android中使用sqlite、复制assets下的数据库到SD卡、支持大于1M的文件

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"></uses-permission>

package cn.arthur.common;
 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;
/**
 * @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    = 1;
    //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        = "/data/data/cn.arthur.examples/databases/";
/*
    //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         = "hello.db";
    private static String ASSETS_NAME     = "hello.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();
                }
                SQLiteDatabase.openOrCreateDatabase(dbf, null);
                // 复制asseets中的db文件到DB_PATH下
                copyDataBase();
            } 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) {
    }
}

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    File f1=new File(Environment.getExternalStorageDirectory(),"aaa");
    f1.mkdir();
    InputStream in = null;
    try {
        Toast.makeText(getBaseContext(), "error", Toast.LENGTH_LONG).show();
        in = getBaseContext().getAssets().open("home");
    } catch (IOException e) {
        // TODO Auto-generated catch block
        Toast.makeText(getBaseContext(), "error", Toast.LENGTH_LONG).show();
        e.printStackTrace();
    }
    OutputStream ou = null;
    try {
        ou = new FileOutputStream(Environment.getExternalStorageDirectory()+"aaa"+ "/"+"home" );
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    try {
        CopyDB(in, ou);
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}
public void CopyDB(InputStream in, OutputStream ou) throws IOException
{
    byte []buffer=new byte[1024];
    int length;
    while((length=in.read(buffer))>0)
    {
        try {
            ou.write(buffer, 0, length);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        }
    in.close();
    ou.close();

}