安卓：错误打开数据库 [英] Android: error opening database

问题描述

我有了这个数据库，从资产的文件夹取，但我不能在我的活动打开它。
我的数据库存储在资产文件夹，命名为 MIO_DATABASE.db ：

I've got this database taken from assets folder, but i can't open it in my activity. My database is stored in the assets folder and named MIO_DATABASE.db :

Database.java：

Database.java:

package it.mi.action.app;

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;

public class Database extends SQLiteOpenHelper{

//The Android's default system path of your application database.
private static final String DB_PATH = "/data/data/it.mi.action.app/databases/";
private static final String DB_NAME = "MIO_DATABASE.db";
private SQLiteDatabase myDataBase;
private final Context myContext;

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

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.getReadableDatabase();
        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(){
    SQLiteDatabase checkDB = null;
    try{
        String myPath = DB_PATH + DB_NAME;
        checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
    }catch(SQLiteException e){
        //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;
    //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{
    //Open the database
    String myPath = DB_PATH + DB_NAME;
    myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}

@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) { }

// 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.

}

我的活动（mia.java）：

my activity (mia.java) :

package it.mi.action.app;

   import java.io.IOException;
   import android.app.Activity;
   import android.database.SQLException;
   import android.os.Bundle;

   public class mia extends Activity{
   @Override
   public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.mia);
      final Database info=new Database(this);
      try {
            info.createDataBase();
       } catch (IOException ioe) {
            throw new Error("Unable to create database");
       } 
       try {
            info.openDataBase();
       }catch(SQLException sqle){
            throw sqle;
       }
   }
}

该应用的工作​​原理，但在LogCat中我看到这个错误：

The app works, but in the LogCat i see this error:

08-01 09:37:32.772: E/Database(1774): sqlite3_open_v2("/data/data/it.mi.action.app/databases/MIO_DATABASE.db", &handle, 1, NULL) failed

这是什么问题？

推荐答案

此错误发生您运行该项目，因为它创建SQLite数据库第一次。检查此链接和通过@大卫的 Android中使用自己的SQLite数据库应用

This error is happened the first time that you run the project because it creates the sqlite database. Check this link and a question which is asked by @David Using your own SQLite database in Android apps

他有同样的错误就像你： sqlite3_open_v2（/数据/数据​​/ com.testapp /数据库/ database.db

He had the same error like you : sqlite3_open_v2("/data/data/com.testapp/databases/database.db

我也有同样的问题。但随后由于@大卫说：
我才意识到，问题不在于它实际上是读取第一次数据库的负载。

I have also had the same problem. but then as @David said : I just realized the issue is not the loading of the database it is actually the first time it is read.

这篇关于安卓：错误打开数据库的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！