商品展示案例

商品展示运行界面如下：



1.在布局文件main_activity.xml创建如下界面：



代码如下：

<?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: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.yx.example01.MainActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/addLL"
android:orientation="horizontal">
<EditText
android:layout_width="0dp"
android:layout_height="wrap_content"
android:id="@+id/nameET"
android:layout_weight="1"
android:hint="商品名称"
android:inputType="textPersonName"/>
<EditText
android:layout_width="0dp"
android:layout_height="wrap_content"
android:id="@+id/balanceET"
android:layout_weight="1"
android:hint="金额"
android:inputType="number"/>
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/addIV"
android:src="@android:drawable/ic_input_add"/>
</LinearLayout>
<ListView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/accountLV"
android:layout_below="@id/addLL"><
4000
;/ListView>

</LinearLayout>

2.运用List View创建布局，界面如下



在res文件夹下创建item.xml，代码如下：

<?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="match_parent">
<TextView
android:layout_width="0dp"
android:layout_weight="1"
android:layout_height="wrap_content"
android:text="13"
android:textColor="#000000"
android:textSize="20sp"
android:id="@+id/idTV"/>
<TextView
android:layout_width="0dp"
android:layout_weight="2"
android:layout_height="wrap_content"
android:text="PQ"
android:textColor="#000000"
android:singleLine="true"
android:textSize="20sp"
android:id="@+id/nameTV"/>
<TextView
android:layout_width="0dp"
android:layout_weight="2"
android:layout_height="wrap_content"
android:text="12345"
android:textColor="#000000"
android:textSize="20sp"
android:id="@+id/balanceTV"/>
<LinearLayout
android:layout_width="wrap_content"
android:orientation="vertical"
android:layout_height="wrap_content">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="2dp"
android:id="@+id/upIV"
android:src="@android:drawable/arrow_up_float"/>
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/downIV"
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>

3编写Account类和MyHelper类进行数据库的创建和对象的封装,在Java文件夹下的com.example文件夹下创建一个新文件夹，用来保存相应操作类



(1).创建Account类：

package com.example.yx.example01.dao;

public class Account {
private Long id;

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;
}

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 String toString() {
return "[序号: " + id + ", 商品名称: " + name + " 余额: " + balance + "]";
}
}

(2).创建MyHelper类进行数据库创建

package com.example.yx.example01.dao;

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

public class MyHelper extends SQLiteOpenHelper {
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AccountDao类进行CRUD操作

package com.example.yx.example01.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;

public class AccountDao {
private MyHelper myHelper;
public AccountDao(Context context){
myHelper=new MyHelper(context);
}
public void insert(Account account){
SQLiteDatabase db=myHelper.getWritableDatabase();
ContentValues contentValues=new ContentValues();
contentValues.put("name",account.getName());
contentValues.put("balance",account.getBalance());
long id=db.insert("account",null,contentValues);
account.setId(id);
db.close();
}
public int delete(long id){
SQLiteDatabase db=myHelper.getWritableDatabase();
int count=db.delete("acount","id=?",new String[]{id+""});
db.close();
return count;
}
public int update(Account account){
SQLiteDatabase db=myHelper.getWritableDatabase();
ContentValues contentValues=new ContentValues();
contentValues.put("name",account.getName());
contentValues.put("balance",account.getBalance());
int count=db.update("account",contentValues,"id=?",new String[]{account.getId()+""});
db.close();
return count;
}
public List<Account> queryAll(){
SQLiteDatabase db=myHelper.getWritableDatabase();
Cursor c=db.query("acocunt",null,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;
}
}

5.在MainActivity类中编写用户界面交互代码

package com.example.yx.example01;

import android.content.DialogInterface;
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.AdapterView;
import android.widget.BaseAdapter;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import com.example.yx.example01.dao.Account;
import com.example.yx.example01.dao.AccountDao;

import java.util.List;

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((ListAdapter) adapter);
}
//编写一个初始化控件的方法
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 {
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(){
public void onClick(View v){
a.setBalance(a.getBalance()+1);
notifyDataSetChanged();
dao.update(a);}
});
downIV.setOnClickListener(new View.OnClickListener(){
public void onClick(View v){
a.setBalance(a.getBalance()-1);
notifyDataSetChanged();
dao.update(a);}
});
deleteIV.setOnClickListener(new View.OnClickListener(){
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("Are you sure delete?");
builder.setPositiveButton("sure", listener);
builder.setPositiveButton("no", 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();
}

}

}

编写完用户交互代码就可以在运行界面中进行CRUD操作了。