IActiveView.PartialRefresh Method
EDN上关于IActiveView.PartialRefresh方法的备注：
The main application window is controlled by a view (IActiveView). ArcMap currently has two view objects: Map (data view) and PageLayout (layout view). Each view has a ScreenDisplay object which performs drawing operations. The ScreenDisplay object also makes it possible for clients to create any number of caches. A cache is an off screen bitmap representing the application's window. Instead of drawing directly to the screen, graphics are drawn into caches, then the caches are drawn on the screen. When the application's window is obscured and requires redrawing, it is done so from the caches instead of from a database. In this way, caches improve drawing performance - bitmap rendering is faster than reading and displaying data from a database.
In general, the Map creates three caches: one for all the layers, another if there are annotation or graphics, and a third cache if there is a feature selection. A layer can create its own private cache if it sets ILayer::Cached equal to TRUE. In this case, the Map will create a separate cache for the layer and groups the layers above and below it into different caches.
IActiveView::PartialRefresh uses its knowledge of the cache layout to invalidate as little as possible. IActiveView::Refresh , on the other hand, invalidates all the caches which is very inefficient. Use PartialRefresh whenever possible.
Both PartialRefresh and Refresh call IScreenDisplay::Invalidate which sets a flag clients watch for. Clients draw a cache from scratch (the database) if its flag is set to true, and from cache if the flag is set to false.
The following table shows the phases each view supports and what they map to:
| phase | Map | Layout |
|---|---|---|
| esriViewBackground | Map grids | Page/snap grid |
| esriViewGeography | Layers | Unused |
| *esriViewGeoSelection | Feature selection | Unused |
| esriViewGraphics | Labels/graphics | Graphics |
| esriViewGraphicSelection | Graphic selection | Element selection |
| esriViewForeground | Unused | Snap guides |
To specify multiple draw phases, combine individual phases together using a bitwise OR. This is equivalent to adding together the integer enumeration values. For example, pass 6 to invalidate both the esriViewGeography (2) and esriViewGeoSelection (4) phases.
Use the data parameter to invalidate just a specific piece of data. For example, if a layer is loaded and its cache property is set to TRUE, this layer alone can be invalidated. A tracking layer is a good example of this.
The envelope parameter specifies a region to invalidate. For example, if a graphic element is added, it is usually only necessary to invalidate the immediate area surrounding the new graphic.
Both the data and envelope parameters are optional.
*When selecting features, you must call PartialRefresh twice, once before and once after the selection operation.
In Visual Basic specify a phase of 6 to invalidate both the esriViewGeography (2) and the esriViewGeoSelection (4).
pActiveView.PartialRefresh esriViewGeography + esriViewGeoSelection, Nothing, Nothing
which is the same as:
pActiveView.PartialRefresh 6, Nothing, Nothing
Below are several usage examples in Visual Basic.
Map:
Refresh layer pActiveView.PartialRefresh esriViewGeography, pLayer, Nothing
Refresh all layers pActiveView.PartialRefresh esriViewGeography, Nothing, Nothing
Refresh selection pActiveView.PartialRefresh esriViewGeoSelection, Nothing, Nothing
Refresh labels pActiveView.PartialRefresh esriViewGraphics, Nothing, Nothing
PageLayout:
Refresh element pActiveView.PartialRefresh esriViewGraphics, pElement, Nothing
Refresh all elements pActiveView.PartialRefresh esriViewGraphics, Nothing, Nothing
Refresh selection pActiveView.PartialRefresh esriViewGraphicSelection, Nothing, Nothing