将位于Assets文件夹中的预填充数据库放入data/data/mypackage/databases。[英] Getting a prepopulated database located in the Assets folder into the data/data/mypackage/databases

本文是小编为大家收集整理的关于将位于Assets文件夹中的预填充数据库放入data/data/mypackage/databases。的处理/解决方法,可以参考本文帮助大家快速定位并解决问题,中文翻译不准确的可切换到English标签页查看源文。

问题描述

我一直在尝试按照以下示例: http://blog.softeq.com/2012/12/using-population-sqlite-database-in.html

此示例应该向您展示如何打开存储在资产文件夹中的预处理数据库.

已经创建了与此主题相关的线程,我尝试了这些建议,但它并没有帮助我弄清楚为什么程序不打开数据库文件.我究竟做错了什么?这是我在logcat的前几行中得到的:

01-13 15:54:33.171: E/Trace(30747): error opening trace file: No such file or directory (2)
01-13 15:54:33.171: D/ActivityThread(30747): setTargetHeapUtilization:0.25
01-13 15:54:33.171: D/ActivityThread(30747): setTargetHeapIdealFree:8388608
01-13 15:54:33.171: D/ActivityThread(30747): setTargetHeapConcurrentStart:2097152
01-13 15:54:33.251: D/AbsListView(30747): Get MotionRecognitionManager
01-13 15:54:33.261: E/SQLiteLog(30747): (14) cannot open file at line 30245 of [00bb9c9ce4]
01-13 15:54:33.261: E/SQLiteLog(30747): (14) os_unix.c:30245: (2) open(/data/data/com.example.prepopdb/databases/yourdb.db) - 
01-13 15:54:33.261: E/SQLiteDatabase(30747): Failed to open database '/data/data/com.example.prepopdb/databases/yourdb.db'.
01-13 15:54:33.261: E/SQLiteDatabase(30747): android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:278)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:217)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:464)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:186)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:178)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:804)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:789)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:694)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:669)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at com.example.prepopdb.ExternalDbOpenHelper.checkDataBase(ExternalDbOpenHelper.java:62)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at com.example.prepopdb.ExternalDbOpenHelper.createDataBase(ExternalDbOpenHelper.java:43)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at com.example.prepopdb.ExternalDbOpenHelper.openDataBase(ExternalDbOpenHelper.java:97)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at com.example.prepopdb.ExternalDbOpenHelper.<init>(ExternalDbOpenHelper.java:37)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at com.example.prepopdb.PrepopSqliteDbActivity.onCreate(PrepopSqliteDbActivity.java:35)

i如上链接中提到的使用SQLITE数据库浏览器创建了测试数据库,除了我的数据库扩展名为" .db",而不是" .sqlite3". (尽管我也尝试使用" .sqlite3",但具有相似/相同的错误).

这是我的prepopsqlitedbactivity的代码:

package com.example.prepopdb;

import com.example.prepopdb.ExternalDbOpenHelper;
import java.util.ArrayList;

import android.app.ListActivity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

public class PrepopSqliteDbActivity extends ListActivity {

private static final String DB_NAME = "yourdb.db";

// Database field names
private static final String TABLE_NAME = "friends";
private static final String FRIEND_ID = "_id";
private static final String FRIEND_NAME = "name";

private SQLiteDatabase database;
private ListView listView;
private ArrayList<String> friends;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    ExternalDbOpenHelper dbOpenHelper = new ExternalDbOpenHelper(this,
            DB_NAME);
    database = dbOpenHelper.openDataBase(); // Database is open

    /*SOME OTHER CODE HERE*/
}

这是我的外部dbopenhelper的代码:

package com.example.prepopdb;

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.SQLiteOpenHelper;
import android.os.Environment;
import android.util.Log;

public class ExternalDbOpenHelper extends SQLiteOpenHelper {

// Path to the device folder with database
public static String DB_PATH;

// Database filename
public static String DB_NAME;
public SQLiteDatabase database;
public final Context context;

public SQLiteDatabase getDb() {
    return database;
}

public ExternalDbOpenHelper(Context context, String databaseName) {
    super(context, databaseName, null, 1);
    this.context = context;

    // Write the full path to the databases of your application
    String packageName = context.getPackageName();
    DB_PATH = String.format("%s/data/%s/databases/", Environment.getDataDirectory(), packageName);
    DB_NAME = databaseName;
    openDataBase();

}

// Create a database if its not yet created
public void createDataBase() {
    boolean dbExist = checkDataBase();
    if (!dbExist) {
        this.getReadableDatabase();
        try {
            copyDataBase();
        } catch (IOException e) {
            Log.e(this.getClass().toString(), "Copying error!");
            throw new Error("Error copying database!");
        }
    } else {
        Log.i(this.getClass().toString(), "Database already exists");
    }
}

//Performing a database existence check
private boolean checkDataBase(){
    SQLiteDatabase checkDb = null;
    try {
        String path = DB_PATH + DB_NAME;
        checkDb = SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READONLY);
    } catch (SQLException e){
        Log.e(this.getClass().toString(), "Error while checking db");
    }

    if (checkDb != null){
        checkDb.close();
    }
    return checkDb !=null;
}

private void copyDataBase() throws IOException {
    //Open a stream for reading, located in the assets
    InputStream externalDbStream = context.getAssets().open(DB_NAME);
    //Path to the created empty database on your Android device
    String outFileName = DB_PATH + DB_NAME;

    //Create a stream for writing the database byte by byte
    OutputStream localDbStream = new FileOutputStream(outFileName);

    //Copy the database
    byte[] buffer = new byte[1024];
    int bytesRead;
    while((bytesRead = externalDbStream.read(buffer)) > 0){
        localDbStream.write(buffer, 0, bytesRead);
    }

    //Close the streams
    localDbStream.close();
    externalDbStream.close();
}

SQLiteDatabase openDataBase() throws SQLException {
    String path = DB_PATH + DB_NAME;
    if (database == null) {
        createDataBase();
        database = SQLiteDatabase.openDatabase(path, null,
                SQLiteDatabase.OPEN_READWRITE);
        //database = getWritableDatabase();
    }
    return database;
}

@Override
public synchronized void close(){
    if (database != null){
        database.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

}
}

更新

谢谢Carlos.我同意将路径进行硬编码不是一个好主意,因为它可能与设备是不同的设备.我按照您的建议进行了更改,但是我仍然遇到同样的错误.我已经验证了yourdb.db文件对所有级别的读取权限.

我在以前的评论中提到了这一点,但是由于我使用了非根手机,这是否会发生?将" yourdb.db"的权限从asssets文件夹复制到/data/data/com.example.prepopdb/databases/之后,是否可以更改它,然后我的程序试图打开它?我知道如何使用ADB更改权限,但是如何从程序中进行此操作?

这是我的logcat所说的:

01-14 12:18:02.240: E/Trace(18167): error opening trace file: No such file or directory (2)
01-14 12:18:02.240: D/ActivityThread(18167): setTargetHeapUtilization:0.25
01-14 12:18:02.240: D/ActivityThread(18167): setTargetHeapIdealFree:8388608
01-14 12:18:02.240: D/ActivityThread(18167): setTargetHeapConcurrentStart:2097152
01-14 12:18:02.360: D/AbsListView(18167): Get MotionRecognitionManager
01-14 12:18:02.370: E/SQLiteLog(18167): (14) cannot open file at line 30245 of [00bb9c9ce4]
01-14 12:18:02.370: E/SQLiteLog(18167): (14) os_unix.c:30245: (2) open(/data/data/com.example.prepopdb/databases/yourdb.db) - 
01-14 12:18:02.370: E/SQLiteDatabase(18167): Failed to open database '/data/data/com.example.prepopdb/databases/yourdb.db'.
01-14 12:18:02.370: E/SQLiteDatabase(18167): android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:278)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:217)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:464)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:186)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:178)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:804)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:789)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:694)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:669)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at com.example.prepopdb.ExternalDbOpenHelper.checkDataBase(ExternalDbOpenHelper.java:63)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at com.example.prepopdb.ExternalDbOpenHelper.createDataBase(ExternalDbOpenHelper.java:45)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at com.example.prepopdb.ExternalDbOpenHelper.openDataBase(ExternalDbOpenHelper.java:97)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at com.example.prepopdb.ExternalDbOpenHelper.<init>(ExternalDbOpenHelper.java:39)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at com.example.prepopdb.PrepopSqliteDbActivity.onCreate(PrepopSqliteDbActivity.java:35)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.app.Activity.performCreate(Activity.java:5048)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2052)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2113)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.app.ActivityThread.access$700(ActivityThread.java:139)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1224)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.os.Handler.dispatchMessage(Handler.java:99)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.os.Looper.loop(Looper.java:137)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.app.ActivityThread.main(ActivityThread.java:4918)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at java.lang.reflect.Method.invokeNative(Native Method)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at java.lang.reflect.Method.invoke(Method.java:511)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1004)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:771)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at dalvik.system.NativeStart.main(Native Method)
01-14 12:18:02.370: E/class com.example.prepopdb.ExternalDbOpenHelper(18167): Error while checking db
01-14 12:18:02.480: D/libEGL(18167): loaded /system/lib/egl/libEGL_adreno200.so
01-14 12:18:02.500: D/libEGL(18167): loaded /system/lib/egl/libGLESv1_CM_adreno200.so
01-14 12:18:02.500: D/libEGL(18167): loaded /system/lib/egl/libGLESv2_adreno200.so
01-14 12:18:02.540: I/Adreno200-EGLSUB(18167): <ConfigWindowMatch:2087>: Format RGBA_8888.
01-14 12:18:02.560: E/(18167): <s3dReadConfigFile:75>: Can't open file for reading
01-14 12:18:02.560: E/(18167): <s3dReadConfigFile:75>: Can't open file for reading
01-14 12:18:02.560: D/OpenGLRenderer(18167): Enabling debug mode 0
01-14 12:18:21.380: W/IInputConnectionWrapper(18167): beginBatchEdit on inactive InputConnection
01-14 12:18:21.380: W/IInputConnectionWrapper(18167): endBatchEdit on inactive InputConnection

推荐答案

您对数据文件夹的假设过多.您应该让系统给您正确的路径. 您可以使用context.getDatabasePath();获得数据库路径,您将所需的名称传递给文件(无论是否存在).实际上,您应该这样做

为此,在您使用String outFileName = DB_PATH + DB_NAME;之类的任何地方 您应该将其更改为

 String outFileName =myContext.getDatabasePath(DB_NAME).getPath() ;

这是您文件的真正有效位置.因此,助手会像这样

public class ExternalDbOpenHelper extends SQLiteOpenHelper {

// Path to the device folder with database
public static String DB_PATH;

// Database filename
public static String DB_NAME;
public SQLiteDatabase database;
public final Context context;

public SQLiteDatabase getDb() {
    return database;
}

public ExternalDbOpenHelper(Context context, String databaseName) {
    super(context, databaseName, null, 1);
    this.context = context;
        DB_NAME = databaseName;
            DB_PATH =context.getDatabasePath(DB_NAME).getPath() ;
    openDataBase();

}

// Create a database if its not yet created
public void createDataBase() {
    boolean dbExist = checkDataBase();
    if (!dbExist) {
        this.getReadableDatabase();
        try {
            copyDataBase();
        } catch (IOException e) {
            Log.e(this.getClass().toString(), "Copying error!");
            throw new Error("Error copying database!");
        }
    } else {
        Log.i(this.getClass().toString(), "Database already exists");
    }
}

//Performing a database existence check
private boolean checkDataBase(){
    SQLiteDatabase checkDb = null;
    try {

        checkDb = SQLiteDatabase.openDatabase(DB_PATH, null, SQLiteDatabase.OPEN_READONLY);
    } catch (SQLException e){
        Log.e(this.getClass().toString(), "Error while checking db");
    }

    if (checkDb != null){
        checkDb.close();
    }
    return checkDb !=null;
}

private void copyDataBase() throws IOException {
    //Open a stream for reading, located in the assets
    InputStream externalDbStream = context.getAssets().open(DB_NAME);



    //Create a stream for writing the database byte by byte
    OutputStream localDbStream = new FileOutputStream(DB_PATH);

    //Copy the database
    byte[] buffer = new byte[1024];
    int bytesRead;
    while((bytesRead = externalDbStream.read(buffer)) > 0){
        localDbStream.write(buffer, 0, bytesRead);
    }

             //FLUSH THE OUT STREAM
             localDbStream.flush();

    //Close the streams
    localDbStream.close();
    externalDbStream.close();
}

SQLiteDatabase openDataBase() throws SQLException {

    if (database == null) {
        createDataBase();
        database = SQLiteDatabase.openDatabase(DB_PATH, null,
                SQLiteDatabase.OPEN_READWRITE);
        //database = getWritableDatabase();
    }
    return database;
}

@Override
public synchronized void close(){
    if (database != null){
        database.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

}
}

与此相关起作用

更新

yo可以考虑一些考虑因素:

  • 看一下数据库返回的系统是什么路径

    DB_PATH =context.getDatabasePath(DB_NAME).getPath() ;
    Log.i ("myApp", DB_PATH);
    
  • 检查模拟器中的代码,以查看是否遇到相同的问题.如上所述

  • 添加 permissions (read_external_storage和write_external_storage).但是我实际上不相信你需要这个

本文地址:https://www.itbaoku.cn/post/102542.html

问题描述

I have been trying to follow the example: http://blog.softeq.com/2012/12/using-pre-populated-sqlite-database-in.html

This example is supposed to show you how to open a prepopulated database stored in the Assets folder.

There have been threads created related to this topic and I have tried the suggestions made, but its not helping me to figure out why the program doesn't open the database file. What am I doing wrong? Here is what I'm getting in the first few lines of LogCat:

01-13 15:54:33.171: E/Trace(30747): error opening trace file: No such file or directory (2)
01-13 15:54:33.171: D/ActivityThread(30747): setTargetHeapUtilization:0.25
01-13 15:54:33.171: D/ActivityThread(30747): setTargetHeapIdealFree:8388608
01-13 15:54:33.171: D/ActivityThread(30747): setTargetHeapConcurrentStart:2097152
01-13 15:54:33.251: D/AbsListView(30747): Get MotionRecognitionManager
01-13 15:54:33.261: E/SQLiteLog(30747): (14) cannot open file at line 30245 of [00bb9c9ce4]
01-13 15:54:33.261: E/SQLiteLog(30747): (14) os_unix.c:30245: (2) open(/data/data/com.example.prepopdb/databases/yourdb.db) - 
01-13 15:54:33.261: E/SQLiteDatabase(30747): Failed to open database '/data/data/com.example.prepopdb/databases/yourdb.db'.
01-13 15:54:33.261: E/SQLiteDatabase(30747): android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:278)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:217)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:464)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:186)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:178)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:804)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:789)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:694)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:669)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at com.example.prepopdb.ExternalDbOpenHelper.checkDataBase(ExternalDbOpenHelper.java:62)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at com.example.prepopdb.ExternalDbOpenHelper.createDataBase(ExternalDbOpenHelper.java:43)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at com.example.prepopdb.ExternalDbOpenHelper.openDataBase(ExternalDbOpenHelper.java:97)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at com.example.prepopdb.ExternalDbOpenHelper.<init>(ExternalDbOpenHelper.java:37)
01-13 15:54:33.261: E/SQLiteDatabase(30747):    at com.example.prepopdb.PrepopSqliteDbActivity.onCreate(PrepopSqliteDbActivity.java:35)

I created the test database with SQLite Database Browser as mentioned in the above link with the exception of my database extension being ".db" instead of ".sqlite3". (Though I have tried using ".sqlite3" as well, with similar/same errors).

Here is the code for my PrepopSqliteDbActivity:

package com.example.prepopdb;

import com.example.prepopdb.ExternalDbOpenHelper;
import java.util.ArrayList;

import android.app.ListActivity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

public class PrepopSqliteDbActivity extends ListActivity {

private static final String DB_NAME = "yourdb.db";

// Database field names
private static final String TABLE_NAME = "friends";
private static final String FRIEND_ID = "_id";
private static final String FRIEND_NAME = "name";

private SQLiteDatabase database;
private ListView listView;
private ArrayList<String> friends;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    ExternalDbOpenHelper dbOpenHelper = new ExternalDbOpenHelper(this,
            DB_NAME);
    database = dbOpenHelper.openDataBase(); // Database is open

    /*SOME OTHER CODE HERE*/
}

Here is the code for my ExternalDbOpenHelper:

package com.example.prepopdb;

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.SQLiteOpenHelper;
import android.os.Environment;
import android.util.Log;

public class ExternalDbOpenHelper extends SQLiteOpenHelper {

// Path to the device folder with database
public static String DB_PATH;

// Database filename
public static String DB_NAME;
public SQLiteDatabase database;
public final Context context;

public SQLiteDatabase getDb() {
    return database;
}

public ExternalDbOpenHelper(Context context, String databaseName) {
    super(context, databaseName, null, 1);
    this.context = context;

    // Write the full path to the databases of your application
    String packageName = context.getPackageName();
    DB_PATH = String.format("%s/data/%s/databases/", Environment.getDataDirectory(), packageName);
    DB_NAME = databaseName;
    openDataBase();

}

// Create a database if its not yet created
public void createDataBase() {
    boolean dbExist = checkDataBase();
    if (!dbExist) {
        this.getReadableDatabase();
        try {
            copyDataBase();
        } catch (IOException e) {
            Log.e(this.getClass().toString(), "Copying error!");
            throw new Error("Error copying database!");
        }
    } else {
        Log.i(this.getClass().toString(), "Database already exists");
    }
}

//Performing a database existence check
private boolean checkDataBase(){
    SQLiteDatabase checkDb = null;
    try {
        String path = DB_PATH + DB_NAME;
        checkDb = SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READONLY);
    } catch (SQLException e){
        Log.e(this.getClass().toString(), "Error while checking db");
    }

    if (checkDb != null){
        checkDb.close();
    }
    return checkDb !=null;
}

private void copyDataBase() throws IOException {
    //Open a stream for reading, located in the assets
    InputStream externalDbStream = context.getAssets().open(DB_NAME);
    //Path to the created empty database on your Android device
    String outFileName = DB_PATH + DB_NAME;

    //Create a stream for writing the database byte by byte
    OutputStream localDbStream = new FileOutputStream(outFileName);

    //Copy the database
    byte[] buffer = new byte[1024];
    int bytesRead;
    while((bytesRead = externalDbStream.read(buffer)) > 0){
        localDbStream.write(buffer, 0, bytesRead);
    }

    //Close the streams
    localDbStream.close();
    externalDbStream.close();
}

SQLiteDatabase openDataBase() throws SQLException {
    String path = DB_PATH + DB_NAME;
    if (database == null) {
        createDataBase();
        database = SQLiteDatabase.openDatabase(path, null,
                SQLiteDatabase.OPEN_READWRITE);
        //database = getWritableDatabase();
    }
    return database;
}

@Override
public synchronized void close(){
    if (database != null){
        database.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

}
}

UPDATE

Thank you Carlos. I agree its not a good idea to hardcode the path as it might be different device to device. I made the changes as you suggested, however I'm still getting the same error. I've verified that the yourdb.db file has read/write permissions for all levels.

I mentioned this in a previous comment, but could any of this be happening because I'm using a non-rooted phone? Could the permission of "yourdb.db" possibly change after copying it from the Asssets folder into /data/data/com.example.prepopdb/databases/ and then my program attempting to open it? I know how to change the permission using adb, but how do go about doing this from within the program?

Here's what my Logcat says:

01-14 12:18:02.240: E/Trace(18167): error opening trace file: No such file or directory (2)
01-14 12:18:02.240: D/ActivityThread(18167): setTargetHeapUtilization:0.25
01-14 12:18:02.240: D/ActivityThread(18167): setTargetHeapIdealFree:8388608
01-14 12:18:02.240: D/ActivityThread(18167): setTargetHeapConcurrentStart:2097152
01-14 12:18:02.360: D/AbsListView(18167): Get MotionRecognitionManager
01-14 12:18:02.370: E/SQLiteLog(18167): (14) cannot open file at line 30245 of [00bb9c9ce4]
01-14 12:18:02.370: E/SQLiteLog(18167): (14) os_unix.c:30245: (2) open(/data/data/com.example.prepopdb/databases/yourdb.db) - 
01-14 12:18:02.370: E/SQLiteDatabase(18167): Failed to open database '/data/data/com.example.prepopdb/databases/yourdb.db'.
01-14 12:18:02.370: E/SQLiteDatabase(18167): android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:278)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:217)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:464)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:186)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:178)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:804)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:789)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:694)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:669)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at com.example.prepopdb.ExternalDbOpenHelper.checkDataBase(ExternalDbOpenHelper.java:63)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at com.example.prepopdb.ExternalDbOpenHelper.createDataBase(ExternalDbOpenHelper.java:45)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at com.example.prepopdb.ExternalDbOpenHelper.openDataBase(ExternalDbOpenHelper.java:97)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at com.example.prepopdb.ExternalDbOpenHelper.<init>(ExternalDbOpenHelper.java:39)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at com.example.prepopdb.PrepopSqliteDbActivity.onCreate(PrepopSqliteDbActivity.java:35)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.app.Activity.performCreate(Activity.java:5048)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2052)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2113)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.app.ActivityThread.access$700(ActivityThread.java:139)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1224)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.os.Handler.dispatchMessage(Handler.java:99)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.os.Looper.loop(Looper.java:137)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at android.app.ActivityThread.main(ActivityThread.java:4918)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at java.lang.reflect.Method.invokeNative(Native Method)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at java.lang.reflect.Method.invoke(Method.java:511)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1004)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:771)
01-14 12:18:02.370: E/SQLiteDatabase(18167):    at dalvik.system.NativeStart.main(Native Method)
01-14 12:18:02.370: E/class com.example.prepopdb.ExternalDbOpenHelper(18167): Error while checking db
01-14 12:18:02.480: D/libEGL(18167): loaded /system/lib/egl/libEGL_adreno200.so
01-14 12:18:02.500: D/libEGL(18167): loaded /system/lib/egl/libGLESv1_CM_adreno200.so
01-14 12:18:02.500: D/libEGL(18167): loaded /system/lib/egl/libGLESv2_adreno200.so
01-14 12:18:02.540: I/Adreno200-EGLSUB(18167): <ConfigWindowMatch:2087>: Format RGBA_8888.
01-14 12:18:02.560: E/(18167): <s3dReadConfigFile:75>: Can't open file for reading
01-14 12:18:02.560: E/(18167): <s3dReadConfigFile:75>: Can't open file for reading
01-14 12:18:02.560: D/OpenGLRenderer(18167): Enabling debug mode 0
01-14 12:18:21.380: W/IInputConnectionWrapper(18167): beginBatchEdit on inactive InputConnection
01-14 12:18:21.380: W/IInputConnectionWrapper(18167): endBatchEdit on inactive InputConnection

推荐答案

You are assuming too much about the data folder. You rather should let the system give you the correct path. You can get database path with context.getDatabasePath(); you pass the desired name to the file (no matter if it exists or not). And actually you are supposed to do it that way

For that, at any place you are using something like String outFileName = DB_PATH + DB_NAME; you should change it for

 String outFileName =myContext.getDatabasePath(DB_NAME).getPath() ;

and that's the real valid location for your file. So wour helper will be like this

public class ExternalDbOpenHelper extends SQLiteOpenHelper {

// Path to the device folder with database
public static String DB_PATH;

// Database filename
public static String DB_NAME;
public SQLiteDatabase database;
public final Context context;

public SQLiteDatabase getDb() {
    return database;
}

public ExternalDbOpenHelper(Context context, String databaseName) {
    super(context, databaseName, null, 1);
    this.context = context;
        DB_NAME = databaseName;
            DB_PATH =context.getDatabasePath(DB_NAME).getPath() ;
    openDataBase();

}

// Create a database if its not yet created
public void createDataBase() {
    boolean dbExist = checkDataBase();
    if (!dbExist) {
        this.getReadableDatabase();
        try {
            copyDataBase();
        } catch (IOException e) {
            Log.e(this.getClass().toString(), "Copying error!");
            throw new Error("Error copying database!");
        }
    } else {
        Log.i(this.getClass().toString(), "Database already exists");
    }
}

//Performing a database existence check
private boolean checkDataBase(){
    SQLiteDatabase checkDb = null;
    try {

        checkDb = SQLiteDatabase.openDatabase(DB_PATH, null, SQLiteDatabase.OPEN_READONLY);
    } catch (SQLException e){
        Log.e(this.getClass().toString(), "Error while checking db");
    }

    if (checkDb != null){
        checkDb.close();
    }
    return checkDb !=null;
}

private void copyDataBase() throws IOException {
    //Open a stream for reading, located in the assets
    InputStream externalDbStream = context.getAssets().open(DB_NAME);



    //Create a stream for writing the database byte by byte
    OutputStream localDbStream = new FileOutputStream(DB_PATH);

    //Copy the database
    byte[] buffer = new byte[1024];
    int bytesRead;
    while((bytesRead = externalDbStream.read(buffer)) > 0){
        localDbStream.write(buffer, 0, bytesRead);
    }

             //FLUSH THE OUT STREAM
             localDbStream.flush();

    //Close the streams
    localDbStream.close();
    externalDbStream.close();
}

SQLiteDatabase openDataBase() throws SQLException {

    if (database == null) {
        createDataBase();
        database = SQLiteDatabase.openDatabase(DB_PATH, null,
                SQLiteDatabase.OPEN_READWRITE);
        //database = getWritableDatabase();
    }
    return database;
}

@Override
public synchronized void close(){
    if (database != null){
        database.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

}
}

with this it should work

UPDATE

Yo can take a few of considerations:

  • take a look at what path is the system returning for your database

    DB_PATH =context.getDatabasePath(DB_NAME).getPath() ;
    Log.i ("myApp", DB_PATH);
    
  • check the code in the emulator, to see if you have the same problems. there you can manually check if the file is actually created, as explained here

  • add permissions to write and read the sdcard (READ_EXTERNAL_STORAGE and WRITE_EXTERNAL_STORAGE). but i dont actually believe you need this