将数据库从资产复制到设备数据文件夹时出现 FileNotFoundException

Question

我尝试了很多方法将我的 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... 这是代码：

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: open failed: ENOENT (No such file or directory) 02-09 01:28:46.384 24222-24222/com.test.michelemadeddu.sociallibraries W/System.err﹕ at libcore.io.IoBridge.open(IoBridge.java:409) 02-09 01:28:46.384 24222-24222/com.test.michelemadeddu.sociallibraries W/System.err﹕ at java.io.FileOutputStream.(FileOutputStream.java:88) 02-09 01:28:46.384 24222-24222/com.test.michelemadeddu.sociallibraries W/System.err﹕ at java.io.FileOutputStream.(FileOutputStream.java:128) 02-09 01:28:46.384 24222-24222/com.test.michelemadeddu.sociallibraries W/System.err﹕ at java.io.FileOutputStream.(FileOutputStream.java:117) 02-09 01:28:46.384 24222-24222/com.test.michelemadeddu.sociallibraries W/System.err﹕ at com.test.michelemadeddu.sociallibraries.DbHandler.checkCopyDb(DbHandler.java:44)

我是不是做错了什么？谢谢

Answer 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/";
}

Answer 2

请尝试此代码... 这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

}    

}

希望对您有所帮助。祝你好运

将数据库从资产复制到设备数据文件夹时出现 FileNotFoundException

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