Question

我的代码如下：

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

@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;
}}

如何从我的资产文件夹中移动现有数据库并将其用作位于我的应用程序沙箱中的本机数据库？任何帮助都非常感谢。

Answer 1

修改createDataBase()中的DatabaseHandler方法，如下面的代码所示：

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();
}

DB_PATH = /data/data/YOUR_PACKAGE_NAME/Databases/，您可以在DatabseHandler的构造中初始化它，如下所示：DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
DB_NAME = YOUR_DATABASE_NAME_THAT_IS_STORED_IN_YOUR_ASSETS_FOLDER

我希望这会有所帮助。

P.S：DB_NAME和DB_PATH都是字符串。

更新：
每当您尝试使用DatabaseHelper类的实例时，只需像这样调用此方法createDatabase()：

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

如果数据库尚未复制到Databases目录，它将从Asset Folder复制现有数据库我希望这会有所帮助。

如何将数据库从资源文件夹复制到数据库文件夹

1 个答案: