tiptestmidlet.java

高级java2 大学教程(含源码,经典的Java学习教程

      // create StringItem showing tip name
      StringItem tipNameItem = 
         new StringItem( "Tip Name:\n", list[ 1 ] );

      // create StringItem showing tip description
      StringItem tipDescriptionItem = 
         new StringItem( "\nTip Description:\n", list[ 2 ] );

      // append StringItems to Form
      answerScreen.append( tipNameItem );
      answerScreen.append( tipDescriptionItem );

      answerScreen.addCommand( nextCommand );

      // allow soft button access for this Screen
      answerScreen.setCommandListener(
         new CommandListener() {

            // invoked when user presses soft button
            public void commandAction( 
               Command command, Displayable displayable )
            {
               // get next question
               String data = getServerData( servletBaseURL + 
                  tipTestServletName );

               // display next question
               display.setCurrent( createTipTestScreen( 
                  servletBaseURL + data ) );
            }

         } // end anonymous inner class
      );

      return answerScreen;

   } // end method createAnswerScreen

   // sends user's test selection to servlet
   private String postData( int selection )
   {
      // connect to server, then post data
      try {

         // connect to server sending User-Agent header
         HttpConnection httpConnection = 
            ( HttpConnection ) Connector.open( 
               servletBaseURL + tipTestServletName, 
                  Connector.READ_WRITE );

         setUserAgentHeader( httpConnection );

         // send sessionID, if one exists
         if ( sessionID != null )
            httpConnection.setRequestProperty( 
               "cookie", sessionID );

         // inform servlet of post request
         httpConnection.setRequestMethod( HttpConnection.POST );

         // open output stream to servlet
         DataOutputStream out = 
            httpConnection.openDataOutputStream();

         // send selection
         out.writeUTF( Integer.toString( selection ) );
         out.flush();

         // get result from servlet
         String data = getData( httpConnection );

         httpConnection.close(); // close connection

         return data;

      } // end try

      // handle if MIDlet cannot open HTTP connection
      catch ( IOException ioException ) {
         ioException.printStackTrace();
      }

      return null;

   } // end method postData

   // string tokenizer parses String into sub-string array
   private String[] parseData( String data, char delimiter )
   {
      int newLines = 0;

      // determine number of delimiter characters in String
      for ( int i = 0; i < data.length(); i++ )

         // increase number of delimiters by one
         if ( data.charAt( i ) == delimiter )
            newLines++;

      // create new String array
      String list[] = new String[ newLines ];

      int oldNewLineIndex = 0;
      int currentNewLineIndex;

      // store Strings into array based on demiliter
      for ( int i = 0; i < newLines; i++ ) {

         // determine index where delimiter occurs
         currentNewLineIndex = 
            data.indexOf( delimiter, oldNewLineIndex );

         // extract String within delimiter characters
         list[ i ] = data.substring( oldNewLineIndex, 
            currentNewLineIndex - 1 );

         oldNewLineIndex = currentNewLineIndex + 1;
      }

      return list;

   } // end method parseData

   // connect to server and receive data
   private String getServerData( String serverUrl )
   {
      // connect to server, then get data
      try {

         // connect to server sending User-Agent header
         HttpConnection httpConnection = 
           ( HttpConnection ) Connector.open( serverUrl );
         setUserAgentHeader( httpConnection );

         // send sessionID to server
         if ( sessionID != null )
            httpConnection.setRequestProperty( 
               "cookie", sessionID );

         // get sessionID from server
         String sessionIDHeaderField = 
            httpConnection.getHeaderField( "Set-cookie" );

         // store sessionID from cookie
         if ( sessionIDHeaderField != null ) {
            int index = sessionIDHeaderField.indexOf( ';' );
            sessionID = 
               sessionIDHeaderField.substring( 0, index );
         }

         // receive server data
         String data = getData( httpConnection );

         httpConnection.close(); // close connection

         return data;

      } // end try

      // handle exception communicating with HTTP server
      catch ( IOException ioException ) {
         ioException.printStackTrace();
      }

      return null;

   } // end method getServerData

   // downloads an image from a server
   private Image getServerImage( String imageUrl )
   {
      // download image
      try {

         // open connection to server
         HttpConnection httpConnection = 
           ( HttpConnection ) Connector.open( imageUrl );

         int connectionSize = ( int ) httpConnection.getLength();
         byte imageBytes[] = new byte[ connectionSize ];

         // read image from server
         InputStream input = httpConnection.openInputStream();
         input.read( imageBytes );

         // create image from imageBytes
         return
            Image.createImage( imageBytes, 0, connectionSize );
      }

      // handle exception if InputStream cannot input bytes
      catch ( IOException ioException  ) {
         ioException.printStackTrace();
      }

      return null;

   } // end method getServerImage

   // set User-Agent header to identify client to servlet
   private void setUserAgentHeader( 
      HttpConnection httpConnection )
   {
      // set User-Agent header
      try {

         // use profile/configuration properties for User-Agent
         String userAgentHeader = "Profile=" +
            System.getProperty( "microedition.profiles" ) +
            " Configuration=" +
            System.getProperty( "microedition.configuration" );

         // set header
         httpConnection.setRequestProperty( 
            "User-Agent", userAgentHeader );
      }

      // handle exception getting request property
      catch ( IOException ioException ) {
         ioException.printStackTrace();
      }

   } // end method setUserAgentHeader

   // open DataInputStream to receive data
   private String getData( HttpConnection httpConnection )
      throws IOException
   {
      String data = ""; // stores data

      // open input stream from connection
      DataInputStream dataInputStream = 
        new DataInputStream( 
           httpConnection.openInputStream() );

      int inputCharacter = dataInputStream.read();

      // read all data
      while ( inputCharacter != -1 ) {
         data = data + ( char ) inputCharacter;
         inputCharacter = dataInputStream.read();
      }

      dataInputStream.close(); // close stream

      return data;

   } // end method getData
}

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