Andrei Pop

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Mar 25, 12

Recently I've been working on a project and was somehow battling with linkifying text in Android and didn't want to go down the route of using HTML. Here is a solution that I've found.

Let's say you have an app and you want to add some links to the terms and conditions of the app and some other links - maybe a link to the about page.

We create a view with a couple of TextViews:

 <TextView  
     android:id="@+id/textView1"  
     android:layout_width="wrap_content"  
     android:layout_height="wrap_content"  
     android:textColor="@color/google_blue"  
     android:textColorLink="@color/google_red"  
     android:lineSpacingExtra="5sp"  
     android:padding="10dp"  
     />  
   <TextView  
     android:id="@+id/textView2"  
     android:layout_width="wrap_content"  
     android:layout_height="wrap_content"  
     android:textColor="@color/google_blue"  
     android:textColorLink="@color/google_red"  
     android:lineSpacingExtra="5sp"  
     android:padding="10dp"  
     android:layout_below="@id/textView1"  
      />

Notice that we assign different colours to the text and link. These colours have been defined in the values folder.

Having created the layout we set up the views by initialising them in the onCreate method. Here is where we linkify the TextViews.

 text1 = (TextView) findViewById(R.id.textView1);  
 text2 = (TextView) findViewById(R.id.textView2);  

           text1.setText(  
               Html.fromHtml(  
               "We got rid of over 60 different privacy policies across Google and replaced them with one that’s a lot shorter and easier to read. " +  
                   "<a href=\"http://www.google.co.uk/intl/en/policies\"> Find out more on our website.</a> "));  
           text1.setMovementMethod(LinkMovementMethod.getInstance());  


           text2.setText(  
               Html.fromHtml("Problems singning into your account?"  
                         + " Visit our " +  
                   "<a href=\"http://support.google.com/?hl=en\">Help Centers</a> "  
                         + " to learn the ins-and-outs of Google products and solve any problems you encounter."));  
            text2.setMovementMethod(LinkMovementMethod.getInstance());

Now we have the following view up and running.

It looks ok, but we can improve this further by removing the link underline. Here is how you would go about doing this.

Firstly we will have to create a new class that handles the URL spanning. It is good practice to add this to a utils package within your app.

 import android.text.TextPaint;  
 import android.text.style.URLSpan;  

 public class URLSpanNoUnderline extends URLSpan {  

   public URLSpanNoUnderline(String url) {  

     super(url);  

   }  

   @Override   
   public void updateDrawState(TextPaint tp) {  

     super.updateDrawState(tp);  
     tp.setUnderlineText(false);  

   }  

 }

Having added the above class to our project we then create a method inside our main activity which will handle the removal of the underline.

 private void stripUnderlines(TextView tv) {  

        Spannable s = (Spannable)tv.getText();  
        URLSpan[] spans = s.getSpans(0, s.length(), URLSpan.class);  

        for (URLSpan span: spans) {  
          int start = s.getSpanStart(span);  
          int end = s.getSpanEnd(span);  
          s.removeSpan(span);  
          span = new URLSpanNoUnderline(span.getURL());  
          s.setSpan(span, start, end, 0);  

        }  

        tv.setText(s);  

      }

We can now simply call the stripUnderlines method in our view set up.

 stripUnderlines(text1);  
 stripUnderlines(text2);

Now we have the same view with clickable text but without the specific link underline.

You can download the source via github.

Developing a Android SAX Parser

Mar 03, 12

SAX Parsing

Simple API for XML (SAX) is one of the two most common and simple ways to retrieve information from an XML document. Unlike, DOM parsing, data parsed with SAX is not entirely stored in memory, making it the 'memory efficient' parser.

If we take for example the BBC Latest UK News feed - http://feeds.bbci.co.uk/news/uk/rss.xml - and open up the XML's document source, we can take a closer look at the way in which the document is structured. This is important as it will give us an idea of how to structure our application from a programming point of view.

Using a SAX parser we will seek to produce an application which will display the latest news in a ListView.

If we analyse the XML source document - view-source:http://feeds.bbci.co.uk/news/uk/rss.xml - we notice that there is a clear structure to it. Each news item has a title, description, link, guide etc. Understanding the structure of the XML source will help us develop a good object orientated back-end.

Application Interface

The interface will be combined of 3 components:

a Refresh button
a ListView of news items
a TextView used when data can't be retrieved

We use the following layout as the main application layout.

 <?xml version="1.0" encoding="utf-8"?>  
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
      android:orientation="vertical"  
      android:layout_width="fill_parent"  
      android:layout_height="fill_parent"  
      >  
      <Button   
      android:id="@+id/refresh"   
      android:layout_gravity="center_horizontal"   
      android:text="@string/refresh"   
      android:layout_width="160dp"   
      android:layout_height="60dp"/>  
      <ListView  
           android:id="@android:id/list"  
           android:layout_width="fill_parent"  
           android:layout_height="wrap_content"/>  
      <TextView  
           android:id="@android:id/empty"  
           android:layout_width="fill_parent"  
           android:layout_height="wrap_content"  
           android:text="No Data Connection" />  
 </LinearLayout>

Manifest

Having created the interface, ensure that you allow the application permissions to connect to the internet. This can be done by adding the following line of code, above the tag in the Android Manifest.

 <uses-permission android:name="android.permission.INTERNET" />

Implementation

The application has been split into 4 classes as follows.

XMLItem - Holds the news item mutator and accessor methods will be defined

 package com.android.bbcxmlfeed;  

 /**  
  * This class handles the mutator and accessors methods of a news item.   
  * For each news item the title and the description is assigned as a string value.  
  *   
  * @author Andrei  
  *  
  */  
 public class XMLItem{  
      // class fields  
      private String title = null;  
      private String description = null;  

      /**  
       * Empty constructor.   
       */  
      public XMLItem(){  

      }  

      /**  
       * Assign the news title to the title field.   
       * @param value Set item title.  
       */  
      public void setTitle(String value){  
           title = value;  
      }  

      /**  
       * Assign the news description to the description field.   
       * @param value  
       */  
      public void setDescription(String value){  
           description = value;  
      }  

      /**  
       * This method returns the news item title.   
       * @return News item title.  
       */  
      public String getTitle(){  
           return title;  
      }  

      /**  
       * This method returns the news item description.  
       * @return News item description.  
       */  
      public String getDescription(){  
           return description;  
      }  

      /**  
       * Create a toString which appends the news item title with the news item description.  
       */  
      @Override  
      public String toString(){  
           return ("Title: "+title+"."+"\n"+"Description: "+description+"\n");  
      }  
 }

XMLFeed - Deals with the XML feed split

 package com.android.bbcxmlfeed;  

 import java.util.List;  
 import java.util.Vector;  

 /**  
  * This class handles the XML feed by creating a list of all the news items   
  * with their titles and descriptions.  
  *   
  * @author Andrei  
  *  
  */  
 public class XMLFeed {  
      // The fields.  
      private String title = null;  
      private String description = null;  

      // The vector array.  
      private List<XMLItem> itemList;  

      /**  
       * A list of items is created and assigned to a constructor with an initial empty initial size.    
       */  
      public XMLFeed(){  
           itemList = new Vector<XMLItem>(0);  
      }  

      /**  
       * Adds a news item to the list of news items.  
       * @param item News item.  
       */  
      public void addItem(XMLItem item){  
           itemList.add(item);  
      }  

      /**  
       * Gets and returns the news item location.  
       * @param location News item array location.  
       * @return The location in the array.   
       */  
      public XMLItem getItem(int location){  
           return itemList.get(location);  
      }  

      /**  
       * Returns the list of new items.  
       * @return News items.   
       */  
      public List<XMLItem> getList(){  
           return itemList;  
      }  

      /**  
       * Assigns string value to the news item title.   
       * @param value The title.  
       */  
      public void setTitle(String value){  
           title = value;  
      }  

      /**  
       * Assigns a string value to the news item description.  
       * @param value The Description.   
       */  
      public void setDescription(String value)  
      {  
           description = value;  
      }  

      /**  
       * Returns the title string.   
       * @return The title.  
       */  
      public String getTitle()  
      {  
           return title;  
      }  

      /**  
       * Returns the description string.  
       * @return The description.  
       */  
      public String getDescription()  
      {  
           return description;  
      }  
 }

XMLHandler - Handles the core sax parsing

 package com.android.bbcxmlfeed;  

 import org.xml.sax.Attributes;  
 import org.xml.sax.SAXException;  
 import org.xml.sax.helpers.DefaultHandler;  

 /**  
  * This class handles the SAX parsing.   
  *   
  * @author Andrei  
  *  
  */  
 public class XMLHandler extends DefaultHandler {  

      static final int state_unknown = 0;  
      static final int state_title = 1;  
      static final int state_description = 2;  

      private int currentState = state_unknown;  

      private XMLFeed feed;  
      private XMLItem item;  

      private boolean itemFound = false;  

      /**  
       * Class constructor method.   
       */  
      public XMLHandler(){  

      }  

      /**  
       * Gets the XML feed items.   
       * @return Feed items.   
       */  
      public XMLFeed getFeed(){  
           return feed;  
      }  

      // SAX parsing elements from here  
      @Override  
      public void startDocument() throws SAXException {  
           // TODO Auto-generated method stub  
           feed = new XMLFeed();  
           item = new XMLItem();  
      }  

      @Override  
      public void endDocument() throws SAXException {  
           // TODO Auto-generated method stub  
      }  

      @Override  
      public void startElement(String uri, String localName, String qName,  
      Attributes attributes) throws SAXException {  
           // TODO Auto-generated method stub  

           if (localName.equalsIgnoreCase("item")){  
                itemFound = true;  
                item = new XMLItem();  
                currentState = state_unknown;  
           }  
           else if (localName.equalsIgnoreCase("title")){  
                currentState = state_title;  
           }  
           else if (localName.equalsIgnoreCase("description")){  
                currentState = state_description;  
           }  
           else{  
                currentState = state_unknown;  
           }  
      }  

      @Override  
      public void endElement(String uri, String localName, String qName)  
      throws SAXException {  
      // TODO Auto-generated method stub  
           if (localName.equalsIgnoreCase("item")){  
                feed.addItem(item);  
           }  
      }  

      @Override  
      public void characters(char[] ch, int start, int length)  
      throws SAXException {  
      // TODO Auto-generated method stub  
           String strCharacters = new String(ch,start,length);  

           if (itemFound==true){  
                //If a news item is found, set it to the item parameter  
                switch(currentState){  
                case state_title:  
                     item.setTitle(strCharacters);  
                     break;  
                case state_description:  
                     item.setDescription(strCharacters);  
                     break;  
                default:  
                     break;  
           }  
      }  
           else{  
                // No news items found, it a feeds parameter  
                switch(currentState){  
                case state_title:  
                     feed.setTitle(strCharacters);  
                     break;  
                case state_description:  
                     feed.setDescription(strCharacters);  
                     break;  
                default:  
                     break;  
                }  
           }  

           currentState = state_unknown;  
      }  
 }

BBCXMLReader - The main app activity where the data is parsed and displayed in a ListView.

 package com.android.bbcxmlfeed;  

 import java.io.IOException;  
 import java.net.MalformedURLException;  
 import java.net.URL;  

 import javax.xml.parsers.ParserConfigurationException;  
 import javax.xml.parsers.SAXParser;  
 import javax.xml.parsers.SAXParserFactory;  

 import org.xml.sax.InputSource;  
 import org.xml.sax.SAXException;  
 import org.xml.sax.XMLReader;  

 import com.android.testfeed3.R;  

 import android.app.ListActivity;  
 import android.app.ProgressDialog;  
 import android.os.Bundle;  
 import android.os.Handler;  
 import android.os.Message;  
 import android.view.View;  
 import android.widget.ArrayAdapter;  
 import android.widget.Button;  

 /**  
  * The application's main activity. Handles the onCreate, onResume,  
  * refresh and getNews methods - which ultimately display the news items.   
  *   
  * @author Andrei  
  *  
  */  
 public class BBCXMLReader extends ListActivity {  

   private static final int THREAD_FINISHED = 0;  
   private XMLFeed myXMLFeed = null;  
   private ProgressDialog progressDialog;  
   private Button refreshFeed;  
   private boolean resumeHasRun = false;  
   //Handler handler = new Handler();  

   /** Called when the activity is first created. */  
   @Override  
   public void onCreate(Bundle savedInstanceState) {  
     super.onCreate(savedInstanceState);  
     setContentView(R.layout.main);  
     //  
     processThread();  
     //Get the UI controls - in this case we only have the refresh button.  
     initControls();  
   }  
   /**  
    * This method is used to handle all the UI controls. In this case it only deals with the refresh button.   
    */  
   public void initControls(){  


      refreshFeed = (Button) findViewById(R.id.refresh);  

      refreshFeed.setOnClickListener(new Button.OnClickListener(){  
        @Override  
        public void onClick(View v){  
          processThread();       
        }  
      });  
   }  
   /**  
    * Tracks to see if onResume has been called before,   
    * to avoid for both onResume and onCreate to be called.   
    */  
   protected void onResume() {  
           super.onResume();  

           if (!resumeHasRun){  
                resumeHasRun = true;  
                return;  
           }  

           processThread();  
      }  
   /**  
    * This method is used as a background processor for the app.   
    * It shows the progress dialog and it retrieves the news items.   
    *   
    */  
   protected void processThread() {  
        //Show a simple progress dialog.   
        progressDialog = ProgressDialog.show(BBCXMLReader.this, "",  
         "Fetching news items...", true, false);  
        //Create a new thread.  
        Thread t = new Thread(){  

             public void run(){  
               //Retrieve the news items from the BBC link.  
               getNews();  
               //Sends message to the handler so it updates the UI.  
               handler.sendMessage(Message.obtain(handler, THREAD_FINISHED));;   
          }  

     };  

     t.start();  

   }  
   /**  
    * The handler mainly deals with the UI of the application.   
    * It handles the loading of the ListView with all the items in it,   
    * and also it handles the dismissal of the progress dialog after the UI has been loaded.   
    */  
   private Handler handler = new Handler() {  
     @Override  
       public void handleMessage(Message msg) {  
         super.handleMessage(msg);  

         switch (msg.what) {  
         case THREAD_FINISHED:  
                         UI();  
               progressDialog.dismiss();  
               break;    
           };  

       };  
   };  
   /**  
    * This method loads the ListView UI.   
    */  
   private void UI(){  
          if (myXMLFeed!=null){  
         ArrayAdapter<XMLItem> adapter =  
           new ArrayAdapter<XMLItem>(this,  
            android.R.layout.simple_list_item_1,myXMLFeed.getList());  
           setListAdapter(adapter);  
       }  
   }  
   /**  
    * This method parses the data from the BBC XML link, via the SAX Parser and XMLHandler class.  
    * @see XMLHandler  
    */  
   private void getNews(){  
     try {  
       URL xmlUrl = new URL("http://feeds.bbci.co.uk/news/uk/rss.xml");  
       SAXParserFactory mySAXParserFactory = SAXParserFactory.newInstance();  
       SAXParser mySAXParser = mySAXParserFactory.newSAXParser();  
       XMLReader myXMLReader = mySAXParser.getXMLReader();  
       XMLHandler myXMLHandler = new XMLHandler();  
       myXMLReader.setContentHandler(myXMLHandler);  
       InputSource myInputSource = new InputSource(xmlUrl.openStream());  
       myXMLReader.parse(myInputSource);  
       myXMLFeed = myXMLHandler.getFeed();   
     }  
     //catch a bunch of exceptions  
     catch (MalformedURLException e) {  
       // TODO Auto-generated catch block  
       e.printStackTrace();  
     }   
     catch (ParserConfigurationException e) {  
       // TODO Auto-generated catch block  
       e.printStackTrace();  
     }   
     catch (SAXException e) {  
       // TODO Auto-generated catch block  
       e.printStackTrace();  
     }   
     catch (IOException e) {  
       // TODO Auto-generated catch block  
       e.printStackTrace();  
     }  
   }  
 }

The full source for this application is available on github.

Developing a Text-to-Speech Android application

Mar 03, 12

Text-to-Speech (TTS) was made available on the Android platform starting with Android 1.6. The TTS library, which comes free with the Android OS, enables the device to speak text of different languages. This post will look to outline the steps one has to take in order to create a simple speech synthesiser in Android.

Application layout

The first step is to implement the application layout. We are going to keep it simple, therefore we will only use 4 layout features:

A text box where users can type what they want to say;
A speak button, which would enable user to "speak" what they have typed;
A clear option used for clearing typed text;
A seek bar, which will allow the user to control the volume of the synthesiser.

The full XML layout can be accessed via github.

Application functionality

Having implemented the application layout we can now start developing the functions needed for this application to run.

The seek bar functionality:

 volumeManager = (AudioManager)getSystemService(Context.AUDIO_SERVICE);  
     int maxVolume = volumeManager.getStreamMaxVolume(AudioManager.STREAM_MUSIC);  
     int curVolume = volumeManager.getStreamVolume(AudioManager.STREAM_MUSIC);  
     SeekBar volumeControl = (SeekBar)findViewById(R.id.VolumeBar);  
     volumeControl.setMax(maxVolume);  
     volumeControl.setProgress(curVolume);  
     volumeControl.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {  

                @Override  
                public void onStopTrackingTouch(SeekBar arg0) {  
                     // TODO Auto-generated method stub  

                }  

                @Override  
                public void onStartTrackingTouch(SeekBar arg0) {  
                     // TODO Auto-generated method stub  

                }  

                @Override  
                public void onProgressChanged(SeekBar arg0, int arg1, boolean arg2) {  
                     // TODO Auto-generated method stub  
                     volumeManager.setStreamVolume(AudioManager.STREAM_MUSIC, arg1, 0);  
                }  
           });

The other user interface controls (text box & buttons) and their methods:

   
 private void initControls() {  
           inputText = (EditText) findViewById(R.id.InputField);  
           speakUp = (Button) findViewById(R.id.SpeakButton);  
           clearText = (Button) findViewById(R.id.ClearField);  


           speakUp.setOnClickListener(new Button.OnClickListener(){  
                @Override  
                public void onClick(View v) {  
                     SpeakText(v);  
                }  
           });  

           clearText.setOnClickListener(new Button.OnClickListener(){  
                public void onClick(View v) {  
                     Clear(v);  
                }  
           });  
      }

 private void SpeakText(View v) {  
           String text = inputText.getText().toString();  
           if(text!=null && text.length()>0) {  
                tts.speak(text, TextToSpeech.QUEUE_ADD, null);  
           }  
      }  

      private void Clear(View v) {  
           inputText.setText("");  
      }

TTS library

The TTS engine works like an API, therefore only a few lines of code will be needed to actually implement the Speak Activity feature.

The TTS feature is included on most devices, however, some might not have this therefore upon creating the activity will have to check if this is installed on the device, if it's missing install it:

 protected void onActivityResult(int requestCode, int resultCode, Intent data) {  
           if (requestCode == MY_DATA_CHECK_CODE) {  
                if (resultCode == TextToSpeech.Engine.CHECK_VOICE_DATA_PASS) {  
                     // success, create the TTS instance  
                     tts = new TextToSpeech(this, this);  
                }   
                else {  
                     // missing data, install it  
                     Intent installIntent = new Intent();  
                     installIntent.setAction(TextToSpeech.Engine.ACTION_INSTALL_TTS_DATA);  
                     startActivity(installIntent);  
                }  
           }  

      }

We also have to implement a validation method, which will notify the user in case the TTS engine fails to load:

 @Override  
      public void onInit(int status) {            
           if (status == TextToSpeech.SUCCESS) {  
                Toast.makeText(SpeakUpActivity.this,   
                          "Text-To-Speech engine is initialized", Toast.LENGTH_LONG).show();  
           }  
           else if (status == TextToSpeech.ERROR) {  
                Toast.makeText(SpeakUpActivity.this,   
                          "Error occurred while initializing Text-To-Speech engine", Toast.LENGTH_LONG).show();  
           }  
      }

You can access the full source code via github.

I am looking to develop this application further, by adding the following functionality:

Phrase list;
Personalised greeting message;
Ability to revert to the last typed phrase.

If you are interested in helping please fork the project on github.

Developing a simple SQLite driven login app

Mar 03, 12

SQLite, is a small yet powerful database engine, which is also one of the most widely deployed SQL database engine in the world. SQLite comes packaged with the Android SDK and it helps easily store and manage data in your Android app.

In developing the application firstly we will have to think of the kind of data we want to hold on the database; in our case purely the login information - a username and a password. It is good practice to also use a unique id which could help at a later stage if you would want to link to tables where data held in a different table is specific to a user.

The full source code for this application is available via GitHub.

Implementing the DatabaseAdapter

This database adapter is handling the queries and works mainly “like an API” which uses the SQLiteHelper built-in methods - add, remove and update items. In implementing this class you would have to take the following steps:

You will first have to start with defining the table name and columns - row id, username and password;
Implement a constructor which handles the relationship with the SQLHelper;
Define some database query methods e.g. in our case createUser, deleteUser, fetchUser etc. - basically the whole idea is to create methods which allow to create, open, close or update the table and table columns.

Below you can view the code for the DatabaseAdapter class.

 package com.android.database;  

 import android.content.ContentValues;  
 import android.content.Context;  
 import android.database.Cursor;  
 import android.database.SQLException;  
 import android.database.sqlite.SQLiteDatabase;  
 /**  
  * Adapts the database to deal with the front end.  
  *   
  * @author Andrei  
  *  
  */  
 public class DatabaseAdapter {  
      //Table name  
      private static final String LOGIN_TABLE = "user";  
      //Table unique id  
      public static final String COL_ID = "id";  
      //Table username and password columns   
      public static final String COL_USERNAME = "username";  
      public static final String COL_PASSWORD = "password";  

      private Context context;  
      private SQLiteDatabase database;  
      private DatabaseHelper dbHelper;  

      /**  
       * The adapter constructor.   
       * @param context  
       */  
      public DatabaseAdapter(Context context) {  
           this.context = context;  
      }  

      /**  
       * Creates the database helper and gets the database.   
       *   
       * @return  
       * @throws SQLException  
       */  
      public DatabaseAdapter open() throws SQLException {  
           dbHelper = new DatabaseHelper(context);  
           database = dbHelper.getWritableDatabase();  
           return this;  
      }  

      /**  
       * Closes the database.  
       */  
      public void close() {  
           dbHelper.close();  
      }  

      /**  
       * Creates the user name and password.  
       *   
       * @param username The username.  
       * @param password The password.  
       * @return  
       */  
      public long createUser(String username, String password) {  
           ContentValues initialValues = createUserTableContentValues(username, password);  
           return database.insert(LOGIN_TABLE, null, initialValues);  
      }  

      /**  
       * Removes a user's details given an id.  
       *   
       * @param rowId Column id.   
       * @return  
       */  
      public boolean deleteUser(long rowId) {  
           return database.delete(LOGIN_TABLE, COL_ID + "=" + rowId, null) > 0;  
      }  

      public boolean updateUserTable(long rowId, String username, String password) {  
           ContentValues updateValues = createUserTableContentValues(username, password);  
           return database.update(LOGIN_TABLE, updateValues, COL_ID + "=" + rowId, null) > 0;  
      }  

      /**  
       * Retrieves the details of all the users stored in the login table.  
       *   
       * @return  
       */  
      public Cursor fetchAllUsers() {  
           return database.query(LOGIN_TABLE, new String[] { COL_ID, COL_USERNAME,   
                     COL_PASSWORD }, null, null, null, null, null);  
      }  

      /**  
       * Retrieves the details of a specific user, given a username and password.  
       *   
       * @return  
       */  
      public Cursor fetchUser(String username, String password) {  
           Cursor myCursor = database.query(LOGIN_TABLE,   
                     new String[] { COL_ID, COL_USERNAME, COL_PASSWORD },   
                     COL_USERNAME + "='" + username + "' AND " +   
                     COL_PASSWORD + "='" + password + "'", null, null, null, null);  

           if (myCursor != null) {  
                myCursor.moveToFirst();  
           }  
           return myCursor;  
      }  

      /**  
       * Returns the table details given a row id.  
       * @param rowId The table row id.   
       * @return  
       * @throws SQLException  
       */  
      public Cursor fetchUserById(long rowId) throws SQLException {  
           Cursor myCursor = database.query(LOGIN_TABLE,   
                     new String[] { COL_ID, COL_USERNAME, COL_PASSWORD },   
                     COL_ID + "=" + rowId, null, null, null, null);  
           if (myCursor != null) {  
                myCursor.moveToFirst();  
           }  
           return myCursor;  
      }  

      /**  
       * Stores the username and password upon creation of new login details.  
       * @param username The user name.  
       * @param password The password.  
       * @return The entered values.   
       */  
      private ContentValues createUserTableContentValues(String username, String password) {  
           ContentValues values = new ContentValues();  
           values.put(COL_USERNAME, username);  
           values.put(COL_PASSWORD, password);  
           return values;  
      }  
 }

Implementing the DatabaseHelper

The following steps need to be taken in creating a Database Helper:

Define database name;
Define database version;
Define the table;
Implement constructor and add methods.

The App Interface

Having created the database adapted and helper we can now proceed to developing the interface for our 3 activities:

Login

Register

Landing page

Don't forget to define the xml strings, which will have to correspond to the names you have used as layout IDs.

The activities code

Each of the activities mentioned above serve as a class object which handles the interface behaviour.

Firstly we implement a Login class which handles the application login behaviour and will also work as application's main activity. Here we define the database, buttons, text boxes and other controls we use in our application.

 /**  
  * The main application activity which serves as a login page.   
  * @author Andrei  
  *  
  */  
 public class login extends Activity {  

      public static final String MY_PREFS = "SharedPreferences";  
      private DatabaseAdapter dbHelper;  
      private EditText theUsername;  
      private EditText thePassword;  
      private Button loginButton;  
      private Button registerButton;  
      private Button clearButton;  
      private Button exitButton;  
      private     CheckBox rememberDetails;  



   /** Called when the activity is first created. */  
   @Override  
   public void onCreate(Bundle savedInstanceState) {  
     super.onCreate(savedInstanceState);  

     SharedPreferences mySharedPreferences = getSharedPreferences(MY_PREFS, 0);  
     Editor editor = mySharedPreferences.edit();  
     editor.putLong("uid", 0);  
     editor.commit();  

     dbHelper = new DatabaseAdapter(this);  
     dbHelper.open();  

     setContentView(R.layout.main);  
     initControls();  
   }  

   private void initControls() {  
        //Set the activity layout.  
        theUsername = (EditText) findViewById(R.id.Username);  
        thePassword = (EditText) findViewById(R.id.Password);  
        loginButton = (Button) findViewById(R.id.Login);  
        registerButton = (Button) findViewById(R.id.Register);  
        clearButton = (Button) findViewById(R.id.Clear);  
        exitButton = (Button) findViewById(R.id.Exit);  
        rememberDetails = (CheckBox) findViewById(R.id.RememberMe);  

        //Create touch listeners for all buttons.  
        loginButton.setOnClickListener(new Button.OnClickListener(){  
             public void onClick (View v){  
                  LogMeIn(v);  
             }  
        });  

        registerButton.setOnClickListener(new Button.OnClickListener(){  
             public void onClick (View v){  
                  Register(v);  
             }  
        });  

        clearButton.setOnClickListener(new Button.OnClickListener(){  
             public void onClick (View v){  
                  ClearForm();  
             }  
        });  

        exitButton.setOnClickListener(new Button.OnClickListener(){  
             public void onClick (View v){  
                  Exit();  
             }  
        });  
        //Create remember password check box listener.  
        rememberDetails.setOnClickListener(new CheckBox.OnClickListener(){  
             public void onClick (View v){  
                  RememberMe();  
             }  
        });  

        //Handle remember password preferences.  
        SharedPreferences prefs = getSharedPreferences(MY_PREFS, 0);  
        String thisUsername = prefs.getString("username", "");  
        String thisPassword = prefs.getString("password", "");  
        boolean thisRemember = prefs.getBoolean("remember", false);  
        if(thisRemember) {  
             theUsername.setText(thisUsername);  
             thePassword.setText(thisPassword);  
             rememberDetails.setChecked(thisRemember);  
        }  

   }

Further to the above we also implement specific methods have been define to deal with each and single one of these tools:

Exit - handles the exit app behaviour;
ClearForm - deals with clearing a completed login form;
RemeberMe - deals with remembering the login details;
LogMeIn - handles the app login process;
Register - takes the user to the registration activity.

   /**  
    * Deals with Exit option - exits the application.  
    */  
   private void Exit()  
   {  
        finish();  
   }  

   /**  
    * Clears the login form.  
    */  
   private void ClearForm() {  
        saveLoggedInUId(0,"","");  
        theUsername.setText("");  
        thePassword.setText("");  
   }  

   /**  
    * Handles the remember password option.  
    */  
   private void RememberMe() {  
        boolean thisRemember = rememberDetails.isChecked();  
        SharedPreferences prefs = getSharedPreferences(MY_PREFS, 0);  
        Editor editor = prefs.edit();  
        editor.putBoolean("remember", thisRemember);  
        editor.commit();  
   }  

   /**  
    * This method handles the user login process.   
    * @param v  
    */  
   private void LogMeIn(View v) {  
        //Get the username and password  
        String thisUsername = theUsername.getText().toString();  
        String thisPassword = thePassword.getText().toString();  

        //Assign the hash to the password  
        thisPassword = md5(thisPassword);  

        // Check the existing user name and password database  
        Cursor theUser = dbHelper.fetchUser(thisUsername, thisPassword);  
        if (theUser != null) {  
             startManagingCursor(theUser);  
             if (theUser.getCount() > 0) {  
                  saveLoggedInUId(theUser.getLong(theUser.getColumnIndex(DatabaseAdapter.COL_ID)), thisUsername, thePassword.getText().toString());  
               stopManagingCursor(theUser);  
               theUser.close();  
               Intent i = new Intent(v.getContext(), Helloworld.class);  
               startActivity(i);  
             }  

             //Returns appropriate message if no match is made  
             else {  
                  Toast.makeText(getApplicationContext(),   
                            "You have entered an incorrect username or password.",   
                            Toast.LENGTH_SHORT).show();  
                  saveLoggedInUId(0, "", "");  
             }  
             stopManagingCursor(theUser);  
             theUser.close();  
        }  

        else {  
             Toast.makeText(getApplicationContext(),   
                       "Database query error",   
                       Toast.LENGTH_SHORT).show();  
        }  
   }  

   /**  
    * Open the Registration activity.  
    * @param v  
    */  
   private void Register(View v)  
   {  
        Intent i = new Intent(v.getContext(), Register.class);  
        startActivity(i);  
   }  

   private void saveLoggedInUId(long id, String username, String password) {  
        SharedPreferences settings = getSharedPreferences(MY_PREFS, 0);  
        Editor myEditor = settings.edit();  
        myEditor.putLong("uid", id);  
        myEditor.putString("username", username);  
        myEditor.putString("password", password);  
        boolean rememberThis = rememberDetails.isChecked();  
        myEditor.putBoolean("rememberThis", rememberThis);  
        myEditor.commit();  
   }

The full source code for the Login class can be found here.

Having written the code for the Login activity we move to implementing the Register class which handles the registration process of the application. The tools and methods we use for this activity are similar to those used in the Login class, the only noticeable difference would be that we now have to define a register method rather than a login method.

       /**  
        * Handles the registration process.  
        * @param v  
        */  
       private void RegisterMe(View v)  
        {  
                 //Get user details.   
             String username = newUsername.getText().toString();  
             String password = newPassword.getText().toString();  
             String confirmpassword = newConfiPass.getText().toString();  

             //Check if all fields have been completed.  
             if (username.equals("") || password.equals("")){  
                  Toast.makeText(getApplicationContext(),   
                            "Please ensure all fields have been completed.",  
                          Toast.LENGTH_SHORT).show();  
                 return;  
             }  

             //Check password match.   
             if (!password.equals(confirmpassword)) {  
                  Toast.makeText(getApplicationContext(),   
                            "The password does not match.",  
                               Toast.LENGTH_SHORT).show();  
                                 newPassword.setText("");  
                                 newConfiPass.setText("");  
                  return;  
             }  

             //Encrypt password with MD5.  
             password = md5(password);  

             //Check database for existing users.  
             Cursor user = dbHelper.fetchUser(username, password);  
             if (user == null) {  
                  Toast.makeText(getApplicationContext(), "Database query error",  
                          Toast.LENGTH_SHORT).show();  
             } else {  
                  startManagingCursor(user);  

                  //Check for duplicate usernames  
                  if (user.getCount() > 0) {  
                       Toast.makeText(getApplicationContext(), "The username is already registered",  
                           Toast.LENGTH_SHORT).show();  
                       stopManagingCursor(user);  
                    user.close();  
                       return;  
                  }  
                  stopManagingCursor(user);  
                  user.close();  
                  user = dbHelper.fetchUser(username, password);  
               if (user == null) {  
                    Toast.makeText(getApplicationContext(), "Database query error",  
                           Toast.LENGTH_SHORT).show();  
                    return;  
               } else {  
                    startManagingCursor(user);  

                    if (user.getCount() > 0) {  
                         Toast.makeText(getApplicationContext(), "The username is already registered",  
                              Toast.LENGTH_SHORT).show();  
                         stopManagingCursor(user);  
                      user.close();  
                         return;  
                    }  
                    stopManagingCursor(user);  
                    user.close();  
               }  
               //Create the new username.  
                  long id = dbHelper.createUser(username, password);  
                  if (id > 0) {  
                       Toast.makeText(getApplicationContext(), "Your username was created",  
                            Toast.LENGTH_SHORT).show();  
                       saveLoggedInUId(id, username, newPassword.getText().toString());  
                       Intent i = new Intent(v.getContext(), Helloworld.class);  
                       startActivity(i);  

                       finish();  
                  } else {  
                       Toast.makeText(getApplicationContext(), "Failt to create new username",  
                            Toast.LENGTH_SHORT).show();  
                  }  
             }  
        }

The full source code for the Register class is available here.

And lastly we implement Helloworld class which will serve as a landing page.

In the near future I’m looking to develop the login application to handle the following:

Forgotten password option
Secure encryption of the file were the login information is stored
Sync with external Server

Fork me on GitHub if you want to help me out in implementing these features.

GitHub

Repositories

Repositories
- LinkifyTextView
  
  Example of how one can linkify a TextView and strip the link underline.
  
  1 fork / 4 watchers / Pushed Mar 25, 12
- XMLParser
  
  XML SAX Parser - displays the latest BBC news (Titles & Description) in a ListView format.
  
  1 fork / 3 watchers / Pushed Jan 14, 12
- SpeakUp
  
  A simple Text to Speech app for Android
  
  1 fork / 2 watchers / Pushed Sep 25, 11
- Android-Login-App
  
  A simple SQLite login application developed for Android. I'm looking to slowly start developing this into a more complex database which would link to an external database and would be able handle more user data.
  
  12 forks / 12 watchers / Pushed Jul 09, 11
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- Andrei Pop
  
  Mobile Apps Developer, Technical Architect, Developer Team Lead
  
  Wireless | United Kingdom, GB
  
  Experience
  - Jan 2012 - Present
    Mobile Apps Developer, Technical Architect, Developer Team Lead / Chelsea Apps Factory
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    Personal Website, Blog
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Mobile Apps Developer, Technical Architect, Developer Team Lead.

UX Enthusiast.

Amateur Photographer.

Contact me.