文章 - DCloud问答

如何解决拖拽功能和长按功能的冲突问题

问题现象
在List组件中，单个ListItem在同时设置拖拽功能与长按功能时，实际运行之后会产生冲突，如何解决单个ListItem拖拽功能和长按功能的冲突问题？

效果预览
点击放大

背景知识
支持统一拖拽提供了一种通过鼠标或手势触屏传递数据的机制，即从一个组件位置拖出数据并将其拖入到另一个组件位置，以触发响应。
长按手势通过长按屏幕触发长按手势事件。
由于拖拽事件和长按手势都需要通过长按来触发，因此这种组合手势类型会出现冲突，例如List组件中每个ListItem都设置单独的长按事件时，拖拽功能和长按手势功能就会出现冲突。
Grid网格容器，由“行”和“列”分割的单元格所组成，通过指定“项目”所在的单元格做出各种各样的布局。
滑动手势PanGesture，能够提供自定义拖拽事件的功能。
解决方案
由于在ListItem中设置单独的长按事件会与拖拽事件产生冲突，因此建议放弃List本身的拖拽事件，使用滑动手势PanGesture，自行实现拖拽过程的逻辑，然后再通过组合手势的功能，去实现其他的长按事件。
import curves from '@ohos.curves';

@Entry
@Component
struct Page {
// 元素数组
@State numbers: number[] = [];
// 多列
private str: string = '';
row: number = 4;
// 元素数组中最后一个元素的索引
@State lastIndex: number = 0;
@State dragItem: number = -1;
@State scaleItem: number = -1;
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 <= 36; i++) {
this.numbers.push(i);
}
this.lastIndex = this.numbers.length - 1;
// 多列
for (let i = 0; i < this.row; i++) {
this.str = this.str + '1fr ';
}
}

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 {
if (!this.isDraggable(index + this.row)) {
return;
}
this.offsetY -= this.FIX_VP_Y;
this.dragRefOffsetY += this.FIX_VP_Y;
// 多列
this.itemMove(index, index + this.row);
}

// 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 - this.row)) {
return;
}
this.offsetY += this.FIX_VP_Y;
this.dragRefOffsetY -= this.FIX_VP_Y;
this.itemMove(index, index - this.row);
}

// 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 + this.row + 1)) {
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 + this.row + 1);
}

// 向右上滑
upperRight(index: number): void {
if (!this.isDraggable(index - (this.row - 1))) {
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 - (this.row - 1));
}

// 向左下滑
lowerLeft(index: number): void {
if (!this.isDraggable(index + (this.row - 1))) {
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 + (this.row - 1));
}

// 向左上滑
upperLeft(index: number): void {
if (!this.isDraggable(index - (this.row + 1))) {
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 - (this.row + 1));
}

// 通过元素的索引，控制对应元素是否能移动排序
isDraggable(index: number): boolean {
console.info(index: ${index});
return index > -1; // 恒成立，所有元素均可移动排序
}
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