数据库操作之商品展示

商品展示充分利用学过的SQLite数据库中的增 删 改 查等功能，以及ListView中的常用属性。

运行效果图：

1.新建商品展示对应的布局文件（activity.main）

<?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:layout_width="match_parent"    android:layout_height="match_parent"    android:layout_margin="8dp"    android:orientation="vertical"    tools:context="cn.edu.bzu.uiapplication.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:id="@+id/addIV"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:onClick="add"            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>

效果图：

2.在layout下新建一个item，对listview控件布局进行设置。

<?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="wrap_content"    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="1"    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="毛巾"        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="100"        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"/>    </LinearLayout>    <ImageView        android:id="@+id/deleteIV"        android:layout_width="25dp"        android:layout_height="25dp"        android:src="@android:drawable/ic_menu_delete"/></LinearLayout>

效果图:

3.数据库操作，新建一个Dao包，在该包下定义一个MyHelper类继承SQLiteOpenHelper,数据库代码如下：

package cn.edu.bzu.uiapplication.dao;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;import android.provider.Settings;/** * Created by Administrator on 2017/4/16. */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");    }}

4.为了操作方便，操作数据库数将数据存放在一个Javabeen中，所以新建一个bean包用于存放Javabean类，在bean定义一个Account类，代码如下：

package cn.edu.bzu.uiapplication.bean;/** * Created by Administrator on 2017/4/16. */public class Account {    private Long id;    private String name;    private Integer 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 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 String toString(){        return "[序号："+id+",商品名称:"+name+",余额："+balance+"]";    }}

5.创建完了数据库和Javabean，接下来就要在dao包下创建一个AccountDao类用于操作数据增删改查。

package cn.edu.bzu.uiapplication.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 cn.edu.bzu.uiapplication.bean.Account;/** * Created by Administrator on 2017/4/16. */public class AccountDao {    private MyHelper helper;    public AccountDao(Context context){        helper=new MyHelper(context);    }       //插入方法 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();    }      //根据ID删除方法 public int delete(long id){        SQLiteDatabase db=helper.getWritableDatabase();        int count=db.delete("account","_id=?",new String[]{id+""});        db.close();        return count;    }      //修改方法 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;    }     //查询所有数据 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<Account>();        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;    }}

6.最后一步就是编写数据库与界面的交互代码，将数据库中的数据在liatview中展示，运用到了基本适配器adapter。

package cn.edu.bzu.uiapplication;import android.content.DialogInterface;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.Adapter;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 java.util.List;import cn.edu.bzu.uiapplication.bean.Account;import cn.edu.bzu.uiapplication.dao.AccountDao;import static android.content.DialogInterface.*;public class MainActivity extends AppCompatActivity {    private List<Account> list;    private AccountDao dao;    private EditText nameET;    private EditText balanceET;    private MyAdapter adapter;//适配器    private ListView accountLV;    @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);    }    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("");}    private class MyAdapter extends BaseAdapter {        @Override        public int getCount() {            return list.size();        }        @Override        public Object getItem(int position) {            return list.get(position);        }        @Override        public long getItemId(int position) {            return position;        }        @Override        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 android.widget.AdapterView.OnItemClickListener {        @Override        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();        }    }}

所有代码编写完成，效果图如下：

点击某一个商品，弹出toast。

对商品进行删除

删除后

价格进行修改

修改后的价格