Java 如何在Arraylist中计算价格并在另一个页面中显示选中的项目（Android Studio）

我的应用程序有三个xml文件和两个java文件。我几乎完成了这项工作，但我坚持让应用程序计算用户检查的餐费，并在发票页面上显示所选餐费的名称。我将向您展示代码，我想知道的是，当用户单击count total按钮并将其显示在invoic_页面的tv_result上时，如何让应用程序计算价格并显示总价。我还想知道如何在发票页面中显示已签入（checkedItems）的膳食名称

活动\u main.xml

    <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.sahora.al_baik.MainActivity">

    <ListView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/listView1"/>

    <Button
        android:text="Count Total"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/findSelected"
        android:layout_alignBottom="@+id/listView1"/>
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:padding="10dp">

    <CheckBox
        android:text="CheckBox"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/checkBox"
        android:focusable="false"
        android:focusableInTouchMode="false"
        android:layout_alignParentLeft="true"/>

    <TextView
        android:id="@+id/price"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/checkBox"
        android:layout_alignBottom="@+id/checkBox"
        android:layout_toRightOf="@+id/checkBox"
        android:text="TextView" />

</RelativeLayout>

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

    <TextView
        android:text="Checked"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/checkedItems"
        android:layout_margin="10dp"/>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceLarge"
            android:id="@+id/tv_result"
            android:layout_centerInParent="true"
            />
    </RelativeLayout>

</LinearLayout>

---

很抱歉，我是编码初学者^ ^

请在复选框中添加一个setOnCheckedChangeListener

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

        ViewHolder holder = null;
        Log.v("ConvertView", String.valueOf(position));

        if (convertView == null) {
            LayoutInflater vi = (LayoutInflater) getSystemService(
                    Context.LAYOUT_INFLATER_SERVICE);
            convertView = vi.inflate(R.layout.food_info, null);

            holder = new ViewHolder();
            holder.price = (TextView) convertView.findViewById(R.id.price);
            holder.name = (CheckBox) convertView.findViewById(R.id.checkBox);
            convertView.setTag(holder);

        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        Food food = foodList.get(position);
        holder.price.setText(" (" + food.getPrice() + ")");
        holder.name.setText(food.getName());
        holder.name.setChecked(food.isSelected());

        holder.name.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
        @Override
        public void onCheckedChanged(CompoundButton compoundButton, boolean b) {
            food.setSelected(b);
        }
       });
        holder.name.setTag(food);

        return convertView;

    }

}

使食物列表成为全球性的。点击按钮

private void checkButtonClick() {

    Button myButton = (Button) findViewById(R.id.findSelected);
    myButton.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            setContentView(R.layout.invoic_page);
            int totalPrice = 0;
            for(Food f : foodList){
                if(f.isSelected){
                totalPrice += f.getPrice();
                }

             //totalPrice variable now has the total of all selected items
        }
    });

}

---

添加新代码后，我发现一些错误。。。请问我该怎么办？以下是错误：[1]：[2]：

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

        ViewHolder holder = null;
        Log.v("ConvertView", String.valueOf(position));

        if (convertView == null) {
            LayoutInflater vi = (LayoutInflater) getSystemService(
                    Context.LAYOUT_INFLATER_SERVICE);
            convertView = vi.inflate(R.layout.food_info, null);

            holder = new ViewHolder();
            holder.price = (TextView) convertView.findViewById(R.id.price);
            holder.name = (CheckBox) convertView.findViewById(R.id.checkBox);
            convertView.setTag(holder);

        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        Food food = foodList.get(position);
        holder.price.setText(" (" + food.getPrice() + ")");
        holder.name.setText(food.getName());
        holder.name.setChecked(food.isSelected());

        holder.name.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
        @Override
        public void onCheckedChanged(CompoundButton compoundButton, boolean b) {
            food.setSelected(b);
        }
       });
        holder.name.setTag(food);

        return convertView;

    }

}

private void checkButtonClick() {

    Button myButton = (Button) findViewById(R.id.findSelected);
    myButton.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            setContentView(R.layout.invoic_page);
            int totalPrice = 0;
            for(Food f : foodList){
                if(f.isSelected){
                totalPrice += f.getPrice();
                }

             //totalPrice variable now has the total of all selected items
        }
    });

}