在j2me＆amp;中运行以下代码的NetBeans：
此代码用于记录过滤（搜索记录）。
问题在于，当我们在j2me中运行此代码时，它从头开始执行搜索，而在NetBeans中则从反向搜索。
import javax.microedition.rms.*;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import java.io.*;
import javax.microedition.rms.RecordFilter;
public class SearchExample extends MIDlet implements CommandListener
{
private Display display;
private Alert alert;
private Form form;
private Command exit;
private Command start;
private RecordStore recordstore = null;
private RecordEnumeration recordEnumeration = null;
private Filter filter = null;
public SearchExample ()
{
display = Display.getDisplay(this);
exit = new Command("Exit", Command.SCREEN, 1);
start = new Command("Start", Command.SCREEN, 1);
form = new Form("Mixed RecordEnumeration", null);
form.addCommand(exit);
form.addCommand(start);
form.setCommandListener(this);
}
public void startApp()
{
display.setCurrent(form);
}
public void pauseApp()
{
}
public void destroyApp( boolean unconditional )
{
}
public void commandAction(Command command, Displayable displayable)
{
if (command == exit)
{
destroyApp(true);
notifyDestroyed();
}
else if (command == start)
{
try
{
recordstore = RecordStore.openRecordStore("myRecordStore", true );
}
catch (Exception error)
{
alert = new Alert("Error Creating",error.toString(), null, AlertType.WARNING);
alert.setTimeout(Alert.FOREVER);
display.setCurrent(alert);
}
try
{
String outputData[] = {"Mary", "Adam","dancebob","bobby","bob1"};
for (int x = 0 ; x < outputData.length; x++)
{
byte[] byteOutputData = outputData[x].getBytes();
recordstore.addRecord(byteOutputData, 0,byteOutputData.length);
}
}
catch ( Exception error)
{
alert = new Alert("Error Writing",error.toString(), null, AlertType.WARNING);
alert.setTimeout(Alert.FOREVER);
display.setCurrent(alert);
}
try
{
filter = new Filter("Bob");
StringBuffer sbuf=new StringBuffer();
recordEnumeration = recordstore.enumerateRecords(filter, null, false);
if (recordEnumeration.numRecords() > 0)
{
for(int i=0;i<recordEnumeration.numRecords();i++){
String string = new String(recordEnumeration.nextRecord());
sbuf.append(string+"\n");
}
alert = new Alert("Reading", sbuf.toString(),null, AlertType.WARNING);
alert.setTimeout(Alert.FOREVER);
display.setCurrent(alert);
}
}
catch (Exception error)
{
alert = new Alert("Error Reading",error.toString(), null, AlertType.WARNING);
alert.setTimeout(Alert.FOREVER);
display.setCurrent(alert);
}
try
{
recordstore.closeRecordStore();
}
catch (Exception error)
{
alert = new Alert("Error Closing",error.toString(), null, AlertType.WARNING);
alert.setTimeout(Alert.FOREVER);
display.setCurrent(alert);
}
if (RecordStore.listRecordStores() != null)
{
try
{
RecordStore.deleteRecordStore("myRecordStore");
recordEnumeration.destroy();
filter.filterClose();
}
catch (Exception error)
{
alert = new Alert("Error Removing",error.toString(), null, AlertType.WARNING);
alert.setTimeout(Alert.FOREVER);
display.setCurrent(alert);
}
}
}
}
}
class Filter implements RecordFilter
{
private String search = null;
private ByteArrayInputStream inputstream = null;
private DataInputStream datainputstream = null;
public Filter(String search)
{
this.search = search.toLowerCase();
}
public boolean matches(byte[] suspect)
{
String string = new String(suspect).toLowerCase();
if (string!= null && string.indexOf(search) != -1)
return true;
else
return false;
}
public void filterClose()
{
try
{
if (inputstream != null)
{
inputstream.close();
}
if (datainputstream != null)
{
datainputstream.close();
}
}
catch ( Exception error)
{
}
}
}
答案 0 :(得分：4)
你的代码片段很大，格式很糟糕，所以可能还有其他一些我没有注意到的错误，但如果你担心的是你在这一行创建的遍历枚举的顺序：
recordEnumeration = recordstore.enumerateRecords(filter, null, false);
然后这是正常行为。 MIDP RMS API documentation表示当第二个参数为null时（代码中 ），则记录将以未定义的顺序遍历。
请参阅下面的引文，并注意与RecordComparator comparator
public RecordEnumeration enumerateRecords(RecordFilter filter,
RecordComparator comparator,
boolean keepUpdated)
throws RecordStoreNotOpenException
Returns an enumeration for traversing a set of records in the record store
in an optionally specified order.
The filter, if non-null, will be used to determine what subset
of the record store records will be used.
The comparator, if non-null, will be used to determine the order
in which the records are returned.
If both the filter and comparator is null, the enumeration will traverse
all records in the record store in an undefined order. This is the most
efficient way to traverse all of the records in a record store. If a filter
is used with a null comparator, the enumeration will traverse the filtered
records in an undefined order. The first call to RecordEnumeration.nextRecord()
returns the record data from the first record in the sequence. Subsequent calls
to RecordEnumeration.nextRecord() return the next consecutive record's data.
To return the record data from the previous consecutive from any given point
in the enumeration, call previousRecord(). On the other hand, if after creation
the first call is to previousRecord(), the record data of the last element
of the enumeration will be returned. Each subsequent call to previousRecord()
will step backwards through the sequence.
Parameters:
filter - if non-null, will be used to determine what subset of the
record store records will be used
comparator - if non-null, will be used to determine the order in which
the records are returned
...
你可能会想到这一点，因为每次你运行你的midlet时，Netbeans模拟器以相同的方式遍历记录只是一个幸运的巧合。理论上允许在每次运行时改变顺序。