思维:

1.当然，它是基于SQLiteOpenHelper.onCreate(第一个呼叫建立)、onUpdate(当所谓的升级计划)

2.用"脚本"(脚本制作详细方法问度娘)做数据库升级,文件名称标识相应版本号,java中依据“上一版本号、当前版本号”选择运行的脚本。

升级时,改动DB_VERSION(当前版本号)就可以。

DBManager.java:

package com.example.test;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.InputStream;

import android.content.Context;

import android.database.sqlite.SQLiteDatabase;

import android.database.sqlite.SQLiteOpenHelper;

public class DBManager extends SQLiteOpenHelper {

private final static String DBNAME = "mydata.db";

private final static int DB_VERSION = 1;

private static DBManager instance;

public DBManager(Context context) {

// TODO Auto-generated constructor stub

super(context, DBNAME, null, DB_VERSION);

}

public static DBManager getThis() {

if (instance == null)

instance = new DBManager(MainActivity.getThis());

return instance;

}

@Override

public void onCreate(SQLiteDatabase db) {

// TODO Auto-generated method stub

initDb(db, 0, DB_VERSION);

}

@Override

public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

// TODO Auto-generated method stub

initDb(db, oldVersion, newVersion);

}

// 初始化db,运行脚本

// 注:1>运行"(oldV,newV]"(全新安装时,oldV=0)间的脚本

// 2>缺失的脚本会直接跳过

private void initDb(SQLiteDatabase db, int oldVersion, int newVersion) {

for (int i = oldVersion + 1; i <= newVersion; i++)

execDBScript(db, "db/update" + i + ".sql");

}

// 运行脚本

private void execDBScript(SQLiteDatabase db, String assetName) {

try {

InputStream is = MainActivity.getThis().getAssets().open(assetName);

String stats = read(is);

execSqls(db, stats);

} catch (Exception e) {

// TODO: handle exception

e.printStackTrace();

}

}

// 批运行,用";"隔开

private void execSqls(SQLiteDatabase db, String stats) {

// onCreate/onUpdate内部已带事务,多层嵌套无影响(最外层起作用)

db.beginTransaction();

String[] sqls = stats.split(";");

for (int i = 0; i < sqls.length; i++) {

String sqlStatement = sqls[i].trim();

// TODO You may want to parse out comments here

if (sqlStatement.length() > 0) {

// 捕获错误,防止运行drop时 直接越过

try {

db.execSQL(sqlStatement + ";");

} catch (Exception e) {

// TODO: handle exception

e.printStackTrace();

}

}

}

db.setTransactionSuccessful();

db.endTransaction();

}

public static String read(InputStream instream) throws IOException {

ByteArrayOutputStream bos = new ByteArrayOutputStream();

byte[] buffer = new byte[1024];

int len = 0;

while ((len = instream.read(buffer)) != -1) {

bos.write(buffer, 0, len);

}

String ret = new String(bos.toByteArray());

return ret;

}

}

db脚本: