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*
*
* Copyright 1990-2007 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
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* General Public License version 2 for more details (a copy is
* included at /legal/license.txt).
*
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package javax.microedition.lcdui;
import com.sun.midp.lcdui.CommandAccess;
/**
* The <code>Command</code> class is a construct that encapsulates
* the semantic information of an action. The behavior that the command
* activates is not encapsulated in this object. This means that command
* contains
* only information about "command" not the actual action
* that happens when
* command
* is activated. The action is defined in a
* {@link CommandListener CommandListener}
* associated
* with the <code>Displayable</code>. <code>Command</code> objects are
* <em>presented</em>
* in the user interface and the way they are presented
* may depend on the semantic information contained within the command.
*
* <P><code>Commands</code> may be implemented in any user interface
* construct that has
* semantics for activating a single action. This, for example, can be a soft
* button, item in a menu, or some other direct user interface construct.
* For example, a
* speech interface may present these commands as voice tags. </P>
*
* <P>The mapping to concrete user interface constructs may also depend on the
* total number of the commands.
* For example, if an application asks for more abstract commands than can
* be mapped onto
* the available physical buttons on a device, then the device may use an
* alternate human interface such as a menu. For example, the abstract
* commands that
* cannot be mapped onto physical buttons are placed in a menu and the label
* "Menu" is mapped onto one of the programmable buttons. </P>
*
* <p>A command contains four pieces of information: a <em>short label</em>,
* an optional <em>long label</em>, a
* <em>type</em>, and a <em>priority</em>.
* One of the labels is used for the visual
* representation of the command, whereas the type and the priority indicate
* the semantics of the command. </p>
*
* <a name="label"></a>
* <h3>Labels</h3>
*
* <p> Each command includes one or two label strings. The label strings are
* what the application requests to be shown to the user to represent this
* command. For example, one of these strings may appear next to a soft button
* on the device or as an element in a menu. For command types other than
* <code>SCREEN</code>, the labels provided may be overridden by a
* system-specific label
* that is more appropriate for this command on this device. The contents of
* the label strings are otherwise not interpreted by the implementation. </p>
*
* <p>All commands have a short label. The long label is optional. If the
* long label is not present on a command, the short label is always used.
* </p>
*
* <p>The short label string should be as short as possible so that it
* consumes a minimum of screen real estate. The long label can be longer and
* more descriptive, but it should be no longer than a few words. For
* example, a command's short label might be "Play", and its
* long label
* might be "Play Sound Clip".</p>
*
* <p>The implementation chooses one of the labels to be presented in the user
* interface based on the context and the amount of space available. For
* example, the implementation might use the short label if the command
* appears on a soft button, and it might use the long label if the command
* appears on a menu, but only if there is room on the menu for the long
* label. The implementation may use the short labels of some commands and
* the long labels of other commands, and it is allowed to switch between
* using the short and long label at will. The application cannot determine
* which label is being used at any given time. </p>
*
* <a name="type"></a>
* <h3>Type</h3>
*
* <p> The application uses the command
* type to specify the intent of this command. For example, if the
* application specifies that the command is of type
* <code>BACK</code>, and if the device
* has a standard of placing the "back" operation on a
* certain soft-button,
* the implementation can follow the style of the device by using the semantic
* information as a guide. The defined types are
* {@link #BACK BACK},
* {@link #CANCEL CANCEL},
* {@link #EXIT EXIT},
* {@link #HELP HELP},
* {@link #ITEM ITEM},
* {@link #OK OK},
* {@link #SCREEN SCREEN},
* and
* {@link #STOP STOP}. </p>
*
* <a name="priority"></a>
* <h3>Priority</h3>
*
* <p> The application uses the priority
* value to describe the importance of this command relative to other commands
* on the same screen. Priority values are integers, where a lower number
* indicates greater importance. The actual values are chosen by the
* application. A priority value of one might indicate the most important
* command, priority values of two, three, four, and so on indicate commands
* of lesser importance. </p>
*
* <p>Typically,
* the implementation first chooses the placement of a command based on
* the type of command and then places similar commands based on a priority
* order. This could mean that the command with the highest priority is
* placed so that user can trigger it directly and that commands with lower
* priority are placed on a menu. It is not an error for there to be commands
* on the same screen with the same priorities and types. If this occurs, the
* implementation will choose the order in which they are presented. </p>
*
* <p>For example, if the application has the following set of commands: </P>
* <TABLE BORDER="2">
* <TR>
* <TD ROWSPAN="1" COLSPAN="1">
* <pre><code>
* new Command("Buy", Command.ITEM, 1);
* new Command("Info", Command.ITEM, 1);
* new Command("Back", Command.BACK, 1); </code></pre>
* </TD>
* </TR>
* </TABLE>
* <P>
* An implementation with two soft buttons may map the
* <code>BACK</code> command to
* the right
* soft button and create an "Options" menu on the left soft
* button to contain
* the other commands.<BR>
* <IMG SRC="doc-files/command1.gif" width=190 height=268><BR>
* When user presses the left soft button, a menu with the two remaining
* <code>Commands</code> appears:<BR>
* <IMG SRC="doc-files/command2.gif" width=189 height=260><BR>
* If the application had three soft buttons, all commands can be mapped
* to soft buttons:
* <BR><IMG SRC="doc-files/command3.gif" width=189 height=261></P>
*
* <p>The application is always responsible for providing the means for the
* user to progress through different screens. An application may set up a
* screen that has no commands. This is allowed by the API but is generally
* not useful; if this occurs the user would have no means to move to another
* screen. Such program would simply considered to be in error. A typical
* device should provide a means for the user to direct the application manager
* to kill the erroneous application.
* @since MIDP 1.0
*/
public class Command {
// public members //
/**
* Specifies an application-defined command that pertains to the current
* screen. Examples could be "Load" and
* "Save". A <code>SCREEN</code> command
* generally applies to the entire screen's contents or to navigation
* among screens. This is in contrast to the <CODE>ITEM</CODE> type,
* which applies to the currently activated or focused item or element
* contained within this screen.
*
* <P>Value <code>1</code> is assigned to <code>SCREEN</code>.</P>
*/
public static final int SCREEN = 1;
/**
* A navigation command that returns the user to the logically
* previous screen.
* The jump to the previous screen is not done automatically by the
* implementation
* but by the {@link CommandListener#commandAction commandAction}
* provided by
* the application.
* Note that the application defines the actual action since the strictly
* previous screen may not be logically correct.
*
* <P>Value <code>2</code> is assigned to <code>BACK</code>.</P>
*
* @see #CANCEL
* @see #STOP
*/
public static final int BACK = 2;
/**
* A command that is a standard negative answer to a dialog implemented by
* current screen.
* Nothing is cancelled automatically by the implementation; cancellation
* is implemented
* by the {@link CommandListener#commandAction commandAction} provided by
* the application.
*
* <p> With this command type, the application hints to the implementation
* that the user wants to dismiss the current screen without taking any
* action
* on anything that has been entered into the current screen, and usually
* that
* the user wants to return to the prior screen. In many cases
* <code>CANCEL</code> is
* interchangeable with <code>BACK</code>, but <code>BACK</code>
* is mainly used for navigation
* as in a browser-oriented applications. </p>
*
* <P>Value <code>3</code> is assigned to <code>CANCEL</code>.</P>
*
* @see #BACK
* @see #STOP
*/
public static final int CANCEL = 3;
/**
* A command that is a standard positive answer to a dialog implemented by
* current screen.
* Nothing is done automatically by the implementation; any action taken
* is implemented
* by the {@link CommandListener#commandAction commandAction} provided by
* the application.
*
* <p> With this command type the application hints to the
* implementation that
* the user will use this command to ask the application to confirm
* the data
* that has been entered in the current screen and to proceed to the next
* logical screen. </p>
*
* <P><code>CANCEL</code> is often used together with <code>OK</code>.</P>
*
* <P>Value <code>4</code> is assigned to <code>OK</code>.</P>
*
* @see #CANCEL
*/
public static final int OK = 4;
/**
* This command specifies a request for on-line help.
* No help information is shown automatically by the implementation.
* The
* {@link CommandListener#commandAction commandAction} provided by the
* application is responsible for showing the help information.
*
* <P>Value <code>5</code> is assigned to <code>HELP</code>.</P>
*/
public static final int HELP = 5;
/**
* A command that will stop some currently running
* process, operation, etc.
* Nothing is stopped automatically by the implementation.
* The cessation must
* be performed
* by the {@link CommandListener#commandAction commandAction} provided by
* the application.
*
* <p> With this command type the application hints to the
* implementation that
* the user will use this command to stop any currently running process
* visible to the user on the current screen. Examples of running processes
* might include downloading or sending of data. Use of the
* <code>STOP</code>
* command does
* not necessarily imply a switch to another screen. </p>
*
* <P>Value <code>6</code> is assigned to <code>STOP</code>.</P>
*
* @see #BACK
* @see #CANCEL
*/
public static final int STOP = 6;
/**
* A command used for exiting from the application. When the user
* invokes this command, the implementation does not exit automatically.
* The application's
* {@link CommandListener#commandAction commandAction}
* will be called, and it should exit the application if it
* is appropriate to do so.
*
* <P>Value <code>7</code> is assigned to <code>EXIT</code>.</P>
*/
public static final int EXIT = 7;
/**
* With this command type the application can hint to the
* implementation that the command is specific to the items of
* the <code>Screen</code> or the elements of a
* <code>Choice</code>. Normally this
* means that command relates to the focused item or element.
* For example, an implementation of <code>List</code> can use
* this information for
* creating context sensitive menus.
*
* <P>Value <code>8</code> is assigned to <code>ITEM</code>.</P>
*/
public static final int ITEM = 8;
// protected members //
/**
* The label rendered on the screen for this Command.
* Chosen from the available set of labels.
*/
String shortLabel;
/**
* The long Label for this Command
*/
String longLabel;
/**
* The type of this Command
*/
int commandType;
/**
* The priority of this Command
*/
int priority;
// private members //
/**
* This is a private id that is set when adding a command to
* a Displayable,
* such that the Command may be easily identified at a later
* date only by its id
*/
private int id;
// Constructors //
/**
* Creates a new command object with the given short
*
* <a href="#label">label</a>,
* <a href="#type">type</a>, and
* <a href="#priority">priority</a>.
*
* The newly created command has no long label. This constructor is
* identical to <code>Command(label, null, commandType, priority)</code>.
*
* @param label the command's short label
* @param commandType the command's type
* @param inp_priority the command's priority value
*
* @throws NullPointerException if label is <code>null</code>
* @throws IllegalArgumentException if the <code>commandType</code>
* is an invalid type
*
* @see #Command(String, String, int, int)
*/
public Command(String label, int commandType, int inp_priority) {
this(label, null, commandType, inp_priority);
}
/**
* Creates a new command object with the given
* <a href="#label">labels</a>,
* <a href="#type">type</a>, and
* <a href="#priority">priority</a>.
*
* <p>The short label is required and must not be
* <code>null</code>. The long label is
* optional and may be <code>null</code> if the command is to have
* no long label.</p>
*
* @param shortLabel the command's short label
* @param longLabel the command's long label, or <code>null</code> if none
* @param commandType the command's type
* @param inp_priority the command's priority value
*
* @throws NullPointerException if <code>shortLabel</code> is
* <code>null</code>
* @throws IllegalArgumentException if the <code>commandType</code> is an
* invalid type
*
*/
public Command(String shortLabel, String longLabel, int commandType,
int inp_priority) {
initialize(commandType, inp_priority);
setLabel(shortLabel, longLabel);
}
// public method implementations //
/**
* Gets the short label of the command.
*
* @return the <code>Command's</code> short label
*/
public String getLabel() {
// SYNC NOTE: return of atomic value, no locking necessary
return shortLabel;
}
/**
* Gets the long label of the command.
*
* @return the <code>Command's</code> long label, or
* <code>null</code> if the <code>Command</code> has no long
* label
*
*/
public String getLongLabel() {
// SYNC NOTE: return of atomic value, no locking necessary
return longLabel;
}
/**
* Gets the type of the command.
*
* @return type of the <code>Command</code>
*/
public int getCommandType() {
// SYNC NOTE: return of atomic value, no locking necessary
return commandType;
}
/**
* Gets the priority of the command.
*
* @return priority of the <code>Command</code>
*/
public int getPriority() {
// SYNC NOTE: return of atomic value, no locking necessary
return priority;
}
// protected method implementations //
/**
* Get the internal ID of this Command
*
* @return int The integer id associated with this specific Command
*/
int getID() {
return id;
}
// package private method implementations //
/**
* Sets the internal id used to uniquely identify
* this command.
* This method is intended to be called from Displayable
* addCommand()
*
* @param num the int to set this id to
*/
void setInternalID(int num) {
this.id = num;
}
// private method implementations //
/**
* Sets the label of the command. If the label is null
* throw NullPointerException.
* @param shortLabel the short Label string
* @param longLabel the long Label string
*/
private void setLabel(String shortLabel, String longLabel) {
if (shortLabel == null) {
throw new NullPointerException();
}
this.shortLabel = shortLabel;
this.longLabel = longLabel;
}
/**
* This method will initialize this Command object is only called
* by its constructors.
*
* @param commandType The command's <a href="#type">type</a>, one of
* {@link #BACK BACK},
* {@link #CANCEL CANCEL},
* {@link #EXIT EXIT},
* {@link #HELP HELP},
* {@link #ITEM ITEM},
* {@link #OK OK},
* {@link #SCREEN SCREEN},
* or
* {@link #STOP STOP}
*
* @param inp_priority The command's <a href="#priority">priority</a>
* value
*
* @throws IllegalArgumentException if the commandType is an invalid
* type
* @throws NullPointerException if label is null, or if any one of
* the array of labels is null
*/
private final void initialize(int commandType, int inp_priority) {
if ((commandType < SCREEN) || (commandType > ITEM)) {
throw new IllegalArgumentException();
}
this.commandType = commandType;
priority = inp_priority;
}
} // class Command
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