【发布时间】：2016-03-28 11:43:24
【问题描述】：
我有两个活动，一个是UserActivity，另一个是CartActivity 我在UserActivity 中显示产品列表。单击按钮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，操作栏中会出现一个购物车图标，并且我有一个 textview 的自定义布局，在该购物车图标上显示购物车计数器。每当我单击按钮AddtoCart 时，该计数器就会更新。现在我转到CartActivity 并从购物车中删除一些产品。当我现在按返回按钮返回到UserActivity 时，计数器文本视图不会更新。
我已经阅读了一些关于在Back button and refreshing previous activity 的问题中给出的按下后退更新的方法。答案中给出的两种方法是覆盖UserActivity 的OnResume() 方法或通过为结果启动活动。
当我按下后退按钮并从计数器TextView 中的原始产品数量中减去它并更新文本视图时，我想我需要将一个名为DeleteCounter 的变量从CartActivity 传递给UserActivity .
这是UserActivity 的部分代码，我只有在单击按钮时才会调用此代码中更新购物车计数器的功能。 onActivityResult() 的代码也对此进行了评论，这是我从上面给出的 SO 问题链接的答案中尝试的。不成功：
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));
}
}
});
}
这里是CartActivity的代码：
public class CartActivity extends AppCompatActivity {
private List<Product> mCartList;
private ProductAdapter mProductAdapter;
private static List<Product> 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<Product> getCart() {
if(cart == null) {
cart = new Vector<Product>();
}
return cart;
}
}
当我使用在两个活动中都被注释掉的代码时，即使用 start 活动作为结果方法时，会发生这种情况：
当我单击删除按钮时，项目会被删除，但 CartActivity 会自动关闭。即使购物车中有产品，带有计数器文本视图的 UserActivity 也会显示为“0”值。
请告诉我您需要从代码中获得的任何其他信息。欢迎在删除CartActivity 中的某些项目后按下后退按钮更新购物车计数器的任何其他方法。任何帮助表示赞赏。
【问题讨论】：
标签： java android cart onactivityresult startactivityforresult