适配器内的按钮 Onclicklistener 问题

Question

我的listview 中有两个按钮+ 和-，用于增加和减少item 的数量。我在adapter class 中写了+ 按钮onclicklistener。当我单击button 时，它只会增加一次数量。初始数量设置为0。第一次点击它变成1。之后，无论我点击多少次button，数量都不会改变。

列表视图布局：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal">


    <ImageView
        android:id="@+id/foodpic"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:padding="10dp"
        app:srcCompat="@mipmap/ic_launcher_round" />

    <TextView
        android:id="@+id/foodname"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_toEndOf="@+id/foodpic"
        android:padding="10dp"
        android:text="name" />

    <TextView
        android:id="@+id/foodprice"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentEnd="true"
        android:layout_alignParentTop="true"
        android:layout_marginEnd="16dp"
        android:padding="10dp"
        android:text="price" />

    <Button
        android:id="@+id/minus"
        android:layout_width="35dp"
        android:layout_height="35dp"
        android:layout_below="@+id/foodname"
        android:layout_toEndOf="@+id/foodpic"
        android:text="-"
        android:textSize="12sp" />

    <EditText
        android:id="@+id/quantity"
        android:layout_width="25dp"
        android:layout_height="30dp"
        android:layout_below="@+id/foodname"
        android:layout_toEndOf="@+id/minus"
        android:ems="10"
        android:inputType="number"
        android:textAlignment="center"
        android:background="@drawable/edittextbackground"
        android:text="0" />

    <Button
        android:id="@+id/plus"
        android:layout_width="35dp"
        android:layout_height="35dp"
        android:layout_alignTop="@+id/quantity"
        android:layout_toEndOf="@+id/quantity"
        android:text="+"
        android:textSize="12sp" />

    <Button
        android:id="@+id/addtocart"
        android:layout_width="35dp"
        android:layout_height="35dp"
        android:layout_alignBaseline="@+id/quantity"
        android:layout_alignBottom="@+id/quantity"
        android:layout_alignEnd="@+id/foodprice"
        android:background="@drawable/ic_shopping_cart_black_24dp" />


</RelativeLayout>

适配器类：

package com.res.easyorder;


import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.zip.Inflater;

public class MyAdapter extends ArrayAdapter<item> {

    int q_ty = 0;
    ArrayList<item> foodlist = new ArrayList<>();

    public MyAdapter(Context context, int textViewResourceId, ArrayList<item> objects){

        super(context, textViewResourceId, objects);
        foodlist = objects;
    }

    @Override
    public int getCount(){

        return super.getCount();
    }

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

        View v = convertView;
        LayoutInflater inflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        v = inflater.inflate(R.layout.list_view_layout, null);

        ImageView foodpic = (ImageView) v.findViewById(R.id.foodpic);
        TextView foodname = (TextView) v.findViewById(R.id.foodname);
        TextView foodprice = (TextView) v.findViewById(R.id.foodprice);
        Button plus = (Button) v.findViewById(R.id.plus);
        final EditText quantity = (EditText) v.findViewById(R.id.quantity);
        Button minus = (Button) v.findViewById(R.id.minus);

        plus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                item item = getItem(position);
                q_ty = Integer.parseInt(item.getQuantity());
                q_ty = q_ty + 1;
                quantity.setText("" +q_ty);
            }
        });


        foodname.setText(foodlist.get(position).getFoodName());
        foodpic.setImageResource(foodlist.get(position).getFoodImage());
        foodprice.setText("BDT: " +foodlist.get(position).getFoodPrice());
        quantity.setText(foodlist.get(position).getQuantity());

        return v;
    }
}

项目java类：

package com.res.easyorder;

/**
 * Created by User on 02-Apr-18.
 */

public class item {

    String foodName, quantity;
    int foodImage, foodPrice;

    public item(String foodName, int foodImage, int foodPrice, String quantity)
    {
        this.foodName = foodName;
        this.foodImage = foodImage;
        this.foodPrice = foodPrice;
        this.quantity = quantity;
    }

    public String getFoodName()
    {
        return foodName;
    }

    public int getFoodImage()
    {
        return foodImage;
    }

    public int getFoodPrice()
    {
        return foodPrice;
    }

    public String getQuantity()
    {
        return quantity;
    }

}

活动布局：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.res.easyorder.foodActivity">

    <ListView
        android:id="@+id/listview"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:divider="#ffff"
        android:dividerHeight="5dp"/>
</RelativeLayout>

Activity java 类：

package com.res.easyorder;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;

import com.google.firebase.auth.FirebaseAuth;

import java.util.ArrayList;

public class foodActivity extends AppCompatActivity {

    private String type = null;

    ListView simplelist;
    ArrayList<item> foodlist = new ArrayList<>();
    private FirebaseAuth firebaseAuth;

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

        firebaseAuth = FirebaseAuth.getInstance();
        simplelist = (ListView) findViewById(R.id.listview);

        type = getIntent().getExtras().getString("type");

        if(type.equals("breakfast"))
        {
            foodlist.add(new item("Rooti",R.drawable.ruti,5,"0"));
            foodlist.add(new item("Parata",R.drawable.porata,8,"0"));
            foodlist.add(new item("Tandoor",R.drawable.tandoor,15,"0"));
            foodlist.add(new item("Vegetable",R.drawable.sodji,10,"0"));
            foodlist.add(new item("Daal",R.drawable.dal,10,"0"));
            foodlist.add(new item("Omelet",R.drawable.dimvaji,15,"0"));
            foodlist.add(new item("Singara",R.drawable.singara,8,"0"));
            foodlist.add(new item("Samosa",R.drawable.samosa,10,"0"));
            foodlist.add(new item("Puri",R.drawable.puri,5,"0"));

        }

        MyAdapter myAdapter = new MyAdapter(this,R.layout.list_view_layout,foodlist);
        simplelist.setAdapter(myAdapter);
    }

}

Answer 1

这不会改变，因为您只是在 UI 中更改项目数量，而不是在实际项目中：

plus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                item item = getItem(position);
                q_ty = Integer.parseInt(item.getQuantity());
                q_ty = q_ty + 1;
                quantity.setText("" +q_ty);
            }
        });

您需要在 item 中设置新数量，这样当您再次单击按钮时，它会检索新数量：

plus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                item item = getItem(position);
                q_ty = Integer.parseInt(item.getQuantity());
                q_ty = q_ty + 1;
                item.setQuantity(q_ty);
                quantity.setText("" +q_ty);
            }
        });

编辑：

添加到您的项目类别：

public void setQuantity(String quantity)
    {
        this.quantity = quantity;
    }

并且在你的点击方法中而不是使用：

item.setQuantity(q_ty);

使用：

item.setQuantity(String.valueOf(q_ty));

Answer 2

问题是你只增加了本地变量q_ty 并且没有为你的类的元素设置新值。您需要将此字符串添加到您的 onClickListener 方法中：

item.setQuantity(q_ty);

Answer 3

如果这样

item item = getItem(position);
                        q_ty = Integer.parseInt(item.getQuantity());
                        q_ty = q_ty + 1;
                        quantity.setText("" +q_ty);

试试这个

    item item = getItem(position);                           
                            q_ty = q_ty + 1;
                            quantity.setText(q_ty);