FabricJS 如何在使用进行分组后，只对选定的分组Polylines进行解组

我们可以通过创建一个 fabric.Polyline 的实例来创建一个Polyline对象。一个折线对象可以由一组连接的直线段来描述。由于它是FabricJS的基本元素之一，我们也可以通过应用角度、不透明度等属性来轻松定制它。对于取消分组的折线对象，我们可以使用 toActiveSelection()方法。

语法

toActiveSelection(): fabric.ActiveSelection

例子1：一键分组所有多段线

在了解如何取消分组之前，让我们先看看如何对对象进行分组。在这个例子中，我们将有一个按钮，点击这个按钮，所有的多段线都将被分组为一个单一的对象。因此，移动该对象将移动所有的多段线，当你调整大小或倾斜时，它将表现为一个单一的对象。

我们将创建一个函数来获取画布中的所有对象并将它们分组为一个单一的对象。

<!DOCTYPE html>
<html>
<head>
   <!-- Adding the Fabric JS Library-->
   <script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/510/fabric.min.js"></script>
</head>
<body>
   <h2>Grouping all the Polyline objects using one click</h2>
   Click on the `Group` Button to group all the Polyline objects in the canvas 
   <canvas id="canvas"></canvas>
   <button type="button" onclick="group()">Group</button>
   <script>

      // Initiate a canvas instance
      var canvas = new fabric.Canvas("canvas");
      canvas.setWidth(document.body.scrollWidth);
      canvas.setHeight(250);

      // Initiate a Polyline object
      var polyLine1 = new fabric.Polyline([
         { x: 500, y: 200 },
         { x: 550, y: 60 },
         { x: 350, y: 100 },
      ], {
         stroke: "green",
         fill: "white",
         strokeWidth: 5,
      });

      // Initiate another Polyline object
      var polyLine2 = new fabric.Polyline([
         { x: 300, y: 200 },
         { x: 150, y: 60 },
         { x: 250, y: 100 },
      ], {
         stroke: "green",
         fill: "white",
         strokeWidth: 5,
      });

      // Add them to the canvas instance
      canvas.add(polyLine1);
      canvas.add(polyLine2);

      // Function to group all the polyline objects into single object
      function group() {

         // Get all the objects as selection
         var sel = new fabric.ActiveSelection(canvas.getObjects(), {
            canvas: canvas,
         });

         // Make the objects active
         canvas.setActiveObject(sel);

         // Group the objects
         canvas.getActiveObject().toGroup();
      } 
   </script>
</body>
</html>

例子 2: 一键解组被选中的多段线

在这个例子中，我们将有一个按钮，点击这个按钮，被选中的分组多段线将被取消分组。因此，这些对象将表现为独立的对象。首先，我们将创建两组多段线，每组将有两个多段线对象。

此外，当一个组被选中并按下解组按钮时，我们将使用 toActiveSelection() 来解组对象。

<!DOCTYPE html>
<html>
<head>
   <!-- Adding the Fabric JS Library-->
   <script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/510/fabric.min.js"></script>
</head>
<body>
   <h2>Ungrouping the selected grouped Polylines using one click</h2>
   Click on the grouped object and click on `Ungroup` button to ungroup the objects, further click in empty space to discard the selection 
   <canvas id="canvas"></canvas>
   <button type="button" onclick="ungroup()">Ungroup</button>
   <script>

      // Initiate a canvas instance
      var canvas = new fabric.Canvas("canvas");
      canvas.setWidth(document.body.scrollWidth);
      canvas.setHeight(250);

      // Initiate another Polyline object
      var polyLine1 = new fabric.Polyline([
         { x: 300, y: 100 },
         { x: 150, y: 60 },
         { x: 250, y: 10 },
      ], {
         stroke: "green", 
         fill: "white",
         strokeWidth: 5,
      });

      // Initiate another Polyline object
      var polyLine2 = new fabric.Polyline([
         { x: 400, y: 200 },
         { x: 250, y: 160 },
         { x: 150, y: 200 },
      ], {
         stroke: "blue",
         fill: "white",
         strokeWidth: 5,
      });

      // Group two objects and add to canvas
      var group1 = new fabric.Group([polyLine1, polyLine2]);
      canvas.add(group1);

      // Initiate another Polyline object
      var polyLine4 = new fabric.Polyline([
         { x: 400, y: 10 },
         { x: 350, y: 60 },
         { x: 450, y: 10 },
      ], {
         stroke: "pink",
         fill: "white",
         strokeWidth: 5,
      });

      // Initiate a Polyline object
      var polyLine3 = new fabric.Polyline([
         { x: 500, y: 200 },
         { x: 550, y: 60 },
         { x: 350, y: 100 },
      ], {
         stroke: "red",
         fill: "white",
         strokeWidth: 5,
      });

      // Group two objects and add to canvas
      var group2 = new fabric.Group([polyLine3, polyLine4]);
      canvas.add(group2); 

      // Function to ungroup the selected grouped polyline objects
      function ungroup() {
         canvas.getActiveObject().toActiveSelection();
      }
   </script>
</body>
</html>