代码 14：无法打开数据库

Question

我知道以前有人问过这个问题。但是，问题是，相同的代码（用于数据库处理程序）适用于另一个应用程序，但不适用于我当前正在处理的应用程序。我什至通过检查设置中的权限来确保已授予权限。这是 logcat:

05-13 15:35:45.693 29696-29696/com.example.hack.corrector E/SQLiteLog: (14) cannot open file at line 31282 of [5a3022e081] (14) os_unix.c:31282: (21) open(/data/user/0/com.example.hack.corrector/databases/) - 05-13 15:35:45.694 29696-29696/com.example.hack.corrector E/SQLiteDatabase: Failed to open database '/data/user/0/com.example.hack.corrector/databases/'. android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method) at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:207) at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:191) at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:463) at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:185) at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:177) at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:806) at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:791) at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:694) at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:669) at com.example.hakc.corrector.VocabDatabase.openDataBase(VocabDatabase.java:127) at com.example.hakc.corrector.scrapeservice.createDB(scrapeservice.java:31) at com.example.hakc.corrector.scrapeservice.onStartCommand(scrapeservice.java:23) at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:3049) at android.app.ActivityThread.access00(ActivityThread.java:154) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1479) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:157) at android.app.ActivityThread.main(ActivityThread.java:5571) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:745) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:635)

这是数据库处理程序代码：

package com.example.hack.corrector;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;

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


public class VocabDatabase extends SQLiteOpenHelper {

//The Android's default system path of your application database.
private static String DB_PATH = "";

private static String DB_NAME = "ztr.db";

private SQLiteDatabase myDataBase;

private final Context myContext;

/**
 * Constructor
 * Takes and keeps a reference of the passed context in order to access to the application assets and resources.
 *
 * @param context
 */
public VocabDatabase(Context context) {

    super(context, DB_NAME, null, 1);
    this.myContext = context;
    this.DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
}

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

    boolean dbExist = checkDataBase();

    if (dbExist) {
        //do nothing - database already exist
    } 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.
        this.getWritableDatabase();

        try {
            copyDataBase();
        } catch (IOException e) {
            throw new Error("Error copying database");

        }

    }

}

/**
 * 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() {
    this.getReadableDatabase();

    SQLiteDatabase checkDB = null;

    try {
        String myPath = DB_PATH;
        checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);

    } catch (SQLiteException e) {
        e.printStackTrace();
    }

    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;

    //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 = 0;
    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 {

    //Open the database
    String myPath = DB_PATH;
    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) {

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    if (newVersion > oldVersion) {
        try {
            copyDataBase();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

// Add your public helper methods to access and get content from the database.
// You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
// to you to create adapters for your views.

//add your public methods for insert, get, delete and update data in database.

public Cursor query(String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy) {
    SQLiteDatabase db = this.getWritableDatabase();
    return db.query(table, columns, selection, selectionArgs, groupBy, having, orderBy);
}

public long insert(String table, String nullColumnHack, ContentValues contentValues) {
    SQLiteDatabase db = this.getWritableDatabase();
    return db.insert(table, nullColumnHack, contentValues);
}

public Cursor rawQuery(String string, String[] selectionArguments) {
    SQLiteDatabase db = this.getWritableDatabase();
    return db.rawQuery(string, selectionArguments);
}

}

我检查了文件资源管理器，数据库已复制并就位。但是，错误仍在发生。我从未遇到过其他实施相同数据库处理程序代码 (Vocabdatabase) 的应用程序的问题。我花了一天半的时间试图解决这个问题，但没有任何效果...

Answer 1

您的问题是您尝试使用不包含数据库名称的路径打开。

即无法打开 14 是为了

/data/user/0/com.example.hack.corrector/databases/

同时打开应该尝试打开 /data/user/0/com.example.hack.corrector/databases/ztr.db

不使用完整路径会导致两个问题，这很可能会造成混淆。

当您检查数据库是否存在时将发出消息（请注意，每次都会复制数据库，因为永远不会找到（打开）数据库）
当您尝试打开数据库时也会发出消息，后者失败。

在这两种情况下，正确的用法应该是 DB_PATH + DB_NAME，而不仅仅是 DB_PATH.

以下是您的数据库处理程序重写以合并上述内容，但也将对数据库的检查更改为对文件的检查，因此不会显示不是错误的打开错误 14（当数据库从资产文件中复制。

评论 //<<<< ???? 表示更改。

:-

public class VocabDatabase extends SQLiteOpenHelper {

    //The Android's default system path of your application database.
    //private static String DB_PATH = ""; //<<<< RMVD
    private static String DB_PATH_ALT; //<<<< ADDED
    private static String DB_NAME = "ztr.db";
    private SQLiteDatabase myDataBase;
    private final Context myContext;

    /**
     * Constructor
     * Takes and keeps a reference of the passed context in order to access to the application assets and resources.
     *
     * @param context
     */
    public VocabDatabase(Context context) {
        super(context, DB_NAME, null, 1);
        this.myContext = context;
        //this.DB_PATH = context.getApplicationInfo().dataDir + "/databases/"; //<<<< RMVD
        this.DB_PATH_ALT = context.getDatabasePath(DB_NAME).getPath(); //<<<< ADDED

    }

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

        //boolean dbExist = checkDataBase();  //<<<< RMVD 
        boolean dbExist = checkDataBaseAlt(); //<<<< CHANGED
        if (dbExist) {
            //do nothing - database already exist
        } 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.
            this.getWritableDatabase();

            try {
                copyDataBase();
            } catch (IOException e) {
                throw new Error("Error copying database");
            }
        }
    }
    //<<<< ADDED Alternative method checks the file rather than database
    //<<<<       as such no open error 14 messages
    /**
     * 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 checkDataBaseAlt() {
        //File chkdb = new File(myContext.getDatabasePath(DB_NAME).getPath()); //<<<< RMVD
        File chkdb = new File(DB_PATH_ALT); //<<<< ADDED
        return chkdb.exists();
    }

    /**
     * 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() {
        this.getReadableDatabase();
        SQLiteDatabase checkDB = null;
        try {
            //String myPath = DB_PATH; //<<<< RMVD so no open error 14 uses alt method
            checkDB = SQLiteDatabase.openDatabase(
                    DB_PATH_ALT, //<<<< CHANGED
                    null, 
                    SQLiteDatabase.OPEN_READWRITE
            ); 

        } catch (SQLiteException e) {
            e.printStackTrace();
        }
        if (checkDB != null) {
            checkDB.close();
        }
        return checkDB != null; //<<<< simplified
    }

    /**
     * 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); //<<<< CHANGED

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

        //Open the empty db as the output stream
        OutputStream myOutput = new FileOutputStream(DB_PATH_ALT); //<<<< CHANGED

        //transfer bytes from the inputfile to the outputfile
        byte[] buffer = new byte[1024];
        int length = 0;
        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 {
        //Open the database
        //String myPath = DB_PATH; //<<<< RMVD
        myDataBase = SQLiteDatabase.openDatabase(
                DB_PATH_ALT, //<<<< CHANGED
                null, 
                SQLiteDatabase.OPEN_READWRITE
        );

    }

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

    @Override
    public void onCreate(SQLiteDatabase db) {
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        if (newVersion > oldVersion) {
            try {
                copyDataBase();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

// Add your public helper methods to access and get content from the database.
// You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
// to you to create adapters for your views.

//add your public methods for insert, get, delete and update data in database.

    public Cursor query(String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy) {
        SQLiteDatabase db = this.getWritableDatabase();
        return db.query(table, columns, selection, selectionArgs, groupBy, having, orderBy);
    }

    public long insert(String table, String nullColumnHack, ContentValues contentValues) {
        SQLiteDatabase db = this.getWritableDatabase();
        return db.insert(table, nullColumnHack, contentValues);
    }

    public Cursor rawQuery(String string, String[] selectionArguments) {
        SQLiteDatabase db = this.getWritableDatabase();
        return db.rawQuery(string, selectionArguments);
    }
}

代码 14：无法打开数据库

Code 14: Unable to open database

java

android

database

sqlite

sqliteopenhelper