品清单UserActivity.点击按钮,AddtoCart我将产品添加到购物车.我正面临这个问题:

当我添加单击按钮AddtoCart时,操作栏中有一个购物车图标,我textview在该购物车图标上有一个显示购物车计数器的自定义布局.每当我点击按钮时,该计数器就会更新AddtoCart.现在我转到CartActivity并删除购物车中的一些产品.现在按回按钮返回时UserActivity,计数器文本视图不会更新.

我已经阅读了几个关于按下后退的更新的方法,如问题中的" 返回"按钮和刷新之前的活动.答案中给出的两种方法是通过覆盖结果的OnResume()方法UserActivity或启动结果的活动.

我想我需要将一个名为DeleteCounterfrom 的变量传递CartActivity给UserActivity当我按下后退按钮并从计数器中的原始产品数中减去它TextView并更新文本视图.

这是部分代码,UserActivity我有这个代码只更新购物车计数器的功能,当我点击一个按钮时调用.另外onActivityResult()在这个评论中的代码我从上面的答案尝试了SO问题链接.它没有成功:

    public class UserActivity extends AppCompatActivity{
            private int cartindex = 0;
            private TextView counterTV = null;

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

                Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
                setSupportActionBar(toolbar);
            }
//    @Override
//    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
//        if (requestCode == 1) {
//
//            if(resultCode == RESULT_OK){
//                  Intent intent = getIntent();
//                  Integer deletecounter = intent.getIntExtra("DeleteCounter",0);
//                  if(deletecounter>0){
//                      UpdateCartCount(Integer.parseInt(counterTV.getText().toString())-deletecounter);
//                  }
//            }
//        }
//    }

        @Override
            public boolean onCreateOptionsMenu(Menu menu) {
                // Inflate the menu; this adds items to the action bar if it is present.
                getMenuInflater().inflate(R.menu.user, menu);
                final View menu_list = menu.findItem(R.id.action_hawk).getActionView();
                counterTV = (TextView) menu_list.findViewById(R.id.cartcounter);
                UpdateCartCount(cartindex);
                new MyMenuItemStuffListener(menu_hotlist, "Show message") {
                    @Override
                    public void onClick(View v) {
                        Intent intent= new  Intent(UserActivity.this,CartActivity.class);
                        intent.putExtra("ProductTitle",pname);
                        intent.putExtra("ProductUrl",purl);
                        intent.putExtra("ProductPrice",pprice);
                        intent.putExtra("BargainPrice",bargainprice);
                        UserActivity.this.startActivity(intent);
                    }
                };
                return true;
    }
    //Function to update cart count
            public void UpdateCartCount(final int new_number) {
                    cartindex = new_number;
                    if (counterTV == null) return;
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            if (new_number == 0)
                                counterTV.setVisibility(View.INVISIBLE);
                            else {
                                counterTV.setVisibility(View.VISIBLE);
                                counterTV.setText(Integer.toString(new_number));
                            }
                        }
                    });
                }

这是代码CartActivity:

    public class CartActivity extends AppCompatActivity {

        private List mCartList;
        private ProductAdapter mProductAdapter;
        private static List cart;
        private static Integer deletecounter= 0;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_cart);
            Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
            setSupportActionBar(toolbar);
            mCartList = getCart();


            Intent intent = getIntent();
            String ProductTitle = intent.getStringExtra("ProductTitle");
            String ProductUrl = intent.getStringExtra("ProductUrl");
            String ProductPrice = intent.getStringExtra("ProductPrice");
            String BargainPrice = intent.getStringExtra("BargainPrice");
            Product product = new Product(ProductTitle, ProductUrl, ProductPrice, BargainPrice);
            mCartList.add(product);
            // Make sure to clear the selections
            for (int i = 0; i < mCartList.size(); i++) {
                mCartList.get(i).selected = false;
            }

            // Create the list
            final ListView listViewCatalog = (ListView) findViewById(R.id.cart_list_view);
            mProductAdapter = new ProductAdapter(mCartList, getLayoutInflater(), true, CartActivity.this);
            listViewCatalog.setAdapter(mProductAdapter);

            listViewCatalog.setOnItemClickListener(new AdapterView.OnItemClickListener() {

                @Override
                public void onItemClick(AdapterView parent, View view, int position,
                                        long id) {

                    Product selectedProduct = mCartList.get(position);
                    if (selectedProduct.selected)
                        selectedProduct.selected = false;
                    else
                        selectedProduct.selected = true;

                    mProductAdapter.notifyDataSetInvalidated();

                }
            });
            FloatingActionButton Delete = (FloatingActionButton) findViewById(R.id.fab);
            delete.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    // Loop through and remove all the products that are selected
                    // Loop backwards so that the remove works correctly

                    for (int i = mCartList.size() - 1; i >= 0; i--) {

                        if (mCartList.get(i).selected) {
                            mCartList.remove(i);
                            deletecounter++;
                        }
                    }
// THIS IS THE CODE I USED TO RETURN DATA TO PREVIOUS ACTIVITY BUT UserActivity STARTS AUTOMATICALLY AFTER DELETION OF SELECTED PRODUCTS AS SOON AS I CLICK THE DELETE BUTTON EVEN WHEN THERE ARE PRODUCTS IN THE CART.
 //                  if(deletecounter!=0) {
//                    Intent i = new Intent(HawkActivity.this, UserActivity.class);
//                    startActivityForResult(i, 1);
//                    Intent returnIntent = new Intent();
//                    returnIntent.putExtra("DeleteCounter", deletecounter);
//                    setResult(RESULT_OK, returnIntent);
//                }
                    mProductAdapter.notifyDataSetChanged();
                    Snackbar.make(view,"Selected items deleted successfully",Snackbar.LENGTH_SHORT).show();
                }
            }
            );
        }
        public static List getCart() {
            if(cart == null) {
                cart = new Vector();
            }

            return cart;
        }
    }

当我使用在两个活动中注释掉的代码,即使用结果方法的启动活动时,会发生这种情况:当我单击删除按钮时,项目会被删除,但会CartActivity自动关闭.在UserActivity与计数器文本视图被示出具有即使存在产品在车"0"值.

请告诉我您需要从代码中获得的任何其他信息.在删除某些项目后,我可以通过按下后退按钮来更新购物车计数器的任何其他方式CartActivity.任何帮助表示赞赏.