javax.microedition.lcdui
Class Alert

java.lang.Object
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  +--javax.microedition.lcdui.Displayable
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        +--javax.microedition.lcdui.Screen
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              +--javax.microedition.lcdui.Alert

public class Alert

extends Screen

An alert is a screen that shows data to the user and waits for a certain period of time before proceeding to the next screen. An alert is an ordinary screen that can contain text (String) and image, and which handles events like other screens.

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 screen 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().

Alerts do not accept application-defined commands.

If the Alert is visible on the display when changes to its contents are requested by the application, the changes take place automatically. That is, applications need not take any special action to refresh a Alert's display after its contents have been modified.

See Also:

AlertType

Field Summary

static Command	DISMISS_COMMAND A Command delivered to a listener to indicate that the Alert has been dismissed.
static int	FOREVER FOREVER indicates that an Alert is kept visible until the user dismisses it.

Constructor Summary

Alert(String title)
Constructs a new, empty Alert object with the given title.

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.

Method Summary

void	addCommand(Command cmd) Commands are not allowed on Alerts, so this method will always throw IllegalStateException whenever it is called.
int	getDefaultTimeout() Gets the default time for showing an Alert.
Image	getImage() Gets the Image used in the Alert.
Gauge	getIndicator() Gets the activity indicator for this Alert.
String	getString() Gets the text string used in the Alert.
int	getTimeout() Gets the time this Alert will be shown.
String	getTitle() Gets the title of the Screen.
AlertType	getType() Gets the type of the Alert.
void	removeCommand(Command cmd) Similar to Displayable.removeCommand(javax.microedition.lcdui.Command), however when the application removes the last command from an Alert, DISMISS_COMMAND is implicitly added.
void	setCommandListener(CommandListener l) Listeners are not allowed on Alerts, so this method will always throw IllegalStateException whenever it is called.
void	setImage(Image img) Sets the Image used in the Alert.
void	setIndicator(Gauge indicator) Sets an activity indicator on this Alert.
void	setString(String str) Sets the text string used in the Alert.
void	setTimeout(int time) Set the time for which the Alert is to be shown.
void	setTitle(String title) Sets the title of the Screen.
void	setType(AlertType type) Sets the type of the Alert.

Methods inherited from class javax.microedition.lcdui.Screen

getTicker, setTicker

Methods inherited from class javax.microedition.lcdui.Displayable

getHeight, getWidth, isShown, sizeChanged

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

FOREVER

public static final int FOREVER

FOREVER indicates that an Alert is kept visible until the user dismisses it. It is used as a value for the parameter to 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 screen.

Value -2 is assigned to FOREVER.

DISMISS_COMMAND

public static final Command DISMISS_COMMAND

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.

Since:

MIDP 2.0

Constructor Detail

Alert

public Alert(String title)

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(String, String, Image, AlertType)

Alert

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(). If an image is provided it must be 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.

Parameters:

title - the title string, or null if there is no title

alertText - the string contents, or null if there is no string

alertImage - the image contents, or null if there is no image

alertType - the type of the Alert, or null if the Alert has no specific type

Throws:

IllegalArgumentException - if the image is mutable

Method Detail

getDefaultTimeout

public int getDefaultTimeout()

Gets the default time for showing an Alert. This is either a positive value, which indicates a time in milliseconds, or the special value 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.

Returns:

default timeout in milliseconds, or FOREVER

getTimeout

public int getTimeout()

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.

Returns:

timeout in milliseconds, or FOREVER

setTimeout

public void setTimeout(int time)

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 is not FOREVER

Since:

JDE 4.0.2

getType

public AlertType getType()

Gets the type of the Alert.

Returns:

a reference to an instance of AlertType, or null if the Alert has no specific type

setType

public void setType(AlertType type)

Sets the type of the Alert. The handling and behavior of specific AlertTypes is described in AlertType.

Parameters:

type - an AlertType, or null if the Alert has no specific type

Since:

JDE 4.0.2

getString

public String getString()

Gets the text string used in the Alert.

Returns:

the Alert's text string, or null if there is no text

setString

public void setString(String str)

Sets the text string used in the Alert.

Parameters:

str - the Alert's text string, or null if there is no text

Since:

JDE 4.0.2

getImage

public Image getImage()

Gets the Image used in the Alert.

Returns:

the Alert's image, or null if there is no image

setImage

public void setImage(Image img)

Sets the Image used in the Alert.

Parameters:

img - the Alert's image, or null if there is no image

Throws:

IllegalArgumentException - if img is mutable

Since:

JDE 4.0.2

setIndicator

public void setIndicator(Gauge indicator)

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 not meet the restrictions for its use in an Alert

Since:

MIDP 2.0

See Also:

getIndicator()

getIndicator

public Gauge getIndicator()

Gets the activity indicator for this Alert.

Returns:

a reference to this Alert's activity indicator, or null if there is none

Since:

MIDP 2.0

See Also:

setIndicator(javax.microedition.lcdui.Gauge)

addCommand

public void addCommand(Command cmd)

Commands are not allowed on Alerts, so this method will always throw IllegalStateException whenever it is called.

Overrides:

addCommand in class Displayable

Parameters:

cmd - the Command

Throws:

IllegalStateException - always

Since:

JDE 4.0.2

removeCommand

public void removeCommand(Command cmd)

Similar to Displayable.removeCommand(javax.microedition.lcdui.Command), however when the application removes the last command from an Alert, DISMISS_COMMAND is implicitly added. Calling this method with DISMISS_COMMAND as the parameter has no effect.

Overrides:

removeCommand in class Displayable

Parameters:

cmd - the command to be removed

Since:

JDE 4.0.2

setCommandListener

public void setCommandListener(CommandListener l)

Listeners are not allowed on Alerts, so this method will always throw IllegalStateException whenever it is called.

Overrides:

setCommandListener in class Displayable

Parameters:

l - the Listener

Throws:

IllegalStateException - always

Since:

JDE 4.0.2

getTitle

public String getTitle()

Description copied from class: Screen

Gets the title of the Screen. Returns null if there is no title.

Overrides:

getTitle in class Screen

Following copied from class: javax.microedition.lcdui.Displayable

Returns:

the title of the instance, or null if no title

See Also:

Displayable.setTitle(java.lang.String)

setTitle

public void setTitle(String title)

Description copied from class: Screen

Sets the title of the Screen. If null is given, removes the title.

If the Screen is physically visible, the visible effect should take place no later than immediately after the callback or startApp returns back to the implementation.

Overrides:

setTitle in class Screen

Since:

JDE 4.0.2