商品展示的案例

在开发中需要用到数据库操作，接下来通过商品展示来实现增删改查。

一，首先进行页面的基础布局，下面是代码

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_show"
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="com.example.bz0209.myapplication.Show">
<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/blanceET"
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/addTV"
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"
/>
</RelativeLayout>

二，还需要编写ListView来建立布局，

<?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: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:textColor="#000000"
android:textSize="20sp"
android:text="12345"
/>

<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:layout_marginBottom="2dp"
android:src="@android:drawable/ic_menu_delete"
/>
</LinearLayout>

三，接下来便是创建数据库，定义一个MyHelper继承SQLiteOpenHelper,

package com.example.bz0209.myapplication.dao;

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

/**
* Created by Administrator on 2017/4/27.
*/

public class MyHelper extends SQLiteOpenHelper {
public MyHelper(Context context){
super(context,"itcast.db",null,2);
}
@Override
public void onCreate(SQLiteDatabase db) {
System.out.println("onCreat");
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bean包存放Javabean类，再定义个Account

package com.example.bz0209.myapplication.bean;

/**
* Created by Administrator on 2017/4/27.
*/

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.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+"]";
}
}

五，下面便是建立AccountDao来用于数据操作

package com.example.bz0209.myapplication.dao;

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

import com.example.bz0209.myapplication.bean.Account;

import java.util.ArrayList;
import java.util.List;

/**
* Created by Administrator on 2017/4/27.
*/

public class AccountDao {
private MyHelper helper;
public AccountDao(Context context){
helper=new MyHelper(context);
}
public void insert(Account account){
SQLiteDatabase db=helper.getReadableDatabase();
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 updata(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.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;
}
}

六，页面交互

package com.example.bz0209.myapplication;

import com.example.bz0209.myapplication.bean.Account;

import android.content.DialogInterface;
import android.os.Build;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
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 com.example.bz0209.myapplication.dao.AccountDao;

import java.util.List;

public class Show extends AppCompatActivity {

private List<Account> list;
private AccountDao dao;
private EditText nameET;
private EditText balanceET;
private MyAdapter myAdapter;
private ListView accountLV;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_show);
initView();
dao=new AccountDao(this);
list=dao.queryAll();
myAdapter=new MyAdapter();
accountLV.setAdapter(myAdapter);
}

private void initView() {
accountLV = (ListView) findViewById(R.id.accountLV);
nameET = (EditText) findViewById(R.id.blanceET);
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);
myAdapter.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.updata(a);
}
});
downIV.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
a.setBalance(a.getBalance() - 1);
notifyDataSetChanged();
dao.updata(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(Show.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_SHORT).show();
}
}
}