org.eclipse.swt.internal

Class Callback

java.lang.Object

org.eclipse.swt.internal.Callback

public class Callback
extends java.lang.Object

Instances of this class represent entry points into Java which can be invoked from operating system level callback routines.

IMPORTANT: A callback is only valid when invoked on the thread which created it. The results are undefined (and typically bad) when a callback is passed out to the operating system (or other code) in such a way that the callback is called from a different thread.

Structure Diagram

Field Summary

Fields

Modifier and Type	Field and Description
(package private) int	address
(package private) int	argCount
(package private) int	errorResult
(package private) boolean	isArrayBased
(package private) boolean	isStatic
(package private) java.lang.String	method
(package private) java.lang.Object	object
(package private) static java.lang.String	PTR_SIGNATURE
(package private) java.lang.String	signature
(package private) static java.lang.String	SIGNATURE_0
(package private) static java.lang.String	SIGNATURE_1
(package private) static java.lang.String	SIGNATURE_2
(package private) static java.lang.String	SIGNATURE_3
(package private) static java.lang.String	SIGNATURE_4
(package private) static java.lang.String	SIGNATURE_N

Constructor Summary

Constructors

Constructor and Description
Callback(java.lang.Object object, java.lang.String method, int argCount) Constructs a new instance of this class given an object to send the message to, a string naming the method to invoke and an argument count.
Callback(java.lang.Object object, java.lang.String method, int argCount, boolean isArrayBased) Constructs a new instance of this class given an object to send the message to, a string naming the method to invoke, an argument count and a flag indicating whether or not the arguments will be passed in an array.
Callback(java.lang.Object object, java.lang.String method, int argCount, boolean isArrayBased, int errorResult) Constructs a new instance of this class given an object to send the message to, a string naming the method to invoke, an argument count, a flag indicating whether or not the arguments will be passed in an array and a value to return when an exception happens.

Method Summary

Methods

Modifier and Type	Method and Description
(package private) static int	bind(Callback callback, java.lang.Object object, java.lang.String method, java.lang.String signature, int argCount, boolean isStatic, boolean isArrayBased, int errorResult) Allocates the native level resources associated with the callback.
void	dispose() Releases the native level resources associated with the callback, and removes all references between the callback and other objects.
int	getAddress() Returns the address of a block of machine code which will invoke the callback represented by the receiver.
static boolean	getEnabled() Returns whether or not callbacks which are triggered at the native level should cause the messages described by the matching Callback objects to be invoked.
static int	getEntryCount() Returns the number of times the system has been recursively entered through a callback.
static java.lang.String	getPlatform() Returns the SWT platform name.
(package private) static java.lang.String	getSignature(int argCount)
(package private) static void	ignoreCallbacks(boolean ignore) Deprecated.
static void	reset() Immediately wipes out all native level state associated with all callbacks.
static void	setEnabled(boolean enable) Indicates whether or not callbacks which are triggered at the native level should cause the messages described by the matching Callback objects to be invoked.
(package private) static void	unbind(Callback callback) Releases the native level resources associated with the callback.

Methods inherited from class java.lang.Object

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

Field Detail

object

java.lang.Object object

method

java.lang.String method

signature

java.lang.String signature

argCount

int argCount

address

int address

errorResult

int errorResult

isStatic

boolean isStatic

isArrayBased

boolean isArrayBased

PTR_SIGNATURE

static final java.lang.String PTR_SIGNATURE

SIGNATURE_0

static final java.lang.String SIGNATURE_0

SIGNATURE_1

static final java.lang.String SIGNATURE_1

SIGNATURE_2

static final java.lang.String SIGNATURE_2

SIGNATURE_3

static final java.lang.String SIGNATURE_3

SIGNATURE_4

static final java.lang.String SIGNATURE_4

SIGNATURE_N

static final java.lang.String SIGNATURE_N

Constructor Detail

Callback

public Callback(java.lang.Object object,
        java.lang.String method,
        int argCount)

Constructs a new instance of this class given an object to send the message to, a string naming the method to invoke and an argument count. Note that, if the object is an instance of Class it is assumed that the method is a static method on that class.

Parameters:

object - the object to send the message to

method - the name of the method to invoke

argCount - the number of arguments that the method takes

Callback

public Callback(java.lang.Object object,
        java.lang.String method,
        int argCount,
        boolean isArrayBased)

Constructs a new instance of this class given an object to send the message to, a string naming the method to invoke, an argument count and a flag indicating whether or not the arguments will be passed in an array. Note that, if the object is an instance of Class it is assumed that the method is a static method on that class.

Parameters:

object - the object to send the message to

method - the name of the method to invoke

argCount - the number of arguments that the method takes

isArrayBased - true if the arguments should be passed in an array and false otherwise

Callback

public Callback(java.lang.Object object,
        java.lang.String method,
        int argCount,
        boolean isArrayBased,
        int errorResult)

Constructs a new instance of this class given an object to send the message to, a string naming the method to invoke, an argument count, a flag indicating whether or not the arguments will be passed in an array and a value to return when an exception happens. Note that, if the object is an instance of Class it is assumed that the method is a static method on that class.

Parameters:

object - the object to send the message to

method - the name of the method to invoke

argCount - the number of arguments that the method takes

isArrayBased - true if the arguments should be passed in an array and false otherwise

errorResult - the return value if the java code throws an exception

Method Detail

bind

static int bind(Callback callback,
       java.lang.Object object,
       java.lang.String method,
       java.lang.String signature,
       int argCount,
       boolean isStatic,
       boolean isArrayBased,
       int errorResult)

Allocates the native level resources associated with the callback. This method is only invoked from within the constructor for the argument.

Parameters:

callback - the callback to bind

object - the callback's object

method - the callback's method

signature - the callback's method signature

argCount - the callback's method argument count

isStatic - whether the callback's method is static

isArrayBased - whether the callback's method is array based

errorResult - the callback's error result

dispose

public void dispose()

Releases the native level resources associated with the callback, and removes all references between the callback and other objects. This helps to prevent (bad) application code from accidentally holding onto extraneous garbage.

getAddress

public int getAddress()

Returns the address of a block of machine code which will invoke the callback represented by the receiver.

Returns:

the callback address

getPlatform

public static java.lang.String getPlatform()

Returns the SWT platform name.

Returns:

the platform name of the currently running SWT

getEntryCount

public static int getEntryCount()

Returns the number of times the system has been recursively entered through a callback.

Note: This should not be called by application code.

Returns:

the entry count

Since:

2.1

getSignature

static java.lang.String getSignature(int argCount)

setEnabled

public static final void setEnabled(boolean enable)

Indicates whether or not callbacks which are triggered at the native level should cause the messages described by the matching Callback objects to be invoked. This method is used to safely shut down SWT when it is run within environments which can generate spurious events.

Note: This should not be called by application code.

Parameters:

enable - true if callbacks should be invoked

getEnabled

public static final boolean getEnabled()

Returns whether or not callbacks which are triggered at the native level should cause the messages described by the matching Callback objects to be invoked. This method is used to safely shut down SWT when it is run within environments which can generate spurious events.

Note: This should not be called by application code.

Returns:

true if callbacks should not be invoked

ignoreCallbacks

static final void ignoreCallbacks(boolean ignore)

Deprecated.

This might be called directly from native code in environments which can generate spurious events. Check before removing it.

Parameters:

ignore - true if callbacks should not be invoked

reset

public static final void reset()

Immediately wipes out all native level state associated with all callbacks.

WARNING: This operation is extremely dangerous, and should never be performed by application code.

unbind

static final void unbind(Callback callback)

Releases the native level resources associated with the callback.

See Also:

dispose()