I want to know whether a particular database file exists in my codenameone app.
Here's the code I have:
if (CN.existsInFileSystem(Display.getInstance()
.getDatabasePath("my.db")))
overwriteDb = false;
It seems that the getDatabasePath method will create the database if it doesn't already exist, at least on the windows/eclipse simulator. (I haven't tried on any devices).
The javadocs say that getDatabasePath will return null when the database doesn't exist, however it returns the path of the newly created db file.
Is there a way to get the path without actually creating a zero byte file?
No it doesn't create the database, I just verified it in the code. The JavaDoc is incorrect and I fixed it for the next update. The code you have should work just fine.
This is the Android implementation of the method:
public String getDatabasePath(String databaseName) {
if (databaseName.startsWith("file://")) {
return databaseName;
}
File db = new File(getContext().getApplicationInfo().dataDir + "/databases/" + databaseName);
return db.getAbsolutePath();
}
You will notice null is never returned and nothing is created. The fixed docs look like this:
Returns the file path of the Database if support for database exists on the platform.
#param databaseName the name of the database with out / or path elements e.g. mydatabase.db
#return the file path of the database or null if database isn't supported
Related
I have the two following methods and I am using them to store a special value locally and be able to access it on application restart:
(Store value locally:)
private void SaveSet(string key, string value)
{
ISharedPreferences prefs = PreferenceManager.GetDefaultSharedPreferences(this);
ISharedPreferencesEditor prefEditor = prefs.Edit();
prefEditor.PutString(key, value);
// editor.Commit(); // applies changes synchronously on older APIs
prefEditor.Apply(); // applies changes asynchronously on newer APIs
}
(Read it again:)
private string RetrieveSet(string key)
{
ISharedPreferences prefs = PreferenceManager.GetDefaultSharedPreferences(this);
return prefs.GetString(key, null);
}
This works perfectly. Now is it possible to access and edit this Shared Preferences externally? Unfortunately, I cannot find any file when searching in folder
Phone\Android\data\com.<company_name>.<application_name>\files
nor anywhere else. I want / try to edit this value from my computer, after connecting the phone to it. Is this possible?
Alternatively: Can anyone maybe show me how to create a new file in the given path above, write/read it programmatically and how it stays there, even if application is closed / started again? So I can then edit this file with my computer anyhow?
I tried it with the following code, but unfortunately it doesn't work / no file is created or at least i cannot see it in the given path above:
//"This code snippet is one example of writing an integer to a UTF-8 text file to the internal storage directory of an application:"
public void SaveValueIntoNewFile(int value)
{
var backingFile = Path.Combine(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal), "newFile.txt");
using (var writer = System.IO.File.CreateText(backingFile))
{
writer.WriteLine(value.ToString());
}
}
Would be very happy about every answer, thanks in advance and best regards
What you're looking for is where Android stores the Shared Preference file for applications that make use of it's default PreferenceManager.
I'd refer to this SO post which answers your question pretty well
SharedPreferences are stored in an xml file in the app data folder,
i.e.
/data/data/YOUR_PACKAGE_NAME/shared_prefs/YOUR_PREFS_NAME.xml
or the default preferences at:
/data/data/YOUR_PACKAGE_NAME/shared_prefs/YOUR_PACKAGE_NAME_preferences.xml
SharedPreferences added during runtime are not stored in the Eclipse
project.
Note: Accessing /data/data/ requires superuser
privileges
A simple method is to use Android Device Monotor,you can open it by clicking Tools--> android-->Android Device Monotor...
For example:
The path in my device is as follows:
/data/data/YOUR_PACKAGE_NAME/shared_prefs/YOUR_PACKAGE_NAME_preferences.xml
And we notice three buttons in the upper right corner of the picture.
The first one is used toPull a file from the device,the second one is used to Push a file onto the device,and the last one is used to delete the preferences.xml file.
So we can pull the preferences.xml file from current device to our computer and edit it as we want, and then push the updated preferences.xml to the folder again.Then we will get the value of preferences.xml file .
I have following C# code in a console application.
Whenever I debug the application and run the query1 (which inserts a new value into the database) and then run query2 (which displays all the entries in the database), I can see the new entry I inserted clearly. However, when I close the application and check the table in the database (in Visual Studio), it is gone. I have no idea why it is not saving.
using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.SqlServerCe;
using System.Data;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
try
{
string fileName = "FlowerShop.sdf";
string fileLocation = "|DataDirectory|\\";
DatabaseAccess dbAccess = new DatabaseAccess();
dbAccess.Connect(fileName, fileLocation);
Console.WriteLine("Connected to the following database:\n"+fileLocation + fileName+"\n");
string query = "Insert into Products(Name, UnitPrice, UnitsInStock) values('NewItem', 500, 90)";
string res = dbAccess.ExecuteQuery(query);
Console.WriteLine(res);
string query2 = "Select * from Products";
string res2 = dbAccess.QueryData(query2);
Console.WriteLine(res2);
Console.ReadLine();
}
catch (Exception e)
{
Console.WriteLine(e);
Console.ReadLine();
}
}
}
class DatabaseAccess
{
private SqlCeConnection _connection;
public void Connect(string fileName, string fileLocation)
{
Connect(#"Data Source=" + fileLocation + fileName);
}
public void Connect(string connectionString)
{
_connection = new SqlCeConnection(connectionString);
}
public string QueryData(string query)
{
_connection.Open();
using (SqlCeDataAdapter da = new SqlCeDataAdapter(query, _connection))
using (DataSet ds = new DataSet("Data Set"))
{
da.Fill(ds);
_connection.Close();
return ds.Tables[0].ToReadableString(); // a extension method I created
}
}
public string ExecuteQuery(string query)
{
_connection.Open();
using (SqlCeCommand c = new SqlCeCommand(query, _connection))
{
int r = c.ExecuteNonQuery();
_connection.Close();
return r.ToString();
}
}
}
EDIT: Forgot to mention that I am using SQL Server Compact Edition 4 and VS2012 Express.
It is a quite common problem. You use the |DataDirectory| substitution string. This means that, while debugging your app in the Visual Studio environment, the database used by your application is located in the subfolder BIN\DEBUG folder (or x86 variant) of your project. And this works well as you don't have any kind of error connecting to the database and making update operations.
But then, you exit the debug session and you look at your database through the Visual Studio Server Explorer (or any other suitable tool). This window has a different connection string (probably pointing to the copy of your database in the project folder). You search your tables and you don't see the changes.
Then the problem get worse. You restart VS to go hunting for the bug in your app, but you have your database file listed between your project files and the property Copy to Output directory is set to Copy Always. At this point Visual Studio obliges and copies the original database file from the project folder to the output folder (BIN\DEBUG) and thus your previous changes are lost.
Now, your application inserts/updates again the target table, you again can't find any error in your code and restart the loop again until you decide to post or search on StackOverflow.
You could stop this problem by clicking on the database file listed in your Solution Explorer and changing the property Copy To Output Directory to Copy If Newer or Never Copy. Also you could update your connectionstring in the Server Explorer to look at the working copy of your database or create a second connection. The first one still points to the database in the project folder while the second one points to the database in the BIN\DEBUG folder. In this way you could keep the original database ready for deployment purposes and schema changes, while, with the second connection you could look at the effective results of your coding efforts.
EDIT Special warning for MS-Access database users. The simple act of looking at your table changes the modified date of your database ALSO if you don't write or change anything. So the flag Copy if Newer kicks in and the database file is copied to the output directory. With Access better use Copy Never.
Committing changes / saving changes across debug sessions is a familiar topic in SQL CE forums. It is something that trips up quite a few people. I'll post links to source articles below, but I wanted to paste the answer that seems to get the best results to the most people:
You have several options to change this behavior. If your sdf file is part of the content of your project, this will affect how data is persisted. Remember that when you debug, all output of your project (including the sdf) if in the bin/debug folder.
You can decide not to include the sdf file as part of your project and manage the file location runtime.
If you are using "copy if newer", and project changes you make to the database will overwrite any runtime/debug changes.
If you are using "Do not copy", you will have to specify the location in code (as two levels above where your program is running).
If you have "Copy always", any changes made during runtime will always be overwritten
Answer Source
Here is a link to some further discussion and how to documentation.
In my code I am prompting the user to load a json file.
I am then attempting to copy this file into an sqlite database.
Once I have the data I am then able to manipulate it as needed - but I need to get it there in the first place.
So step 1 is to get the data in.
I have progressed as far as prompting the user to navigate to the file they want - but when I try and read the file I get this error ..
ERROR: resources must reside in the root directory thus must start with a '/' character in Codename One! Invalid resource: file:///tmp/temp3257201851214246357..json
So I think that I need to copy this file to the root directory
I cannot find a link that shows me how to do this.
Here is my code so far ...
case "Import Script":
try
{
JSONParser json = new JSONParser();
if (FileChooser.isAvailable()) {
FileChooser.showOpenDialog(".json", e2-> {
String file = (String)e2.getSource();
if (file == null) {
home.add("No file was selected");
home.revalidate();
} else {
home.add("Please wait - busy importing");
home.revalidate();
String extension = null;
if (file.lastIndexOf(".") > 0) {
extension = file.substring(file.lastIndexOf(".")+1);
}
if ("json".equals(extension)) {
FileSystemStorage fs = FileSystemStorage.getInstance();
try {
InputStream fis = fs.openInputStream(file);
try(Reader r = new InputStreamReader(Display.getInstance().getResourceAsStream(getClass(), file), "UTF-8"))
{
Map<String, Object> data = json.parseJSON(r);
Result result = Result.fromContent(data);
...... I progress from here
The error is occurring on this line ...
try(Reader r = new InputStreamReader(Display.getInstance().getResourceAsStream(getClass(), file), "UTF-8"))
If I hard code a filename and manually place it in the /src folder it works ... like this ...
try(Reader r = new InputStreamReader(Display.getInstance().getResourceAsStream(getClass(), '/test.json'), "UTF-8"))
But that defeats the purpose of them selecting a file
Any help would be appreciated
Thanks
I suggest watching this video.
It explains the different ways data is stored. One of the core sources of confusion is the 3 different ways to store files:
Resources
File System
Storage
getResourceAsStream returns a read only path that's physically embedded in the jar. It's flat so all paths to getResourceAsStream must start with / and must have only one of those. I would suggest avoiding more than one . as well although this should work in theory.
The sqlite database must be stored in file system which is encapsulated as FileSystemStorage and that's really the OS native file system. But you can't store it anywhere you want you need to give the DB name to the system and it notifies you where the file is stored and that's whats explained in the code above.
I want to change the database name in SqlMapConfig.xml file from the application, does any one help me?
You can override the database when you instantiate the Ibatis mapper instance; I do this for switching between debug and release builds of the application and hence accessing a different target database.
If your xml file is in an assembly called DatalayerAssembly for example, you might have a method for returning your new Ibatis instance based on a database name like this:
public IBatisNet.DataMapper.ISqlMapper CreateNewIbatis(
String serverName,
String databaseName)
{
// Load the config file (embedded resource in assembly).
System.Xml.XmlDocument xmlDoc = IBatisNet.Common.Utilities.Resources.GetEmbeddedResourceAsXmlDocument("SqlMapConfig.xml, DatalayerAssembly");
// Overwrite the connectionString in the XmlDocument, hence changing database.
// NB if your connection string needs extra parameters,
// such as `Integrated Security=SSPI;` for user authentication,
// then append that to InnerText too.
xmlDoc["sqlMapConfig"]["database"]["dataSource"]
.Attributes["connectionString"]
.InnerText = "Server=" + serverName + ";Database=" + databaseName;
// Instantiate Ibatis mapper using the XmlDocument via a Builder,
// instead of Ibatis using the config file.
IBatisNet.DataMapper.Configuration.DomSqlMapBuilder builder = new IBatisNet.DataMapper.Configuration.DomSqlMapBuilder();
IBatisNet.DataMapper.ISqlMapper ibatisInstance = builder.Configure(xmlDoc);
// Now use the ISqlMapper instance ("ibatisInstance") as normal.
return ibatisInstance;
}
I'm using this approach in Ibatis 1.6.2.0 on .Net but the exact SqlMap config file might vary depending by version. Either way the approach is the same; you just might need a different Xml path (i.e. the bit that reads ["sqlMapConfig"]["database"] etc may need changing for your config file)
Hope that helps.
I already found out that there is no way to bundle files in an .apk and have them on /sdcard, the best option so far being to download the large files upon first run. I came accross a tutorial saying how to bundle an sqlite db with the apk and then copy it so that it can be accessed with SQLiteDatabase (thus doubling the space needed, and not using /sdcard at all).
http://developer.android.com/guide/topics/data/data-storage.html#db says all databases MUST be in /data/data/package_name/databases.
Is that really so? Is there a way to trick the framework into opening a database that is placed on the /sdcard partition? Is there a way to use another SQLite java wrapper/framework to access such databases?
If the answer to the above is 'No', what other options do I have? My data is very well represented in a relational model, but is just too big, plus, I want to be able to update it without the need to reinstall/upgrade the entire app.
Sure you can. The docs are a little conflicting about this as they also say that no limitations are imposed. I think they should say that relative paths are to the above location and dbs there ARE private. Here is the code you want:
File dbfile = new File("/sdcard/mydb.sqlite" );
SQLiteDatabase db = SQLiteDatabase.openOrCreateDatabase(dbfile, null);
System.out.println("Its open? " + db.isOpen());
Try this:
String dir = Environment.getExternalStorageDirectory().getPath()
File dbfile = new File(dir+"/mydb.sqlite");
SQLiteDatabase db = SQLiteDatabase.openOrCreateDatabase(dbfile, null);
System.out.println("Its open? " + db.isOpen());
Just an idea:
you can put your database.db into the assets folder.
if your database.db file is larger than 2Mb the system is unable to compress it, so you need other one options
you can rename your database.db for example database.jit or database.mp3 - which are not compressed, than at the first run you can rename it to database.db
check this out ...
storing android application data on SD Card
I share next code. Declare opcionesMenu Vector<String>
Vector < String > opcionesMenu = new Vector< String >();
// the database is SDCard. I saw the code to Blackberry (net.rim)
String rutaDB = "/storage/extSdCard/Android/databases/Offshore.db";
SQLiteDatabase db = SQLiteDatabase.openOrCreateDatabase(rutaDB, null);
Cursor cursor = db.rawQuery("SELECT Codigo, Nombre FROM Ruta ORDER BY Codigo, Nombre", null);
if (cursor.moveToFirst())
{
do
{
opcionesMenu.add(cursor.getString(0) + " - " + cursor.getString(1));
} while(cursor.moveToNext());
}
db.close();