商品展示案例（SQLite数据库存储和ListView的使用）

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1.创建程序

首先创建一个名为“DisplayProduct”的应用程序，设计用户交互界面，如下图所示：

其相应的布局文件（activity_main.xml）如下所示：

<?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"    android:layout_margin="8dp"    tools:context="cn.edu.bzu.displayproduct.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.创建ListView Item布局

由于本案例用到了ListView布局，因此需要编写一个ListView Item的布局文件。在res/layout目录下创建一个item.xml文件，编写出如下图所示的界面：

其代码如下：

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:orientation="horizontal"    android:layout_width="match_parent"    android:layout_height="wrap_content"    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:singleLine="true"        android:text="PQ"        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:singleLine="true"        android:text="123456"        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>

3.创建数据库

创建数据库属于数据操作，因此需要在cn.edu.bzu.product包下创建一个名为dao的包，并在该包下定义一个MyHelper类继承自SQLiteOpenHelper，创建数据库的代码如下：

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.创建Account类

在操作数据库时将数据存放至一个JavaBean对象中操作起来会比较方便。因此，需要在cn.edu.bzu.product包下创建一个bean包用于存放JavaBean类，然后在cn.edu.bzu.product。bean包下定义一个Account类，具体代码如下：

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.创建数据操作逻辑类

在cn.edu.bzu.product。dao包下创建一个AccountDao类用于操作数据，具体代码如下：

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();    }    //根据id删除数据    public int delete(long id){        SQLiteDatabase db=helper.getWritableDatabase();        int count=db.delete("account","_id=?",new String[]{id+""});        db.close();        return count;    }    //更新数据库    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;    }    //查询所有数据倒序排列    public List<Account> queryAll(){        SQLiteDatabase db=helper.getReadableDatabase();        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.编写界面交互代码（MainActivity）

数据库的操作完成之后需要界面与数据库进行交互，用于实现将数据库中的数据以ListView的形式展示在界面上，具体代码如下所示：

public class MainActivity extends Activity {    private List<Account> list;    private  AccountDao dao;    private EditText nameET;    private EditText balanceET;    private ListView accountLV;    private MyAdapter adapter;    @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 view){        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{       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 {        @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_SHORT).show();        }    }}