从getView的onClickListener内部更新ArrayAdapter

Question

我正在制作一个购物车应用程序，用户可以从购物车中添加和删除项目。当用户查看购物车时，将显示他们添加的商品列表。这个列表是使用ArrayAdapter创建的。每行包含一个删除按钮，用户可以在其中删除购物车中的商品。我已经成功地从Cart对象中删除了该项目。然而，当用户点击删除按钮更新屏幕时，我遇到了麻烦。我听说过适配器的notifydatasetchanged()方法，但我不确定如何从getView中的OnClickListener内部实现。下面是代码:

CartScreen.java

package com.livilatenight.livilatenight;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ListView;
import android.widget.Toast;
import com.parse.ParseException;
import com.parse.ParseUser;
import com.parse.SaveCallback;
public class CartScreen extends ActionBarActivity {
    ListView items;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_cart_screen);
        final ParseUser current = ParseUser.getCurrentUser();
        try{
            Cart userCart = (Cart) current.fetchIfNeeded().get("cart");
            String[] itemNames = userCart.getItems();
            String[] itemPrices = userCart.getPrices();
            int[] quantities = userCart.getQuantities();
            Integer[] itemPictures = userCart.getPictures();
            CartListAdapter adapter = new CartListAdapter(CartScreen.this, itemNames,itemPrices,quantities,itemPictures);
            items = (ListView) findViewById(R.id.listView);
            items.setAdapter(adapter);
        }catch(ParseException e){
            Toast.makeText(CartScreen.this, e.toString(),Toast.LENGTH_LONG).show();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_cart_screen, menu);
        return true;
    }
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

CartListAdapter.java

package com.livilatenight.livilatenight;
import android.app.Activity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
import com.parse.ParseUser;
public class CartListAdapter extends ArrayAdapter<String> {
    private final Activity context;
    private final String[] items;
    private final String[] prices;
    private final int[] quantities;
    private final Integer[] pictures;
    public CartListAdapter(Activity context, String[] itemnames, String[] prices, int[] quantities, Integer[] pictures) {
        super(context, R.layout.item_list, itemnames);
        this.context=context;
        this.items=itemnames;
        this.prices=prices;
        this.quantities=quantities;
        this.pictures=pictures;
    }
    public View getView(final int position,View view,ViewGroup parent) {
        LayoutInflater inflater=context.getLayoutInflater();
        View rowView=inflater.inflate(R.layout.cart_item, null,true);
        TextView itemName = (TextView) rowView.findViewById(R.id.tvItemName);
        TextView itemPrice = (TextView) rowView.findViewById(R.id.tvPrice);
        ImageView itemPicture = (ImageView) rowView.findViewById(R.id.ivItemPicture);
        View blankView = (View) rowView.findViewById(R.id.blankView);
        Button removeCart = (Button) rowView.findViewById(R.id.btnRemoveCart);
        final Spinner spinner = (Spinner) rowView.findViewById(R.id.spinnerQty);
        ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(context, R.array.spinner_numbers, android.R.layout.simple_spinner_item);
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner.setAdapter(adapter);

        spinner.setSelection(quantities[position]-1);
        itemName.setText(items[position]);
        itemPrice.setText(prices[position]);
        itemPicture.setImageResource(pictures[position]);
        removeCart.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ParseUser current = ParseUser.getCurrentUser();
                int quantity = spinner.getSelectedItemPosition()+1;
                Cart userCart = (Cart) current.get("cart");
                boolean success = userCart.removeFromCart(items[position]);
                if(success){
                    Toast.makeText(getContext(), "Removed from Cart", Toast.LENGTH_LONG).show();
                }else{
                    Toast.makeText(getContext(), "Item is already in your shopping cart", Toast.LENGTH_LONG).show();
                }
                current.saveInBackground();
            }
        });
        return rowView;
    };
}

我想在用户单击removeCart按钮时更新购物车列表。我怎么能这么做?

我做了一个解决方案，我只是设置一个新的适配器，每次项目被删除。这不是我想做的，但它可以工作，所以我保持它的方式。

Answer 1

try this

if (success) {
                    Toast.makeText(getContext(), "Removed from Cart", Toast.LENGTH_LONG).show();
                    final String s = items[position];
                    List<String> list = new ArrayList<String>(Arrays.asList(items));
                    list.remove(s);
                    items = list.toArray(array);
                    this.notifyDataSetChanged()
                }

Answer 2

在自定义适配器中调用this.notifyDataSetChanged();你正在执行删除功能，并从设置为适配器的arrayList中删除该元素。你也必须从你设置到适配器的ArrayList中删除那条记录如果你知道是哪条记录你可以使用ArrayList。remove(index);然后使用notifyDataSetChanged();

编辑:转到适配器并添加一个方法delete();

public void delete(int position){
data.remove(position);
notifyItemRemoved(position);
}

在你的onClick();方法:

delete(getPosition());

Answer 3

这是我的解决方案。

在你的CartListAdapter重写Array Adapter的remove方法中

@Override
public void remove(String var){
    // Call your utility methods you defined to delete the item
    // Notify ListView that their is a change
    notifyDataSetChanged();
}

在单击侦听器

中进行以下更改

    removeCart.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            // Call this.remove(var) with String you want to delete
        }
    });

notifyDataSetChanged()仅对add()、insert()、remove()、clear()有效。读

HTH