Java me j2me-按两个或多个条件筛选结果
我正在尝试使用界面过滤一些记录。在我的应用程序中，我有两个类似于此的界面，用户可以在上面输入ID或名称（他/她可以同时输入，也可以不输入） 以下是我迄今为止所做的工作： 客户过滤器 在这里，如果用户没有输入ID，我会将0作为默认值传递，这就是我评估Java me j2me-按两个或多个条件筛选结果,java-me,Java Me,我正在尝试使用界面过滤一些记录。在我的应用程序中，我有两个类似于此的界面，用户可以在上面输入ID或名称（他/她可以同时输入，也可以不输入） 以下是我迄今为止所做的工作： 客户过滤器 在这里，如果用户没有输入ID，我会将0作为默认值传递，这就是我评估customerID的原因=0 public class CustomerFilter implements RecordFilter { private String mName_Filter; private int mID_F
customerID的原因=0public class CustomerFilter implements RecordFilter {
private String mName_Filter;
private int mID_Filter;
public CustomerFilter(String name_Filter, int id_Filter) {
this.mName_Filter = name_Filter.toLowerCase();
this.mID_Filter = id_Filter;
}
public boolean matches(byte[] candidate) {
try {
ByteArrayInputStream bis = new ByteArrayInputStream(candidate);
DataInputStream dis = new DataInputStream(bis);
int customerID = dis.readInt();
String customerName = dis.readUTF().toLowerCase();
if ((customerName != null && customerName.indexOf(mName_Filter) != -1) && (customerID != 0 && customerID == mID_Filter))
return true;
if (customerName != null && customerName.indexOf(mName_Filter) != -1 && customerID == 0)
return true;
if (customerName == null && (customerID != 0 && customerID == mID_Filter))
return true;
if (customerName == null && customerID == 0)
return true;
} catch (IOException ex) {
//What's the point in catching a exception here???
}
return false;
}
}
public Customer[] search(int id, String name) throws RecordStoreException, IOException {
RecordStore rs = null;
RecordEnumeration recEnum = null;
Customer[] customerList = null;
try {
rs = RecordStore.openRecordStore(mRecordStoreName, true);
if (rs.getNumRecords() > 0) {
CustomerFilter filter = new CustomerFilter(name, id);
try {
recEnum = rs.enumerateRecords(filter, null, false);
if (recEnum.numRecords() > 0) {
customerList = new Customer[recEnum.numRecords()];
int counter = 0;
while (recEnum.hasNextElement()) {
Customer cust;
int idRecord = recEnum.nextRecordId();
byte[] filterRecord = rs.getRecord(idRecord);
cust = parseRecord(filterRecord);
cust.idRecord = idRecord;
customerList[counter] = cust;
counter++;
}
}
else{
customerList = new Customer[0];
//How to send a message to the midlet from here
//saying something like "No Record Exists.Please select another filter"
}
} finally {
recEnum.destroy();
}
}
else{
//How to send a message to the midlet from here
//saying something like "No Record Exists.Please Add record"
}
} finally {
rs.closeRecordStore();
}
return customerList;
}
CustomerFilterpublic class CustomerFilter implements RecordFilter {
private String mName_Filter;
//Use Integer instead of int.
//This way we can use null instead of zero if the user didn't type an ID.
//This allows us to store IDs with values like 0, -1, etc.
//It is a bit less memory efficient,
//but you are not creating hundreds of filters, are you? (If you are, don't).
private Integer mID_Filter;
public CustomerFilter(String name_Filter, Integer id_Filter) {
this.mName_Filter = normalizeString(mName_Filter);
this.mID_Filter = id_Filter;
}
//You should move this function to an StringUtils class and make it public.
//Other filters might need it in the future.
private static String normalizeString(final String s){
if(s != null){
//Warning: you might want to replace accentuated chars as well.
return s.toLowerCase();
}
return null;
}
public boolean matches(byte[] candidate) {
ByteArrayInputStream bis = new ByteArrayInputStream(candidate);
DataInputStream dis = new DataInputStream(bis);
try {
if(mID_Filter != null){
//If the ID is unique, and the search is ID OR other fields, this is fine
int customerID = dis.readInt();
if(mID_Filter.intValue == customerID){
return true;
} else {
return false;
}
}
if(mName_Filter != null){
String customerName = normalizeString(dis.readUTF());
if(customerName != null && customerName.indexOf(mName_Filter) != -1){
return true;
}
}
if(mID_Filter == null && mName_Filter == null){
return true; // No filtering, every record matches.
}
} catch (IOException ex) {
//Never swallow exceptions.
//Even if you are using an underlying ByteArrayInputStream, an exception
//can still be thrown when reading from DataInputStream if you try to read
//fields that do not exists.
//But even if no exceptions were ever thrown, never swallow exceptions :)
System.err.println(ex);
//Optional: throw ex;
} finally {
//Always close streams.
if(bis != null){
try {
bis.close();
} catch(IOException ioe){
System.err.println(ioe);
}
}
if(dis != null){
try {
dis.close();
} catch(IOException ioe){
System.err.println(ioe);
}
}
}
return false;
}
}
如果我有更多的过滤器怎么办？我会测试所有可能的过滤器吗 组合 这取决于您的项目。通常ID是唯一的，并且不存在具有相同ID的两条记录。在这种情况下，您应该明确设计屏幕，以便用户了解他键入的ID或他填写的其他字段。条件如下：
idMatches OR (field1Matches AND field2Matches AND ... fieldNMatches)
如果用户既不输入ID也不输入名称，我应该显示吗 所有记录或我应该显示一条消息“请输入姓名或 身份证？，在这种情况下你会怎么做 视情况而定。是否有其他方式查看所有记录？如果有，则显示消息
当我做不到的时候，为什么我必须在过滤器里放一个试捕器 有什么吗？我不能从那里显示任何警报，或者我可以吗 您不应该这样做。此类只负责筛选，不负责与用户交互。您仍然可以从catch子句中记录错误，然后再次抛出异常。这将将异常传播到
RMSCustomer.search如何从该方法向用户显示正确的消息？ 类似于“无记录”（请参阅代码中的“其他”部分） 您不应该从RMSCustomer类中执行任何与GUI相关的操作（如显示对话框）。即使您没有使用模型-视图-控制器模式，您仍然希望让您的类专注于单个职责（管理记录）。这称为。 保持类与GUI隔离将允许您在没有GUI的环境中测试和重用它。
当结果为零时，屏幕应处理无记录的情况。此处可以使用lenght==0的数组，屏幕将显示“无结果”消息。对于其他类型的错误，您可以从
RMSCustomer.searchRecordParsingException