模仿购物车实现ListView中商品数量的添加以及总价的调整

     最近在写一个类似于点餐系统的项目，想起来还没写过博客，而且目前面临着即将走出校门找工作，所以打算写几篇博客，顺便记录一下用到的知识点，方便以后查看。回归主题，今天写的是关于ListView中每个Item中商品数量的增加删除并且总价跟着改变。

效果图如下

    首先介绍每个Item中商品数量改变，一开始只是知道每个Item点击有OnItemClickListener方法，但是不知道能不能实现单个Item内如果有点击时间之后的处理，所以就尝试了一下在Adapter中给相应的控件加监听事件，结果实现了，代码如下。

每个Item的布局如下

相应的Adapter代码为

package com.lylk.hcwy.adapter;

import android.content.Context;
import android.os.Handler;
import android.os.Message;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.TextView;
import android.widget.Toast;

import com.lylk.hcwy.R;

import java.util.LinkedList;

/**
 * Created by LYLK on 2017/5/4.
 */
public class DiyListAdapter extends BaseAdapter {

    private Context context;
    private LinkedList name;
    private LinkedList unit;
    private LinkedList unit_price;
    private Handler handler;

    public DiyListAdapter(Context context,LinkedList name,LinkedList unit,
                          LinkedList unit_price,Handler handle) {
        this.context = context;
        this.name = name;
        this.unit = unit;
        this.unit_price = unit_price;
        this.handler = handle;
    }

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

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

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder;
        if (convertView == null) {
            convertView = LayoutInflater.from(context).inflate(R.layout.diy_item, null);
            viewHolder = new ViewHolder();
            viewHolder.ck = (CheckBox) convertView.findViewById(R.id.cb_diy_item_check);
            viewHolder.tv_name = (TextView) convertView.findViewById(R.id.tv_diy_item_wine);
            viewHolder.tv_unit = (TextView) convertView.findViewById(R.id.tv_diy_item_unit);
            viewHolder.tv_minus = (TextView) convertView.findViewById(R.id.tv_diy_item_minus);
            viewHolder.tv_total = (TextView) convertView.findViewById(R.id.tv_diy_item_total);
            viewHolder.tv_add = (TextView) convertView.findViewById(R.id.tv_diy_item_add);
            viewHolder.tv_count = (TextView) convertView.findViewById(R.id.tv_diy_item_count);
            convertView.setTag(viewHolder);
        }else {
            viewHolder = (ViewHolder) convertView.getTag();
        }

        init(viewHolder, position,unit_price.get(position));


        return convertView;
    }

    private void init(final ViewHolder viewHolder, int position, final int price) {
        viewHolder.tv_name.setText(name.get(position));
        viewHolder.ck.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                if(isChecked){
                    viewHolder.tv_total.setText("1");
                    viewHolder.tv_count.setText("¥"+price);
                    Message msg = Message.obtain();
                    msg.arg1 = price;
                    handler.sendMessage(msg);
                }else {
                    int pre_total = Integer.parseInt(viewHolder.tv_total.getText().toString());
                    int pre_count = pre_total*price;
                    viewHolder.tv_total.setText("0");
                    viewHolder.tv_count.setText("¥0");
                    Message msg = Message.obtain();
                    msg.arg1 = 0-pre_count;
                    handler.sendMessage(msg);
                }
            }
        });


        viewHolder.tv_minus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String total = viewHolder.tv_total.getText().toString();
                if(total.equals("0")){
                    Toast.makeText(context,"此酒未被选择",Toast.LENGTH_SHORT).show();
                }else if(total.equals("1")){
                    viewHolder.tv_total.setText("0");
                    viewHolder.ck.setChecked(false);
//                    Message msg = Message.obtain();
//                    msg.arg1 = 0-price;
//                    handler.sendMessage(msg);
                }else {
                    int num = Integer.parseInt(total);
                    num--;
                    viewHolder.tv_count.setText("¥"+price*num);
                    viewHolder.tv_total.setText(String.valueOf(num));
                    Message msg = Message.obtain();
                    msg.arg1 = 0-price;
                    handler.sendMessage(msg);
                }
            }
        });

        viewHolder.tv_add.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String total = viewHolder.tv_total.getText().toString();
                int num = Integer.parseInt(total);
                if(total.equals("0")){
                    viewHolder.ck.setChecked(true);
                    num++;
                    viewHolder.tv_count.setText("¥"+price*num);
                    viewHolder.tv_total.setText(String.valueOf(num));
//                    Message msg = Message.obtain();
//                    msg.arg1 = price;
//                    handler.sendMessage(msg);
                }else {
                    num++;
                    viewHolder.tv_count.setText("¥"+price*num);
                    viewHolder.tv_total.setText(String.valueOf(num));
                    Message msg = Message.obtain();
                    msg.arg1 = price;
                    handler.sendMessage(msg);
                }
            }
        });
        int total = Integer.parseInt(viewHolder.tv_total.getText().toString());
        viewHolder.tv_count.setText("¥"+price*total);
    }

    private class ViewHolder {
        public CheckBox ck;
        public TextView tv_name;
        public TextView tv_unit;
        public TextView tv_minus;
        public TextView tv_total;
        public TextView tv_add;
        public TextView tv_count;
    }
}

只需要在绑定布局的时候加入相应的点击时间就可以实现。

viewHolder.tv_minus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String total = viewHolder.tv_total.getText().toString();
                if(total.equals("0")){
                    Toast.makeText(context,"此酒未被选择",Toast.LENGTH_SHORT).show();
                }else if(total.equals("1")){
                    viewHolder.tv_total.setText("0");
                    viewHolder.ck.setChecked(false);
//                    Message msg = Message.obtain();
//                    msg.arg1 = 0-price;
//                    handler.sendMessage(msg);
                }else {
                    int num = Integer.parseInt(total);
                    num--;
                    viewHolder.tv_count.setText("¥"+price*num);
                    viewHolder.tv_total.setText(String.valueOf(num));
                    Message msg = Message.obtain();
                    msg.arg1 = 0-price;
                    handler.sendMessage(msg);
                }
            }
        });

        viewHolder.tv_add.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String total = viewHolder.tv_total.getText().toString();
                int num = Integer.parseInt(total);
                if(total.equals("0")){
                    viewHolder.ck.setChecked(true);
                    num++;
                    viewHolder.tv_count.setText("¥"+price*num);
                    viewHolder.tv_total.setText(String.valueOf(num));
//                    Message msg = Message.obtain();
//                    msg.arg1 = price;
//                    handler.sendMessage(msg);
                }else {
                    num++;
                    viewHolder.tv_count.setText("¥"+price*num);
                    viewHolder.tv_total.setText(String.valueOf(num));
                    Message msg = Message.obtain();
                    msg.arg1 = price;
                    handler.sendMessage(msg);
                }
            }
        });

接下来说一下如何实现动态的实现总价的修改，其实也很简单，利用一个Handler即可实现，写这部分功能之前想了很多方法，比如遍历ListView什么的，但是最后一一排除之后选择使用Handler来实现。在此之前也没有查过资料，只是想验证一下自己的想法是否可以实现，最终实现完成之后查看资料发现很多人都是使用这种方式实现的，瞬间感觉自己想的还是挺对的。废话不多说，直接看代码吧。

首先在Fragment中定义一个Handler

public Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            Double pre_count = Double.parseDouble(tv_count.getText().toString());
            super.handleMessage(msg);
            tv_count.setText(String.valueOf(pre_count+msg.arg1));
        }
    };

然后在Adapter构造函数中把这个Handler传递过去，在Adapter中每个商品价格改变的位置把改变的价格发送回去就可以了。

viewHolder.tv_add.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String total = viewHolder.tv_total.getText().toString();
                int num = Integer.parseInt(total);
                if(total.equals("0")){
                    viewHolder.ck.setChecked(true);
                    num++;
                    viewHolder.tv_count.setText("¥"+price*num);
                    viewHolder.tv_total.setText(String.valueOf(num));
//                    Message msg = Message.obtain();
//                    msg.arg1 = price;
//                    handler.sendMessage(msg);
                }else {
                    num++;
                    viewHolder.tv_count.setText("¥"+price*num);
                    viewHolder.tv_total.setText(String.valueOf(num));
                    Message msg = Message.obtain();
                    msg.arg1 = price;
                    handler.sendMessage(msg);
                }
            }
        });

以上就是这次记录的内容，还有一个小小的问题，就是现在没有测试在Adadpter中给空间添加的点击事件与OnItemClickListener会不会产生冲突，等之后测试一下在写测试结果吧，现在就先写这么多。第一次写博客，写的不好请大家见谅，有什么不好的地方希望大家能给指正。