当我尝试用sqlite数据库打开数据库文件时，它会显示以下错误：
[2014-05-19 23:50:51] Failed to open database file db_penpal.db
[2014-05-19 23:50:51] null
这是否意味着我的数据库包含一些错误？如果是，我该如何解决？
提前谢谢。
public class Database_handler extends SQLiteOpenHelper {
private static final int database_version = 1;
public static final String database_name = "db_e_pal.db";
public Database_handler(Context context) {
super(context, database_name, null, database_version);
}
@Override
public void onCreate(SQLiteDatabase db) {
//Creation de la table user
String create_t_user
= "CREATE TABLE IF NOT EXISTS user ("
+ "ID INTEGER PRIMARY KEY AUTOINCREMENT,"
+ "username varchar(20) NOT NULL,"
+ "password varchar(20) NOT NULL,"
+ "connected INTEGER(0) NOT NULL);";
String create_t_friend_request
= "CREATE TABLE IF NOT EXISTS friend_request ("
+ "ID INTEGER PRIMARY KEY AUTOINCREMENT,"
+ "username varchar(20) NOT NULL,"
+ "ID_last_message INTEGER NOT NULL);";
String create_t_friend
= "CREATE TABLE IF NOT EXISTS friend ("
+ "ID INTEGER PRIMARY KEY AUTOINCREMENT,"
+ "username varchar(20) NOT NULL,"
+ "connected INTEGER(0) NOT NULL);";
String create_t_message
= "CREATE TABLE IF NOT EXISTS message ("
+ "ID INTEGER PRIMARY KEY AUTOINCREMENT,"
+ "ID_friend INTEGER NOT NULL,"
+ "Sent bit(1) NOT NULL,"
+ "Body text NOT NULL,"
+ "DATE datetime NOT NULL);";
//execution des requetes
db.execSQL(create_t_user);
db.execSQL(create_t_friend_request);
db.execSQL(create_t_friend);
db.execSQL(create_t_message);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Supprimer les anciennes tables si elles existent
// Requetes pou les suppressions
String drop_t_user = "DROP TABLE IF EXISTS user";
String drop_t_message = "DROP TABLE IF EXISTS message";
String drop_t_friend = "DROP TABLE IF EXISTS friend";
String drop_t_friend_request = "DROP TABLE IF EXISTS friend_request";
// Suppression des tables
db.execSQL(drop_t_user);
db.execSQL(drop_t_message);
db.execSQL(drop_t_friend);
db.execSQL(drop_t_friend_request);
// Create tables again
onCreate(db);
}
//Les operation faites sur la bd "les CRUD"
//Vider la base de donnée
public void empty() {
SQLiteDatabase db = this.getWritableDatabase();
db.delete("user", null, null);
db.delete("message", null, null);
db.delete("friend", null, null);
db.delete("friend_request", null, null);
db.close();
}
}
这是日志：
05-20 04:35:10.757: D/dalvikvm(3907): GC_EXTERNAL_ALLOC freed 458K, 55% free 3317K/7303K,
external 1070K/1570K, paused 72ms
05-20 04:35:37.117: D/dalvikvm(3907): GC_CONCURRENT freed 435K, 47% free 3887K/7303K,
external 1530K/2027K, paused 4ms+5ms
05-20 04:35:37.117: D/Cursor(3907): Database path: db_e_pal.db
05-20 04:35:37.117: D/Cursor(3907): Table name : null
05-20 04:35:37.117: D/Cursor(3907): Database path: db_e_pal.db
05-20 04:35:37.117: D/Cursor(3907): Table name : null
public class DbHelper extends SQLiteOpenHelper {
// The Android's default system path of your application database.
private static String PACKAGENAME = "com.xyz";
private static String DB_PATH = "/data/data/" + PACKAGENAME + "/databases/";
public static String DB_NAME = "abc.db";
public static int DELETED = 1;
public static int UPDATED = 2;
public static int NEW_RECORD = 3;
private static final String TAG = "DbHelper";
private SQLiteDatabase myDataBase;
private final Context myContext;
/**
* Constructor Takes and keeps a reference of the passed context in order to
* access to the application assets and resources.
*
* @param context
*/
public DbHelper(final Context context) {
super(context, DB_NAME, null, 1);
this.myContext = context;
}
/**
* Creates a empty database on the system and rewrites it with your own
* database.
* */
public final void createDataBase() throws IOException {
final boolean dbExist = checkDataBase();
SQLiteDatabase db_Read = null;
if (dbExist) {
String create_t_user
= "CREATE TABLE IF NOT EXISTS user ("
+ "ID INTEGER PRIMARY KEY AUTOINCREMENT,"
+ "username varchar(20) NOT NULL,"
+ "password varchar(20) NOT NULL,"
+ "connected INTEGER(0) NOT NULL);";
String create_t_friend_request
= "CREATE TABLE IF NOT EXISTS friend_request ("
+ "ID INTEGER PRIMARY KEY AUTOINCREMENT,"
+ "username varchar(20) NOT NULL,"
+ "ID_last_message INTEGER NOT NULL);";
String create_t_friend
= "CREATE TABLE IF NOT EXISTS friend ("
+ "ID INTEGER PRIMARY KEY AUTOINCREMENT,"
+ "username varchar(20) NOT NULL,"
+ "connected INTEGER(0) NOT NULL);";
String create_t_message
= "CREATE TABLE IF NOT EXISTS message ("
+ "ID INTEGER PRIMARY KEY AUTOINCREMENT,"
+ "ID_friend INTEGER NOT NULL,"
+ "Sent bit(1) NOT NULL,"
+ "Body text NOT NULL,"
+ "DATE datetime NOT NULL);";
//execution des requetes
db_Read .execSQL(create_t_user);
db_Read .execSQL(create_t_friend_request);
db_Read .execSQL(create_t_friend);
db_Read .execSQL(create_t_message);
} 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.
// 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.
// db_Read = this.getReadableDatabase(DB_Internal);
db_Read = this.getReadableDatabase();
db_Read.close();
copyDataBase();
}
}
/**
* Restore whole database without any data
*
* @throws IOException
*/
public final void RestoreDatabase() throws IOException {
SQLiteDatabase db_Read = this.getReadableDatabase();
db_Read.close();
copyDataBase();
Log.i(TAG, "Database REstored");
}
/**
* 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() {
final File dbFile = new File(DB_PATH + DB_NAME);
return dbFile.exists();
}
/**
* 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.
*
* @throws IOException
* */
private void copyDataBase() throws IOException {
// Open your local db as the input stream
final InputStream myInput = myContext.getAssets().open(DB_NAME);
// Path to the just created empty db
final String outFileName = DB_PATH + DB_NAME;
// Open the empty db as the output stream
final OutputStream myOutput = new FileOutputStream(outFileName);
// transfer bytes from the inputfile to the outputfile
final 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 final SQLiteDatabase openDataBase() {
// Open the database
final String myPath = DB_PATH + DB_NAME;
if (myDataBase != null && myDataBase.isOpen()) {
myDataBase.close();
}
return myDataBase = SQLiteDatabase.openDatabase(myPath, null,
SQLiteDatabase.OPEN_READWRITE);
}
public final synchronized void closeDatabase() {
if (myDataBase != null)
myDataBase.close();
super.close();
}
@Override
public void onCreate(final SQLiteDatabase arg0) {
}
@Override
public void onUpgrade(final SQLiteDatabase arg0, final int arg1,
final int arg2) {
}
}
在您的代码中，您没有放入创建数据库的代码(从data/databases/ddd.db复制数据库(，因此您必须得到这种类型的错误。。
请试试这个。我希望它对你有用。。