Android SQLite案例

重点掌握execSQL()和rawQuery()方法,rawQuery()方法用于执行select语句。

SQLiteOpenHelper,实现了onCreate和onUpgrade方法。

第一次创建之后接着会调用onCreate方法(我们在这里创建了数据表),之后onCreate就不再被调用。

DatabaseHelper类:

package com.example.hellodatabases;

import android.content.Context;
import android.database.DatabaseErrorHandler;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

//参考:http://blog.csdn.net/liuhe688/article/details/6715983

public class DatabaseHelper extends SQLiteOpenHelper// 继承SQLiteOpenHelper类
{

    // 数据库版本号
    private static final int DATABASE_VERSION = 1;
    // 数据库名
    private static final String DATABASE_NAME = "TestDB.db";

    // 数据表名,一个数据库中可以有多个表(虽然本例中只建立了一个表)
    public static final String TABLE_NAME = "PersonTable";

    // 构造函数,调用父类SQLiteOpenHelper的构造函数
    public DatabaseHelper(Context context, String name, CursorFactory factory,
            int version, DatabaseErrorHandler errorHandler)
    {
        super(context, name, factory, version, errorHandler);

    }

    public DatabaseHelper(Context context, String name, CursorFactory factory,
            int version)
    {
        super(context, name, factory, version);
        // SQLiteOpenHelper的构造函数参数:
        // context:上下文环境
        // name:数据库名字
        // factory:游标工厂(可选)
        // version:数据库模型版本号
    }

    public DatabaseHelper(Context context)
    {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);

        // 数据库实际被创建是在getWritableDatabase()或getReadableDatabase()方法调用时
        Log.d(AppConstants.LOG_TAG, "DatabaseHelper Constructor");
        // CursorFactory设置为null,使用系统默认的工厂类
    }

    // 继承SQLiteOpenHelper类,必须要覆写的三个方法:onCreate(),onUpgrade(),onOpen()
    @Override
    public void onCreate(SQLiteDatabase db)
    {
        // 调用时间:数据库第一次创建时onCreate()方法会被调用

        // onCreate方法有一个 SQLiteDatabase对象作为参数,根据需要对这个对象填充表和初始化数据
        // 这个方法中主要完成创建数据库后对数据库的操作

        Log.d(AppConstants.LOG_TAG, "DatabaseHelper onCreate");

        // 构建创建表的SQL语句(可以从SQLite Expert工具的DDL粘贴过来加进StringBuffer中)
        StringBuffer sBuffer = new StringBuffer();

        sBuffer.append("CREATE TABLE [" + TABLE_NAME + "] (");
        sBuffer.append("[_id] INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, ");
        sBuffer.append("[name] TEXT,");
        sBuffer.append("[age] INTEGER,");
        sBuffer.append("
TEXT)
"); // 执行创建表的SQL语句 db.execSQL(sBuffer.toString()); // 即便程序修改重新运行,只要数据库已经创建过,就不会再进入这个onCreate方法 } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // 调用时间:如果DATABASE_VERSION值被改为别的数,系统发现现有数据库版本不同,即会调用onUpgrade // onUpgrade方法的三个参数,一个 SQLiteDatabase对象,一个旧的版本号和一个新的版本号 // 这样就可以把一个数据库从旧的模型转变到新的模型 // 这个方法中主要完成更改数据库版本的操作 Log.d(AppConstants.LOG_TAG, "DatabaseHelper onUpgrade"); db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME); onCreate(db); // 上述做法简单来说就是,通过检查常量值来决定如何,升级时删除旧表,然后调用onCreate来创建新表 // 一般在实际项目中是不能这么做的,正确的做法是在更新数据表结构时,还要考虑用户存放于数据库中的数据不丢失 } @Override public void onOpen(SQLiteDatabase db) { super.onOpen(db); // 每次打开数据库之后首先被执行 Log.d(AppConstants.LOG_TAG, "DatabaseHelper onOpen"); } }

Person类:

package com.example.hellodatabases;

public class Person
{
    public int _id;
    public String name;
    public int age;
    public String info;

    public Person()
    {
    }

    public Person(String name, int age, String info)
    {
        this.name = name;
        this.age = age;
        this.info = info;
    }

}

管理类DBManager:

package com.example.hellodatabases;

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

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

//参考:http://blog.csdn.net/liuhe688/article/details/6715983
public class DBManager
{
    private DatabaseHelper helper;
    private SQLiteDatabase db;

    public DBManager(Context context)
    {
        Log.d(AppConstants.LOG_TAG, "DBManager --> Constructor");
        helper = new DatabaseHelper(context);
        // 因为getWritableDatabase内部调用了mContext.openOrCreateDatabase(mName, 0,
        // mFactory);
        // 所以要确保context已初始化,我们可以把实例化DBManager的步骤放在Activity的onCreate里
        db = helper.getWritableDatabase();
    }

    /**
     * add persons
     * 
     * @param persons
     */
    public void add(List<Person> persons)
    {
        Log.d(AppConstants.LOG_TAG, "DBManager --> add");
        // 采用事务处理,确保数据完整性
        db.beginTransaction(); // 开始事务
        try
        {
            for (Person person : persons)
            {
                db.execSQL("INSERT INTO " + DatabaseHelper.TABLE_NAME
                        + " VALUES(null, ?, ?, ?)", new Object[] { person.name,
                        person.age, person.info });
                // 带两个参数的execSQL()方法,采用占位符参数?,把参数值放在后面,顺序对应
                // 一个参数的execSQL()方法中,用户输入特殊字符时需要转义
                // 使用占位符有效区分了这种情况
            }
            db.setTransactionSuccessful(); // 设置事务成功完成
        }
        finally
        {
            db.endTransaction(); // 结束事务
        }
    }

    /**
     * update person's age
     * 
     * @param person
     */
    public void updateAge(Person person)
    {
        Log.d(AppConstants.LOG_TAG, "DBManager --> updateAge");
        ContentValues cv = new ContentValues();
        cv.put("age", person.age);
        db.update(DatabaseHelper.TABLE_NAME, cv, "name = ?",
                new String[] { person.name });
    }

    /**
     * delete old person
     * 
     * @param person
     */
    public void deleteOldPerson(Person person)
    {
        Log.d(AppConstants.LOG_TAG, "DBManager --> deleteOldPerson");
        db.delete(DatabaseHelper.TABLE_NAME, "age >= ?",
                new String[] { String.valueOf(person.age) });
    }

    /**
     * query all persons, return list
     * 
     * @return List<Person>
     */
    public List<Person> query()
    {
        Log.d(AppConstants.LOG_TAG, "DBManager --> query");
        ArrayList<Person> persons = new ArrayList<Person>();
        Cursor c = queryTheCursor();
        while (c.moveToNext())
        {
            Person person = new Person();
            person._id = c.getInt(c.getColumnIndex("_id"));
            person.name = c.getString(c.getColumnIndex("name"));
            person.age = c.getInt(c.getColumnIndex("age"));
            person.info = c.getString(c.getColumnIndex("info"));
            persons.add(person);
        }
        c.close();
        return persons;
    }

    /**
     * query all persons, return cursor
     * 
     * @return Cursor
     */
    public Cursor queryTheCursor()
    {
        Log.d(AppConstants.LOG_TAG, "DBManager --> queryTheCursor");
        Cursor c = db.rawQuery("SELECT * FROM " + DatabaseHelper.TABLE_NAME,
                null);
        return c;
    }

    /**
     * close database
     */
    public void closeDB()
    {
        Log.d(AppConstants.LOG_TAG, "DBManager --> closeDB");
        // 释放数据库资源
        db.close();
    }

}

Activity:

HelloDBActivity

package com.example.hellodatabases;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import android.app.Activity;
import android.database.Cursor;
import android.database.CursorWrapper;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.SimpleCursorAdapter;

//参考:http://blog.csdn.net/liuhe688/article/details/6715983

public class HelloDBActivity extends Activity
{
    private DBManager dbManager;
    private ListView listView;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_hello_db);

        listView = (ListView) findViewById(R.id.listView);
        // 初始化DBManager
        dbManager = new DBManager(this);

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu)
    {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.hello_db, menu);
        return true;
    }

    @Override
    protected void onDestroy()
    {
        super.onDestroy();
        dbManager.closeDB();// 释放数据库资源
    }

    public void add(View view)
    {
        ArrayList<Person> persons = new ArrayList<Person>();

        Person person1 = new Person("Ella", 22, "lively girl");
        Person person2 = new Person("Jenny", 22, "beautiful girl");
        Person person3 = new Person("Jessica", 23, "sexy girl");
        Person person4 = new Person("Kelly", 23, "hot baby");
        Person person5 = new Person("Jane", 25, "a pretty woman");

        persons.add(person1);
        persons.add(person2);
        persons.add(person3);
        persons.add(person4);
        persons.add(person5);

        dbManager.add(persons);
    }

    public void update(View view)
    {
        // 把Jane的年龄改为30(注意更改的是数据库中的值,要查询才能刷新ListView中显示的结果)
        Person person = new Person();
        person.name = "Jane";
        person.age = 30;
        dbManager.updateAge(person);
    }

    public void delete(View view)
    {
        // 删除所有三十岁以上的人(此操作在update之后进行,Jane会被删除(因为她的年龄被改为30))
        // 同样是查询才能查看更改结果
        Person person = new Person();
        person.age = 30;
        dbManager.deleteOldPerson(person);
    }

    public void query(View view)
    {
        List<Person> persons = dbManager.query();
        ArrayList<Map<String, String>> list = new ArrayList<Map<String, String>>();
        for (Person person : persons)
        {
            HashMap<String, String> map = new HashMap<String, String>();
            map.put("name", person.name);
            map.put("info", person.age + " years old, " + person.info);
            list.add(map);
        }
        SimpleAdapter adapter = new SimpleAdapter(this, list,
                android.R.layout.simple_list_item_2, new String[] { "name",
                        "info" }, new int[] { android.R.id.text1,
                        android.R.id.text2 });
        listView.setAdapter(adapter);
    }

    @SuppressWarnings("deprecation")
    public void queryTheCursor(View view)
    {
        Cursor c = dbManager.queryTheCursor();
        startManagingCursor(c); // 托付给activity根据自己的生命周期去管理Cursor的生命周期
        CursorWrapper cursorWrapper = new CursorWrapper(c)
        {
            @Override
            public String getString(int columnIndex)
            {
                // 将简介前加上年龄
                if (getColumnName(columnIndex).equals("info"))
                {
                    int age = getInt(getColumnIndex("age"));
                    return age + " years old, " + super.getString(columnIndex);
                }
                return super.getString(columnIndex);
            }
        };
        // 确保查询结果中有"_id"列
        SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,
                android.R.layout.simple_list_item_2, cursorWrapper,
                new String[] { "name", "info" }, new int[] {
                        android.R.id.text1, android.R.id.text2 });
        ListView listView = (ListView) findViewById(R.id.listView);
        listView.setAdapter(adapter);
    }

}

布局:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:onClick="add"
        android:text="add" />

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:onClick="update"
        android:text="update" />

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:onClick="delete"
        android:text="delete" />

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:onClick="query"
        android:text="query" />

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:onClick="queryTheCursor"
        android:text="queryTheCursor" />

    <ListView
        android:id="@+id/listView"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

 常量:

package com.example.hellodatabases;

public class AppConstants
{
    public static final String LOG_TAG="Hello DB";

}

官网Training: Saving Data in SQL Databases

  http://developer.android.com/training/basics/data-storage/databases.html

  Android中SQLite应用详解:

  http://blog.csdn.net/liuhe688/article/details/6715983

  关于Cursor类的介绍:

  http://www.cnblogs.com/TerryBlog/archive/2010/07/05/1771459.html

  Android 小项目之–SQLite 使用法门 (附源码):

  http://www.cnblogs.com/TerryBlog/archive/2010/06/12/1757166.html

    原文作者:sqlite
    原文地址: https://www.cnblogs.com/zhujiabin/p/4219977.html
    本文转自网络文章,转载此文章仅为分享知识,如有侵权,请联系博主进行删除。
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