我目前正在开发一个j2me应用程序，而且我很难处理命令按钮。有人可以帮帮我吗。按钮被假定为第二种形式，但是当我点击它时，它不起作用。这是我的代码：
import javax.microedition.midlet .*;
import javax.microedition.lcdui .*;
import javax.microedition.lcdui.StringItem;
import javax.microedition.lcdui.TextField;
import javax.microedition.lcdui.DateField;
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.Alert;
import javax.microedition.pim.PIM;
import javax.microedition.pim.PIMItem;
import javax.microedition.pim.PIMException;
import java.util.Date;
import java.util.Enumeration;
import javax.microedition.lcdui.Choice;
import javax.microedition.lcdui.List;
import javax.microedition.pim.ToDo;
import javax.microedition.pim.ToDoList;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Form;
import javax.microedition.lcdui.CommandListener;
public class MainMidlet extends MIDlet implements CommandListener,
ItemCommandListener {
private Form aform, bform, addToDoForm;
private Command okCommand;
private Command exitCommand;
private Command cmdAddTodo;
private Command cmdretrieveTodo;
private Command cmdExit;
private Command backCommand;
private Command hllinkCommand;
private Command b1Command, b2Command;
private Display aDisplay;
private StringItem hlstringItem,hlstringItem2;
private StringItem b1stringItem, b2stringItem, b1stringItem2, b2stringItem2;
private Alert hlAlert;
private Alert b1Alert, b2Alert;
private TextField summaryField;
// Date field for Due data of ToDo.
private DateField dueDateField;
// Date field for end data of ToDo.
private TextField noteField;
// Text field to set priority of ToDo.
private TextField priorityField;
private List listTodos;
private ToDoList todoList;
private ToDo todo;
public MainMidlet () {
okCommand = new Command ( "OK", Command.OK, 1);
exitCommand = new Command ( "EXIT", Command.EXIT, 1);
backCommand = new Command ( "BACK", Command.BACK, 1);
hllinkCommand = new Command ( "LINK", Command.ITEM, 2);
b1Command = new Command ( "BUTTON", Command.ITEM, 2);
b2Command = new Command ( "BUTTON", Command.ITEM, 2);
aform = new Form ( "CyberMe");
// if click hyperlink "here", display anAlert
hlstringItem = new StringItem (null, "here", Item.HYPERLINK);
hlstringItem.setItemCommandListener (this);
hlstringItem.setDefaultCommand (hllinkCommand);
b1stringItem = new StringItem (null, "Make ToDo", Item.BUTTON);
b1stringItem.setItemCommandListener (this);
b1stringItem.setDefaultCommand (b1Command);
b2stringItem = new StringItem (null, "Set Alarm", Item.BUTTON);
b2stringItem.setItemCommandListener (this);
b2stringItem.setDefaultCommand (b2Command);
/*hlstringItem2 = new StringItem (null, "here", Item.HYPERLINK);
hlstringItem2.setItemCommandListener (this);
hlstringItem2.setDefaultCommand (hllinkCommand);
b1stringItem2 = new StringItem (null, "Make ToDo", Item.BUTTON);
b1stringItem2.setItemCommandListener (this);
b1stringItem2.setDefaultCommand (b1Command);
b2stringItem2 = new StringItem (null, "Set Alarm", Item.BUTTON);
b2stringItem2.setItemCommandListener (this);
b2stringItem2.setDefaultCommand (b2Command);*/
hlAlert = new Alert ( "Item.HYPERLINK", "You Can Call Me 800-8101234"
, null, AlertType.INFO);
b1Alert = new Alert ( "Item.Button", "You click ToDo!"
, null, AlertType.INFO);
//b2Alert = new Alert ( "Item.Button", "You click Alarm!"
//, null, AlertType.INFO);
aform.append ( "What do you want to do?");
aform.append (hlstringItem);
aform.append (b1stringItem);
aform.append (b2stringItem);
aform.addCommand (okCommand);
aform.addCommand (exitCommand);
aform.setCommandListener (this);
/*bform.append ( "What do you want to do?");
bform.append (hlstringItem2);
bform.append (b1stringItem2);
bform.append (b2stringItem2);
bform.addCommand (okCommand);
bform.addCommand (backCommand);
bform.setCommandListener (this); */
}
/*public void SecondPage(){
if(checkPIMSupport() == false) {
exitMIDlet();
}
setComponents();
}
/**
* Initializes components of MIDlet.
*/
public void setComponents() {
aDisplay = Display.getDisplay(this);
// Create form for adding ToDo.
addToDoForm = new Form("ToDo");
// Add commands to form and set listener for it.
cmdAddTodo = new Command("Add Todo", Command.SCREEN, 0);
cmdretrieveTodo = new Command("Retrieve All Todos", Command.SCREEN, 0);
addToDoForm.addCommand(cmdAddTodo);
addToDoForm.addCommand(cmdretrieveTodo);
cmdExit = new Command("Exit", Command.EXIT, 0);
addToDoForm.addCommand(cmdExit);
addToDoForm.setCommandListener(this);
listTodos = new List("ToDo list", Choice.IMPLICIT);
backCommand =new Command("Back", Command.BACK, 0);
listTodos.addCommand(backCommand);
listTodos.setCommandListener(this);
try {
StringBuffer supported = new StringBuffer();
// Get list of ToDos.
todoList = (ToDoList)PIM.getInstance().openPIMList(
PIM.TODO_LIST, PIM.READ_WRITE);
// Create controls based on supported fields for ToDo.
if(todoList.isSupportedField(ToDo.SUMMARY) == true) {
summaryField = new TextField("Summary", null, 20,
TextField.ANY);
addToDoForm.append(summaryField);
}
else {
supported.append("Summary field\n");
removeCommand();
}
if(todoList.isSupportedField(ToDo.DUE) == true) {
dueDateField = new DateField("Date",
DateField.DATE_TIME);
dueDateField.setDate(new Date());
addToDoForm.append(dueDateField);
}
else {
supported.append("Due date field\n");
removeCommand();
}
if(todoList.isSupportedField(ToDo.NOTE) == true) {
noteField = new TextField("Information", null, 20, TextField.ANY);
addToDoForm.append(noteField);
}
else {
supported.append("Note field\n");
}
if(todoList.isSupportedField(ToDo.PRIORITY) == true) {
priorityField = new TextField("Priority", null, 20,
TextField.NUMERIC);
addToDoForm.append(priorityField);
}
else {
supported.append("Priority field\n");
removeCommand();
}
if(supported.length()!=0){
StringItem si = new StringItem("ToDo field not supported", "");
si.setText(supported.toString());
addToDoForm.append(si);
}
} catch(PIMException pimExc) {
// TODO: Handle error on working with PIM.
}
catch(SecurityException secExc) {
// TODO: Handle error on access to PIM.
}
catch(Exception exc) {
// If unknown error was caught, show it to the end user.
showAlert("Info", exc.toString());
}
}
// Remove the command for adding ToDos
public void removeCommand(){
addToDoForm.removeCommand(cmdAddTodo);
}
public void listToDos() {
Enumeration todos = null;
try {
todoList = (ToDoList) PIM.getInstance().openPIMList(PIM.TODO_LIST, PIM.READ_WRITE);
} catch (PIMException e) {
// Cannot open ToDo list
showAlert("Info", "Failed to open a ToDo list: "+e.toString());
return;
} catch (SecurityException e) {
// User rejects application's request for reading ToDo list
showAlert("Info", "Reading ToDo List rejected: "+e.toString());
return;
}
try {
// Get the enumeration of all ToDo elements
todos = todoList.items();
} catch (PIMException e) {
// Failed to retrieve elements
showAlert("Info", "This application cannot retrieve ToDos: "+e.toString());
}
if (listTodos.size() > 0) {
listTodos.deleteAll();
}
while (todos.hasMoreElements()) {
todo = (ToDo) todos.nextElement();
String todoInfo = null;
try {
todoInfo = todo.getString(ToDo.SUMMARY, PIMItem.ATTR_NONE);
} catch (Exception ex) {
showAlert("Info",ex.getMessage());
continue;
}
if (todoInfo != null) {
listTodos.append(todoInfo, null);
}
}
}
/**
* Checks PIM support.
* @return - true if PIM is supported, false otherwise.
*/
private boolean checkPIMSupport() {
String propValue = System.getProperty("microedition.pim.version");
if(propValue != null) {
return true;
} else {
return false;
}
}
private void getToDoList() {
listToDos();
aDisplay.setCurrent(listTodos);
}
/**
* Adds ToDo to list of ToDos.
* Gets data for ToDo from addToDoForm controls.
*/
private void addToDo() {
try {
// Get list of ToDos.
todoList = (ToDoList)PIM.getInstance().openPIMList(
PIM.TODO_LIST, PIM.READ_WRITE);
// Create new ToDo.
todo = todoList.createToDo();
// Get data from controls
if(todoList.isSupportedField(ToDo.SUMMARY) == true) {
if(summaryField.size()==0){
showAlert("Info", "Summary missing, please enter a summary");
return;
}
String summary =summaryField.getString();
todo.addString(ToDo.SUMMARY, PIMItem.ATTR_NONE, summary);
} else {
// At least summary must be supported.
closeToDoList();
showAlert("Info", "Summary field for ToDo is not supported");
}
if(todoList.isSupportedField(ToDo.DUE) == true) {
long startDate = dueDateField.getDate().getTime();
todo.addDate(ToDo.DUE, PIMItem.ATTR_NONE, startDate);
}
if(todoList.isSupportedField(ToDo.NOTE) == true) {
String note = noteField.getString();
todo.addString(ToDo.NOTE, PIMItem.ATTR_NONE, note);
}
if(todoList.isSupportedField(ToDo.PRIORITY) == true) {
if(priorityField.size()==0){
showAlert("Info", "Priority is missing, please enter a priority");
return;
}
else {
String location = priorityField.getString();
int i=Integer.parseInt(location);
if(i > 9){
showAlert("Info","Priority exceeded, please enter a priority between 0-9");
return;
}
todo.addInt(ToDo.PRIORITY, PIMItem.ATTR_NONE, i);
}
}
// Commit ToDo.
todo.commit();
// Notify user that ToDo was added
showAlert("Info", "ToDo was successfully added");
} catch(PIMException pimExc) {
// TODO: Handle error on working with PIM.
showAlert("Info", pimExc.getMessage());
}
catch(SecurityException secExc) {
// TODO: Handle error on access to PIM.
showAlert("Info", secExc.getMessage());
}
catch(Exception exc) {
// TODO: Handle all other errors.
showAlert("Info", exc.toString());
}
}
/**
* Shows alert with specified title and text.
* @param title - Title of alert.
* @param message - text of alert.
*/
private void showAlert(String title, String message) {
Alert alert = new Alert(title);
alert.setString(message);
alert.setTimeout(2000);
aDisplay.setCurrent(alert);
}
/**
* From MIDlet.
* Signals the MIDlet that it has entered the Active state.
*/
public void startApp () {
aDisplay = Display.getDisplay (this);
aDisplay.setCurrent (aform);
}
public void pauseApp () {
}
public void destroyApp (boolean unconditional) {
}
private void exitMIDlet() {
notifyDestroyed();
}
private void closeToDoList() {
if (todoList != null) {
try {
todoList.close();
} catch (PIMException ex) {
showAlert("Info","Error in closing ToDo list: "+ex.toString());
}
}
todoList = null;
}
public void commandAction (Command c, Displayable d) {
if (c == exitCommand) {
destroyApp (false);
notifyDestroyed ();
}
if(c == backCommand){
aDisplay.setCurrent(aform);
}
}
public void commandAction (Command c, Item i) {
if (c == hllinkCommand) {
aDisplay.setCurrent (hlAlert, aform);
}
if (c == b1Command) {
aDisplay.setCurrent (b1Alert, aform);
}
if (c == b2Command){
aDisplay.setCurrent (addToDoForm);
}
}
}
答案 0 :(得分：3)
您的即时错误 - 这是您所有问题的最轻微 - 是您忘记在okCommand中处理commandAction(Command, Displayable)。
因此，当用户单击“确定”时，没有任何反应 - 只是因为没有代码可以处理此问题。
这个错误很容易修复 - 只需添加到commandAction中 - 进入处理Displayable而不是Item的代码 - 代码如下，你就完成了：
if(c == okCommand){
// show whatever screen you need
aDisplay.setCurrent(new Form("whatever"));
}
但这并不能解决你的麻烦，因为有了这样的代码你就会注定要犯下微妙的错误，并且要解决这些问题。
既然我们完成了一些小问题，那么错误错误中的第一个错误就是缺少用户操作点和catch块内的日志记录（为什么我提到了catch块，在Web上搜索 Java swallow exceptions ）。
这使得在调试时不必要地计算出那里发生了什么。如果在那里登录，只需运行MIDlet并查看模拟器控制台就可以很容易地找到上面错过okCommand处理的错误。
我建议记录的用户操作点数在commandAction以及调用setCurrent时。在开发时，可以随意添加更多（如果使用Canvas，keyPressed看起来也是一个很好的候选者）。
public class Log {
// utility class to keep logging code in one place
public static void log (String message) {
System.out.println(message);
// when debugging at real device, S.o.p above can be refactored
// - based on ideas like one used here (with Form.append):
// http://stackoverflow.com/questions/10649974
// - Another option would be to write log to RMS
// and use dedicated MIDlet to read it from there
// - If MIDlet has network connection, an option is
// to pass log messages over the network. Etc etc...
}
}
// ... other classes...
// ...
catch (Exception e) {
Log.log("unexpected exception: [" + e + "]");
}
// ...
public void commandAction(Command c, Displayable s) {
Log.log("command: [" + c.getCommandLabel()
+ "] at screen: [" + d.getTitle() + "]");
// ...
}
// ...
public void commandAction(Command c, Item i) {
Log.log("command: [" + c.getCommandLabel()
+ "] at item: [" + i.getLabel() + "]");
// ...
}
// ...
Log.log("set current: [" + someDisplayable.getTitle() + "]");
display.setCurrent(someDisplayable);
// ...
protected void keyPressed(int key) { // in Canvas
Log.log("key pressed: [" + getKeyName(key) + "]");
// ...
}
代码中的另一个非常糟糕的错误是它是God object。这使得修改和调试变得不必要地困难。将您的应用程序拆分为较小的类，没有必要将它们全部保存在一个地方。
首先，考虑将CommandListener和ItemCommandListener移动到单独的类中，而不是让MainMidlet实现这些。请记住，可能有多个Item / CommandListener，例如每个屏幕一个。
将与aform内容相关的代码拆分为单独的类。与bform，addToDoForm，listTodos相同。等等。