开发一个简单的购物车：
（1）需要将购物车中的商品以列表的形式展示
（2）并且还需要对购物车中的 商品进行增删改查操作。
（3）要实现这些功能就需要使用 ListView 和 SQLite 数据库。
1.创建一个名为ProdectDisplay的程序
2.（1）在activity_main.xml文件中设计布局：
<?xml version="1.0" encoding="utf-8"?> <LinearLayout 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:orientation="vertical" tools:context="bzu.edu.cn.prodectdisply.MainActivity"> <LinearLayout android:id="@+id/addLL" android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="horizontal"> <EditText android:id="@+id/nameET" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:hint="商品名称" android:inputType="textPersonName" /> <EditText android:id="@+id/balanceET" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:hint="金额" android:inputType="number" /> <ImageView android:onClick="add" android:id="@+id/addIV" android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@android:drawable/ic_input_add" /> </LinearLayout> <ListView android:id="@+id/accountLV" android:layout_width="match_parent" android:layout_height="match_parent" android:layout_below="@id/addLL"> </ListView> </LinearLayout>
（2）在layout下创建一个item.xml，编写一个ListViewItem的布局：
<?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="match_parent" android:orientation="horizontal" android:padding="10dp"> <TextView android:id="@+id/idTV" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:text="13" android:textColor="#000000" android:textSize="20sp" /> <TextView android:id="@+id/nameTV" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="2" android:text="PQ" android:singleLine="true" android:textColor="#000000" android:textSize="20sp" /> <TextView android:id="@+id/balanceTV" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="2" android:text="12345" android:singleLine="true" android:textColor="#000000" android:textSize="20sp" /> <LinearLayout android:layout_width="wrap_content" android:layout_height="wrap_content" android:orientation="vertical"> <ImageView android:id="@+id/upIV" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginBottom="2dp" android:src="@android:drawable/arrow_up_float" /> <ImageView android:id="@+id/downIV" android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@android:drawable/arrow_down_float" /> <ImageView android:id="@+id/deleteIV" android:layout_width="25dp" android:layout_height="25dp" android:src="@android:drawable/ic_menu_delete" /> </LinearLayout> </LinearLayout>
3.(1)创建数据库，在包dao下创建一个MyHelper类，继承SQLiteOpenHelper：
package bzu.edu.cn.prodectdisply.dao; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; /** * Created by gxw on 2017/5/3. */ public class MyHelper extends SQLiteOpenHelper { public MyHelper(Context context) { super(context,"itcast.db",null,2); } @Override public void onCreate(SQLiteDatabase db) { System.out.println("onCreate"); db.execSQL("CREATE TABLE account(_id INTEGER PRIMARY KEY AUTOINCREMENT,name VARCHAR(20),balance INTEGER)"); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { System.out.println("onUpgrade"); } }
(2)在包dao下创建类AccountDao类，用于操作数据库：
package bzu.edu.cn.prodectdisply.dao; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import java.util.ArrayList; import java.util.List; import bzu.edu.cn.prodectdisply.bean.Account; /** * Created by gxw on 2017/4/17. */ public class AccountDao { private MyHelper helper; public AccountDao(Context context){ helper=new MyHelper(context); } public void insert(Account account){ SQLiteDatabase db=helper.getWritableDatabase(); ContentValues values=new ContentValues(); values.put("name",account.getName()); values.put("balance",account.getBalance()); long id=db.insert("account",null,values); account.setId(id); db.close(); } public int delete(long id){ SQLiteDatabase db=helper.getWritableDatabase(); int count=db.delete("account","_id=?",new String[]{id+""}); db.close(); return count; } public int update(Account account){ SQLiteDatabase db=helper.getWritableDatabase(); ContentValues values=new ContentValues(); values.put("name",account.getName()); values.put("balance",account.getBalance()); int count=db.update("account",values,"_id=?",new String[]{account.getId()+""}); db.close(); return count; } public List<Account> queryAll(){ SQLiteDatabase db=helper.getWritableDatabase(); Cursor c=db.query("account",null,null,null,null,null,"balance DESC"); List<Account> list=new ArrayList<>(); while(c.moveToNext()){ long id=c.getLong(c.getColumnIndex("_id")); String name=c.getString(1); int balance=c.getInt(2); list.add(new Account(id,name,balance)); } c.close(); db.close(); return list; } }
4.创建一个bean包，用于存放JavaBean类，此包下创建一个Account类：
package bzu.edu.cn.prodectdisply.bean; /** * Created by gxw on 2017/5/3. */ public class Account { private Long id; private String name; private Integer balance; public Long getId(){ return id; } public void setId(Long id) { this.id=id; } public String getName(){ return name; } public void setName(String name){ this.name=name; } public Integer getBalance(){ return balance; } public void setBalance(Integer balance){ this.balance=balance; } public Account(Long id,String name,Integer balance){ super(); this.id=id; this.name=name; this.balance=balance; } public Account(String name,Integer balance){ super(); this.name=name; this.balance=balance; } public Account(){ super(); } public String toString(){ return "[序号："+id+",商品名称："+name+",余额："+balance+"]"; } }
5.编写界面交互代码：
package bzu.edu.cn.prodectdisply; import android.content.DialogInterface; import android.net.Uri; import android.support.v7.app.AlertDialog; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.support.v7.app.NotificationCompat; import android.view.View; import android.view.ViewGroup; import android.widget.AdapterView; import android.widget.BaseAdapter; import android.widget.EditText; import android.widget.ImageView; import android.widget.ListView; import android.widget.TextView; import android.widget.Toast; import com.google.android.gms.appindexing.Action; import com.google.android.gms.appindexing.AppIndex; import com.google.android.gms.appindexing.Thing; import com.google.android.gms.common.api.GoogleApiClient; import java.util.List; import bzu.edu.cn.prodectdisply.bean.Account; import bzu.edu.cn.prodectdisply.dao.AccountDao; public class MainActivity extends AppCompatActivity { private List<Account> list; private AccountDao dao; private EditText nameET; private EditText balanceET; private MyAdapter adapter; private ListView accountLV; private GoogleApiClient client; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); initView(); dao = new AccountDao(this); list = dao.queryAll(); adapter = new MyAdapter(); accountLV.setAdapter(adapter); client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build(); } private void initView() { accountLV = (ListView) findViewById(R.id.accountLV); nameET = (EditText) findViewById(R.id.nameET); balanceET = (EditText) findViewById(R.id.balanceET); accountLV.setOnItemClickListener(new MyOnItemClickListener()); } public void add(View v) { String name = nameET.getText().toString().trim(); String balance = balanceET.getText().toString().trim(); Account a = new Account(name, balance.equals("") ? 0 : Integer.parseInt(balance)); dao.insert(a); list.add(a); adapter.notifyDataSetChanged(); accountLV.setSelection(accountLV.getCount() - 1); nameET.setText(""); balanceET.setText(""); } public Action getIndexApiAction() { Thing object = new Thing.Builder().setName("Main Page") // TODO: Define a title for the content shown. // TODO: Make sure this auto-generated URL is correct. .setUrl(Uri.parse("http://[ENTER-YOUR-URL-HERE]")) .build(); return new Action.Builder(Action.TYPE_VIEW) .setObject(object) .setActionStatus(Action.STATUS_TYPE_COMPLETED) .build(); } @Override public void onStart() { super.onStart(); client.connect(); AppIndex.AppIndexApi.start(client, getIndexApiAction()); } @Override public void onStop() { super.onStop(); AppIndex.AppIndexApi.end(client, getIndexApiAction()); client.disconnect(); } private class MyAdapter extends BaseAdapter { public int getCount() { return list.size(); } public Object getItem(int position) { return list.get(position); } public long getItemId(int position) { return position; } public View getView(int position, View convertView, ViewGroup parent) { View item = convertView != null ? convertView : View.inflate(getApplicationContext(), R.layout.item, null); TextView idTV = (TextView) item.findViewById(R.id.idTV); TextView nameTV = (TextView) item.findViewById(R.id.nameTV); TextView balanceTV = (TextView) item.findViewById(R.id.balanceTV); final Account a = list.get(position); idTV.setText(a.getId() + ""); nameTV.setText(a.getName() + ""); balanceTV.setText(a.getBalance() + ""); ImageView upIV = (ImageView) item.findViewById(R.id.upIV); ImageView downIV = (ImageView) item.findViewById(R.id.downIV); ImageView deleteIV = (ImageView) item.findViewById(R.id.deleteIV); upIV.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { a.setBalance(a.getBalance() + 1); notifyDataSetChanged(); dao.update(a); } }); downIV.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { a.setBalance(a.getBalance() - 1); notifyDataSetChanged(); dao.update(a); } }); deleteIV.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { android.content.DialogInterface.OnClickListener listener=new android.content.DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int which) { list.remove(a); dao.delete(a.getId()); notifyDataSetChanged(); } }; AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this); builder.setTitle("确定要删除吗？"); builder.setPositiveButton("确定", listener); builder.setNegativeButton("取消", null); builder.show(); } }); return item; } } private class MyOnItemClickListener implements AdapterView.OnItemClickListener { public void onItemClick(AdapterView<?> parent,View view,int position,long id){ Account a=(Account) parent.getItemAtPosition(position); Toast.makeText(getApplicationContext(),a.toString(),Toast.LENGTH_LONG).show(); } }} 最终效果图如下所示： 1.添加商品，点击右上方加号可以添加商品 2.点击垃圾桶图标，会出现一个确认对话框，点击确定，会将商品删除 3.可以对商品数量进行修改，点击向上的箭头商品数量加1，点击向下的箭头商品数量减1 4.点击列表，会出现商品的序号，名称，余额等信息
