对象模型图-arcgis开发和应用全教程

对象模型图Object model overview From the simple object model diagram above, you can tell that a PageLayout is composed of (potentially) several Element objects. Element is an abstract class that has several sub-types. On the IElement interface (implemented by every subclass of Element) there is a Geometry property. An element added to a layout or map uses this property to specify its location. An element’s geometry can be defined in map units or page units, whichever is appropriate. Graphic and Frame elements The two direct sub-types of Element are themselves abstract classes and represent the two fundamental types of elements: GraphicElements—text, shape, and picture elements FrameElements—MapFrames (i.e., data frames), TableFrames, OLEFrames, and MapSurroundFrames (e.g., north arrows, legends, and scalebars) Apart from a handful of abstract classes, all elements are creatable (coclasses). As a programmer, you can create new text, graphic, or map elements to add to your layout. Most graphic elements will have a Symbol property that allows you to control the color and style of the graphics you create. Frame elements are used as containers in the layout. MapFrames contain a collection of layers (in other words, a data frame), while a MapSurroundFrame element is used to contain objects that are related to a particular Map, such as a scalebar, north arrow, or legend. It is important to make a distinction between a MapSurroundFrame, and the object it contains, a MapSurround. MapSurrounds, such as a Legend, are related directly to a Map (data frame), and must be contained within a MapSurroundFrame in order to be represented on the layout. Other types of FrameElements include TableFrame, for containing a Table object, and an OLEFrame, for containing another application (such as a Microsoft Word document).