Android 案例---SQLite数据库的学习

本次博文通过创建一个购物车像购物车中添加商品 并对商品进行删除来实现对SQLite 数据库的学习

用户界面

布局文件
ativity_main.xml 代码

<?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=".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:hint="@string/et_name"            android:layout_weight="1"            android:inputType="textPersonName"            />        <EditText            android:id="@+id/moneyET"            android:layout_width="0dp"            android:layout_height="wrap_content"            android:hint="@string/et_money"            android:layout_weight="1"            android:inputType="number"/>        <ImageView            android:id="@+id/addIV"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:src="@android:drawable/ic_input_add"            android:onClick="add"/>    </LinearLayout>    <ListView        android:id="@+id/accountLV"        android:layout_width="match_parent"        android:layout_height="match_parent"        android:layout_below="@id/addLL"        ></ListView></LinearLayout>

listview.xml

<?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:layout_width="0dp"        android:layout_height="wrap_content"        android:layout_weight="1"        android:text="13"        android:textColor="#000000"        android:textSize="20sp"        android:id="@+id/idTV"/>    <TextView        android:layout_width="0dp"        android:layout_height="wrap_content"        android:layout_weight="2"        android:text="PQ"        android:textColor="#000000"        android:textSize="20sp"        android:id="@+id/nameTV"/>    <TextView        android:layout_width="0dp"        android:layout_height="wrap_content"        android:layout_weight="2"        android:text="12345"        android:textColor="#000000"        android:textSize="20sp"        android:id="@+id/moneyTV"/>    <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:layout_marginBottom="2dp"            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

Account(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，所以在bean包里边存放Javabean类。)

package com.example.administrator.displaygoods.bean;/** * Created by Administrator on 2017/4/17. */public class Account {    private Long id;    private String name;    private Integer money;    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 getMoney() {        return money;    }    public void setMoney(Integer money) {        this.money = money;    }    public Account(Long id,String name,Integer money){        super();        this.id=id;        this.name=name;        this.money=money;    }    public Account(String name,Integer money){        super();        this.name=name;        this.money=money;    }    public Account(){        super();    }    public String toString(){        return "[序号："+id+",商品名称："+name+",余额："+money+"]";    }}

MainActivity(数据库的操作完成后需要界面与数据库进行交互，用于实现数据库中的数据已ListView的形式展现在界面上)

package com.example.administrator.displaygoods;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.ListView;import android.widget.TextView;import android.widget.Toast;import com.example.administrator.displaygoods.bean.Account;import com.example.administrator.displaygoods.dao.AccountDao;import java.util.List;public class MainActivity extends AppCompatActivity {    //需要适配的数据集合    private List<Account> list;    //数据库增删改查操作类    private AccountDao dao;    //输入姓名的EditText    private EditText nameET;    //输入金额的EditText    private EditText moneyET;    //适配器    private MyAdapter adapter;    //List View    private ListView accountLV;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        //初始化控件        initView();        dao = new AccountDao(this);        //从数据库查询出所有数据        list = dao.queryAll();        adapter = new MyAdapter();        accountLV.setAdapter(adapter);  //给ListView添加适配器(自动把数据生成条目)    }    //初始化控件    private void initView() {        accountLV = (ListView) findViewById(R.id.accountLV);        nameET = (EditText) findViewById(R.id.nameET);        moneyET = (EditText) findViewById(R.id.moneyET);        //添加监听器,监听条目点击事件        accountLV.setOnItemClickListener(new MyOnItemClickListener());    }    //activity_main.xml对应ImageView的点击事件出发的方法    public void add(View v) {        String name = nameET.getText().toString().trim();        String money = moneyET.getText().toString().trim();        //三目运算money.equals("")则等于0        //如果money不是空字符串,则进行类型转换        Account a = new Account(name, money.equals("") ? 0 : Integer.parseInt(money));        dao.insert(a);//插入数据库        list.add(a);  //插入集合        adapter.notifyDataSetChanged();  //刷新界面        //选中最后一个        accountLV.setSelection(accountLV.getCount() - 1);        nameET.setText("");        moneyET.setText("");    }    //自定义一个适配器(把数据装到ListView的工具)    private class MyAdapter extends BaseAdapter {        public int getCount() {      //获取条目总数            return list.size();        }        public Object getItem(int position) {    //根据位置获取对象            return list.get(position);        }        public long getItemId(int position) {    //根据位置获取id            return position;        }        //获取一个条目视图        public View getView(int position, View convertView, ViewGroup parent) {            //重用convertView            View item = convertView != null ? convertView : View.inflate(getApplicationContext(), R.layout.listview, null);            //获取该试图中的TextView            TextView idTV = (TextView) item.findViewById(R.id.idTV);            TextView nameTV = (TextView) item.findViewById(R.id.nameTV);            TextView moneyTV = (TextView) item.findViewById(R.id.moneyTV);            //根据当前位置获取Account对象            final Account a = list.get(position);            //把Account对象中的数据放到TextView中            idTV.setText(a.getId() + "");            nameTV.setText(a.getName());            moneyTV.setText(a.getMoney() + "");            ImageView upIV = (ImageView) item.findViewById(R.id.upIV);            ImageView downIV = (ImageView) item.findViewById(R.id.downIV);            ImageView deleteIV = (ImageView) item.findViewById(R.id.deleteIV);            //向上箭头的点击事件触发的方法            upIV.setOnClickListener(new View.OnClickListener() {                @Override                public void onClick(View v) {                    a.setMoney(a.getMoney() + 1);                    notifyDataSetChanged();                    dao.update(a);                }            });            //向下箭头的点击事件触发的方法            downIV.setOnClickListener(new View.OnClickListener() {                @Override                public void onClick(View v) {                    a.setMoney(a.getMoney() - 1);                    notifyDataSetChanged();                    dao.update(a);                }            });            //删除图片的点击事件触发的方法            deleteIV.setOnClickListener(new View.OnClickListener() {                @Override                public void onClick(View v) {                    //删除数据之前先弹出一个对话框                    android.content.DialogInterface.OnClickListener listener = new android.content.DialogInterface.OnClickListener() {                        public void onClick(DialogInterface dialog, int which) {                            list.remove(a);      //从集合中删除                            dao.delete(a.getId()); //从数据库中删除                            notifyDataSetChanged(); //刷新界面                        }                    };                    //创建对话框                    AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);                    builder.setTitle("确定要删除吗?");  //设置标题                    //设置确定按钮的文本以及监听器                    builder.setPositiveButton("确定", listener);                    builder.setNegativeButton("取消", null);   //设置取消按钮                    builder.show();    //显示对话框                }            });            return item;        }    }    //ListView 的Item点击事件    private class MyOnItemClickListener implements AdapterView.OnItemClickListener {        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {            //获取点击位置上的数据            Account a = (Account) parent.getItemAtPosition(position);            Toast.makeText(getApplicationContext(), a.toString(), Toast.LENGTH_SHORT).show();        }    }}

MyHelper

package com.example.administrator.displaygoods.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{    public MyHelper(Context context) {        super(context, "product.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),money INTEGER)");    }    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {        System.out.println("onUpgrade");    }}

AccountDao (创建数据操作逻辑类)

package com.example.administrator.displaygoods.dao;import android.content.ContentValues;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import com.example.administrator.displaygoods.bean.Account;import java.util.ArrayList;import java.util.List;/** * Created by Administrator on 2017/4/17. */public class AccountDao {    private MyHelper helper;    public AccountDao(Context context){        //创建Dao时，创建Helper        helper=new MyHelper(context);    }    //插入    public void insert(Account account){        //获取数据库对象        SQLiteDatabase db=helper.getWritableDatabase();        //用来装载要插入的数据的Map<列名，列的值>        ContentValues values=new ContentValues();        values.put("name",account.getName());        values.put("money",account.getMoney());        //向account表插入数据values        long id=db.insert("account",null,values);        account.setId(id);  //得到id        db.close();         //关闭数据库    }    //删除    public int delete(long id){        SQLiteDatabase db=helper.getWritableDatabase();        //按条件删除        int count=db.delete("account","id=?",new String[]{id+""});        db.close();        return count;    }    //更新    public  int update(Account account ){        SQLiteDatabase db=helper.getWritableDatabase();        ContentValues values=new ContentValues();        values.put("name",account.getName());        values.put("money",account.getMoney());        int count =db.update("account",values,"id=?",                new String []{account.getId()+""});  //更新并得到行数        db.close();        return count;    }    public List<Account> queryAll(){        SQLiteDatabase db=helper.getReadableDatabase();        Cursor c=db.query("account",null,null,null,null,null,"money DESC");        List<Account> list=new ArrayList<Account>();        while(c.moveToNext()){            //可以根据列名获取索引            long id=c.getLong(c.getColumnIndex("id"));            String name=c.getString(1);            int money=c.getInt(2);            list.add(new Account(id,name,money));        }        c.close();        db.close();        return list;    }}