Java 代码14：无法打开数据库

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）正在为另一个应用程序工作，但不是我当前正在开发的应用程序。我甚至通过检查“设置”中的权限来确保授予了权限。下面是日志：

05-13 15:35:45.693 29696-29696/com.example.hack.corrector E/SQLiteLog:（14）无法打开[5a3022e081]第31282行的文件 （14） os_unix.c:31282:（21）打开（/data/user/0/com.example.hack.corrector/databases/）- 05-13 15:35:45.694 29696-29696/com.example.hack.corrector E/SQLiteDatabase:未能打开数据库“/data/user/0/com.example.hack.corrector/databases/”。 android.database.sqlite.SQLiteCantoPendDatabaseException:未知错误（代码14）：无法打开数据库 位于android.database.sqlite.SQLiteConnection.nativeOpen（本机方法） 位于android.database.sqlite.SQLiteConnection.open（SQLiteConnection.java:207） 位于android.database.sqlite.SQLiteConnection.open（SQLiteConnection.java:191） 位于android.database.sqlite.SQLiteConnectionPool.openConnectionLocked（SQLiteConnectionPool.java:463） 位于android.database.sqlite.SQLiteConnectionPool.open（SQLiteConnectionPool.java:185） 位于android.database.sqlite.SQLiteConnectionPool.open（SQLiteConnectionPool.java:177） 位于android.database.sqlite.SQLiteDatabase.openInner（SQLiteDatabase.java:806） 位于android.database.sqlite.SQLiteDatabase.open（SQLiteDatabase.java:791） 位于android.database.sqlite.SQLiteDatabase.openDatabase（SQLiteDatabase.java:694） 位于android.database.sqlite.SQLiteDatabase.openDatabase（SQLiteDatabase.java:669） 位于com.example.habc.corrector.VocabDatabase.openDataBase（VocabDatabase.java:127） 位于com.example.habc.corrector.scrapeservice.createDB（scrapeservice.java:31） 位于com.example.habc.corrector.scrapeservice.onStartCommand（scrapeservice.java:23） 位于android.app.ActivityThread.handleServiceArgs（ActivityThread.java:3049） 在android.app.ActivityThread.access$2300（ActivityThread.java:154） 在android.app.ActivityThread$H.handleMessage（ActivityThread.java:1479）上 位于android.os.Handler.dispatchMessage（Handler.java:102） 位于android.os.Looper.loop（Looper.java:157） 位于android.app.ActivityThread.main（ActivityThread.java:5571） 位于java.lang.reflect.Method.invoke（本机方法） 在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run（ZygoteInit.java:745）上 位于com.android.internal.os.ZygoteInit.main（ZygoteInit.java:635）

下面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);
}

}

---

我已经检查了文件资源管理器，数据库已经复制并就位。但是，错误仍在发生。我从来没有遇到过其他实现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…

您的问题是试图使用不包含数据库名称的路径打开

i、 e.无法打开14是为了

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

当打开时，应尝试打开

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

不使用完整路径将导致两个问题，这很可能导致混淆

当您检查数据库是否存在时，将发出这些消息（请注意，每次都会复制数据库，因为数据库永远不会被找到（打开））

当您尝试打开数据库时，也会发出这些消息，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

以下是重写的数据库处理程序，用于合并上述内容，但也用于将对数据库的检查更改为对文件的检查，以便不显示非错误的打开错误14（从资产文件复制数据库时）

---

• 注释

  //相同的代码在其他应用程序中工作。但是，我还是尝试了你的建议，但还是出现了同样的错误。有一件事：错误表明它无法打开数据库。@/data/user/0/com.example.hack.corrector/databases/。但当我在文件资源管理器中查找复制的数据库时，该数据库位于@/data/data/com.example.hack.corrector/databases/。但程序能够复制dbm，但无法在相同的地址is wierd中打开它。我最近将android studio更新为3.1。这可能是问题所在吗？如果是的话，我怎么解决呢？谢谢。那很有效！这似乎是新AS更新的问题..嗨！代码运行良好。但在重新安装并再次运行应用程序后，只创建了大小为12kb的空数据库@/data/data/com.example.corrector/databases。我把它拿出来检查。没有表，但名称相同：ztr.db。未复制任何表：（资产中的db文件为16Mb。。
  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);
      }
  }