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。