|
Eclipse Platform 2.0 |
||||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | ||||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |
Interface to an object capable of supplying properties for display by the
standard property sheet page implementation (PropertySheetPage
).
This interface should be implemented by clients.
PropertySheetPage
discovers the properties to display from
currently selected elements. Elements that implement IPropertySource
directly are included, as are elements that implement IAdaptable
and have an IPropertySource
adapter. Clients should implement
this interface for any newly-defined elements that are to have properties
displayable by PropertySheetPage
. Note that in the latter case,
the client will also need to register a suitable adapter factory with the
platform's adapter manager (Platform.getAdapterManager
).
IAdaptable
,
Platform.getAdapterManager()
,
PropertySheetPage
Method Summary | |
Object |
getEditableValue()
Returns a value for this property source that can be edited in a property sheet. |
IPropertyDescriptor[] |
getPropertyDescriptors()
Returns the list of property descriptors for this property source. |
Object |
getPropertyValue(Object id)
Returns the value of the property with the given id if it has one. |
boolean |
isPropertySet(Object id)
Returns whether the value of the property with the given id has changed from its default value. |
void |
resetPropertyValue(Object id)
Resets the property with the given id to its default value if possible. |
void |
setPropertyValue(Object id,
Object value)
Sets the property with the given id if possible. |
Method Detail |
public Object getEditableValue()
This value is used when this IPropertySource
is appearing
in the property sheet as the value of a property of some other
IPropertySource
This value is passed as the input to a cell editor opening on an
IPropertySource
.
This value is also used when an IPropertySource
is being
used as the value in a setPropertyValue
message. The reciever
of the message would then typically use the editable value to update the
original property source or construct a new instance.
For example an email address which is a property source may have an editable value which is a string so that it can be edited in a text cell editor. The email address would also have a constructor or setter that takes the edited string so that an appropriate instance can be created or the original instance modified when the edited value is set.
This behavior is important for another reason. When the property sheet is showing properties for more than one object (multiple selection), a property sheet entry will display and edit a single value (typically coming from the first selected object). After a property has been edited in a cell editor, the same value is set as the property value for all of the objects. This is fine for primitive types but otherwise all of the objects end up with a reference to the same value. Thus by creating an editable value and using it to update the state of the original property source object, one is able to edit several property source objects at once (multiple selection).
public IPropertyDescriptor[] getPropertyDescriptors()
getPropertyValue
and setPropertyValue
methods
are used to read and write the actual property values by specifying
the property ids from these property descriptors.
Implementors should cache the descriptors as they will be asked for the descriptors with any edit/update. Since descriptors provide cell editors, returning the same descriptors if possible allows for efficient updating.
public Object getPropertyValue(Object id)
null
if this source if the property's value is
null
value or if this source does not have the specified
property.
id
- the id of the property being set
null
setPropertyValue(java.lang.Object, java.lang.Object)
public boolean isPropertySet(Object id)
false
if the notion of default value
is not meaningful for the specified property, or if this source does not have
the specified property.
id
- the id of the property
true
if the value of the specified property has changed
from its original default value, and false
otherwisepublic void resetPropertyValue(Object id)
id
- the id of the property being resetpublic void setPropertyValue(Object id, Object value)
In general, a property source should not directly reference the value parameter unless it is an atomic object that can be shared such as a string.
An important reason for this is that several property sources with compatible descriptors could be appearing in the property sheet at the same time. An editor produces a single edited value which is passed at the value parameter of this message to all the property sources. Thus to avoid a situation where all of the property sources reference the same value they should use the value parameter to create a new instance of the real value for the given property.
There is another reason why a level of indirection is useful. The real
value of property may be a type that cannot be edited with a standard cell
editor. However instead of of returning the real value in getPropertyValue
,
the value could be converted to a String
which could be edited
with a standard cell editor. The edited value will be passed to this method
which can then turn it back into the real property value.
Another variation on returning a value other than the real property value in
getPropertyValue
is to return a value which is an
IPropertySource
(or for which the property sheet can obtain an
IPropertySource
). This allows the property sheet to properties
for the value itself. In this case the value to edit is obtained from the
child property source using getEditableValue
. It is this editable value
that will be passed back via this method when the it has been edited
id
- the id of the property being setvalue
- the new value for the property; null
is allowedgetPropertyValue(java.lang.Object)
,
getEditableValue()
|
Eclipse Platform 2.0 |
||||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | ||||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |