将位于 Assets 文件夹中的预填充数据库放入 data/data/mypackage/databases

【问题标题】：Getting a prepopulated database located in the Assets folder into the data/data/mypackage/databases将位于 Assets 文件夹中的预填充数据库放入 data/data/mypackage/databases
【发布时间】：2014-01-13 21:15:59
【问题描述】：

我一直在尝试效仿：http://blog.softeq.com/2012/12/using-pre-populated-sqlite-database-in.html

本示例旨在向您展示如何打开存储在 Assets 文件夹中的预填充数据库。

已经创建了与该主题相关的线程，我已经尝试了提出的建议，但这并不能帮助我弄清楚程序为什么没有打开数据库文件。我究竟做错了什么？这是我在 LogCat 的前几行中得到的内容：

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)

我使用上面链接中提到的 SQLite 数据库浏览器创建了测试数据库，但我的数据库扩展名是“.db”而不是“.sqlite3”。 （虽然我也尝试过使用“.sqlite3”，但有类似/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 ExternalDbOpenHelper 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

谢谢卡洛斯。我同意硬编码路径不是一个好主意，因为它可能是不同的设备。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 yourdb.db 文件具有所有级别的读/写权限。

我在之前的评论中提到了这一点，但由于我使用的是非 root 手机，是否会发生这种情况？将“yourdb.db”的权限从Asssets文件夹复制到/data/data/com.example.prepopdb/databases/然后我的程序尝试打开它后，它的权限可能会改变吗？我知道如何使用 adb 更改权限，但是如何在程序中执行此操作？

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

【问题讨论】：

  • github.com/jgilfelt/android-sqlite-asset-helper
  • 同意。请使用SQLiteAssetHelper。您使用的代码很糟糕。
  • 感谢您的建议。我尝试了你们提供的链接中的示例，但是我收到的错误与我之前的代码相同。我真的不明白我做错了什么。这可能与我的手机没有 root 权限有关吗？
  • LogCat: 01-13 17:07:42.064: E/Trace(4960): 打开跟踪文件时出错：没有这样的文件或目录 (2) 01-13 17:07:42.064: D/ ActivityThread(4960): setTargetHeapUtilization:0.25 01-13 17:07:42.064: D/ActivityThread(4960): setTargetHeapIdealFree:8388608 01-13 17:07:42.064: D/ActivityThread(4960): setTargetHeapConcurrentStart:2097152 01-13 ：07：42.124：E / SQLiteLog（4960）：（14）无法在[00bb9c9ce4] 01-13 17：02：15.055的第30245行打开文件：E / SQLiteLog（4363）：（14）os_unix.c：30245： (2) 打开(/data/data/com.example.assethelper/databases/northwind) -
  • @hkg 你不需要root手机。别担心。它也与文件权限无关，因为创建文件的用户与尝试读取文件的用户相同。可能与写入权限有关，如果文件正在写入外部 sdcard 或类似的东西。请看看我的更新。

标签： android database


【解决方案1】：

您对数据文件夹的假设过多。你宁愿让系统给你正确的路径。 您可以使用context.getDatabasePath(); 获取数据库路径，并将所需的名称传递给文件（无论它是否存在）。实际上你应该这样做

为此，您可以在任何地方使用String outFileName = DB_PATH + DB_NAME; 之类的东西 你应该改变它

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

这是您文件的真正有效位置。所以wour helper会是这样的

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

}
}

这个应该可以工作

更新

您可以考虑以下几点：

  • 查看系统为您的数据库返回的路径

    DB_PATH =context.getDatabasePath(DB_NAME).getPath() ;
Log.i ("myApp", DB_PATH);

  • 检查模拟器中的代码，看看是否有同样的问题。在那里您可以手动检查文件是否实际创建，如here

    • 所述

  • 添加 permissions 以写入和读取 SD 卡（READ_EXTERNAL_STORAGE 和 WRITE_EXTERNAL_STORAGE）。但我真的不相信你需要这个

【讨论】：

  • 我做了 Log.i 并验证了系统正在将我的数据库发送到正确的路径。我无法检查是否像您在帖子中提到的那样使用模拟器创建文件，因为我没有根电话，但我可以看到使用 adb shell 创建的文件。在单步执行我的代码时，我可以看到文件大小从 0 增加到 3K，这是我要复制的实际文件的大小。该文件的权限如下：-rw-rw----。根据所有这些信息，文件似乎在那里并且应该能够打开。难道yourdb.db的格式不对？
  • 是的，可能是文件不正确。我放弃了它，因为在 logcat 中它用来说“文件在第 x 行损坏”之类的东西。如果你愿意，你可以试着检查一下，我在这里解释http://stackoverflow.com/a/20455597/2357411
  • 无论如何，如我所见，您得到的异常是 checkDataBase() 中的 android.database.SQLException，并且该异常被捕获，这就是我们所期望的，因为之后我们从 assets 中复制文件。所以无论如何你都会创建文件，我不确定你是否在openDataBase（）中抛出了任何进一步的异常。你？您可以到达的代码中的最后一点是什么？你从哪里知道文件没有打开？
  • 我添加了一个尝试 SQLiteDatabase.openDatabase() 并按照您的建议在打开 db 时捕获错误。当我运行代码时，它并没有落入 catch 语句，所以这一定意味着数据库正在打开。如果您查看最后 9 到 10 个 LogCat 条目，则会有一个显示“<75>
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