Question

我从资产文件夹中获取了此数据库，但我无法在我的活动中打开它。我的数据库存储在assets文件夹中，名为MIO_DATABASE.db：

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）：

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;
       }
   }
}

该应用程序有效，但在LogCat中我看到此错误：

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

有什么问题？

Answer 1

第一次运行项目时会发生此错误，因为它会创建sqlite数据库。查看此链接以及@David Using your own SQLite database in Android apps

提出的问题

他遇到了和你一样的错误：sqlite3_open_v2(“/data/data/com.testapp/databases/database.db

我也有同样的问题。但随后@David说： I just realized the issue is not the loading of the database it is actually the first time it is read.

Answer 2

您应该检查您的数据库是否存在于指定的路径中。有关详细信息，请参阅here。

此外，尝试将数据库存储在内部或外部存储器中，因为您只在应用程序的asset文件夹中具有读取权限。有关详细信息，请参阅here。

Android：错误打开数据库

2 个答案: