I have two databases, one database is the primary. This primary DB is responsible for holding the current data which is up to date and my secondary DB is populated via a cron job, once the primary DB gets obsolete I want to replace it with the secondary DB via a file operation of just over writing the existing DB and refreshing my views. Is it possible to do this, is there a better way?
So far what I have done is:
public void writeToSD() throws IOException {
File f=new File("/mnt/sdcard/dump.db");
FileInputStream fis=null;
FileOutputStream fos=null;
try{
fis=new FileInputStream(f);
fos=new FileOutputStream("/data/data/com.one.two/databases/Bdr");
while(true){
int i=fis.read();
if(i!=-1){
fos.write(i);
}
else{
break;
}
}
fos.flush();
}
catch(Exception e){
e.printStackTrace();
}
finally{
try{
fos.close();
fis.close();
}
catch(IOException ioe){
System.out.println(ioe);
}
}
How about always using the same database files (let's say dbA, dbB) with two instances of SQLiteOpenHelper and using an utility class like this instead of using raw SQLiteOpenHelper:
class Db {
private SQLiteOpenHelper mPrimaryDb;
private SQLiteOpenHelper mSecondaryDb;
public Db(Context context) {
mPrimaryDb = new MyDbHelper(context, "db_a");
mSecondaryDb = new MyDbHelper(context, "db_b");
}
public SQLiteOpenHelper getPrimaryDb() {
return mPrimaryDb;
}
public SQLiteOpenHelper getSecondaryDb() {
return mSecondaryDb;
}
public void swapDb() {
SQLiteOpenHelper tmp = mPrimaryDb;
mPrimaryDb = mSecondaryDb;
mSecondaryDb = tmp;
// TODO: notify data users that data has changed, cleanup the old primary database, etc.
}
{
If you want to use file operations, renaming the data base files is faster. But during file operations all connections have to be closed before any action.
If insertion is too slow, I would not overwrite the database file. I would generate the new database with a temp name and the same table and view structure. After finishing writing to the temp file I would rename the file to the same name as the invariant part of the old database plus a version number or a timestamp . And in my application I would look periodically for a new version, if found I would close all connections to the old file and open the new database.
Related
My question is that I want to restore my application's sqlite database after I overwrite the same app on my device. I don't like to add settings again and again on start up of my app.
So is it possible in android to save the database somewhere from which I can again restore it ?
I have searched for more than hours on Google and SO but couldnt ind any solution.
EDIT: Its not a fixed database. So I can't store it in Assets Folder. It is editable by user but by default it should carry the last edited values(values before the app overwrite).
This method I find very helpful:
public static void movedb(File srcdb, File destdb)
{
try
{
if (Environment.getExternalStorageDirectory().canWrite())
{
if (srcdb.exists())
{
FileChannel src = new FileInputStream(srcdb).getChannel();
FileChannel dst = new FileOutputStream(destdb).getChannel();
dst.transferFrom(src, 0, src.size());
src.close();
dst.close();
}
else
{
//ERROR: "Database file references are incorrect"
}
}
else
{
//ERROR: "Cannot write to file"
}
}
catch (Exception e)
{
//ERROR: e.getMessage()
}
}
Then I just call
movedb(this, new File(<context>.getDatabasePath("...your DB name...")), new File("... your location ..."));
To back up, and then to restore:
movedb(this, new File("... your location ..."), new File(<context>.getDatabasePath("...your DB name...")));
I'm using ORMLite and, apart from storing the database in the external public directory, after I restore the file to the database directory, I have to re-instantiate the DatabaseHelper singleton and create a new one.
Here is my version, omitting every try/catch block for the sake of simplicitiy:
public boolean restoreBackup(Context context){
String databasePath = "data/data/my.package.name/databases/myDatabase.sqlite";
String backUpPath = context.getDatabaseDir("myDatabase.sqlite");
// Copies back-up to database directory
new File(databasePath).delete();
FileInputStream streemToBackUp = new FileInputStream(new File(backUpPath));
OutputStream streamToDatabaseFile = new FileOutputStream(databasePath);
byte[] buffer = new byte[1024];
int length;
while ((length = streamToBackUp.read(buffer)) > 0) {
streamToDatabaseFile.write(buffer, 0, length);
}
streamToDatabaseFile.flush();
streamToDatabaseFile.close();
streamToBackUp.close();
// Re-instantiate DatabasHelper singleton
DatabaseHelper.closeHelper();
}
The body of closeHelper() is as follows:
public static void closeHelper() {
helper.close();
}
#Override
public void close() {
super.close();
myDao = null; // Set to null every day you have
helper = null; // Set to null the singleton instance of the helper
}
This will work as long as you don't use OpenHelperManager class to instantiate the helper, and always use getHelper() whenever you need the database instead of storing the instance returned.
I have a problem with a database file not being read
I have added the database file in assets called mydb but when i run my code it says its not being located. It is calling this toast Toast.makeText(this, "No contact found", Toast.LENGTH_LONG).show(); This is being called because no records are being returned. Also I know it is finding the file as there is no FileNotFoundException exception. This is an example form Android Application Development book.
public class DatabaseActivity extends Activity {
/** Called when the activity is first created. */
TextView quest, response1, response2;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
TextView quest = (TextView) findViewById(R.id.quest);
try {
String destPath = "/data/data/" + getPackageName() + "/databases/MyDB";
File f = new File(destPath);
if (!f.exists()) {
CopyDB( getBaseContext().getAssets().open("mydb"),
new FileOutputStream(destPath));
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
DBAdapter db = new DBAdapter(this);
//---get a contact---
db.open();
Cursor c = db.getContact(2);
if (c.moveToFirst())
DisplayContact(c);
else
Toast.makeText(this, "No contact found", Toast.LENGTH_LONG).show();
db.close();
}
public void CopyDB(InputStream inputStream, OutputStream outputStream)
throws IOException {
//---copy 1K bytes at a time---
byte[] buffer = new byte[1024];
int length;
while ((length = inputStream.read(buffer)) > 0) {
outputStream.write(buffer, 0, length);
}
inputStream.close();
outputStream.close();
}
public void DisplayContact(Cursor c)
{
quest.setText(String.valueOf(c.getString(1)));
//quest.setText(String.valueOf("this is a text string"));
}
}
Is there a better way to upload data.
A couple of things come to mind here...
because of the !f.exists() check, then once the database exists (and maybe empty) then it will never copy it again. So maybe for now, copy it all the time, until you work out kinks and then add in the !f.exists()
I've had mixed results with e.printStackTrace(), maybe change to Log.e(TAG, "message", e) and see if you start seeing errors showing up in LogCat
As for a better way... I've done this a couple different ways...
1. Is to create a file (json, cvs, etc) and then process and load it, if the database is empty
2. Similar to the first, except that I create a java serialized object array and load it to the database, if the database is empty.
Also I don't know what DBAdapter looks like, and since it wraps the database the issue may be there.
I wish to pack a lot of data in my android package. May I use database for this? If yes, then how to pack database tables with APK?
You may put your database in the assets/ folder and when your application is run for the first time use the following code to copy your databases where they are supposed to be:
private void copyFromAssets() {
InputStream istream = null;
OutputStream ostream = null;
try {
istream = context.getAssets().open(DATABASE_NAME);
File path = context.getDatabasePath(DATABASE_NAME);
if (path.exists() == false)
path.createNewFile();
ostream = new FileOutputStream(path);
byte[] buffer = new byte[8192];
int length;
while ((length = istream.read(buffer))>0) {
ostream.write(buffer, 0, length);
}
ostream.flush();
} catch (Exception e) {
e.printStackTrace();
Log.e(TAG, "Failed to copy database: " + DATABASE_NAME);
} finally {
try {
if (ostream != null) ostream.close();
if (istream != null) istream.close();
} catch (IOException e) {}
}
}
After that you may use your database the usual way.
To create the table you can use the SQLiteOpenHelper (ref here and credit there)
private class MyOpenHelper extends SQLiteOpenHelper {
public MyOpenHelper(Context context)
{
super(context, DB_NAME, null, DB_VERSION);
}
#Override public void onCreate(SQLiteDatabase db)
{
// Replace this SQL code with the code for your database.
String query = "CREATE TABLE people (" +
"_id integer primary key autoincrement not null, " +
"first_name text, last_name text);";
db.execSQL(query);
}
#Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
// Called when the database needs to be upgraded. The implementation
// should use this method to drop tables, add tables, or do anything
// else it needs to upgrade to the new schema version.
}
}
The table will be created or updated when accessed if needed.
You can also populate the database if needed after table creation.
You might want to provide a web-service to feed the initial data if it can help decreasing the size of the APK (and if size is your concern).
Since APKs are still limited to 50MB you could try adding the database as an expansion file, separately from the application. Here are more details: http://android-developers.blogspot.com/2012/03/android-apps-break-50mb-barrier.html
I use the following code to add rows to my database :
public void insert(String kern, String woord) {
SQLiteDatabase db = getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KERN, kern);
values.put(WOORD, woord);
db.insertOrThrow(TABLE_NAME, null, values);
return;
Currently, I'm invoking this insert() 3.455 times, to add all words to the database, using : insert("Fruits", "Banana"); It takes forever.
How can I change this code to work faster? I'm thinking in the line of foreach, but don't know how to implement.. Thanks!
/Edit; The solution provided by #hovanessyan works and will do the job. AND.. note that if you have a lot of lines that have to be put in, you might be confronted with the method exceeds max byte limit error. In that case, review the other solution, that suggests packing the database in the actual .APK file.
You can wrap-up those inserts into transaction.
db.beginTransaction();
try {
// do all the inserts here
//method call here, that does 1 insert; For example
addOneEntry(kern,woord);
...
db.setTransactionSuccessful();
} catch (SQLException e) {
//catch exceptions
} finally {
db.endTransaction();
}
private void addOneEntry(String kern, String woord) {
//prepare ContentValues
//do Insert
}
You can use bulkInsert:
ContentValues[] cvArr = new ContentValues[rows.size()];
int i = 0;
for (MyObject row : rows) {
ContentValues values = new ContentValues();
values.put(KERN, myObject.getKern());
values.put(WOORD, myObject.getWoord);
cvArr[i++] = values;
}// end for
resolver.bulkInsert(Tasks.CONTENT_URI, cvArr);
Using the tips of both hovanessyan and Damian (remind me to rep+1 you as soon as I reach 15 ;), I came up with the following solution:
For relatively small databases (<1,5Mb)
I created the database using SQLite Database Browser, and put it in my Assets folder.
Then, the following code copies the database to the device, if it's not already there:
boolean initialiseDatabase = (new File(DB_DESTINATION)).exists();
public void copyDB() throws IOException{
final String DB_DESTINATION = "/data/data/happyworx.nl.Flitswoorden/databases/WoordData.db";
// Check if the database exists before copying
Log.d("Database exist", "" + initialiseDatabase);
Log.d("Base Context", "" + getBaseContext());
if (initialiseDatabase == false) {
// Open the .db file in your assets directory
InputStream is = getBaseContext().getAssets().open("WoordData.db");
// Copy the database into the destination
OutputStream os = new FileOutputStream(DB_DESTINATION);
byte[] buffer = new byte[1024];
int length;
while ((length = is.read(buffer)) > 0){
os.write(buffer, 0, length);
}
os.flush();
os.close();
is.close();
}}
In my app, a portion of the database is User-customizable.
I call the code above in onStart() with :
try {
copyDB();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
So, when the user presses "reset database to standard" (in preferences screen), I just set the Boolean initialiseDatabase to "false" and wait for the user to go back to the main activity. (thus calling onstart and copying the original database).
I tried to call the Activity.copyDB() from the preferences.java. It's neater, because it doesn't require the user to go back to the main activity to rebuild the database. However, I get an error about not being able to call static references to non-static methods. I don't understand that, but will look into it.
SqliteOpenHelper by default creates database in mode_private. How can we create world readable/writable db using SqliteOpenHelper ?
Or Else Do I need to use Context.openOrCreateDatabase()
How can we create world readable/writable db using SqliteOpenHelper ?
We can't do that. ContextImpl.openOrCreateDatabase() actually opens/creates database using SQLiteDatabase.openOrCreateDatabase() method and then sets the permission for the database file using class android.os.FileUtils which is not part of the public API. So unless you want to use reflection the only possible way to make database world-readable/-writable is to use Context.openOrCreateDatabase().
Opening a Database as world Readable/writable is definitely possible. But then what is the necessity of a Database? You can use files instead..!!
Opening a Database as world Readable/writable is not recommended.
Always remember this:
Open a database only when necessary,
because it is costly.
Open only in the mode necessary either
read or write or both.
Close it as soon as the manipulations
are over.
If you want to share a Database or a resource among your applications you can use SharedUserID. Inorder to use SharedUserID, the applications must be signed by the same Key.
For More info see my post here at sree.cc
http://sree.cc/google/android/sharing-resources-in-different-aplications-using-shareduserid
Here is the code Snippet for the same:
private void getDB() {
//accessing file using SHAREDUSERID
try
{
//creating context from mainAPP for accessing database
ctx = createPackageContext(
"com.schogini.sharedDB.pack",
Context.CONTEXT_IGNORE_SECURITY);
if(ctx==null){
return;
}
}
catch (PackageManager.NameNotFoundException e) {
//package not found
Log.e("Error",e.getMessage());
}
try
{
File myDbFile = ctx.getDatabasePath("sharedDB.db");
if (myDbFile.exists())
{
dbb = openOrCreateDatabase(myDbFile.getPath(), SQLiteDatabase.OPEN_READWRITE, null);
dbb.setVersion(1);
dbb.setLocale(Locale.getDefault());
dbb.setLockingEnabled(true);
try{
cur=dbb.rawQuery("select * from TABLENAME;",null);
try{
cur.moveToFirst();
int k=cur.getColumnCount();
lv_arr=new String[k];
for(int i=0;i<k;i++)
{
lv_arr[i]=""+cur.getString(i);
Toast.makeText(LaunchActivity.this, "Data "+i, Toast.LENGTH_SHORT).show();
}
}
catch(Exception e)
{
//may be an empty database
Log.e("Error",e.getMessage());
dbb.close();
}
}
catch(Exception e)
{
Log.e("Error",e.getMessage());
dbb.close();
}
}
else
{
//database not found
Toast.makeText(LaunchActivity.this, "DataBase Doesnot Exist", Toast.LENGTH_SHORT).show();
}
}
catch(Exception e)
{
Log.i("\n\nTAG",e.toString());
}
}
Not recommended:
If you want the word readable, then create it world readable. Use openFileOutput() or openOrCreateDatabase(). Declare the context that creates the DB as World readable. Note this method is not safe by any means.
Do a reference here.
http://developer.android.com/reference/android/content/Context.html#MODE_WORLD_READABLE