将 db 从资产复制到设备数据文件夹时出现 FileNotFoundException

Posted 2023-04-14

【中文标题】将 db 从资产复制到设备数据文件夹时出现 FileNotFoundException

【英文标题】：FileNotFoundException while copying db from assets to device data folder

【发布时间】：2015-04-08 16:35:15

【问题描述】：

我尝试了多种方法将我的 sqlite db 文件复制到我的 /data/data/packagename/databases 文件夹，但我仍然卡在 FileNotFoundException 中，由 FileOutputStream 对象触发... 代码如下：

public static boolean checkCopyDb(Context c, DbHandler _db) 
    try 
        String destPath = "/data/data/" + c.getPackageName() + "/databases/db_sociallibraries.db";

        File dbFile = new File(destPath);

        if(!dbFile.exists()) 
            _db.copyDb(c.getAssets().open(DB_NAME), new FileOutputStream(destPath)); // Line 44 - Throws the exception
        
        return true;
    
    catch (IOException e) 
        e.printStackTrace();
        return false;
    


private void copyDb(InputStream inputStream, OutputStream outputStream) throws IOException 

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

    while((length = inputStream.read(buffer)) > 0) 
        outputStream.write(buffer,0,length);
    

    inputStream.close();
    outputStream.close();

这是错误：

02-09 01:28:46.384 24222-24222/com.test.michelemadeddu.sociallibraries W/System.err: java.io.FileNotFoundException: /data/data/com.test.michelemadeddu.sociallibraries/databases/db_sociallibraries .db：打开失败：ENOENT（没有这样的文件或目录） 02-09 01:28:46.384 24222-24222/com.test.michelemadeddu.sociallibraries W/System.err：在 libcore.io.IoBridge.open(IoBridge.java:409) 02-09 01:28:46.384 24222-24222/com.test.michelemadeddu.sociallibraries W/System.err：在 java.io.FileOutputStream.(FileOutputStream.java:88) 02-09 01:28:46.384 24222-24222/com.test.michelemadeddu.sociallibraries W/System.err：在 java.io.FileOutputStream.(FileOutputStream.java:128) 02-09 01:28:46.384 24222-24222/com.test.michelemadeddu.sociallibraries W/System.err：在 java.io.FileOutputStream.(FileOutputStream.java:117) 02-09 01:28:46.384 24222-24222/com.test.michelemadeddu.sociallibraries W/System.err：在 com.test.michelemadeddu.sociallibraries.DbHandler.checkCopyDb(DbHandler.java:44)

我做错了吗？ 谢谢

【问题讨论】：

'c.getPackageName()' 是否返回您所期望的结果？

是的@prudhvi，我也尝试过明确写包名，但结果是一样的。实际上，如果您查看控制台消息，它会说错误在 FileOutPutStream 中，而不是 InputStream

我的假设是，您的文件不存在，因此您的“如果”条件评估为真。检查您是否在该路径中有文件。

我不能@prudhvi，设备本身无法访问该文件夹

【参考方案1】：

为了兼容性，也许您可​​以将内部数据库路径更改为以下

if(android.os.Build.VERSION.SDK_INT >= 17) 
   DB_PATH = context.getApplicationInfo().dataDir + "/databases/";         
 else 
   DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";

【参考方案2】：

请尝试此代码... 这就是我使用的并且工作正常。

只需替换 DB_NAME、DATABASE_NAME 和 DB_PATH 变量即可。

package your.packagename;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class database extends SQLiteOpenHelper

//The Android's default system path of your application database.
private static String DB_PATH = "/data`/data/com.example.applicationame/databases/";`

// Database Name
private static String DB_NAME = "DB.sqlite";

// Logcat tag
private static final String LOG = "database";

// Database Version
private static final int DATABASE_VERSION = 1;

// Database Name
private static final String DATABASE_NAME = "DB.sqlite";

// Table Names
private static final String TABLE_COUNTIES = "Counties";
private static final String TABLE_DESCRIPTIONS = "Descriptions";
private static final String TABLE_NEIGHBORHOODS = "Neighborhoods";

// Common column names
private static final String KEY_ID = "_id";

// TABLE_COUNTIES Table - column names
private static final String COL_COUNTYDETAIL = "countyDetail";
// TABLE_DESCRIPTIONS Table - column names
private static final String COL_DESCRIPTIONDETAIL = "descriptionDetail";
// TABLE_NEIGHBORHOODS Table - column names
private static final String COL_NEIGHBORHOODDETAIL = "neighborhoodDetail";

private SQLiteDatabase myDataBase; 

private final Context myContext;

public static long INSERT_ERROR = -1;
/**
 * Constructor
 * Takes and keeps a reference of the passed context in order to access to the application assets and resources.
 * @param context
 */
public database(Context context) 
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
    this.myContext = context;

   

/**
 * Creates a empty database on the system and rewrites it with your own database.
 * */
public void createDataBase() throws IOException

    Log.d(LOG, "Calling checkDataBase() Method");

    boolean dbExist = checkDataBase();

    if(dbExist)
        //do nothing - database already exist
        Log.d(LOG, "!!!Database Found!!!");
    else
        //By calling this method and empty database will be created into the default system path
        //of your application so we are gonna be able to overwrite that database with our database.
        Log.d(LOG, "!!!Creating Empy Database!!!");
        this.getReadableDatabase();
        this.close();
        try 
            Log.d(LOG, "!!!Coping Database!!!");
            copyDataBase();
         catch (IOException e) 
            throw new Error(e);
        
     


/**
 * Check if the database already exist to avoid re-copying the file each time you open the application.
 * @return true if it exists, false if it doesn't
 */
private boolean checkDataBase()

    SQLiteDatabase checkDB = null;

    try
        String myPath = DB_PATH + DB_NAME;

        Log.d(LOG, "looking database at " + myPath);

        checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

    catch(SQLiteException e)
        //database does't exist yet.
        Log.e(LOG, "Exception: 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(DB_NAME);

    // Path to the just created empty db
    String outFileName = DB_PATH + DB_NAME;

    Log.d(LOG, "Coping database from " + myInput + ", to " + outFileName);

    //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();



public void openDataBase() throws SQLException
    openDataBase(true);


public void openDataBase(boolean readonly) throws SQLException
    //Open the database
    String myPath = DB_PATH + DB_NAME;

    if (readonly)
        myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
    else
        myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);


@Override
public synchronized void close() 
    if(myDataBase != null)
        myDataBase.close();

    super.close();


@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

    

我希望它有所帮助。 祝你好运