SQLite数据库应用之商品展示

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一、设计主界面

使用系统自带的图片作为drawable使用的图片

主布局：activity_main

<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:layout_width="0dp"        android:layout_height="wrap_content"        android:id="@+id/idTV"        android:layout_weight="1"        android:text="13"        android:textColor="#000000"        android:textSize="20sp" />    <TextView        android:layout_width="0dp"        android:layout_height="wrap_content"        android:id="@+id/nameTV"        android:layout_weight="2"        android:text="PQ"        android:singleLine="true"        android:textColor="#000000"        android:textSize="20sp" />    <TextView        android:layout_width="0dp"        android:layout_height="wrap_content"        android:id="@+id/balanceTV"        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:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/upIV"            android:layout_marginBottom="2dp"            android:src="@android:drawable/arrow_up_float"/>        <ImageView            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/downIV"            android:layout_marginBottom="2dp"            android:src="@android:drawable/arrow_down_float"/>    </LinearLayout>    <ImageView        android:layout_width="25dp"        android:layout_height="25dp"        android:id="@+id/deleteIV"        android:src="@android:drawable/ic_menu_delete"/></LinearLayout>

二、创建ListView Item布局

创建了三个TextView和三个ImageView

<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:layout_width="0dp"        android:layout_height="wrap_content"        android:id="@+id/idTV"        android:layout_weight="1"        android:text="13"        android:textColor="#000000"        android:textSize="20sp" />    <TextView        android:layout_width="0dp"        android:layout_height="wrap_content"        android:id="@+id/nameTV"        android:layout_weight="2"        android:text="PQ"        android:singleLine="true"        android:textColor="#000000"        android:textSize="20sp" />    <TextView        android:layout_width="0dp"        android:layout_height="wrap_content"        android:id="@+id/balanceTV"        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:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/upIV"            android:layout_marginBottom="2dp"            android:src="@android:drawable/arrow_up_float"/>        <ImageView            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/downIV"            android:layout_marginBottom="2dp"            android:src="@android:drawable/arrow_down_float"/>    </LinearLayout>    <ImageView        android:layout_width="25dp"        android:layout_height="25dp"        android:id="@+id/deleteIV"        android:src="@android:drawable/ic_menu_delete"/></LinearLayout>


三、创建数据库

在系统包下创建一个名为dao的包 定义一个MyHelper类继承SQLiteOpenHelper

代码如下:

public class MyHelper extends SQLiteOpenHelper {    public MyHelper(Context context) {        super(context,"18Lab10.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");    }}
四、创建Account类

在操作数据库时将数据存放在一个对象中操作会更方便，因此需要创建一个bean包来存放Javabean类然后再定义一个类Account

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();    }        @Override    public String toString() {        return "[序号：" + id +                ", 商品名称'" + name + '\'' +                ", 余额：" + balance +                ']';    }}
五、创建数据操作逻辑类
在dao包下创建一个AccountDao类用于操作数据
public class AccountDao {    private MyHelper helper;    SQLiteDatabase db=helper.getWritableDatabase();    public AccountDao(Context context) {        helper=new MyHelper(context);    }    public void insert(Account account){        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){        int count=db.delete("account","_id=?",new String[] {id+""});        db.close();        return count;    }    public int update(Account account){        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(){        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;    }}

六、编写界面交互代码（main_activity）
public class MainActivity extends AppCompatActivity {    private List<Account> list;    private AccountDao dao;    private EditText nameET;    private EditText balanceET;    private MyAdapter adapter;    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("");    }    public 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;        }        @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) {                DialogInterface.OnClickListener listener=new 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.setNegativeButton("取消",null);                    builder.setPositiveButton("确定",listener);                    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();        }    }}
上面的代码中我们引用了一个AlertDialog，并用Builder方法形成了一个对象链，通过一系列的设置方法，
构造出我们需要的对话框，然 后调用show方法显示出来，
在onCreate方法中调用，只需传入this即 可。

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