| java.lang.Object
 javax.microedition.lcdui.Displayable
javax.microedition.lcdui.Screen
javax.microedition.lcdui.Alert
All known Subclasses: com.sun.midp.main.HeadlessAlert, com.sun.midp.lcdui.SystemAlert,
| Alert | | public class Alert extends Screen (Code) | | An alert is a screen that shows data to the user and waits for a certain
period of time before proceeding to the next
Displayable. An alert can
contain a text string and an image.
The intended use of Alert is to inform the user about
errors and other
exceptional conditions.
The application can set the alert time to be infinity with
setTimeout(Alert.FOREVER)
in which case the Alert is considered to be modal and
the implementation provide a feature that allows the
user to "dismiss" the alert, whereupon the next
Displayable
is displayed as if the timeout had expired immediately.
If an application specifies an alert to be of a
timed variety and gives it too much content such that it must
scroll,
then it automatically becomes a modal alert.
An alert may have an AlertType associated with it
to provide an indication of the nature of the alert.
The implementation may use this type to play an
appropriate sound when the Alert is presented to the user.
See
AlertType.playSound(javax.microedition.lcdui.Display) AlertType.playSound() .
An alert may contain an optional Image. The
Image may be mutable or
immutable. If the Image is mutable, the effect is as
if a snapshot of its
contents is taken at the time the Alert is constructed
with this Image and
when setImage is called with an Image.
This snapshot is used whenever the contents of the
Alert are to be
displayed. Even if the application subsequently draws into the
Image, the
snapshot is not modified until the next call to setImage. The
snapshot is not updated when the Alert
becomes current or becomes
visible on the display. (This is because the application does not have
control over exactly when Displayables appear and
disappear from the
display.)
Activity Indicators
An alert may contain an optional
Gauge object that is used as an
activity or progress indicator. By default, an Alert
has no activity
indicator; one may be set with the
Alert.setIndicator method.
The Gauge
object used for the activity indicator must conform to all of the following
restrictions:
- it must be non-interactive;
- it must not be owned by another container (
Alert
or Form);
- it must not have any
Commands;
- it must not have an
ItemCommandListener;
- it must not have a label (that is, its label must be
null;
- its preferred width and height must both be unlocked; and
- its layout value must be
LAYOUT_DEFAULT.
It is an error for the application to attempt to use a
Gauge object that
violates any of these restrictions. In addition, when the
Gauge object is
being used as the indicator within an Alert, the
application is prevented
from modifying any of these pieces of the Gauge's state.
Commands and Listeners
Like the other Displayable classes, an
Alert can accept Commands, which
can be delivered to a CommandListener set by the
application. The Alert
class adds some special behavior for Commands and listeners.
When it is created, an Alert implicitly has the
special Command
Alert.DISMISS_COMMAND present on it. If the application adds any
other Commands to the Alert,
DISMISS_COMMAND is implicitly removed. If the
application removes all other Commands,
DISMISS_COMMAND is implicitly
restored. Attempts to add or remove DISMISS_COMMAND
explicitly are
ignored. Thus, there is always at least one Command
present on an Alert.
If there are two or more Commands present on the
Alert, it is
automatically turned into a modal Alert, and the
timeout value is always
Alert.FOREVER . The Alert remains on the display
until a Command is
invoked. If the Alert has one Command (whether it is DISMISS_COMMAND or it
is one provided by the application), the Alert may have
the timed behavior
as described above. When a timeout occurs, the effect is the same as if
the user had invoked the Command explicitly.
When it is created, an Alert implicitly has a
CommandListener called the
default listener associated with it. This listener may be
replaced by an application-provided listener through use of the
Alert.setCommandListener method. If the application removes its listener by
passing null to the setCommandListener method,
the default listener is implicitly restored.
The
Display.setCurrent(AlertDisplayable) method and the
Display.setCurrent(Displayable) method (when called with an
Alert) define
special behavior for automatically advancing to another
Displayable after
the Alert is dismissed. This special behavior occurs
only when the default
listener is present on the Alert at the time it is
dismissed or when a
command is invoked. If the user invokes a Command and
the default listener
is present, the default listener ignores the Command
and implements the
automatic-advance behavior.
If the application has set its own CommandListener, the
automatic-advance behavior is disabled. The listener code is responsible
for advancing to another Displayable. When the
application has provided a
listener, Commands are invoked normally by passing
them to the listener's
commandAction method. The Command passed
will be one of the
Commands present on the Alert: either
DISMISS_COMMAND or one of the
application-provided Commands.
The application can restore the default listener by passing
null to the setCommandListener method.
Note: An application may set a
Ticker Ticker with
Displayable.setTicker Displayable.setTicker on an
Alert, however it may not be displayed due to
implementation restrictions.
See Also: AlertType
since:
MIDP 1.0 |
| Constructor Summary | |
| public | Alert(String title)
Constructs a new, empty Alert object with the
given title. | | public | Alert(String title, String alertText, Image alertImage, AlertType alertType)
Constructs a new Alert object with the given title,
content
string and image, and alert type.
The layout of the contents is implementation dependent.
The timeout value of this new alert is the same value that is
returned by getDefaultTimeout().
The Image provided may either be mutable or immutable.
The handling and behavior of specific AlertTypes
is described in
AlertType . |
| DISMISS_COMMAND | | final public static Command DISMISS_COMMAND(Code) | | A Command delivered to a listener to indicate that
the Alert has been
dismissed. This Command is implicitly present an on
Alert whenever
there are no other Commands present. The field values of
DISMISS_COMMAND are as follows:
- label = "" (an empty string)
- type = Command.OK
- priority = 0
The label value visible to the application must be as specified
above. However, the implementation may display
DISMISS_COMMAND to the
user using an implementation-specific label.
Attempting to add or remove DISMISS_COMMAND
from an Alert has no
effect. However, DISMISS_COMMAND is treated as an
ordinary Command if
it is used with other Displayable types.
|
| FOREVER | | final public static int FOREVER(Code) | | FOREVER indicates that an Alert is
kept visible until the user
dismisses it. It is used as a value for the parameter to
Alert.setTimeout(int) setTimeout() to indicate that the alert is modal. Instead of waiting for a
specified period of time, a modal Alert will wait
for the user to take
some explicit action, such as pressing a button, before proceeding to
the next Displayable.
Value -2 is assigned to FOREVER.
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| alertLF | | AlertLF alertLF(Code) | | The Alert look&feel object associated with this Alert
|
| indicator | | Gauge indicator(Code) | | The activity indicator for this alert
|
| returnScreen | | Displayable returnScreen(Code) | | The screen which the display will return to when this Alert
is completed
|
| text | | String text(Code) | | The layout object for the alert text string
|
| time | | int time(Code) | | The timeout value of this alert
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| Alert | | public Alert(String title)(Code) | | Constructs a new, empty Alert object with the
given title. If null is
passed, the Alert will have no title. Calling
this constructor is
equivalent to calling
Alert(title, null, null, null)
Parameters:
title - the title string, or null
See Also: Alert.Alert(String,String,Image,AlertType) |
| Alert | | public Alert(String title, String alertText, Image alertImage, AlertType alertType)(Code) | | Constructs a new Alert object with the given title,
content
string and image, and alert type.
The layout of the contents is implementation dependent.
The timeout value of this new alert is the same value that is
returned by getDefaultTimeout().
The Image provided may either be mutable or immutable.
The handling and behavior of specific AlertTypes
is described in
AlertType . null is allowed as the value
of the alertType
parameter and indicates that the Alert is not to
have a specific alert
type. DISMISS_COMMAND is the only
Command present on the new
Alert. The CommandListener
associated with the new Alert is the
default listener. Its behavior is described in more detail in
the section Commands and Listeners.
Parameters:
title - the title string, or null if there is no title
Parameters:
alertText - the string contents, or null if there is no string
Parameters:
alertImage - the image contents, or null if there is no image
Parameters:
alertType - the type of the Alert, ornullif the Alert has nospecific type |
| getDefaultTimeout | | public int getDefaultTimeout()(Code) | | Gets the default time for showing an Alert. This
is either a
positive value, which indicates a time in milliseconds, or the special
value
Alert.FOREVER FOREVER ,
which indicates that Alerts are modal by default. The
value returned will vary across implementations and is presumably
tailored to be suitable for each.
default timeout in milliseconds, or FOREVER |
| getImage | | public Image getImage()(Code) | | Gets the Image used in the Alert.
the Alert's image, or null if there is no image
See Also: Alert.setImage |
| getIndicator | | public Gauge getIndicator()(Code) | | Gets the activity indicator for this Alert.
a reference to this Alert's activity indicator,or null if there is none
See Also: Alert.setIndicator |
| getReturnScreen | | Displayable getReturnScreen()(Code) | | Get the screen that the display should return to
when this Alert is dismissed.
The Displayable to display when this Alert is completed |
| getString | | public String getString()(Code) | | Gets the text string used in the Alert.
the Alert's text string, or null if there is no text
See Also: Alert.setString |
| getTimeout | | public int getTimeout()(Code) | | Gets the time this Alert will be shown. This is
either a positive
value, which indicates a time in milliseconds, or the special value
FOREVER, which indicates that this
Alert is modal. This value is not
necessarily the same value that might have been set by the
application
in a call to
Alert.setTimeout . In particular, if the
Alert is made
modal because its contents is large enough to scroll, the value
returned by getTimeout will be FOREVER.
timeout in milliseconds, or FOREVER
See Also: Alert.setTimeout |
| getType | | public AlertType getType()(Code) | | Gets the type of the Alert.
a reference to an instance of AlertType,or nullif the Alerthas no specific type
See Also: Alert.setType |
| lDismiss | | void lDismiss()(Code) | | Dismisses this alert.
|
| removeCommand | | public void removeCommand(Command cmd)(Code) | | Similar to
Displayable.removeCommand , however when the
application removes the last command from an
Alert,
Alert.DISMISS_COMMAND is implicitly
added. Calling this method with DISMISS_COMMAND
as the parameter has no effect.
Parameters:
cmd - the command to be removed |
| setImage | | public void setImage(Image img)(Code) | | Sets the Image used in the Alert.
The Image may be mutable or
immutable. If img is null, specifies
that this Alert has no image.
If img is mutable, the effect is as if a snapshot is taken
of img's contents immediately prior to the call to
setImage. This
snapshot is used whenever the contents of the
Alert are to be
displayed. If img is already the
Image of this Alert, the effect
is as if a new snapshot of img's contents is taken. Thus, after
painting into a mutable image contained by an Alert, the
application can call
alert.setImage(alert.getImage());
|
to refresh the Alert's snapshot of its
Image.
If the Alert is visible on the display when its
contents are updated
through a call to setImage, the display will be
updated with the new
snapshot as soon as it is feasible for the implementation to do so.
Parameters:
img - the Alert's image, or nullif there is no image
See Also: Alert.getImage |
| setIndicator | | public void setIndicator(Gauge indicator)(Code) | | Sets an activity indicator on this Alert. The
activity indicator is a
Gauge object. It must be in a restricted state in order for it
to be used as the activity indicator for an Alert.
The restrictions
are listed above. If the
Gauge object
violates any of these restrictions,
IllegalArgumentException is thrown.
If indicator is null, this removes any
activity indicator present on this Alert.
Parameters:
indicator - the activity indicator for this Alert,or null if there is to be none
throws:
IllegalArgumentException - if indicator does notmeet the restrictions for its use in an Alert
See Also: Alert.getIndicator |
| setReturnScreen | | void setReturnScreen(Displayable d)(Code) | | Set the screen that the display should return to
when this Alert is dismissed.
Parameters:
d - The Displayable to display when this Alert is completed |
| setString | | public void setString(String str)(Code) | | Sets the text string used in the Alert.
If the Alert is visible on the display when its
contents are updated
through a call to setString, the display will be
updated with the new
contents as soon as it is feasible for the implementation to do so.
Parameters:
str - the Alert's text string, or nullif there is no text
See Also: Alert.getString |
| setTimeout | | public void setTimeout(int time)(Code) | | Set the time for which the Alert is to be shown.
This must either
be a positive time value in milliseconds, or the special value
FOREVER.
Parameters:
time - timeout in milliseconds, or FOREVER
throws:
IllegalArgumentException - if time is not positive and isnot FOREVER
See Also: Alert.getTimeout |
| setType | | public void setType(AlertType type)(Code) | | Sets the type of the Alert.
The handling and behavior of specific AlertTypes
is described in
AlertType .
Parameters:
type - an AlertType, or null if theAlert has nospecific type
See Also: Alert.getType |
| uNotifyTimeout | | void uNotifyTimeout()(Code) | | LF notifies that the Alert is dismissed due to timeout,
instead of user action.
Commandlistener will be notified with the default Command.
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