jun01_ericg.txt

TechTips j2me的常用技巧. 网络功能

            bout.reset();
        }
        catch( Exception e ){
        }
    }

    // Fill record store with some precanned names

    private void fillRecordStore(){
        ByteArrayOutputStream bout = new ByteArrayOutputStream();
        DataOutputStream dout = new DataOutputStream( bout );

        for( int i = 0; i < names.length; ++i ){
            addName( names[i][0], names[i][1], bout, dout );
        }
    }

    // Open record store, if empty then fill it

    private boolean openRecordStore(){
        try {
            if( rs != null ) closeRecordStore();

            rs = RecordStore.openRecordStore( "EnumDemo", true );
            if( rs.getNumRecords() == 0 ){
                fillRecordStore();
            }
            return true;
        }
        catch( RecordStoreException e ){
            return false;
        }
    }

    // Close record store

    private void closeRecordStore(){
        if( rs != null ){
            try {
                rs.closeRecordStore();
            }
            catch( RecordStoreException e ){
            }

            rs = null;
        }
    }

    // Move to and read in a record

    private boolean readRecord( int id, Record r ){
        boolean ok = false;

        r.firstName = null;
        r.lastName = null;

        if( rs != null ){
            try {
                rs.getRecord( id, data, 0 );
                r.firstName = din.readUTF();
                r.lastName = din.readUTF();
                din.reset();

                ok = true;
            }
            catch( Exception e ){
            }
        }

        return ok;
    }

    // Event handling

    public void commandAction( Command c, Displayable d ){
        if( c == exitCommand ){
            exitMIDlet();
        } else if( c == sortCommand ){
            display.setCurrent( sortOptionsScreen );
        } else if( d == sortOptionsScreen ){
            if( c == okCommand ){
                enumListScreen.resort();
            }
            
            display.setCurrent( enumListScreen );
        }
    }

    // Main screen -- a list of names

    class EnumList extends List
                   implements RecordComparator, RecordFilter {
        private int    sortBy;
        private int    filterBy;
        private String filterText;
        private Record r1 = new Record();
        private Record r2 = new Record();

        // Constructor

        EnumList(){
            super( "Enum Demo", IMPLICIT );
            addCommand( exitCommand );
            addCommand( sortCommand );
            setCommandListener( EnumDemo.this );
        }

        // Resort the data and refill the list

        public void resort(){
            sortBy = sortOptionsScreen.getSortType();
            filterBy = sortOptionsScreen.getFilterType();
            filterText = sortOptionsScreen.getFilterText();

            RecordComparator comparator = null;
            RecordFilter     filter = null;

            if( sortBy != 0 ){
                comparator = this;
            }

            if( filterBy != 0 ){
                filter = this;
            }

            deleteAll();

            try {
                RecordEnumeration enum = rs.enumerateRecords( 
                                     filter, comparator, false );
                Record            r = new Record();

                while( enum.hasNextElement() ){
                    int id = enum.nextRecordId();
                    if( readRecord( id, r ) ){
                        if( sortBy == SORT_LAST_FIRST ){
                            append( r.lastName + ", " + 
                                             r.firstName, null );
                        } else {
                            append( r.firstName + " " + 
                                              r.lastName, null );
                        }
                    }
                }

                enum.destroy();
            }
            catch( RecordStoreException e ){
            }
        }

        // Delete all items in the list

        private void deleteAll(){
            int n = size();
            while( n > 0 ){
                delete( --n );
            }
        }

        // The comparator

        public int compare( byte[] rec1, byte[] rec2 ){
            try {
                ByteArrayInputStream  bin = 
                                new ByteArrayInputStream( rec1 );
                DataInputStream       din = 
                                      new DataInputStream( bin );

                r1.firstName = din.readUTF();
                r1.lastName = din.readUTF();

                bin = new ByteArrayInputStream( rec2 );
                din = new DataInputStream( bin );

                r2.firstName = din.readUTF();
                r2.lastName = din.readUTF();

                if( sortBy == SORT_FIRST_LAST ){
                    int cmp = r1.firstName.compareTo( 
                                                  r2.firstName );
                 System.out.println( r1.firstName + 
                  " compares to " + r2.firstName + 
                                               " gives " + cmp );
                    if( cmp != 0 ) return ( 
                                  cmp < 0 ? PRECEDES : FOLLOWS );
                    cmp = r2.lastName.compareTo( r2.lastName );
                    if( cmp != 0 ) return ( 
                                  cmp < 0 ? PRECEDES : FOLLOWS );
                } else if( sortBy == SORT_LAST_FIRST ){
                    int cmp = r1.lastName.compareTo( 
                                                   r2.lastName );
                    if( cmp != 0 ) return ( 
                                  cmp < 0 ? PRECEDES : FOLLOWS );
                    cmp = r2.firstName.compareTo( r2.firstName );
                    if( cmp != 0 ) return ( 
                                  cmp < 0 ? PRECEDES : FOLLOWS );
                }
            }
            catch( Exception e ){
            }

            return EQUIVALENT;
        }

        // The filter

        public boolean matches( byte[] rec ){
            try {
                ByteArrayInputStream  bin = 
                                 new ByteArrayInputStream( rec );
                DataInputStream       din = 
                                      new DataInputStream( bin );

                r1.firstName = din.readUTF();
                r1.lastName = din.readUTF();

                if( filterBy == FILTER_STARTSWITH ){
                    return( r1.firstName.startsWith( filterText ) 
                            ||
                          r1.lastName.startsWith( filterText ) );
                } else if( filterBy == FILTER_CONTAINS ){
                    return( r1.firstName.indexOf( filterText ) 
                            >= 0 ||
                        r1.lastName.indexOf( filterText ) >= 0 );
                }
            }
            catch( Exception e ){
            }

            return false;
        }
    }

    // The options screen for choosing which sort and filter modes
    // to use, including the filter text

    class SortOptions extends Form {

        // Constructor

        SortOptions(){
            super( "Sort Options" );
            addCommand( okCommand );
            addCommand( cancelCommand );
            setCommandListener( EnumDemo.this );

            append( sortTypes );
            append( filterTypes );
            append( filterText );
        }

        // Return current sort type

        public int getSortType(){
            return sortTypes.getSelectedIndex();
        }

        // Return current filter type

        public int getFilterType(){
            return filterTypes.getSelectedIndex();
        }

        // Return current filter text

        public String getFilterText(){
            return filterText.getString();
        }

        // Labels and user interface components

        private String[] sortLabels = 
                         { "None", "First Last", "Last, First" };

        private String[] filterLabels = 
                           { "None", "Starts With", "Contains" };

        private ChoiceGroup sortTypes = new ChoiceGroup( 
                                                    "Sort Type:",
                                           ChoiceGroup.EXCLUSIVE,
                                              sortLabels, null );

        private ChoiceGroup filterTypes = new ChoiceGroup( 
                                                  "Filter Type:",
                                           ChoiceGroup.EXCLUSIVE,
                                            filterLabels, null );

        private TextField filterText = new TextField( 
                                                  "Filter Text:",
                                                   null, 20, 0 );
    }
}
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June 22, 2001

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