Android笔记(七十六) 点菜DEMO

      一个朋友让看一下他的代码，一个点菜的功能，他和我一样，初学者，代码比我的都混乱，也是醉了，干脆想着自己写个demo给他看，原本想着听简单，半个小时应该就可以搞定，真正写的时候，画了3h+，汗颜。。。

      现在将过程捋一下，做个备忘：

      原本想的时候，不就是一个ListView么，每个item除了菜品信息之外，包含两个按钮，和一个EditText，用来修改数量，于是有了第一版（请忽略界面）：

MainActivity.java

package com.example.menutest;

import java.util.ArrayList;
import java.util.List;

import com.example.menutest.adapter.ShowFoodAdapter;
import com.example.menutest.bean.Food;

import android.app.Activity;
import android.os.Bundle;
import android.widget.Button;
import android.widget.ListView;

public class MainActivity extends Activity {

    private ListView lv_foods;
    private Button bt_submit;
    private List<Food> foodsList = new ArrayList<Food>();
    private ShowFoodAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
        initData();
        adapter = new ShowFoodAdapter(foodsList, this);
        lv_foods.setAdapter(adapter);

    }

    // 初始化菜品数据
    private void initData() {
        foodsList.add(new Food("bawangshizitou", "霸王狮子头", 23));
        foodsList.add(new Food("dongbeiguobaorou", "东北锅包肉", 34));
        foodsList.add(new Food("haomiganfanbazirou", "好米干饭把子肉", 45));
        foodsList.add(new Food("jidanzhajiangmian", "鸡蛋炸酱面", 56));
        foodsList.add(new Food("kaoquanyang", "烤全羊", 67));
        foodsList.add(new Food("laobeijingchaogeda", "老北京炒疙瘩", 78));
        foodsList.add(new Food("lizhirou", "荔枝肉", 89));
        foodsList.add(new Food("niunaikekeqiu", "牛奶可可球", 90));
        foodsList.add(new Food("peigenjinzhengu", "培根金针菇", 30));
        foodsList.add(new Food("qincaixiarenshuijiao", "芹菜虾仁水饺", 37));
        foodsList.add(new Food("qingmingtuanzi", "清明团子", 48));
        foodsList.add(new Food("shufulei", "舒芙蕾", 39));
        foodsList.add(new Food("wuxiangjianglvrou", "五香酱驴肉", 27));
        foodsList.add(new Food("xianshaobai", "咸烧白", 14));
        foodsList.add(new Food("xinjiangchaokaorou", "新疆炒烤肉", 28));
        foodsList.add(new Food("xuedouduntihua", "雪豆炖蹄花", 10));
        foodsList.add(new Food("yangzasui", "羊杂碎", 27));
        foodsList.add(new Food("yerongtianjiangmaifen", "椰蓉甜姜麦芬", 16));
        foodsList.add(new Food("zhenfengji", "蒸风鸡", 53));
    }

    // 查找组件
    private void initView() {
        lv_foods = (ListView) findViewById(R.id.lv_foods);
        bt_submit = (Button) findViewById(R.id.bt_submit);
    }
}

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.example.menutest.MainActivity" >
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="选择菜品" />
    <ListView
        android:id="@+id/lv_foods"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1" >
    </ListView>
    <Button
        android:id="@+id/bt_submit"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="OK" />
</LinearLayout>

Food.java

package com.example.menutest.bean;

public class Food {
    private String foodImageName;
    private String foodName;
    private int foodPrice;
    private int foodCount;
    public Food(String foodImageName, String foodName, int foodPrice, int foodCount) {
        super();
        this.foodImageName = foodImageName;
        this.foodName = foodName;
        this.foodPrice = foodPrice;
        this.foodCount = foodCount;
    }
    public Food(String foodName, int foodPrice, int foodCount) {
        super();
        this.foodName = foodName;
        this.foodPrice = foodPrice;
        this.foodCount = foodCount;
    }
    public Food(String foodImageName, String foodName, int foodPrice) {
        super();
        this.foodImageName = foodImageName;
        this.foodName = foodName;
        this.foodPrice = foodPrice;
    }
    public Food() {
        super();
    }
    public String getFoodImageName() {
        return foodImageName;
    }
    public void setFoodImageName(String foodImageName) {
        this.foodImageName = foodImageName;
    }
    public String getFoodName() {
        return foodName;
    }
    public void setFoodName(String foodName) {
        this.foodName = foodName;
    }
    public int getFoodPrice() {
        return foodPrice;
    }
    public void setFoodPrice(int foodPrice) {
        this.foodPrice = foodPrice;
    }
    public int getFoodCount() {
        return foodCount;
    }
    public void setFoodCount(int foodCount) {
        this.foodCount = foodCount;
    }
}

ShowFoodAdapter.java

package com.example.menutest.adapter;

import java.io.IOException;
import java.util.List;

import com.example.menutest.R;
import com.example.menutest.bean.Food;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.TextView;

public class ShowFoodAdapter extends BaseAdapter {

    private List<Food> mList;
    private Context mContext;
    private int foodCount;
    private ViewHolder viewHolder;

    public ShowFoodAdapter(List<Food> list, Context context) {
        this.mContext = context;
        this.mList = list;
    }

    @Override
    public int getCount() {
        return mList.size();
    }

    @Override
    public Object getItem(int position) {
        return mList.get(position);
    }

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return position;
    }

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

        if (convertView == null) {
            viewHolder = new ViewHolder();
            convertView = LayoutInflater.from(mContext).inflate(R.layout.item_show_foods, null);
            viewHolder.iv_food_image = (ImageView) convertView.findViewById(R.id.iv_food_image);
            viewHolder.tv_food_name = (TextView) convertView.findViewById(R.id.tv_food_name);
            viewHolder.tv_food_price = (TextView) convertView.findViewById(R.id.tv_food_price);
            viewHolder.et_food_count = (EditText) convertView.findViewById(R.id.et_food_count);
            viewHolder.bt_minus = (Button) convertView.findViewById(R.id.bt_minus);
            viewHolder.bt_plus = (Button) convertView.findViewById(R.id.bt_plus);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }

        try {
            Bitmap bitmap = BitmapFactory
                    .decodeStream(mContext.getAssets().open(mList.get(position).getFoodImageName() + ".jpg"));
            viewHolder.iv_food_image.setImageBitmap(bitmap);
        } catch (IOException e) {
            Log.d("TTTT", "图片设置失败，位置：" + position);
            e.printStackTrace();
        }

        viewHolder.tv_food_name.setText(mList.get(position).getFoodName());
        viewHolder.tv_food_price.setText(mList.get(position).getFoodPrice() + "元/份");

        viewHolder.bt_minus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                viewHolder.et_food_count.setText(--foodCount + "");
            }
        });

        viewHolder.bt_plus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                viewHolder.et_food_count.setText(++foodCount + "");
            }
        });

        return convertView;
    }

    // ViewHolder
    class ViewHolder {
        ImageView iv_food_image;
        TextView tv_food_name, tv_food_price;
        EditText et_food_count;
        Button bt_minus, bt_plus;
    }

}

item_show_food.xml

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

    <ImageView
        android:id="@+id/iv_food_image"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/bawangshizitou" />

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical" >

        <TextView
            android:id="@+id/tv_food_name"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="红烧肉" />

        <TextView
            android:id="@+id/tv_food_price"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="10" />
    </LinearLayout>

    <Button
        android:id="@+id/bt_minus"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="-" />

    <EditText
        android:id="@+id/et_food_count"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="0" />

    <Button
        android:id="@+id/bt_plus"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="+" />

</LinearLayout>

      但是点击+-按钮却没有效果，通过log发现foodCount值是随着点击按钮变化的，只是没有更新在UI上而已，添加并执行notifyDataSetChanged()方法之后，还是出现了问题，倒是可以修改EditText控件了，但是是修改的别的Item的，也就是说点了AItem中的按钮，BItem中的EditText改变了，并且滑动屏幕的话，也会随机改变。这招行不通，找别的办法，想想在点击的时候，传入position，然后根据position来修改控件内容。那么就需要自定义点击事件了。

ShowFoodAdapter.java

package com.example.menutest.adapter;

import java.io.IOException;
import java.util.List;

import com.example.menutest.R;
import com.example.menutest.bean.Food;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.TextView;

public class ShowFoodAdapter extends BaseAdapter {

    private List<Food> mList;
    private Context mContext;
    // private int foodCount;
    private ViewHolder viewHolder;

    public ShowFoodAdapter(List<Food> list, Context context) {
        this.mContext = context;
        this.mList = list;
    }

    @Override
    public int getCount() {
        return mList.size();
    }

    @Override
    public Object getItem(int position) {
        return mList.get(position);
    }

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return position;
    }

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

        if (convertView == null) {
            viewHolder = new ViewHolder();
            convertView = LayoutInflater.from(mContext).inflate(R.layout.item_show_foods, null);
            viewHolder.iv_food_image = (ImageView) convertView.findViewById(R.id.iv_food_image);
            viewHolder.tv_food_name = (TextView) convertView.findViewById(R.id.tv_food_name);
            viewHolder.tv_food_price = (TextView) convertView.findViewById(R.id.tv_food_price);
            viewHolder.et_food_count = (EditText) convertView.findViewById(R.id.et_food_count);
            viewHolder.bt_minus = (Button) convertView.findViewById(R.id.bt_minus);
            viewHolder.bt_plus = (Button) convertView.findViewById(R.id.bt_plus);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }

        try {
            Bitmap bitmap = BitmapFactory
                    .decodeStream(mContext.getAssets().open(mList.get(position).getFoodImageName() + ".jpg"));
            viewHolder.iv_food_image.setImageBitmap(bitmap);
        } catch (IOException e) {
            Log.d("TTTT", "图片设置失败，位置：" + position);
            e.printStackTrace();
        }

        viewHolder.tv_food_name.setText(mList.get(position).getFoodName());
        viewHolder.tv_food_price.setText(mList.get(position).getFoodPrice() + "元/份");
        // 直接从数据源中拿取数量，下面的按钮点击，直接修改数据源中的数据
        viewHolder.et_food_count.setText(mList.get(position).getFoodCount() + "");

        viewHolder.bt_minus.setOnClickListener(new ItemButtonOnClickListener(position));
        viewHolder.bt_plus.setOnClickListener(new ItemButtonOnClickListener(position));

        return convertView;
    }

    // ViewHolder
    class ViewHolder {
        ImageView iv_food_image;
        TextView tv_food_name, tv_food_price;
        EditText et_food_count;
        Button bt_minus, bt_plus;

        @Override
        public String toString() {
            return tv_food_name.getText().toString();
        }
    }

    class ItemButtonOnClickListener implements View.OnClickListener {

        private int position;
        // 获取EditeText此时正显示的数量
        private int foodCount = Integer.parseInt(viewHolder.et_food_count.getText().toString());

        public ItemButtonOnClickListener(int position) {
            this.position = position;
        }

        @Override
        public void onClick(View v) {
            switch (v.getId()) {
            case R.id.bt_plus:
                // 数量+1
                foodCount++;
                // 将数据源中的数量修改
                mList.get(position).setFoodCount(foodCount);
                // 刷新显示
                notifyDataSetChanged();
                break;
            case R.id.bt_minus:
                foodCount--;
                if (foodCount <= 0) {
                    mList.get(position).setFoodCount(0);
                } else {
                    mList.get(position).setFoodCount(foodCount);
                }
                notifyDataSetChanged();
                break;
            }
        }
    }
}

      然后在提交菜单的时候又遇到问题了，我是使用for循环，配合ListView的getChildCount()和getChildAt()来获取修改了数量的菜品，但是发现这个方法只能获取到屏幕中显示的Item中的数据，而没有显示的Item则获取不到，直接使用下标来获取没有显示的Item的内容，会报空指针，QQ群里求助，被告知数据和界面要分开，也就是M层和V层要剥离开来，这种情况，可以直接在数据源下手，那么问题迎刃而解，数据是在Adapter中修改的，那么在Adapter中加一个直接返回修改后的数据源的方法不就行了！

　　ShowFoodAdapter.java

package com.example.menutest.adapter;

import java.io.IOException;
import java.util.List;

import com.example.menutest.R;
import com.example.menutest.bean.Food;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.TextView;

public class ShowFoodAdapter extends BaseAdapter {

    private List<Food> mList;
    private Context mContext;
    // private int foodCount;
    private ViewHolder viewHolder;

    public ShowFoodAdapter(List<Food> list, Context context) {
        this.mContext = context;
        this.mList = list;
    }

    // 返回修改过数量之后的List
    public List getSelectedFoodList() {
        return mList;
    }

    @Override
    public int getCount() {
        return mList.size();
    }

    @Override
    public Object getItem(int position) {
        return mList.get(position);
    }

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return position;
    }

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

        if (convertView == null) {
            viewHolder = new ViewHolder();
            convertView = LayoutInflater.from(mContext).inflate(R.layout.item_show_foods, null);
            viewHolder.iv_food_image = (ImageView) convertView.findViewById(R.id.iv_food_image);
            viewHolder.tv_food_name = (TextView) convertView.findViewById(R.id.tv_food_name);
            viewHolder.tv_food_price = (TextView) convertView.findViewById(R.id.tv_food_price);
            viewHolder.et_food_count = (EditText) convertView.findViewById(R.id.et_food_count);
            viewHolder.bt_minus = (Button) convertView.findViewById(R.id.bt_minus);
            viewHolder.bt_plus = (Button) convertView.findViewById(R.id.bt_plus);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }

        try {
            Bitmap bitmap = BitmapFactory
                    .decodeStream(mContext.getAssets().open(mList.get(position).getFoodImageName() + ".jpg"));
            viewHolder.iv_food_image.setImageBitmap(bitmap);
        } catch (IOException e) {
            Log.d("TTTT", "图片设置失败，位置：" + position);
            e.printStackTrace();
        }

        viewHolder.tv_food_name.setText(mList.get(position).getFoodName());
        viewHolder.tv_food_price.setText(mList.get(position).getFoodPrice() + "元/份");
        // 直接从数据源中拿取数量，下面的按钮点击，直接修改数据源中的数据
        viewHolder.et_food_count.setText(mList.get(position).getFoodCount() + "");

        viewHolder.bt_minus.setOnClickListener(new ItemButtonOnClickListener(position));
        viewHolder.bt_plus.setOnClickListener(new ItemButtonOnClickListener(position));

        return convertView;
    }

    // ViewHolder
    class ViewHolder {
        ImageView iv_food_image;
        TextView tv_food_name, tv_food_price;
        EditText et_food_count;
        Button bt_minus, bt_plus;

        @Override
        public String toString() {
            return tv_food_name.getText().toString();
        }
    }

    class ItemButtonOnClickListener implements View.OnClickListener {

        private int position;
        // 获取EditeText此时正显示的数量
        private int foodCount = Integer.parseInt(viewHolder.et_food_count.getText().toString());

        public ItemButtonOnClickListener(int position) {
            this.position = position;
        }

        @Override
        public void onClick(View v) {
            switch (v.getId()) {
            case R.id.bt_plus:
                // 数量+1
                foodCount++;
                // 将数据源中的数量修改
                mList.get(position).setFoodCount(foodCount);
                // 刷新显示
                notifyDataSetChanged();
                break;
            case R.id.bt_minus:
                foodCount--;
                if (foodCount <= 0) {
                    mList.get(position).setFoodCount(0);
                } else {
                    mList.get(position).setFoodCount(foodCount);
                }
                notifyDataSetChanged();
                break;
            }
        }
    }
}

MainActivity.java

package com.example.menutest;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

import com.example.menutest.adapter.ShowFoodAdapter;
import com.example.menutest.bean.Food;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ListView;

public class MainActivity extends Activity {

    private ListView lv_foods;
    private Button bt_submit;
    private List<Food> foodsList = new ArrayList<Food>();
    private ShowFoodAdapter adapter;

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

        initView();
        initData();
        adapter = new ShowFoodAdapter(foodsList, this);
        lv_foods.setAdapter(adapter);

        bt_submit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                List<Food> selectedFoodList = adapter.getSelectedFoodList();
                Intent intent = new Intent(MainActivity.this, SelectFoodActivity.class);
                intent.putExtra("selectFood", (Serializable) selectedFoodList);
                startActivity(intent);
            }
        });
    }

    // 初始化菜品数据
    private void initData() {
        foodsList.add(new Food("bawangshizitou", "霸王狮子头", 23));
        foodsList.add(new Food("dongbeiguobaorou", "东北锅包肉", 34));
        foodsList.add(new Food("haomiganfanbazirou", "好米干饭把子肉", 45));
        foodsList.add(new Food("jidanzhajiangmian", "鸡蛋炸酱面", 56));
        foodsList.add(new Food("kaoquanyang", "烤全羊", 67));
        foodsList.add(new Food("laobeijingchaogeda", "老北京炒疙瘩", 78));
        foodsList.add(new Food("lizhirou", "荔枝肉", 89));
        foodsList.add(new Food("niunaikekeqiu", "牛奶可可球", 90));
        foodsList.add(new Food("peigenjinzhengu", "培根金针菇", 30));
        foodsList.add(new Food("qincaixiarenshuijiao", "芹菜虾仁水饺", 37));
        foodsList.add(new Food("qingmingtuanzi", "清明团子", 48));
        foodsList.add(new Food("shufulei", "舒芙蕾", 39));
        foodsList.add(new Food("wuxiangjianglvrou", "五香酱驴肉", 27));
        foodsList.add(new Food("xianshaobai", "咸烧白", 14));
        foodsList.add(new Food("xinjiangchaokaorou", "新疆炒烤肉", 28));
        foodsList.add(new Food("xuedouduntihua", "雪豆炖蹄花", 10));
        foodsList.add(new Food("yangzasui", "羊杂碎", 27));
        foodsList.add(new Food("yerongtianjiangmaifen", "椰蓉甜姜麦芬", 16));
        foodsList.add(new Food("zhenfengji", "蒸风鸡", 53));
    }

    // 查找组件
    private void initView() {
        lv_foods = (ListView) findViewById(R.id.lv_foods);
        bt_submit = (Button) findViewById(R.id.bt_submit);
    }
}

SelectFoodActivity.java

package com.example.menutest;

import java.util.ArrayList;
import java.util.List;

import com.example.menutest.bean.Food;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class SelectFoodActivity extends Activity {

    private ListView lv_select_food;
    private TextView tv_money_count;
    private ArrayAdapter<String> adapter;
    private int moneyCount;
    private List<String> list = new ArrayList<String>();

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

        initView();
        Intent intent = getIntent();
        List<Food> selectFood = (List<Food>) intent.getSerializableExtra("selectFood");
        for (int i = 0; i < selectFood.size(); i++) {

            if (selectFood.get(i).getFoodCount() == 0) {
                continue;
            } else {
                list.add(selectFood.get(i).getFoodName() + ",共 " + selectFood.get(i).getFoodCount() + " 份,每份 "
                        + selectFood.get(i).getFoodPrice() + " 元");
                moneyCount += selectFood.get(i).getFoodPrice() * selectFood.get(i).getFoodCount();
            }
        }
        adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, list);
        lv_select_food.setAdapter(adapter);
        tv_money_count.setText("共计： " + moneyCount + " 元");
    }

    private void initView() {
        lv_select_food = (ListView) findViewById(R.id.lv_select_food);
        tv_money_count = (TextView) findViewById(R.id.tv_money_count);
    }

}

　　至此，功能完成，当然还有很多需要优化的地方，譬如界面，因为仅仅是说明一下思路，这里就不展开了，回头有时间写个完整的。