我正在开发一个应用程序，我希望使用持久存储来存储许多数据条目。问题是每当新条目生成时它都会替换现有条目。 这是我的代码请帮助我。
import net.rim.device.api.ui.*;
import net.rim.device.api.ui.component.*;
import net.rim.device.api.ui.container.*;
import net.rim.device.api.system.*;
import net.rim.device.api.util.*;
import java.util.*;
/*An application in which user enters the data. this data is displayed when user press the save button*/
public class Display extends UiApplication {
/*declaring Strings to store the data of the user*/
String getFirstName;
String getLastName;
String getEmail;
String getGender;
String getStatus;
/*declaring text fields for user input*/
private AutoTextEditField firstName;
private AutoTextEditField lastName;
private EmailAddressEditField email;
/*declaring choice field for user input*/
private ObjectChoiceField gender;
/*declaring check box field for user input*/
private CheckboxField status;
//Declaring button fields
private ButtonField save;
private ButtonField close;
/*declaring vector*/
private static Vector _data;
/*declaring persistent object*/
private static PersistentObject store;
/*creating an entry point*/
public static void main(String[] args)
{
/*creating instance of the class */
Display app = new Display();
app.enterEventDispatcher();
}
/*creating default constructor*/
public Display()
{
/*Creating an object of the main screen class to use its functionalities*/
MainScreen mainScreen = new MainScreen();
//setting title of the main screen
mainScreen.setTitle(new LabelField("Enter Your Data"));
//creating text fields for user input
firstName = new AutoTextEditField("First Name: ", "");
lastName= new AutoTextEditField("Last Name: ", "");
email= new EmailAddressEditField("Email:: ", "");
//creating choice field for user input
String [] items = {"Male","Female"};
gender= new ObjectChoiceField("Gender",items);
//creating Check box field
status = new CheckboxField("Active",true);
//creating Button fields and adding functionality using listeners
save = new ButtonField("Save",ButtonField.CONSUME_CLICK);
save.setChangeListener(new FieldChangeListener()
{
public void fieldChanged(Field field, int context)
{
save();
}
});
close = new ButtonField("Close",ButtonField.CONSUME_CLICK);
close.setChangeListener(new FieldChangeListener()
{
public void fieldChanged(Field field, int context)
{
onClose();
}
});
//adding the input fields to the main screen
mainScreen.add(firstName);
mainScreen.add(lastName);
mainScreen.add(email);
mainScreen.add(gender);
mainScreen.add(status);
//adding buttons to the main screen
mainScreen.add(close);
mainScreen.add(save);
//adding menu items
mainScreen.addMenuItem(saveItem);
mainScreen.addMenuItem(getItem);
//pushing the main screen
pushScreen(mainScreen);
}
//adding functionality to menu item "saveItem"
private MenuItem saveItem = new MenuItem("Save", 110, 10)
{
public void run()
{
//Calling save method
save();
}
};
//adding functionality to menu item "saveItem"
private MenuItem getItem = new MenuItem("Get", 110, 11)
{
//running thread for this menu item
public void run()
{
//synchronizing thread
synchronized (store)
{
//getting contents of the persistent object
_data = (Vector) store.getContents();
//checking for empty object
if (!_data.isEmpty())
{
//if not empty
//create a new object of Store Info class
StoreInfo info = (StoreInfo)
//returning last component of the vector
_data.lastElement();
//storing information retrieved in strings
getFirstName = (info.getElement(StoreInfo.NAME));
getLastName = (info.getElement(StoreInfo.LastNAME));
getEmail = (info.getElement(StoreInfo.EMail));
getGender = (info.getElement(StoreInfo.GenDer));
getStatus = (info.getElement(StoreInfo.setStatus));
//calling the show method
show();
}
}
}
};
//coding for persistent store
static {
store =
PersistentStore.getPersistentObject(0xdec6a67096f833cL);
synchronized (store) {
if (store.getContents() == null) {
store.setContents(new Vector());
store.commit();
}
}
_data = new Vector();
_data = (Vector) store.getContents();
}
//new class store info implementing persistable
private static final class StoreInfo implements Persistable
{
//declaring variables
private Vector _elements;
public static final int NAME = 0;
public static final int LastNAME = 1;
public static final int EMail= 2;
public static final int GenDer = 3;
public static final int setStatus = 4;
public StoreInfo()
{
_elements = new Vector(5);
for (int i = 0; i < _elements.capacity(); ++i)
{
_elements.addElement(new String(""));
}
}
public String getElement(int id)
{
return (String) _elements.elementAt(id);
}
public void setElement(int id, String value)
{
_elements.setElementAt(value, id);
}
}
//details for show method
public void show()
{
Dialog.alert("Name is "+getFirstName+" "+getLastName+"\nGender is "+getGender+"\nE-mail: "+getEmail+"\nStatus is "+getStatus);
}
//creating save method
public void save()
{
//creating an object of inner class StoreInfo
StoreInfo info = new StoreInfo();
//getting the test entered in the input fields
info.setElement(StoreInfo.NAME, firstName.getText());
info.setElement(StoreInfo.LastNAME,lastName.getText());
info.setElement(StoreInfo.EMail, email.getText());
info.setElement(StoreInfo.GenDer,gender.toString());
if(status.getChecked())
info.setElement(StoreInfo.setStatus, "Active");
else
info.setElement(StoreInfo.setStatus, "In Active");
//adding the object to the end of the vector
_data.addElement(info);
//synchronizing the thread
synchronized (store)
{
store.setContents(_data);
store.commit();
}
//resetting the input fields
Dialog.inform("Success!");
firstName.setText(null);
lastName.setText(null);
email.setText("");
gender.setSelectedIndex("Male");
status.setChecked(true);
}
//overriding onClose method
public boolean onClose()
{
System.exit(0);
return true;
}
}
答案 0 :(得分：8)
实际上它可以完美地保存所有内容，但只检索最后一条记录：
StoreInfo info = (StoreInfo)_data.lastElement();
尝试此操作以显示每条记录：
for (int i = 0; i < _data.size(); i++) {
StoreInfo info = (StoreInfo)_data.elementAt(i);
...
show();
}