从assets文件夹复制SQLite数据库

Question

我想从assets文件夹中复制SQLite数据库。这是我的DatabaseAdapter.java类

package com.example.dictionary;

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.SQLiteOpenHelper;

public class DatabaseAdapter extends SQLiteOpenHelper {

    static String DB_PATH = "/data/data/com.example.dictionary/databases/";
    static String DB_NAME = "dict.db";
    SQLiteDatabase db;
    private final Context mContext;

    public DatabaseAdapter(Context context) {
        super(context, DB_NAME, null, 1);
        this.mContext = context;
    }

    public void createDB(){
        boolean dbExist = checkDB();
        if (dbExist) {

        } else {
            this.getReadableDatabase();

            try {
                copyDB();
            } catch (Exception e) {
                throw new Error("Error copying DB");

            }

        }
    }

    private void copyDB() throws IOException {
        InputStream dbInput = mContext.getAssets().open(DB_NAME);
        String outFile = DB_PATH + DB_NAME;
        OutputStream dbOutput = new FileOutputStream(outFile);

        byte[] buffer = new byte[1024];
        int length;
        while ((length = dbInput.read(buffer))>0) {
            dbOutput.write(buffer,0,length);
        }

        dbOutput.flush();
        dbOutput.close();
        dbInput.close();

    }

    private boolean checkDB() {
        SQLiteDatabase check = null;
        try {
            String dbPath = DB_PATH+DB_NAME;
            check = SQLiteDatabase.openDatabase(dbPath, null, SQLiteDatabase.OPEN_READONLY);
        } catch (Exception e) {
            // TODO: handle exception
        }
        if (check!=null) {
            check.close();
        }

        return check != null ? true : false;
    }

    public void openDB(){
        String dbPath = DB_PATH+DB_NAME;
        db = SQLiteDatabase.openDatabase(dbPath, null, SQLiteDatabase.OPEN_READONLY);
    }

    public synchronized void close(){
        if(db != null)
            db.close();
        super.close();
    }
    @Override
    public void onCreate(SQLiteDatabase db) {

    }

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

    }

}

当我运行应用程序时，没有错误。但是当我检查数据库文件夹时，我看到了一个名为“dict.db”的文件，但只有12.00K，并且只有android_metadata表。请帮助我。谢谢。

- user2336813

---

请使用 SQLiteAssetHelper 进行操作：https://github.com/jgilfelt/android-sqlite-asset-helper - CommonsWare

请注意，从Android Pie开始，以下解决方案可能不再适用。请查看https://dev59.com/U1UL5IYBdhLWcg3wWG5I获取答案。 - Rockvole

Answer 1

把所有这些方法放在您的帮助类中。

public DataBaseHelper(Context context) {

    super(context, DATABASE_NAME, null, DATABASE_VERSION);
    // TODO Auto-generated constructor stub
    mContext = context;
}

@Override
public void onCreate(SQLiteDatabase db) {
    // TODO Auto-generated method stub

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // TODO Auto-generated method stub

}

/**
 * This method will create database in application package /databases
 * directory when first time application launched
 **/
public void createDataBase() throws IOException {
    boolean mDataBaseExist = checkDataBase();
    if (!mDataBaseExist) {
        this.getReadableDatabase();
        try {
            copyDataBase();
        } catch (IOException mIOException) {
            mIOException.printStackTrace();
            throw new Error("Error copying database");
        } finally {
            this.close();
        }
    }
}

/** This method checks whether database is exists or not **/
private boolean checkDataBase() {
    try {
        final String mPath = DATABASE_PATH + DATABASE_NAME;
        final File file = new File(mPath);
        if (file.exists())
            return true;
        else
            return false;
    } catch (SQLiteException e) {
        e.printStackTrace();
        return false;
    }
}

/**
 * This method will copy database from /assets directory to application
 * package /databases directory
 **/
private void copyDataBase() throws IOException {
    try {

        InputStream mInputStream = mContext.getAssets().open(DATABASE_NAME);
        String outFileName = DATABASE_PATH + DATABASE_NAME;
        OutputStream mOutputStream = new FileOutputStream(outFileName);
        byte[] buffer = new byte[1024];
        int length;
        while ((length = mInputStream.read(buffer)) > 0) {
            mOutputStream.write(buffer, 0, length);
        }
        mOutputStream.flush();
        mOutputStream.close();
        mInputStream.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

/** This method open database for operations **/
public boolean openDataBase() throws SQLException {
    String mPath = DATABASE_PATH + DATABASE_NAME;
    myDataBase = SQLiteDatabase.openDatabase(mPath, null,
            SQLiteDatabase.OPEN_READWRITE);
    return myDataBase.isOpen();
}

/** This method close database connection and released occupied memory **/
@Override
public synchronized void close() {
    if (myDataBase != null)
        myDataBase.close();
    SQLiteDatabase.releaseMemory();
    super.close();
}

- Ketan Mehta

---

能否从资产中复制/创建仅表格？ - Prashanth Debbadwar

@PrashanthDebbadwar 是的，这是可能的。 - Ketan Mehta

请问您能提供任何网址吗？ - Prashanth Debbadwar

@PrashanthDebbadwar，你可以使用上面的代码来处理资产数据库。 - Ketan Mehta

Answer 2

 public void CopyDatabase() throws IOException {
    openOrCreateDatabase("you_db_file.db", 0, null);
    InputStream mInput = getAssets().open("databases/forall.db");
    OutputStream mOutput = new FileOutputStream("/data/data/" + getPackageName() + "/databases/you_db_file.db");
    byte[] mBuffer = new byte[1024];
    while (true) {
        int mLength = mInput.read(mBuffer);
        if (mLength > 0) {
            mOutput.write(mBuffer, 0, mLength);
        } else {
            mOutput.flush();
            mOutput.close();
            mInput.close();
            return;
        }
    }
}

- Raj008

Answer 3

这是正确的做法，使用getDatabasePath()

    String dbFilePath = getDatabasePath("main.db").getAbsolutePath();
    File dbFile = new File(dbFilePath);
    try {
        InputStream inputStream = getAssets().open("main.db");
        OutputStream outputStream = new FileOutputStream(dbFile);
        byte[] buffer = new byte[8192];
        int read;
        while ((read = inputStream.read(buffer)) != -1) {
            outputStream.write(buffer, 0, read);
        }
    } catch (Exception e) {
        e.printStackTrace();
        throw new IllegalStateException("failed to copy db file");
    }

- Nick

Answer 4

DataBaseHelper myDbHelper = new DataBaseHelper();
      myDbHelper = new DataBaseHelper(this);
      try {
            myDbHelper.createDataBase();

      } catch (IOException ioe) {

            throw new Error("Unable to create database");
      }

      try {      
            myDbHelper.openDataBase();

      }catch(SQLException sqle){

            throw sqle;
      }

复制数据库时，这些方法非常有用

 private void copyDataBase() throws IOException
      {
            String outFileName = DATABASE_PATH + DATABASE_NAME;
            OutputStream myOutput = new FileOutputStream(outFileName);
            InputStream myInput = myContext.getAssets().open(DATABASE_NAME);

            byte[] buffer = new byte[1024];
            int length;
            while ((length = myInput.read(buffer)) > 0)
            {
                  myOutput.write(buffer, 0, length);
            }
            myInput.close();
            myOutput.flush();
            myOutput.close();
      }

参考自: http://androidtutorials60.blogspot.in/2013/03/1.html

- Bhushan Shirsath

Answer 5

这是我的可用代码...

void copyDataBase() throws IOException {

        String outFileName = DB_PATH + DB_NAME;

        OutputStream myOutput = new FileOutputStream(outFileName);

        byte[] buffer = new byte[1024];
        int length;

        InputStream myInput = myContext.getAssets().open("mydb.sqlite");
        while ((length = myInput.read(buffer)) > 0) {
            myOutput.write(buffer, 0, length);
        }
        myInput.close();

        myOutput.flush();
        myOutput.close();

    }

- Saravanakumar