package com.droid.carson;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import com.quark.jianzhidaren.ApplicationControl;
/**
* @author Joshua 用法： DBHelper dbHelper = new DBHelper(this);
* dbHelper.createDataBase(); SQLiteDatabase db =
* dbHelper.getWritableDatabase(); Cursor cursor = db.query()
* db.execSQL(sqlString); 注意：execSQL不支持带;的多条SQL语句，只能一条一条的执行，晕了很久才明白
* 见execSQL的源码注释 (Multiple statements separated by ;s are not
* supported.) 将把assets下的数据库文件直接复制到DB_PATH，但数据库文件大小限制在1M以下
* 如果有超过1M的大文件，则需要先分割为N个小文件，然后使用copyBigDatabase()替换copyDatabase()
*/
public class DBHelper extends SQLiteOpenHelper {
// 用户数据库文件的版本
private static final int DB_VERSION = 3;
// 数据库文件目标存放路径为系统默认位置，cn.arthur.examples 是你的包名
private static String DB_PATH = ApplicationControl.getInstance().getFilesDir().getPath();
/*
* //如果你想把数据库文件存放在SD卡的话 private static String DB_PATH =
* android.os.Environment.getExternalStorageDirectory().getAbsolutePath() +
* "/arthurcn/drivertest/packfiles/";
*/
private static String DB_NAME = "qm_cities.db";
private static String ASSETS_NAME = "qm_cities.db";
private SQLiteDatabase myDataBase = null;
private final Context myContext;
/**
* 如果数据库文件较大，使用FileSplit分割为小于1M的小文件 此例中分割为 hello.db.101 hello.db.102
* hello.db.103
*/
// 第一个文件名后缀
private static final int ASSETS_SUFFIX_BEGIN = 101;
// 最后一个文件名后缀
private static final int ASSETS_SUFFIX_END = 103;
/**
* 在SQLiteOpenHelper的子类当中，必须有该构造函数
*
* @param context
* 上下文对象
* @param name
* 数据库名称
* @param factory
* 一般都是null
* @param version
* 当前数据库的版本，值必须是整数并且是递增的状态
*/
public DBHelper(Context context, String name, CursorFactory factory,
int version) {
// 必须通过super调用父类当中的构造函数
super(context, name, null, version);
this.myContext = context;
}
public DBHelper(Context context, String name, int version) {
this(context, name, null, version);
}
public DBHelper(Context context, String name) {
this(context, name, DB_VERSION);
}
public DBHelper(Context context) {
this(context, DB_PATH + DB_NAME);
}
public void createDataBase() throws IOException {
boolean dbExist = checkDataBase();
if (dbExist) {
// 数据库已存在，do nothing.
} else {
// 创建数据库
try {
File dir = new File(DB_PATH);
if (!dir.exists()) {
dir.mkdirs();
}
File dbf = new File(DB_PATH + DB_NAME);
if (dbf.exists()) {
dbf.delete();
}
// 复制asseets中的db文件到DB_PATH下
copyDataBase();
SQLiteDatabase.openOrCreateDatabase(dbf, null);
} catch (IOException e) {
throw new Error("数据库创建失败");
}
}
}
// 检查数据库是否有效
private boolean checkDataBase() {
SQLiteDatabase checkDB = null;
String myPath = DB_PATH + DB_NAME;
try {
checkDB = SQLiteDatabase.openDatabase(myPath, null,
SQLiteDatabase.OPEN_READONLY);
} catch (SQLiteException e) {
// database does't exist yet.
}
if (checkDB != null) {
checkDB.close();
}
return checkDB != null ? true : false;
}
/**
* Copies your database from your local assets-folder to the just created
* empty database in the system folder, from where it can be accessed and
* handled. This is done by transfering bytestream.
* */
private void copyDataBase() throws IOException {
// Open your local db as the input stream
InputStream myInput = myContext.getAssets().open(ASSETS_NAME);
// Path to the just created empty db
String outFileName = DB_PATH + DB_NAME;
// Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
// transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer)) > 0) {
myOutput.write(buffer, 0, length);
}
// Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}
// 复制assets下的大数据库文件时用这个
private void copyBigDataBase() throws IOException {
InputStream myInput;
String outFileName = DB_PATH + DB_NAME;
OutputStream myOutput = new FileOutputStream(outFileName);
for (int i = ASSETS_SUFFIX_BEGIN; i < ASSETS_SUFFIX_END + 1; i++) {
myInput = myContext.getAssets().open(ASSETS_NAME + "." + i);
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer)) > 0) {
myOutput.write(buffer, 0, length);
}
myOutput.flush();
myInput.close();
}
myOutput.close();
}
@Override
public synchronized void close() {
if (myDataBase != null) {
myDataBase.close();
}
super.close();
}
/**
* 该函数是在第一次创建的时候执行， 实际上是第一次得到SQLiteDatabase对象的时候才会调用这个方法
*/
@Override
public void onCreate(SQLiteDatabase db) {
}
/**
* 数据库表结构有变化时采用
*/
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}