何為ERP
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模糊 晦涩 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.
一个Cache是一个独立于屏幕的位图,代表着应用程序窗口.
ScreenDisplay可以是客户创建任意数量的Cache.
图象并不是直接画在屏幕上,而是先画在caches中,然后由caches画到屏幕上.
当应用程序窗口模糊需要重画的时候,直接从caches中而不是从database中进行.
通过这种方式,caches提高了效率---------位图渲染比从数据库中读显数据快得多.
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.
一般而言,地图建立三个caches:一个是为所有图层用的,另一个是在由annotation或graphics的时候用,第三个是为selection准备的.
如果图层把它的cached属性设为TRUE,这个图层(Layer)可以用来建立自己的私有cache.这样,地图将为这个图层建立一个单独的cache,地图把其他图层放在它之前或之后的不同caches中.
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.
使用IActiveView::Refresh效率极低,它会使所有的caches无效重画.
尽可能使用IActiveView::PartialRefresh
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.
PartialRefresh和Refresh会调用IScreenDisplay::Invalidate ,如果设为true,客户端从数据库画一个cache,如果false,则从cache画一个cache
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.
可以通过OR组合使用参数.
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.
使用参数,只会使某些数据无效重画,例如,如果一个图层被加载进来并且其cached属性设为TRUE,这个图层可以单独被invalidated,A tracking layer就是一个极好的例子.
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.
envelope参数指定了一个重画的区域.例如,如果一个元素被添加了,只需要重画元素周围的区域.
Both the data and envelope parameters are optional.
*When selecting features, you must call PartialRefresh twice, once before and once after the selection operation.
选择元素的时候,你必须使用PartialRefresh两次,一次在选择操作之前,一次在选择操作之后.
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
The example shows how to select and refresh graphics and features using
PartialRefresh.