SQLite数据库--案例：商品展示

来源：互联网发布：js改变display属性编辑：程序博客网时间：2024/05/17 21:45

导语：在实际开发中，往往避免不了在界面上操作数据库。例如，开发一个购物车，需要将购物车中的商品以列表的形式展示，并且还需要对购物车中的商品进行增删改查操作。要实现这些功能就需要使用ListView和SQLite数据库。接下来通过一个 “商品展示“案例来实现在界面上操作数据库。

1.创建程序

首先创建一个名为“商品展示”的应用程序。添加3个TextView,分别用于显示数据库中的某条数据的id，商品名称，金额。三个ImageView用于增加金额，减少金额，删除数据。设计用户交互界面如图：

<?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:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="product.itcast.cn.shangpinzhanshi.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" />
</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

代码展示如下：

<?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="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="12345"
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_down_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，因此创建一个名为model的包，
并在该包中定义一个类继承自SQLiteOpenHelper,代码如下：

MyHelper
package product.itcast.cn.shangpinzhanshi.dao;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

/**
* Created by Administrator on 2017/4/17.
*/

public class MyHelper extends SQLiteOpenHelper {
//由于父类没有无参构造函数，所以子类必须指定调用父类哪个有参的构造函数
public MyHelper(Context context) {
super(context, "itcast.db", null, 2);
}
public void onCreate(SQLiteDatabase db) {
System.out.println("onCreate");
db.execSQL("CREATE TABLE account(_id INTEGER PRIMARY KEY AUTOINCREMENT,name VARCHAR(20),balance INTEGER");
}
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。
因此在model包下定义一个类Account,代码如下：

package product.itcast.cn.shangpinzhanshi.bean;

/**
* Created by Administrator on 2017/4/17.
*/

public class Account {
private Long id;
private String name;
private Integer balance;
public Long getId() {
return 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model包下创建一个AccountDao类用于操作数据，来实现数据库的增、删、改、查。代码如下：

AccountDao
package product.itcast.cn.shangpinzhanshi.dao;

import android.accounts.Account;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

import java.util.List;

import static android.R.id.list;

/**
* Created by Administrator 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 {
db = helper.getReadableDatabase();
Cursor c = db.query("account", null, null, null, null, null, "balance DESC");
while (c.moveToNext()) {
long id = c.getLong(c.getColumnIndex("_id"));
String name = c.getString(1);
int balance = c.getInt(2);
queryAll.add();
}
c.close();
db.close();
return list();
}
}
}

6.编辑界面交互代码MainActivity

public class MainActivity extends Activity {
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.lv01);
nameET=(EditText)findViewById(R.id.et01);
balanceET=(EditText)findViewById(R.id.et02);
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{

@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.listview_itemd,null);
TextView tvid=(TextView)item.findViewById(R.id.tvid);
TextView tvname=(TextView)item.findViewById(R.id.tvname);
TextView tvbalance =(TextView)item.findViewById(R.id.tvprice);
final Account a=list.get(position);
tvid.setText(a.getId()+"");
tvname.setText(a.getName());
tvbalance.setText(a.getBalance()+"");
ImageView ivup=(ImageView)item.findViewById(R.id.ivup);
ImageView ivdown=(ImageView)item.findViewById(R.id.ivdown);
ImageView ivdelete=(ImageView)item.findViewById(R.id.ivdelete);
ivup.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
a.setBalance(a.getBalance()+1);
notifyDataSetChanged();
dao.update(a);
}
});
ivdown.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
a.setBalance(a.getBalance()-1);
notifyDataSetChanged();
dao.update(a);
}
});
ivdelete.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
android.content.DialogInterface.OnClickListener listener=new android.content.DialogInterface.OnClickListener(){
public void onClick(DialogInterface dialogInterface,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();
}
}
}

1.ListView的setOnClickListener()方法：该方法用于监听Item的点击事件，在使用过该方法时需要传入一个OnItemClickListener的实现类对象，并且需要实现OnitemClick 方法。当点击ListView的Item时就会触发Item的点击事件然后会回调OnItemClick()方法。
2..ListView的setSelection()方法：该方法的作用是设置当前选中的条目。价格当前屏幕一屏只能显示10条数据，当添加到1条数据时，调用此方法就会将第11条数据显示在屏幕上，将第1条数据滑出屏幕外。
3.Adapter的notifyDataSetChange()方法：该方法是用于重新数据，当数据适配器中的内容发生变化时，会调用此方法，重新执行BaseAdapter中的getView()方法。

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