如何从资源文件夹数据库复制到数据库文件夹 [英] How to copy Database from Asset Folder to Databases Folder

问题描述

我的code如下：

My code is as Follows:

dbhelper.java

dbhelper.java

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    if (oldVersion >= newVersion) return;
    db.execSQL("DROP DATABASE IF EXISTS " + DATABASE_NAME +";");
    onCreate(db);
}
@Override
public void onCreate(SQLiteDatabase db) {

    //here is the database definition
    db.execSQL("CREATE TABLE dhivehienglish " +
            "(mv TEXT, en TEXT);");
    //insert pre-configured records
    db.execSQL("INSERT INTO dhivehienglish (mv, en) VALUES('ކާރު','car');");
    db.execSQL("INSERT INTO dhivehienglish (mv, en) VALUES('ޖަހާ','hit');");
    db.execSQL("INSERT INTO dhivehienglish (mv, en) VALUES('އިނުން','sit');");
    db.execSQL("INSERT INTO dhivehienglish (mv, en) VALUES('ކެއުން','eat');");
}

}

MainActivity.java

MainActivity.java

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

    //listing data processes
    //-initiate the database connector
    db = dbhelper.getReadableDatabase();

    txtmelayu=(EditText)findViewById(R.id.txtmelayu);
    btncari=(Button)findViewById(R.id.btncari);
    btncari.setOnClickListener(this);
    lblmakna=(TextView)findViewById(R.id.lblmakna);

}//end onCreate

public void onClick(View v){
    //fetch kata melayu dr textbox
    String carimelayu=txtmelayu.getText().toString();
    //kena letak dalam onclick
    //-run SELECT command to fetch data from table
    if (v.getId()==R.id.btncari){
        Cursor cmelayu=db.rawQuery("SELECT * FROM dhivehienglish " +
                "WHERE mv='"+carimelayu+"';", null);
        //-fetch record
        if(cmelayu.getCount()!=0){
            cmelayu.moveToFirst();//go to first row
            String en=cmelayu.getString(1).toString();
            lblmakna.setText(en);
        }
        else{
            //display some notice here saying no data found
            lblmakna.setText("Not found!");}}

}//end onCLick

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

//when menu is selected
@Override
public boolean onOptionsItemSelected(MenuItem item) {
    //call about screen, if user hit "Tentang kami" menu
    if (item.getItemId()==R.id.minsert){
        Intent ins= new Intent (this, InsertActivity.class);
        startActivity(ins);
    }
    return true;
}}

我怎样才能将现有数据库从我的资产文件夹，并把它作为位于我的应用程序的沙箱中的本地数据库？任何帮助是非常AP preciated。

How can i move my existing Database from my Assets Folder and use it as a native database located within my Application's Sandbox ? Any Help is highly appreciated.

推荐答案

修改你的的CreateDatabase（）方法，在你的数据库处理器像下面的code：

Modify your createDataBase() method in your DatabaseHandler like the code below:

的CreateDatabase（）：

 public void createDataBase() throws IOException
{
    //If database not exists copy it from the assets

    boolean mDataBaseExist = checkDataBase();
    if(!mDataBaseExist)
    {
        this.getReadableDatabase();
        this.close();
        try 
        {
            //Copy the database from assests
            copyDataBase();
            System.out.println("createDatabase database created");
        } 
        catch (IOException mIOException) 
        {
            throw new Error("ErrorCopyingDataBase");
        }
    }
}

checkDataBase（）：

private boolean checkDataBase()
{
    File dbFile = new File(DB_PATH + DB_NAME);
    //Log.v("dbFile", dbFile + "   "+ dbFile.exists());
    return dbFile.exists();
}

copyDataBase（）：

//Copy the database from assets
private void copyDataBase() throws IOException
{
    InputStream mInput = mContext.getAssets().open(DB_NAME);
    String outFileName = DB_PATH + DB_NAME;

    OutputStream mOutput = new FileOutputStream(outFileName);
    byte[] mBuffer = new byte[1024];
    int mLength;
    while ((mLength = mInput.read(mBuffer))>0)
    {
        mOutput.write(mBuffer, 0, mLength);
    }
    mOutput.flush();
    mOutput.close();
    mInput.close();
}

其中， DB_PATH = /数据/数据​​/ YOUR_PACKAGE_NAME /数据库/ ，您可以在DatabseHandler的构建初始化像这样： DB_PATH = context.getApplicationInfo（）DATADIR +/数据库/;
DB_NAME = YOUR_DATABASE_NAME_THAT_IS_STORED_IN_YOUR_ASSETS_FOLDER

Where DB_PATH = /data/data/YOUR_PACKAGE_NAME/Databases/, You can initialize it in your DatabseHandler's Construct like this : DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
DB_NAME = YOUR_DATABASE_NAME_THAT_IS_STORED_IN_YOUR_ASSETS_FOLDER

我希望这有助于。

P.S：DB_NAME和DB_PATH都是字符串

P.S: DB_NAME and DB_PATH are both Strings.

更新：
当你要使用你的 DatabaseHelper 类的一个实例，只需要调用这个方法的CreateDatabase（）是这样的：

UPDATE :
Whenever you are trying to use an instance of your DatabaseHelper Class, just call this method createDatabase() like this :

DatabaseHandler db = new DatabaseHandler(context);
   try 
    {
        db.createDataBase();
    } 
    catch (IOException io) 
    {
        throw new Error("Unable to create database");
    }

这将复制从资源文件夹现有的数据库，如果数据库还没有被复制到数据库目录。
我希望这有助于。

It will copy the existing Database from Asset Folder if the Database has not been copied to the Databases directory.
I hope this helps.

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