Android 尝试打开在资产文件夹中预先创建的SQLite数据库时出错
我在SQLite中预先创建了一个数据库，并将其插入到assets文件夹中，不幸的是，我无法访问该数据库 例如，当我尝试使用命令访问数据库时Android 尝试打开在资产文件夹中预先创建的SQLite数据库时出错,android,database,sqlite,Android,Database,Sqlite,我在SQLite中预先创建了一个数据库，并将其插入到assets文件夹中，不幸的是，我无法访问该数据库 例如，当我尝试使用命令访问数据库时 DataBaseHelper myDbHelper = new DataBaseHelper(this); myDbHelper = new DataBaseHelper(this); try { myDbHelper.openDataBase(); }catch(SQLEx
DataBaseHelper myDbHelper = new DataBaseHelper(this);
myDbHelper = new DataBaseHelper(this);
try {
myDbHelper.openDataBase();
}catch(SQLException sqle){
throw sqle;
}
E/AndroidRuntime(5390): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mysoftware.app/com.mysoftware.app.Home}: android.database.sqlite.SQLiteException: unable to open database file
public class DataBaseHelper extends SQLiteOpenHelper{
private static String DB_PATH = "/data/data/com.mysoftware.app/databases/";
private static String DB_NAME = "DBTestate";
private SQLiteDatabase myDataBase;
private final Context myContext;
public DataBaseHelper(Context context) {
super(context, DB_NAME, null, 1);
this.myContext = context;
}
public void createDataBase() throws IOException{
boolean dbExist = checkDataBase();
SQLiteDatabase db_Read = null;
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();
db_Read = this.getReadableDatabase();
db_Read.close();
try {
copyDataBase();
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
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;
}
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) {
}
....
}
只需使用它，这是正在运行的代码，将生成与资产文件夹类似的数据库
private static String LOG_TAG = "DATABASE";
private static String DB_PATH = "/data/data/you_package_name/databases/";
private static String DB_NAME = "Your_DB_Name";
private static String myPath = DB_PATH + DB_NAME;
private SQLiteDatabase myDataBase;
private final Context myContext;
public DatabaseHelper(Context context) {
// TODO Auto-generated constructor stub
super(context, DB_NAME, null, 1);
this.myContext=context;
}
public void creatDataBase () throws IOException {
boolean dbExist = checkDataBase();
if(dbExist){
Log.d(LOG_TAG,"DATABASE EXIST");
}else{
this.getReadableDatabase();
copyDataBase();
}
}
private void copyDataBase() throws IOException {
// TODO Auto-generated method stub
InputStream myInput = myContext.getAssets().open(DB_NAME);
String outFileName = DB_PATH + DB_NAME;
OutputStream myOutput = new FileOutputStream (outFileName);
byte[] buffer = new byte[1024];
int length;
while((length = myInput.read(buffer))>0)
myOutput.write(buffer,0,length);
myOutput.flush();
myOutput.close();
myInput.close();
}
private boolean checkDataBase() {
// TODO Auto-generated method stub
File dbFile = new File(DB_PATH + DB_NAME);
return dbFile.exists();
}
public void openDataBase() throws SQLiteException {
myDataBase = SQLiteDatabase.openDatabase(myPath,null, SQLiteDatabase.NO_LOCALIZED_COLLATORS);
}
@Override
public synchronized void close() {
// TODO Auto-generated method stub
if(myDataBase != null)
myDataBase.close();
super.close();
}
可以找到代码解释和详细信息。验证
com.mysoftware.app是否为应用程序的实际名称，以及文件结构和实际数据库是否在DDMS文件资源管理器中可见
此外，在本例中，您必须将预构建的数据库放到Eclipse项目的“资产”文件夹中 我有邓恩的理由
:
@AndreaF…这听起来很无聊，但请检查一下数据库名称。显然，数据库名称匹配XD@YaqubAhmad在发布之前，我已经跟随了你链接的教程。我的实现就是基于此。很遗憾，这不起作用。请尝试以下简单代码：
public class DatabaseHelper extends SQLiteOpenHelper{
//The Android's default system path of your application database.
String DB_PATH =null;
private static String DB_NAME = "extenalDB";
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 DatabaseHelper(Context context) {
super(context, DB_NAME, null, 1);
this.myContext = context;
DB_PATH="/data/data/"+context.getPackageName()+"/"+"databases/";
}
/**
* Creates a empty database on the system and rewrites it with your own database.
* */
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) {
}
//return cursor
public Cursor query(String table,String[] columns, String selection,String[] selectionArgs,String groupBy,String having,String[] orderBy,String youare,String myname, Object object, Object object2, Object object3, Object object4){
return myDataBase.query("EMP_TABLE", null, null, null, null, null, null, null);
}
}