android - 如何在Activity之前调用Adapter类

Log：

D/CartActivity-onCreate(18171): onCreate
D/CartActivity-TOTAL-InsideFORLOOP:(18171): 0.0
D/CartActivity-onResume(18171): onResume
D/CartAdapter-TOTAL:(18171): 12.95

正如您在上面的日志中看到的，循环首先在cartactivity中执行，在执行了cartactivity的onResume()方法之后，cartadapter正在执行这一行，因此对于我来说，在Total中cartactivity的For loop值是0.0。
原因不是我要添加到数据arrayList的位置，问题是cartactivity在cartadapter执行之前执行（where i am getting value for Total）
所以，如果我想在执行cartactivity的where i am setting value for Total方法之前调用下面的行，我必须做的是

  CartArrayList.cartArraylist.get(position).setTotal(totalPrice);

cartactivity.java：

public class CartActivity extends Activity {
       .....

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d("CartActivity-onCreate", "onCreate");
        setContentView(R.layout.activity_cart);

        .......
        adapter = new CartAdapter(getApplicationContext(), R.layout.adapter_cart, CartArrayList.cartArraylist);
        for (int d = 0; d < CartArrayList.cartArraylist.size(); d++) {
            subTotal = subTotal + CartArrayList.cartArraylist.get(d).getTotal();
            Log.d("CartActivity-TOTAL-InsideFORLOOP:", String.valueOf(CartArrayList.cartArraylist.get(d).getTotal()));
        }
        listview.setAdapter(adapter);
        adapter.notifyDataSetChanged();
        textSubTotal.setText(decimalFormat.format(subTotal));
    }

    @Override
    public void onResume() {
        super.onResume();
        Log.d("CartActivity-onResume", "onResume");
    }
}

cartadapter.java：

public class CartAdapter extends BaseAdapter {

.....

@Override
public View getView(final int position, View convertView, ViewGroup parent) {

    ......

    totalPrice = cart.getQuantity() * cart.getPrice();
    CartArrayList.cartArraylist.get(position).setTotal(totalPrice);
    Log.d("CartAdapter-TOTAL:", String.valueOf(CartArrayList.cartArraylist.get(position).getTotal()));

    .....

    return convertView;
}

}

最佳答案

在适配器中设置数组列表之前，必须先计算实体中的总值，而不是在getView中计算。
代码段：

for (int d=0; d<CartArrayList.cartArraylist.size(); d++) {
   // calculate total value

   Double totalPrice = CartArrayList.cartArraylist.get(d).getQuantity() * CartArrayList.cartArraylist.get(d).getPrice();
   CartArrayList.cartArraylist.get(d).setTotal(totalPrice);

   // set it for subTotal
   subTotal = subTotal + totalPrice;
}

adapter = new CartAdapter(getApplicationContext(), R.layout.adapter_cart, CartArrayList.cartArraylist);
listview.setAdapter(adapter);

希望对你有帮助