购物车逻辑

效果图

1.MainActivity
public class MainActivity extends BaseActivity implements View.OnClickListener {

private Button mShouBtn;
private Button mDingBtn;
private Button mWoBtn;
private FragmentManager manager;
private AFragment aFragment;
private BFragment bFragment;
private CFragment cFragment;

@Override
protected int getLayout() {
    return R.layout.activity_main;
}

@Override
protected void initView() {

    mShouBtn = findViewById(R.id.Btn_ShouYe);
    mDingBtn = findViewById(R.id.Btn_DingDan);
    mWoBtn = findViewById(R.id.Btn_WoDe);
    manager = getSupportFragmentManager();
    //初始化
    aFragment = new AFragment();
    bFragment = new BFragment();
    cFragment = new CFragment();
}

@Override
protected void setOnclick() {
    mShouBtn.setOnClickListener(this);
    mDingBtn.setOnClickListener(this);
    mWoBtn.setOnClickListener(this);
}

@Override
protected void pageLogic() {
    manager.beginTransaction().replace(R.id.Fram_Lay,aFragment).commit();
}

@Override
public void onClick(View v) {
    switch (v.getId()){
        case R.id.Btn_ShouYe:
            manager.beginTransaction().replace(R.id.Fram_Lay,aFragment).commit();
            break;
        case R.id.Btn_DingDan:
            manager.beginTransaction().replace(R.id.Fram_Lay,bFragment).commit();
            break;
        case R.id.Btn_WoDe:
            manager.beginTransaction().replace(R.id.Fram_Lay,cFragment).commit();
            break;
    }
}

}

主布局
<RelativeLayout xmlns:android=“http://schemas.android.com/apk/res/android”

xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">

<LinearLayout
    android:id="@+id/Lay_Out"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:orientation="horizontal">

    <Button
        android:id="@+id/Btn_ShouYe"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="首页" />

    <Button
        android:id="@+id/Btn_DingDan"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="订单" />

    <Button
        android:id="@+id/Btn_WoDe"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="我的" />
</LinearLayout>

<FrameLayout
    android:id="@+id/Fram_Lay"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_above="@+id/Lay_Out"></FrameLayout>

/RelativeLayout>

自己添加两个boolean类型 用来判断是否选中


2.BFragment
public class BFragment extends Fragment implements IVIew {

private CheckBox Check_All;
private TextView All_Price;
private TextView Go_To_JS;
private String mUrl = "http://www.wanandroid.com/tools/mockapi/6523/restaurant-list";
private ArrayList<MyData.DataBean> mList = new ArrayList<>();
private ExpandableListView mExpandView;
private GWAdapter mAdapter;
private PresenterImpl presenter;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view = inflater.inflate(R.layout.fragment_b, null);
    initView(view);
    pageLogic();
    return view;
}

private void pageLogic() {
    presenter = new PresenterImpl(this);
    presenter.startRequest(mUrl, null);
}

private void initView(View view) {
    Check_All = view.findViewById(R.id.Check_All);
    All_Price = view.findViewById(R.id.All_Price);
    Go_To_JS = view.findViewById(R.id.Go_To_JS);

    mExpandView = view.findViewById(R.id.Expand_View);
    mAdapter = new GWAdapter(mList, getContext());
    mExpandView.setAdapter(mAdapter);


    //去掉自带的小箭头
    mExpandView.setGroupIndicator(null);
    mAdapter.setCallBack(new GWAdapter.AdapterCallback() {
        @Override
        public void setGroupCheck(int groupPosition) {
            //是否被全选中
            boolean childAllCheck = mAdapter.isChildAllCheck(groupPosition);
            mAdapter.childAllCheck(groupPosition, !childAllCheck);
            mAdapter.notifyDataSetChanged();
            flushBottomLayout();

        }

        @Override
        public void setChildCheck(int groupPosition, int childPosition) {
            //得到你要点击的商品Child是否是选中状态
            boolean childChecked = mAdapter.isChildChecked(groupPosition, childPosition);
            mAdapter.setChildChecked(groupPosition, childPosition, !childChecked);
            mAdapter.notifyDataSetChanged();
            flushBottomLayout();
        }

        @Override
        public void setNumber(int groupPosition, int childPosition, int number) {
            mAdapter.setShangPinNumber(groupPosition, childPosition, number);
            mAdapter.notifyDataSetChanged();
            flushBottomLayout();
        }
    });


    //底部全选监听事件
    Check_All.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            boolean allGoods = mAdapter.isAllGoods();
            mAdapter.setAllGoodsIsChecked(!allGoods);
            mAdapter.notifyDataSetChanged();
            flushBottomLayout();
        }
    });



}

@Override
public void success(Object data) {
    MyData myData = (MyData) data;
    mList.addAll(myData.getData());
    mAdapter.notifyDataSetChanged();
    //首次加载全展开
    for (int i = 0; i <mList.size() ; i++) {
        mExpandView.expandGroup(i);
    }
    //不能伸缩
    mExpandView.setOnGroupClickListener(new ExpandableListView.OnGroupClickListener() {
        @Override
        public boolean onGroupClick(ExpandableListView parent, View v, int groupPosition, long id) {
            return true;
        }
    });
}

@Override
public void error(Object error) {

}

private void flushBottomLayout() {
    //刷新全选
    boolean allGoods = mAdapter.isAllGoods();
    Check_All.setChecked(allGoods);
    float allGoodPrice = mAdapter.getAllGoodPrice();
    int allGoodNumber = mAdapter.getAllGoodNumber();
    All_Price.setText("价格："+allGoodPrice);
    Go_To_JS.setText("去结算（"+allGoodNumber+")");
}


@Override
public void onStop() {
    super.onStop();
    mList.clear();
}

}

3.BFargment布局

<RelativeLayout
    android:id="@+id/bottom_layout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true">

    <CheckBox
        android:id="@+id/Check_All"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="全选" />

    <TextView
        android:id="@+id/All_Price"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:text="价格" />

    <TextView
        android:id="@+id/Go_To_JS"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_centerVertical="true"
        android:text="去结算(0)" />
</RelativeLayout>

<ExpandableListView
    android:id="@+id/Expand_View"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_above="@+id/bottom_layout" />

4.适配器 public class GWAdapter extends BaseExpandableListAdapter {

    private ArrayList<MyData.DataBean> mList;
     private Context mContext;
public GWAdapter(ArrayList<MyData.DataBean> mList, Context mContext) {

    this.mList = mList;
    this.mContext = mContext;
}

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

@Override
public int getChildrenCount(int groupPosition) {
    return mList.get(groupPosition).getSpus().size();
}

@Override
public Object getGroup(int groupPosition) {
    return null;
}

@Override
public Object getChild(int groupPosition, int childPosition) {
    return null;
}

@Override
public long getGroupId(int groupPosition) {
    return 0;
}

@Override
public long getChildId(int groupPosition, int childPosition) {
    return 0;
}

@Override
public boolean hasStableIds() {
    return false;
}

@Override
public View getGroupView(final int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
    GroupHolder holder = null;
    if (convertView == null) {
        convertView = View.inflate(mContext, R.layout.group_item, null);
        holder = new GroupHolder();
        holder.mGroupCheck = convertView.findViewById(R.id.Group_Check);
        holder.mGroupTv = convertView.findViewById(R.id.Group_Name);
        convertView.setTag(holder);
    } else {
        holder = (GroupHolder) convertView.getTag();
    }

    holder.mGroupTv.setText(mList.get(groupPosition).getName() + "");
    //自动选中  当子条目全部选中 小组的checkbox自动会被选中
    boolean childAllCheck = isChildAllCheck(groupPosition);
    holder.mGroupCheck.setChecked(childAllCheck);

    //点击事件
    holder.mGroupCheck.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (adapterCallback != null) {
                adapterCallback.setGroupCheck(groupPosition);
            }
        }
    });

    return convertView;
}

@Override
public View getChildView(final int groupPosition, final int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
    ChildHolder cholder = null;
    if (convertView == null) {
        convertView = View.inflate(mContext, R.layout.childe_item, null);
        cholder = new ChildHolder();
        cholder.mChildCheck = convertView.findViewById(R.id.Child_Check);
        cholder.mChildTitle = convertView.findViewById(R.id.Child_title);
        cholder.mChildPrice = convertView.findViewById(R.id.Child_price);
        cholder.mImage = convertView.findViewById(R.id.Child_Icon);
        cholder.jiaJianView = convertView.findViewById(R.id.jia_jian_view);
        convertView.setTag(cholder);
    } else {
        cholder = (ChildHolder) convertView.getTag();
    }
    MyData.DataBean.SpusBean spusBean = mList.get(groupPosition).getSpus().get(childPosition);
    Glide.with(mContext).load(spusBean.getPic_url()).into(cholder.mImage);
    cholder.mChildPrice.setText(spusBean.getSkus().get(0).getPrice());
    cholder.mChildTitle.setText(spusBean.getName() + "");
    //子checkbox
    cholder.mChildCheck.setChecked(spusBean.isChildChecked());
    //通过方法赋值
    cholder.jiaJianView.setNumber(spusBean.getPraise_num());
    cholder.mChildCheck.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (adapterCallback != null) {
                adapterCallback.setChildCheck(groupPosition, childPosition);
            }
        }
    });
    //加减
    cholder.jiaJianView.setOnChange(new JiaJianView.OnCountChange() {
        @Override
        public void setCount(int count) {
            if (adapterCallback != null) {
                adapterCallback.setNumber(groupPosition, childPosition, count);
            }
        }
    });
    return convertView;
}

@Override
public boolean isChildSelectable(int groupPosition, int childPosition) {
    return false;
}

class GroupHolder {
    private CheckBox mGroupCheck;
    private TextView mGroupTv;
}

class ChildHolder {
    private CheckBox mChildCheck;
    private TextView mChildTitle;
    private ImageView mImage;
    private TextView mChildPrice;
    private JiaJianView jiaJianView;
}

//1.点击group的checkbox让child的全选中   只有全选  全不选功能
public void childAllCheck(int groupPosition, boolean isCheck) {
    MyData.DataBean dataBean = mList.get(groupPosition);
    List<MyData.DataBean.SpusBean> spus = dataBean.getSpus();
    for (int i = 0; i < spus.size(); i++) {
        MyData.DataBean.SpusBean spusBean = spus.get(i);
        spusBean.setChildChecked(isCheck);
    }
}

//3.判断小组是否全部选中
public boolean isChildAllCheck(int groupPosition) {
    boolean boo = true;
    MyData.DataBean dataBean = mList.get(groupPosition);
    List<MyData.DataBean.SpusBean> spus = dataBean.getSpus();
    for (int i = 0; i < spus.size(); i++) {
        MyData.DataBean.SpusBean spusBean = spus.get(i);
        //只要有一个没选中  点击checkbox就是全选功能
        if (!spusBean.isChildChecked()) {
            return false;
        }
    }
    return boo;
}

//4.点击child给他赋值
public void setChildChecked(int groupPosition, int childPosition, boolean isCheckBox) {
    MyData.DataBean.SpusBean spusBean = mList.get(groupPosition).getSpus().get(childPosition);
    spusBean.setChildChecked(isCheckBox);
}

//5.查看当前商品是否被选中
public boolean isChildChecked(int groupPosition, int childPosition) {
    MyData.DataBean.SpusBean spusBean = mList.get(groupPosition).getSpus().get(childPosition);
    if (spusBean.isChildChecked()) {
        return true;
    }
    return false;
}

//6.给商品数量赋值
public void setShangPinNumber(int groupPosition, int childPosition, int number) {
    MyData.DataBean.SpusBean spusBean = mList.get(groupPosition).getSpus().get(childPosition);
    spusBean.setPraise_num(number);
}

//7.底部视图有一个全选按钮   得到所有条目的状态
public boolean isAllGoods() {
    boolean boo = true;
    for (int i = 0; i < mList.size(); i++) {
        MyData.DataBean dataBean = mList.get(i);
        for (int j = 0; j < dataBean.getSpus().size(); j++) {
            MyData.DataBean.SpusBean spusBean = dataBean.getSpus().get(j);
            if (!spusBean.isChildChecked()) {
                boo = false;
            }
        }
    }
    return boo;
}

//8.全选反选功能
public void setAllGoodsIsChecked(boolean isAllCheck) {
    for (int i = 0; i < mList.size(); i++) {
        MyData.DataBean dataBean = mList.get(i);
        for (int j = 0; j < dataBean.getSpus().size(); j++) {
            MyData.DataBean.SpusBean spusBean = dataBean.getSpus().get(j);
            spusBean.setChildChecked(isAllCheck);
        }
    }
}

//9.计算所有商品的价格
public float getAllGoodPrice() {
    float allPrice = 0;
    for (int i = 0; i < mList.size(); i++) {
        MyData.DataBean dataBean = mList.get(i);
        for (int j = 0; j < dataBean.getSpus().size(); j++) {
            MyData.DataBean.SpusBean spusBean = dataBean.getSpus().get(j);
            if (spusBean.isChildChecked()) {
                allPrice += spusBean.getPraise_num() * Float.parseFloat(spusBean.getSkus().get(0).getPrice());
            }
        }
    }
    return allPrice;
}

//10.计算所有的商品数量
public int getAllGoodNumber() {
    int allNumber = 0;
    for (int i = 0; i < mList.size(); i++) {
        MyData.DataBean dataBean = mList.get(i);
        for (int j = 0; j < dataBean.getSpus().size(); j++) {
            MyData.DataBean.SpusBean spusBean = dataBean.getSpus().get(j);
            if (spusBean.isChildChecked()) {
                allNumber += spusBean.getPraise_num();
            }
        }
    }
    return allNumber;
}


//2.接口回调  声明一个接口
public interface AdapterCallback {
	//小组
    void setGroupCheck(int groupPosition);
    //子条目
    void setChildCheck(int groupPosition, int childPosition);

    //点击加减按钮刷新
    void setNumber(int groupPosition, int childPosition, int number);
}

private AdapterCallback adapterCallback;

public void setCallBack(AdapterCallback madapterCallback) {
    this.adapterCallback = madapterCallback;
}

}

5.group_item

6.child_item

7.自定义view 加减器
public class JiaJianView extends LinearLayout implements View.OnClickListener {

private TextView mAdd;
private TextView mDelete;
private TextView mNumber;

//商品数量
private int mCount;


public JiaJianView(Context context, AttributeSet attrs) {
    super(context, attrs);
    LayoutInflater.from(context).inflate(R.layout.add_remove_view_layout, this);
    initView();

}

private void initView() {
    mAdd = findViewById(R.id.add_tv);
    mDelete = findViewById(R.id.delete_tv);
    mNumber = findViewById(R.id.product_number_tv);
    mAdd.setOnClickListener(this);
    mDelete.setOnClickListener(this);
}

public void setNumber(int number) {
    this.mCount = number;
    mNumber.setText(number + "");
}

@Override
public void onClick(View v) {
    switch (v.getId()) {
        case R.id.delete_tv:
            if (mCount > 0) {
                mCount--;
                mNumber.setText(mCount + "");
                if (mOnCountChange != null) {
                    mOnCountChange.setCount(mCount);
                }
            } else {
                Toast.makeText(getContext(), "商品已售空", Toast.LENGTH_SHORT).show();
            }
            break;
        case R.id.add_tv:
            mCount++;
            mNumber.setText(mCount + "");
            if (mOnCountChange != null) {
                mOnCountChange.setCount(mCount);
            }
            break;
    }
}

//接口回调
public interface OnCountChange {
    void setCount(int count);
}

private OnCountChange mOnCountChange;

public void setOnChange(OnCountChange onCountChange) {
    this.mOnCountChange = onCountChange;
}

}

8.自定义布局

<LinearLayout xmlns:android=“http://schemas.android.com/apk/res/android”

android:layout_width="wrap_content"
android:layout_height="30dp"
android:layout_gravity="center_vertical"
android:layout_marginLeft="10dp"
android:background="#99000000"
android:gravity="center_vertical"
android:padding="2dp">

<TextView
    android:id="@+id/delete_tv"
    android:layout_width="10dp"
    android:layout_height="match_parent"
    android:background="#ffffff"
    android:gravity="center"
    android:text="-"
    android:textSize="16sp" />

<TextView
    android:id="@+id/product_number_tv"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_marginLeft="2dp"
    android:layout_weight="1"
    android:background="#ffffff"
    android:gravity="center"
    android:text="1" />

<TextView
    android:id="@+id/add_tv"
    android:layout_width="10dp"
    android:layout_height="match_parent"
    android:layout_marginLeft="2dp"
    android:background="#ffffff"
    android:gravity="center"
    android:text="+"
    android:textSize="16sp" />

/LinearLayout>

9.OkUtils 导依赖 okhttp
public class OkUtils {

private OkHttpClient okHttpClient;

private OkUtils() {
    okHttpClient = new OkHttpClient.Builder().build();
}

public static OkUtils getInstance() {
    return OkHolder.okutils;
}

//私有静态方法
private static class OkHolder {
    //实例化
    private static final OkUtils okutils = new OkUtils();
}

public void getAsync(String url, Callback callback){
    Request request=new Request.Builder().url(url).build();
    okHttpClient.newCall(request).enqueue(callback);
}

}

10.model
public class ModelImpl implements Model{

private Handler mHandler=new Handler(){
    @Override
    public void handleMessage(Message msg) {
        if(msg.what==0){
           String str= (String) msg.obj;
            Gson gson=new Gson();
            MyData myData = gson.fromJson(str, MyData.class);
            callback.setData(myData);
        }
    }
};
private MyCallback callback;
@Override
public void getData(String url, String params, MyCallback callback) {
    this.callback=callback;
    OkUtils.getInstance().getAsync(url, new Callback() {
        @Override
        public void onFailure(Call call, IOException e) {

        }

        @Override
        public void onResponse(Call call, Response response) throws IOException {
            String string = response.body().string();
            mHandler.sendMessage(mHandler.obtainMessage(0,string));
        }
    });
}

}