2022-11-17学习内容

1.案例-购物车-购物车列表展示

1.1ShoppingCartActivity.java

package com.example.chapter06;

import androidx.appcompat.app.AppCompatActivity;

import android.net.Uri;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;

import com.example.chapter06.database.ShoppingDBHelper;
import com.example.chapter06.entity.CartInfo;
import com.example.chapter06.entity.GoodsInfo;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class ShoppingCartActivity extends AppCompatActivity implements View.OnClickListener {

    private TextView tv_count;
    private LinearLayout ll_cart;
    private ShoppingDBHelper mDBHelper;
    // 声明一个购物车中的商品信息列表
    private List<CartInfo> mCartList;
    // 声明一个根据商品编号查找商品信息的映射，把商品信息缓存起来，这样不用每一次都查询数据库
    private Map<Integer, GoodsInfo> mGoodsMap = new HashMap<>();
    private TextView tv_total_price;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_shopping_cart);
        TextView tv_title = findViewById(R.id.tv_title);
        tv_title.setText("购物车");
        ll_cart = findViewById(R.id.ll_cart);
        tv_total_price = findViewById(R.id.tv_total_price);

        tv_count = findViewById(R.id.tv_count);
        tv_count.setText(String.valueOf(MyApplication.getInstance().goodsCount));

        mDBHelper = ShoppingDBHelper.getInstance(this);

        findViewById(R.id.iv_back).setOnClickListener(this);
    }

    @Override
    protected void onResume() {
        super.onResume();
        showCart();
    }

    // 展示购物车中的商品列表
    private void showCart() {
        // 移除下面的所有子视图
        ll_cart.removeAllViews();
        // 查询购物车数据库中所有的商品记录
        mCartList = mDBHelper.queryAllCartsInfo();
        if (mCartList.size() == 0) {
            return;
        }
        for (CartInfo info : mCartList) {
            // 根据商品编号查询商品数据库中的商品记录
            GoodsInfo goods = mDBHelper.queryGoodsInfoById(info.goodsId);
            mGoodsMap.put(info.goodsId, goods);

            // 获取布局文件item_cart.xml的根视图
            View view = LayoutInflater.from(this).inflate(R.layout.item_cart, null);
            ImageView iv_thumb = view.findViewById(R.id.iv_thumb);
            TextView tv_name = view.findViewById(R.id.tv_name);
            TextView tv_desc = view.findViewById(R.id.tv_desc);
            TextView tv_count = view.findViewById(R.id.tv_count);
            TextView tv_price = view.findViewById(R.id.tv_price);
            TextView tv_sum = view.findViewById(R.id.tv_sum);

            iv_thumb.setImageURI(Uri.parse(goods.picPath));
            tv_name.setText(goods.name);
            tv_desc.setText(goods.description);
            tv_count.setText(String.valueOf(info.count));
            tv_price.setText(String.valueOf((int)goods.price));
            // 设置商品总价
            tv_sum.setText(String.valueOf((int)info.count * goods.price));

            // 往购物车列表添加该商品行
            ll_cart.addView(view);
        }

        // 重新计算购物车中的商品总金额
        refreshTotalPrice();
    }

    // 重新计算购物车中的商品总金额
    private void refreshTotalPrice() {
        int totalPrice = 0;
        for (CartInfo info : mCartList) {
            GoodsInfo goods = mGoodsMap.get(info.goodsId);
            totalPrice += goods.price * info.count;
        }
        tv_total_price.setText(String.valueOf(totalPrice));
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.iv_back:
                // 点击了返回图标
                // 关闭当前页面
                finish();
                break;
        }
    }
}

1.2效果：