我一直在尝试以下示例：http://blog.softeq.com/2012/12/using-pre-populated-sqlite-database-in.html
本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。
已经创建了与此主题相关的线程，我尝试了提出的建议，但这无助于我弄清楚程序为什么不打开数据库文件。我做错了什么？以下是我在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SQLite数据库浏览器创建了测试数据库，如上面链接中所述，但我的数据库扩展名是".db"而不是".sqlite3"。
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*/
}
以下是我的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
谢谢你，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。我按照你的建议进行了更改，但是我仍然会遇到同样的错误。我已验证您的db.db文件是否具有所有级别的读/写权限。
我在之前的评论中提到过这一点，但这可能是因为我使用的是无根手机吗？在将"yourdb.db"从Asssets文件夹复制到/data/data/com.example.propdb/databases/，然后我的程序试图打开它之后，它的权限可能会改变吗？我知道如何使用adb更改权限，但如何在程序中进行更改？
以下是我的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
您对数据文件夹的假设太多了。你应该让系统给你正确的路径。您可以使用context.getDatabasePath();获取数据库路径，然后将所需的名称传递给文件(无论该文件是否存在)。实际上你应该这样做
为此，在任何地方，您都可以使用类似String outFileName = DB_PATH + DB_NAME;的东西你应该把它换成
String outFileName =myContext.getDatabasePath(DB_NAME).getPath() ;
这才是你文件的真正有效位置。所以你的助手会像这个一样
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
}
}
有了这个，它应该可以工作
更新
Yo可以考虑以下几点：
查看系统返回数据库的路径
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。在那里你可以手动检查文件是否真的创建了，如所述
添加写入和读取SD卡的权限(read_EXTERNAL_STORAGE和write_EXTERNAL_STORAGE)。但我真的不相信你需要这个