HarmonyOS grid 触发拖拽的中途, 怎么才可以做到禁止修改第1个和最后一个item的位置？

import curves from '@ohos.curves' 
@Entry 
@Component 
struct GridItemExample { 
  @State numbers: number[] = [] 
  @State dragItem: number = -1 
  @State scaleItem: number = -1 
  @State item: number = -1 
  private dragRefOffsetx: number = 0 
  private dragRefOffsety: number = 0 
  @State offsetX: number = 0 
  @State offsetY: number = 0 
  private FIX_VP_X: number = 108 
  private FIX_VP_Y: number = 120 
  aboutToAppear() { 
    for (let i = 1; i <= 11; i++) { 
      this.numbers.push(i) 
    } 
  } 
  itemMove(index: number, newIndex: number): void { 
    console.info('index:' + index + ' newIndex:' + newIndex) 
    if (!this.isDraggable(newIndex)) { 
      return 
    } 
    let tmp = this.numbers.splice(index, 1) 
    this.numbers.splice(newIndex, 0, tmp[0]) 
  } 
  //向下滑 
  down(index: number): void { 
    // 指定固定GridItem不响应事件 
    if (!this.isDraggable(index + 3)) { 
      return 
    } 
    this.offsetY -= this.FIX_VP_Y 
    this.dragRefOffsety += this.FIX_VP_Y 
    this.itemMove(index, index + 3) 
  } 
  //向下滑(右下角为空) 
  down2(index: number): void { 
    if (!this.isDraggable(index + 3)) { 
      return 
    } 
    this.offsetY -= this.FIX_VP_Y 
    this.dragRefOffsety += this.FIX_VP_Y 
    this.itemMove(index, index + 3) 
  } 
  //向上滑 
  up(index: number): void { 
    if (!this.isDraggable(index - 3)) { 
      return 
    } 
    this.offsetY += this.FIX_VP_Y 
    this.dragRefOffsety -= this.FIX_VP_Y 
    this.itemMove(index, index - 3) 
  } 
  //向左滑 
  left(index: number): void { 
    if (!this.isDraggable(index - 1)) { 
      return 
    } 
    this.offsetX += this.FIX_VP_X 
    this.dragRefOffsetx -= this.FIX_VP_X 
    this.itemMove(index, index - 1) 
  } 
  //向右滑 
  right(index: number): void { 
    if (!this.isDraggable(index + 1)) { 
      return 
    } 
    this.offsetX -= this.FIX_VP_X 
    this.dragRefOffsetx += this.FIX_VP_X 
    this.itemMove(index, index + 1) 
  } 
  //向右下滑 
  lowerRight(index: number): void { 
    if (!this.isDraggable(index + 4)) { 
      return 
    } 
    this.offsetX -= this.FIX_VP_X 
    this.dragRefOffsetx += this.FIX_VP_X 
    this.offsetY -= this.FIX_VP_Y 
    this.dragRefOffsety += this.FIX_VP_Y 
    this.itemMove(index, index + 4) 
  } 
  //向右上滑 
  upperRight(index: number): void { 
    if (!this.isDraggable(index - 2)) { 
      return 
    } 
    this.offsetX -= this.FIX_VP_X 
    this.dragRefOffsetx += this.FIX_VP_X 
    this.offsetY += this.FIX_VP_Y 
    this.dragRefOffsety -= this.FIX_VP_Y 
    this.itemMove(index, index - 2) 
  } 
  //向左下滑 
  lowerLeft(index: number): void { 
    if (!this.isDraggable(index + 2)) { 
      return 
    } 
    this.offsetX += this.FIX_VP_X 
    this.dragRefOffsetx -= this.FIX_VP_X 
    this.offsetY -= this.FIX_VP_Y 
    this.dragRefOffsety += this.FIX_VP_Y 
    this.itemMove(index, index + 2) 
  } 
  //向左上滑 
  upperLeft(index: number): void { 
    if (!this.isDraggable(index - 4)) { 
      return 
    } 
    this.offsetX += this.FIX_VP_X 
    this.dragRefOffsetx -= this.FIX_VP_X 
    this.offsetY += this.FIX_VP_Y 
    this.dragRefOffsety -= this.FIX_VP_Y 
    this.itemMove(index, index - 4) 
  } 
  isDraggable(index: number): boolean { 
    console.info('index:' + index) 
    return index > 0 && index!= this.numbers.length -1; 
  } 
  build() { 
    Column({space:10}) { 
      Column({space:5}) { 
        Text("Grid拖拽排序动效") 
        Text("第一个和最后一个组件不可拖拽") 
      } 
      Grid() { 
        ForEach(this.numbers, (item: number) => { 
          GridItem() { 
            Text(item + '') 
              .fontSize(16) 
              .width('100%') 
              .textAlign(TextAlign.Center) 
              .height(100) 
              .borderRadius(10) 
              .backgroundColor(0xFFFFFF) 
              .shadow(this.scaleItem == item ? { 
                radius: 70, 
                color: '#15000000', 
                offsetX: 0, 
                offsetY: 0 
              } : 
                { 
                  radius: 0, 
                  color: '#15000000', 
                  offsetX: 0, 
                  offsetY: 0 
                }) 
              .animation({ curve: Curve.Sharp, duration: 300 }) 
          } 
          // 指定固定GridItem不响应事件 
          .hitTestBehavior(this.isDraggable(this.numbers.indexOf(item)) ? HitTestMode.Default : HitTestMode.None) 
          .scale({ x: this.scaleItem == item ? 1.05 : 1, y: this.scaleItem == item ? 1.05 : 1 }) 
          .zIndex(this.dragItem == item ? 1 : 0) 
          .translate(this.dragItem == item ? { x: this.offsetX, y: this.offsetY } : { x: 0, y: 0 }) 
          .padding(10) 
          .gesture( 
            // 以下组合手势为顺序识别，当长按手势事件未正常触发时则不会触发拖动手势事件 
            GestureGroup(GestureMode.Sequence, 
              LongPressGesture({ repeat: true }) 
                .onAction((event?: GestureEvent) => { 
                  animateTo({ curve: Curve.Friction, duration: 300 }, () => { 
                    this.scaleItem = item 
                  }) 
                }) 
                .onActionEnd(() => { 
                  animateTo({ curve: Curve.Friction, duration: 300 }, () => { 
                    this.scaleItem = -1 
                  }) 
                }), 
              PanGesture({ fingers: 1, direction: null, distance: 0 }) 
                .onActionStart(() => { 
                  this.dragItem = item 
                  this.dragRefOffsetx = 0 
                  this.dragRefOffsety = 0 
                }) 
                .onActionUpdate((event: GestureEvent) => { 
                  this.offsetY = event.offsetY - this.dragRefOffsety 
                  this.offsetX = event.offsetX - this.dragRefOffsetx 
                  animateTo({ curve: curves.interpolatingSpring(0, 1, 400, 38) }, () => { 
                    let index = this.numbers.indexOf(this.dragItem) 
                    if (this.offsetY >= this.FIX_VP_Y / 2 && (this.offsetX <= 44 && this.offsetX >= -44) 
                      && ![8, 9, 10].includes(index)) { 
                      //向下滑 
                      this.down(index) 
                    } else if (this.offsetY <= -this.FIX_VP_Y / 2 && (this.offsetX <= 44 && this.offsetX >= -44) 
                      && ![0, 1, 2].includes(index)) { 
                      //向上滑 
                      this.up(index) 
                    } else if (this.offsetX >= this.FIX_VP_X / 2 && (this.offsetY <= 50 && this.offsetY >= -50) 
                      && ![2, 5, 8, 10].includes(index)) { 
                      //向右滑 
                      this.right(index) 
                    } else if (this.offsetX <= -this.FIX_VP_X / 2 && (this.offsetY <= 50 && this.offsetY >= -50) 
                      && ![0, 3, 6, 9].includes(index)) { 
                      //向左滑 
                      this.left(index) 
                    } else if (this.offsetX >= this.FIX_VP_X / 2 && this.offsetY >= this.FIX_VP_Y / 2 
                      && ![2, 5, 7, 8, 9, 10].includes(index)) { 
                      //向右下滑 
                      this.lowerRight(index) 
                    } else if (this.offsetX >= this.FIX_VP_X / 2 && this.offsetY <= -this.FIX_VP_Y / 2 
                      && ![0, 1, 2, 5, 8].includes(index)) { 
                      //向右上滑 
                      this.upperRight(index) 
                    } else if (this.offsetX <= -this.FIX_VP_X / 2 && this.offsetY >= this.FIX_VP_Y / 2 
                      && ![0, 3, 6, 9, 10].includes(index)) { 
                      //向左下滑 
                      this.lowerLeft(index) 
                    } else if (this.offsetX <= -this.FIX_VP_X / 2 && this.offsetY <= -this.FIX_VP_Y / 2 
                      && ![0, 1, 2, 3, 6, 9].includes(index)) { 
                      //向左上滑 
                      this.upperLeft(index) 
                    } else if (this.offsetX >= this.FIX_VP_X / 2 && this.offsetY >= this.FIX_VP_Y / 2 
                      && [7].includes(index)) { 
                      //向右下滑(右下角为空) 
                      this.down2(index) 
                    } 
                  }) 
                }) 
                .onActionEnd(() => { 
                  animateTo({ curve: curves.interpolatingSpring(0, 1, 400, 38) }, () => { 
                    this.dragItem = -1 
                  }) 
                  animateTo({ 
                    curve: curves.interpolatingSpring(14, 1, 170, 17), delay: 150 
                  }, () => { 
                    this.scaleItem = -1 
                  }) 
                }) 
            ) 
              .onCancel(() => { 
                animateTo({ curve: curves.interpolatingSpring(0, 1, 400, 38) }, () => { 
                  this.dragItem = -1 
                }) 
                animateTo({ 
                  curve: curves.interpolatingSpring(14, 1, 170, 17) 
                }, () => { 
                  this.scaleItem = -1 
                }) 
              }) 
          ) 
        }, (item: number) => item.toString()) 
      } 
      .width('90%') 
      .editMode(true) 
      .scrollBar(BarState.Off) 
      .columnsTemplate("1fr 1fr 1fr") 
    }.width('100%').height('100%').backgroundColor('#0D182431').padding({ top: 5 }) 
  } 
}