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Monthly Archives: September 2011

Using your own SQLite database in Android applications

Most all of the Android examples and tutorials out there assume you want to create and populate your database at runtime and not to use and access an independent, preloaded database with your Android application.

The method I’m going to show you takes your own SQLite database file from the “assets” folder and copies into the system database path of your application so the SQLiteDatabase API can open and access it normally.

 

1. Preparing the SQLite database file.

Assuming you already have your sqlite database created, we need to do some modifications to it.
If you don’t have a sqlite manager I recommend you to download the opensourceSQLite Database Browser available for Win/Linux/Mac.

Open your database and add a new table called “android_metadata”, you can execute the following SQL statement to do it:

CREATE TABLE "android_metadata" ("locale" TEXT DEFAULT 'en_US')

Now insert a single row with the text ‘en_US’ in the “android_metadata” table:

INSERT INTO "android_metadata" VALUES ('en_US')

Then, it is necessary to rename the primary id field of your tables to “_id” so Android will know where to bind the id field of your tables.
You can easily do this with SQLite Database Browser by pressing the edit table button Edit Table, then selecting the table you want to edit and finally selecting the field you want to rename.

After renaming the id field of all your data tables to “_id” and adding the “android_metadata” table, your database it’s ready to be used in your Android application.

Modified databaseModified database

Note: in this image we see the tables “Categories” and “Content” with the id field renamed to “_id” and the just added table “android_metadata”.

2. Copying, opening and accessing your database in your Android application.

Now just put your database file in the “assets” folder of your project and create a Database Helper class by extending the SQLiteOpenHelper class from the “android.database.sqlite” package.

Make your DataBaseHelper class look like this:

public class DataBaseHelper extends SQLiteOpenHelper{

    //The Android's default system path of your application database.
    private static String DB_PATH = "/data/data/YOUR_PACKAGE/databases/";

    private static String DB_NAME = "myDBName";

    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;
    }	

  /**
     * 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) {

	}

        // Add your public helper methods to access and get content from the database.
       // You could return cursors by doing "return myDataBase.query(....)" so it'd be easy
       // to you to create adapters for your views.

}

That’s it.
Now you can create a new instance of this DataBaseHelper class and call the createDataBase() and openDataBase() methods. Remember to change the “YOUR_PACKAGE” to your application package namespace (i.e: com.examplename.myapp) in the DB_PATH string.

       ...

        DataBaseHelper myDbHelper = new DataBaseHelper();
        myDbHelper = new DataBaseHelper(this);

        try {

        	myDbHelper.createDataBase();

 	} catch (IOException ioe) {

 		throw new Error("Unable to create database");

 	}

 	try {

 		myDbHelper.openDataBase();

 	}catch(SQLException sqle){

 		throw sqle;

 	}

        ...


Referenced by: http://www.reigndesign.com/blog/using-your-own-sqlite-database-in-android-applications/
 
2 Comments

Posted by on September 28, 2011 in Android, Mobile Development

 

Add comments in Eclipse with a single keystroke

When you want to work with comments in Eclipse, you could use the slow way of moving to the start of the line, pressing // and then repeating this for all the lines you have.

Or you could use the quick way of adding a comment with a single keystroke no matter where the cursor’s positioned in the statement.

The same goes for Javadocs – there are just too many things to type before you can start commenting the good stuff. That’s why Eclipse also has a shortcut that let’s you add Javadoc to a field, method or class.

 

Keyboard shortcuts for comments and JavaDocs

Here are the keyboard shortcuts for manipulating comments.

Shortcut
Command Description
Ctrl+/ Toggle Comment Add/remove line comments (//…) from the current line. The position of the cursor can be anywhere on the line. Works with multiple selected lines as well.Alternatively, you can also use Ctrl+Shift+C, which probably works better on a QWERTZ keyboard (eg. German layout), or Ctrl+7.
Ctrl+Shift+/ Add Block Comment Wrap the selected lines in a block comment (/*… */).
Ctrl+Shift+\ Remove Block Comment Remove a block comment (/*… */) surrounding the selected lines.
Alt+Shift+J Add Javadoc Comment Add a Javadoc comment to the active field/method/class. See the notes below for more details on where to position the cursor.
 
4 Comments

Posted by on September 23, 2011 in Eclipse

 

Share Root Drive(\\RemoteMachine\C$) in Windows 7

User Account Control (UAC) is a new security component of Windows Vista. UAC enables users to perform common day-to-day tasks as non-administrators. These users are called “standard users” in Windows Vista. User accounts that are members of the local Administrators group will run most applications by using the principle of “least privilege.” In this scenario, least-privileged users have rights that resemble the rights of a standard user account. However, when a member of the local Administrators group has to perform a task that requires administrator rights, Windows Vista automatically prompts the user for approval.

To disable UAC remote restrictions, follow these steps:

  1. Click Start, click Run, type regedit, and then press ENTER.
  2. Locate and then click the following registry subkey:HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
  3. If the LocalAccountTokenFilterPolicy registry entry does not exist, follow these steps:
    1. On the Edit menu, point to New, and then click DWORD Value.
    2. Type LocalAccountTokenFilterPolicy, and then press ENTER.
  4. Right-click LocalAccountTokenFilterPolicy, and then click Modify.
  5. In the Value data box, type 1, and then click OK.
  6. Exit Registry Editor.
There is a registry key which will be able to utilize to alter this performance to work the similar as Windows XP. This will create your PC less safe, and I can’t suggest that you do this but it’s also fine to appreciate how Windows executes.

Manual Registry Hack

Explore regedit.exe during the start menu search or run box, and after that navigate down to the below key, making another key if it doesn’t be present.

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\Curr entVersion\Policies\System

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On the right hand side of window, place a new 32-bit DWORD figure known as LocalAccountTokenFilterPolicy and put the figure to 1.

To delete this tweak you will able to locate the value to 0 or just remove the key.

Now you will be able to map to the C$ share and also execute a few other administrative task distantly. You will require activating file sharing in the network and distributing center, and then make certain that your firewall configurations will permit sharing.

 
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Posted by on September 1, 2011 in General