Android SQLite 数据库存储

1、创建数据库

      Android 为了让我们能够更加方便地管理数据库，专门提供了一个 SQLiteOpenHelper 帮助类，借助这个类就可以非常简单地对数据库进行创建和升级。首先你要知道 SQLiteOpenHelper 是一个抽象类，这意味着如果我们想要使用它的话， 就需要创建一个自己的帮助类去继承它。SQLiteOpenHelper 中有两个抽象方法，分别是 onCreate()和 onUpgrade()，我们必须在自己的帮助类里面重写这两个方法，然后分别在这
两个方法中去实现创建、升级数据库的逻辑。 SQLiteOpenHelper 中还有两个非 常重要的实例方法， getReadableDatabase()和 getWritableDatabase()。这两个方法都可以创建或打开一个现有的数据库（如果数据库已存 在则直接打开，否则创建一个新的数据库），并返回一个可对数据库进行读写操作的对象。 不同的是，当数据库不可写入的时候（如磁盘空间已满）getReadableDatabase()方法返回的 对象将以只读的方式去打开数据库，而etWritableDatabase()方法则将出现异常。SQLiteOpenHelper
中有两个构造方法可供重写，一般使用参数少一点的那个构造方法即 可。这个构造方法中接收四个参数，第一个参数是 Context，这个没什么好说的，必须要有 它才能对数据库进行操作。第二个参数是数据库名，创建数据库时使用的就是这里指定的名 称。第三个参数允许我们在查询数据的时候返回一个自定义的 Cursor，一般都是传入 null。 第四个参数表示当前数据库的版本号，可用于对数据库进行升级操作。构建出 SQLiteOpenHelper 的实例之后，再调用它的 getReadableDatabase()或 getWritableDatabase()
方法就能够创建数据库了，数据库文件会存放在/data/data/<package name>/databases/目录下。 此时，重写的 onCreate()方法也会得到执行，所以通常会在这里去处理一些创建表的逻辑。

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity" >

<Button
android:id="@+id/create_database"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Create database" />

<Button
android:id="@+id/add_data"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Add data" />

<Button
android:id="@+id/update_data"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Upadte data" />

<Button
android:id="@+id/delete_data"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Delete data" />

<Button
android:id="@+id/query_data"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Query data" />

<Button
android:id="@+id/replace_data"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Replace data" />

</LinearLayout>book.java
package cn.bzu.bztc.databasetest.entity;

public class Book {
private int id;
private String author;
private float price;
private int pages;
private String name;
public Book(){
super();
}
public Book( String author, float price, int pages, String name) {
super();
this.author = author;
this.price = price;
this.pages = pages;
this.name = name;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getAuthor() {
return author;
}
public void setAuthor(String author) {
this.author = author;
}
public float getPrice() {
return price;
}
public void setPrice(float price) {
this.price = price;
}
public int getPages() {
return pages;
}
public void setPages(int pages) {
this.pages = pages;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "Book [id=" + id + ", author=" + author + ", price=" + price
+ ", pages=" + pages + ", name=" + name + "]";
}

}


BookDao.java
package cn.bzu.bztc.databasetest.dao;

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 cn.bzu.bztc.databasetest.db.MyDatabaseHelper;
import cn.bzu.bztc.databasetest.entity.Book;

public class BookDao {
private MyDatabaseHelper myDatabaseHelper;
private SQLiteDatabase sqLiteDatabase;
public BookDao(Context context){
myDatabaseHelper=new MyDatabaseHelper(context, "bookdb", null, 1);
}
public void add(Book book){
sqLiteDatabase=myDatabaseHelper.getWritableDatabase();
ContentValues contentValues=new ContentValues();
contentValues.put("author", book.getAuthor());
contentValues.put("price", book.getPrice());
contentValues.put("pages", book.getPages());
contentValues.put("name", book.getName());
sqLiteDatabase.insert("book", "author", contentValues);
}
public List<Book> getAllBooks(){
List<Book> books=new ArrayList<Book>();
sqLiteDatabase=myDatabaseHelper.getReadableDatabase();
Cursor cursor=sqLiteDatabase.query("book", null, null, null, null, null, null);
if(cursor.moveToFirst()){
do{
String author=cursor.getString(cursor.getColumnIndex("author"));
float price=cursor.getFloat(cursor.getColumnIndex("price"));
int pages=cursor.getInt(cursor.getColumnIndex("pages"));
String name=cursor.getString(cursor.getColumnIndex("name"));
Book book=new Book(author,price,pages,name);
}while(cursor.moveToNext());
}
return books;
}

}
MyDatabaseHelper.java
package cn.bzu.bztc.databasetest.db;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.widget.Toast;

public class MyDatabaseHelper extends SQLiteOpenHelper{

public static final String CREATE_BOOK="create table book(" +
"id integer primary key autoincrement," +
"author text," +
"price real," +
"pages integer," +
"name text," +
"category_id integer)";
public static final String CREATE_CATEGORY="create table Category(" +
"id integer primary key autoincrement," +
"category_name text," +
"category_code integer)";
private Context mContext;

public MyDatabaseHelper(Context context, String name,
CursorFactory factory, int version) {
super(context, name, factory, version);
// TODO Auto-generated constructor stub
//mContext=context;
}

@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
// TODO Auto-generated method stub
sqLiteDatabase.execSQL(CREATE_BOOK);
sqLiteDatabase.execSQL(CREATE_CATEGORY);
Toast.makeText(mContext, "Create succeeded", Toast.LENGTH_SHORT).show();

}

@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
/*db.execSQL("drop table if exists Book");
db.execSQL("drop table if exists Category");
onCreate(db);
*/
/*switch (oldVersion){
case 1:
sqLiteDatabase.execSQL(CREATE_CATEGORY);
case 2:
sqLiteDatabase.execSQL("alter table Book add column category_id integer");
default:
}*/
sqLiteDatabase.execSQL("drop table if exits Book");
sqLiteDatabase.execSQL("drop table if exits CateGory");
onCreate(sqLiteDatabase);
}

}


MainActivity.java
package cn.bzu.bztc.databasetest;

import cn.bzu.bztc.databasetest.dao.BookDao;
import cn.bzu.bztc.databasetest.db.MyDatabaseHelper;
import android.os.Bundle;
import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity {
private BookDao bookDao;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bookDao=new BookDao(this);
}
public void addData(View view){

}
/*private MyDatabaseHelper dbHelper;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dbHelper=new MyDatabaseHelper(this, "BookStore.db", null, 2);
Button createDatabase=(Button) findViewById(R.id.create_database);
createDatabase.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
dbHelper.getWritableDatabase();

}
});
//Button addData=(Button) findViewById(R.id.add_data);
addData.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
SQLiteDatabase db=dbHelper.getWritableDatabase();
ContentValues values=new ContentValues();
values.put("name", "The Da Vinci Code");
values.put("author", "Dan Brown");
values.put("pages", 454);
values.put("price", 16.95);
db.insert("Book", null, values);
}
});
Button updateData=(Button) findViewById(R.id.update_data);
updateData.setOnClickListener(new OnClickListener() {

@Override
public v
a59e
oid onClick(View v) {
// TODO Auto-generated method stub
SQLiteDatabase db=dbHelper.getWritableDatabase();
ContentValues values=new ContentValues();
values.put("price", 10.99);
db.update("Book", values, "name=?", new String[]{"The Da Vinci Code"});

}
});
Button deleteButton=(Button) findViewById(R.id.delete_data);
deleteButton.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
SQLiteDatabase db=dbHelper.getWritableDatabase();
db.delete("Book", "pages>?", new String[]{"500"});
}
});
Button queryButton=(Button) findViewById(R.id.query_data);
queryButton.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
SQLiteDatabase db=dbHelper.getWritableDatabase();
Cursor cursor=db.query("Book", null, null, null, null, null, null);
if(cursor.moveToFirst()){
do{
String name=cursor.getString(cursor.getColumnIndex("name"));
String author=cursor.getString(cursor.getColumnIndex("author"));
int pages=cursor.getInt(cursor.getColumnIndex("pages"));
double price=cursor.getDouble(cursor.getColumnIndex("price"));
Log.d("MainActivity", "book name is "+name);
Log.d("MainActivity", "book author is "+author);
Log.d("MainActivity", "book pages is "+ pages);
Log.d("MainActivity", "book price is "+ price);
}while(cursor.moveToNext());
}
cursor.close();
}
});
Button replaceData=(Button) findViewById(R.id.replace_data);
replaceData.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
SQLiteDatabase db=dbHelper.getWritableDatabase();
db.beginTransaction();
try{
db.delete("Book", null, null);
if(true){
throw new NullPointerException();
}
ContentValues values =new ContentValues();
values.put("name", "Game of Thrones");
values.put("author", "George Martin");
values.put("pages", 720);
values.put("price", 20.85);
db.insert("Book", null, values);
db.setTransactionSuccessful();
}catch (Exception e){
e.printStackTrace();
}finally{
db.endTransaction();
}
}
});
}*/

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

}
BookDaoTest.java
package cn.bzu.bztc.databasetest.test;

import java.util.List;

import cn.bzu.bztc.databasetest.dao.BookDao;
import cn.bzu.bztc.databasetest.entity.Book;
import android.test.AndroidTestCase;

public class BookDaoTest extends AndroidTestCase{
public void testAdd(){
BookDao bookDao=new BookDao(getContext());
bookDao.add(new Book("耿祥义",32.8f,328,"Java"));
}
public void testGetAllBooks(){
BookDao bookDao=new BookDao(getContext());
List<Book> books=bookDao.getAllBooks();
System.out.println(books);
}

}