1

我有一个 LWUIT 应用程序,它应该显示 LWUIT 列表中的记录数。

为了获取所有记录,我使用了一个getRecordData()将所有记录作为字符串数组返回的方法,它可以正常工作。

但是我如何计算这些记录的数量?

import java.util.*;
import com.sun.lwuit.events.*;
import javax.microedition.midlet.*;
import com.sun.lwuit.*;
import com.sun.lwuit.plaf.*;
import javax.microedition.rms.RecordStore;
import javax.microedition.rms .*;
public class number_of_records extends MIDlet {
    private RecordStore recordStore;
    // Refresh2( ) method for getting the time now
    public String Refresh2()
    {
        java.util.Calendar calendar = java.util.Calendar.getInstance();
        Date myDate = new Date();
        calendar.setTime(myDate);
        StringBuffer time = new StringBuffer();
        time.append(calendar.get(java.util.Calendar.HOUR_OF_DAY)).append(':');
        time.append(calendar.get(java.util.Calendar.MINUTE)) ;
        // time.append(calendar.get(java.util.Calendar.SECOND));
        String tt = time.toString();
        return tt;
    }
    // return all records of recordStore RecordStore
    public String [] getRecordData( )
    {
        String[] str = null;
        int counter = 0;
        try
        {
            RecordEnumeration enumeration = recordStore.enumerateRecords(null, null, false);
            str = new String[recordStore.getNumRecords()];
            while(enumeration.hasNextElement())
            {
                try
                {
                    str[counter] = (new String(enumeration.nextRecord()));
                    counter ++;
                }
                catch(javax.microedition.rms.RecordStoreException e)
                {
                }
            }
        }
        catch(javax.microedition.rms.RecordStoreNotOpenException e)
        {
        }
        catch(java.lang.NullPointerException n)
        {
        }
        return str;
    }
    public void startApp()
    {
        com.sun.lwuit.Display.init(this);
        final Button addition = new Button("add a goal");
        final com.sun.lwuit.TextField tf = new com.sun.lwuit.TextField();
        final com.sun.lwuit.List mylist = new com.sun.lwuit.List();
        final Button All = new Button("All Goals");
        final com.sun.lwuit.Form ff = new com.sun.lwuit.Form();
        final com.sun.lwuit.Form g = new com.sun.lwuit.Form();
        ff.getStyle().setBgColor(0X99CCFF);
        All.getStyle().setBgColor(0X0066CC);
        Style g_style5 = g.getSelectedStyle() ;
        g.addComponent(tf);
        g.addComponent(addition);
        addition.getStyle().setBgColor(0X0066CC);
        g.addComponent(All);
        g.getStyle().setBgColor(0X99CCFF);
        addition.addActionListener(new ActionListener()
        { 
            public void actionPerformed(ActionEvent ae)
            {
                //
                String s =tf.getText();
                if( s!=null && s.length() > 0)
                {
                    try
                    {
                        // Store the time in the String k
                        String k = Refresh2();
                        // The record and the time stored in KK String
                        String kk =tf.getText()+"-"+k;
                        // Add an item (the kk String) to mylist List.
                        mylist.addItem(kk);
                        byte bytestream[] = kk.getBytes() ;
                        // Add a record to recordStore.
                        int i = recordStore.addRecord(bytestream, 0, bytestream.length);
                    }
                    catch(Exception ex) { }
                    // Inform the User that he added the a record.
                    Dialog validDialog = new Dialog(" ");
                    Style Dialogstyle = validDialog.getSelectedStyle() ;
                    validDialog.setScrollable(false);
                    validDialog.getDialogStyle().setBgColor(0x0066CC);
                    validDialog.setTimeout(1000); // set timeout milliseconds
                    TextArea textArea = new TextArea("...."); //pass the alert text here
                    textArea.setFocusable(false);
                    textArea.setText("A goal has been added"+"" );
                    validDialog.addComponent(textArea);
                    validDialog.show(0, 10, 10, 10, true);
                }
                // Information to user that he/she didn’t add a record
                else if((s==null || s.length()<= 0))
                {
                    Dialog validDialo = new Dialog(" ");
                    validDialo.setScrollable(false);
                    validDialo.getDialogStyle().setBgColor(0x0066CC);
                    validDialo.setTimeout(5000); // set timeout milliseconds
                    TextArea textArea = new TextArea("...."); //pass the alert text here
                    textArea.setFocusable(false);
                    textArea.setText("please enter scorer name or number");
                    validDialo.addComponent(textArea);
                    validDialo.show(50, 50, 50, 50, true);
                }
            }
        });
        /*Action here for displaying all records of recordStore RecordStore in a new form */
        All.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ae) {
                try
                {
                    recordStore = RecordStore.openRecordStore("My Record Store", true);
                }
                catch(Exception ex) {} 
                try
                {
                    com.sun.lwuit.Label l = new com.sun.lwuit.Label(" Team Goals") ;
                    ff.addComponent(l);
                    // Store the records of recordStore in string array
                    String [] record= getRecordData();
                    int j1;
                    String valueToBeInserted2="";
                    int k=getRecordData().length;
                    for( j1=0;j1< getRecordData().length;j1++)
                    {
                        valueToBeInserted2=valueToBeInserted2 + " " + record[j1];
                        if(j1==getRecordData().length)
                        {
                            mylist.addItem(record[j1]);
                            int m = getRecordData().length;
                            // Counting the number of records
                            String goals =""+getRecordData().length;
                            /* I tried to use for…loop to count them by length of the recordStore and render it.
                               This list also should display the number of records on the form.
                               But it didn’t !!!
                            */
                            mylist.addItem(goals);
                        }
                    }
                    ff.addComponent(mylist);
                }
                catch(java.lang.IllegalArgumentException e)
                {
                }
                finally
                {
                    ff.show();
                }
            }
        }
        );
        g.show();
    }
    public void pauseApp()
    {
    }
    public void destroyApp(boolean unconditional) {
    }
}

我写了这段代码,但它给出了NullPointerException at recordStore.enumerateRecords (null, null,true);

所以我觉得问题就在这里。

请帮忙。

myButton.addActionListener( new ActionListener()
{
    public void actionPerformed(ActionEvet av)
    { 
        try
        {
            RecordEnumeration enumeration = recordStore.enumerateRecords (null, null,true); 
            int o =recordStore.getNumRecords () ; 
        } 
        catch(Exception e)
        { 
        } 
    } 
}); 
4

3 回答 3

0

你需要的是 enumeration.numRecords(); 我认为 recordStore.getNumRecords() 也应该可以工作,因为这是您使用的填充数组,您甚至可以使用数组本身的长度。这些选项都在代码中,最好多探索一下并查看文档以解决琐碎的问题。

于 2013-07-17T18:49:42.543 回答
0

您可以使用数组的长度或为您的记录存储设置一个 RecordListener 并在将记录添加到记录存储时增加一个计数器。

于 2013-08-02T21:21:10.010 回答
0

这是我的问题的解决方案,我做了一个 for 循环来获取数量

数组的元素。

计数器应该是数组的长度

    count.addActionListener( new ActionListener()
    {
    public void actionPerformed(ActionEvent av)
   {

            try
           {

          recordStore = RecordStore.openRecordStore("recordStore", true);

            }
            catch(Exception e)

            { }

            try
             {

        RecordEnumeration enumeration = recordStore.enumerateRecords (null,  null,true);

               }
             catch(Exception e)
             {

             }
            String record[] = getRecordData();
            int j;


             j =   record.length-1;

                Dialog validDialog = new Dialog(" ");
                Style Dialogstyle = validDialog.getSelectedStyle() ;
                validDialog.setScrollable(false);
                validDialog.getDialogStyle().setBgColor(0x0066CC);
                validDialog.setTimeout(1000); // set timeout milliseconds
                TextArea textArea = new TextArea("....");  
                textArea.setFocusable(false);
                textArea.setText("Number Counted"+j );
                validDialog.addComponent(textArea);
                validDialog.show(0, 10, 10, 10, true);

                   }});
于 2013-08-14T00:14:37.897 回答