2.6 实战：两点画线工具

通用应用BIMBase API实现一个两点画线功能了解BIMBase基本工具。

BIMBase API提供了两种实现两点画线功能的机制。一是通过IBPPointCommand提供的接口实现，一是在IBPFunctionCommand中通过类ADS/ARX的拾取点接口实现。

• 在IBPPointCommand实现
  IBPPointCommand是BIMBase API提供的一种交互机制，IBPPointCommand类中对于工具启动、左键点击、右键点击、鼠标移动等都提供了虚接口，通过实现这些虚接口即可实现相应的功能，如下代码所示。

[BPExternalCommandAttribute(name = "ExlLayoutLineDemo")]
    public class ExLayoutLine : IBPPointCommand
    {
        GePoint3d m_ptS;
        int m_nFlag;
        public ExLayoutLine()
        {
            m_nFlag = 0;
        }
        private BPGraphics getGraphic(GePoint3d sPoint, GePoint3d ePoint)
        {
            BPViewport vp = BPApplication.singleton().activeDocument.viewManager.getActivedViewport();

        BPModel model = vp.targetModel;
            BPGraphics graphic = new BPGraphics(model);
            GeSegment3d line = new GeSegment3d(sPoint, ePoint);
            graphic.addCurve(IGeCurveBase.createSegment(line));
            return graphic;
        }
        public override bool onLeftClick(BPCommandContext context)
        {
            if (m_nFlag == 0)
            {
                m_nFlag = 1;
                m_ptS = context.mousePoint;
            }
            else if (m_nFlag == 1)
            {
                m_nFlag = 0;
                BPGraphics graphic = getGraphic(m_ptS, context.mousePoint);
                graphic.save();
            }
            return true;
        }
        public override bool onRightClick(BPCommandContext context)
        {
            callExitTool();
            return true;
        }
        public override void onDynamicDraw(BPCommandContext context)
        {
            if (m_nFlag == 0) return;
            BPViewport vp = BPApplication.singleton().activeDocument.viewManager.getActivedViewport();
            BPGraphics graphic = getGraphic(m_ptS, context.mousePoint);
            vp.dynamicDraw(graphic);
        }
    }

该例子通过重写IBPPointCommand类中onLeftClick接口实现在第一次左键点击时确认线段的第一个点，第二次左键点击时得到线段的第二个点，并用第一个点和第二个点构造线段并保存到工程；重写onDynamicDraw接口，通过得到的动态点与第一个点构造线段并动态显示，实现线段的动态预览。

• 在IBPFunctionCommand实现
  
  通过BIMBase API提供的拾取点接口，可在IBPFunctionCommand中实现两点画线功能。
  

public class AdsCommand : IBPFunctionCommand
    {
        public override void onExcute(BPCommandContext context)
        {
            BPDocument doc = BPApplication.singleton().activeDocument;
            BPModel model = doc.modelManager.activeModel;
            BPGraphics graphic = new BPGraphics();

            GePoint3d ptBase = GePoint3d.createByZero();
            GePoint3d pt = GePoint3d.createByZero();
            BPAdsFun.GetPoint(null, "Select first point", ref ptBase);
            BPAdsFun.GetPoint(ptBase, "Select second point", ref pt);
            graphic.addCurve(IGeCurveBase.createSegment(new GeSegment3d(ptBase, pt)));

            graphic.save();

            base.onExcute(context);
        }
    }