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前言

项目需求是展示标签，标签的个数不定，一行展示不行就自行换行。但是，使用鸿蒙原生的 Grid 后发现特别的难看。然后就想着自定义控件。找了官方文档，发现2个重要的实现方法，但是，官方的demo中讲的很少，需要自己去看去思考。

效果图如下：

注意点：

1. 需要计算整体布局的宽高，这和 Android 差不多。
2. 注意 margin 的计算

具体的代码如下：

/*** 自定义标签页面*/
@Component struct CustomTagView {screenWidth: number = 0aboutToAppear(): void {let dis = display.getDefaultDisplaySync();let width = dis.widthlet height = dis.height// width 是单位是 px, 转换为 vp ,因为 onMeasureSize 和 onPlaceChildren 得到的 width margin 以及 padding 都是 vplet w = px2vp(width)let h = px2vp(height)this.screenWidth = wconsole.log("TagView aboutToAppear width = " + width + " , height = " + height + ", w = " + w + ", h = " + h)}@Builder childBuilder() {}@BuilderParam buildTagView: () => void = this.childBuilderresult: SizeResult = {width: 0,height: 0}// 第一步：计算各子组件的实际大小以及设置布局本身的大小onMeasureSize(selfLayoutInfo: GeometryInfo, children: Array<Measurable>, constraint: ConstraintSizeOptions) {let parentWidth = selfLayoutInfo.widthlet parentHeight = selfLayoutInfo.heightconsole.log("TagView onMeasureSize parentWidth = " + parentWidth + " , parentHeight = " + parentHeight)let startPosX = 0let columNumber = 1let childHeight = 0children.forEach((child) => {// 得到子控件的实际大小let result: MeasureResult = child.measure({minHeight: constraint.minHeight,minWidth: constraint.minWidth,maxWidth: constraint.maxWidth,maxHeight: constraint.maxHeight})let padding = child.getPadding()let border = child.getBorderWidth()console.log("TagView onMeasureSize = child width = " + result.width + "  ,  height = " + result.height+ " , padding = [" + padding.start + ", " + padding.end + ", " + padding.top + ", " + padding.bottom +"], border = ["+ border.start + ", " + border.end + ", " + border.top + ", " + border.bottom + "]")/// 计算 布局所需的高度， 宽度默认为屏幕的宽度childHeight = result.height + child.getMargin().topstartPosX += result.width + child.getMargin().startif (startPosX > parentWidth) {columNumber++startPosX = result.width + child.getMargin().start}})// 父布局的宽和高，即承载 child 布局的宽和高，这里指的就是 TagView 的宽和高this.result.width = this.screenWidth;this.result.height = childHeight * columNumber + 10 // 加10是为了底部多点空间return this.result;}// 第二步：放置各子组件的位置onPlaceChildren(selfLayoutInfo: GeometryInfo, children: Array<Layoutable>, constraint: ConstraintSizeOptions) {let startPosX = 0let startPosY = 0let posY = 0let parentWidth = selfLayoutInfo.widthconsole.log("TagView onPlaceChildren parentWidth = " + selfLayoutInfo.width + " , parentHeight = " + selfLayoutInfo.height)children.forEach((child) => {startPosX += child.getMargin().start// 如果一行的控件的长度大于屏幕宽度则换行if (startPosX + child.measureResult.width > parentWidth) {startPosY += child.measureResult.height + child.getMargin().topstartPosX = child.getMargin().start}posY = startPosYconsole.log("TagView child width = " + child.measureResult.width + "  ,  height = " + child.measureResult.height +" , margin left = " + child.getMargin().start)child.layout({ x: startPosX, y: posY })startPosX += child.measureResult.width})}build() {this.buildTagView()}
}

调用的方法也很简单，下面是个调用的demo

@Entry
@Component
struct TestPage {@State name: string = 'hello'// @Provide 参数 key 必须是 string@Provide('provideName') pName: string = "哈哈"@Provide('count') count: number = 4textWidth: number = 0aboutToAppear(): void {let width = MeasureText.measureText({ textContent: '返厂无忧券1', fontSize: '13vp' });let w = px2vp(width)console.log("TestPage aboutToAppear >>>> width = " + width + " , w = " + w)// 如果有换行，那么长度等于最长的一行let textSize = MeasureText.measureTextSize({ textContent: '返厂无忧券1\n返厂无忧券1234', fontSize: '13vp' })let w2 = textSize.widthlet h2 = textSize.heightthis.textWidth = px2vp(w2 as number)console.log("TestPage aboutToAppear >>>> w2 = " + w2 + " , h2 = " + h2)}// @Build 参数按值传递，状态变量改变不会引起 @Build 方法内的 UI 刷新// 但是，Text(" ----- " + this.name) 中的 UI 会刷新@BuildernameView(name: string) {Text(name)}//  @Build 参数按引用传递的话，状态变量(@State name) 改变，@Build 方法内的 UI 会刷新@BuildernameView2(tmp: Tmp) {Text('V2 : name = ' + tmp.params)}// 通过builder的方式传递多个组件，作为自定义组件的一级子组件（即不包含容器组件，如Column）@BuilderTagViewChildren() {ForEach(['你好，哪吒2', '大圣归来啊', '我是名字超长的但是很厉害', 'hello world', '你真的好厉害啊哈哈', '没空看', '非凡','再来一个很长的名字啊', 'OK'],(data: string, index: number) => { // 暂不支持lazyForEach的写法Text(data).fontSize(13).fontColor(Color.Red).margin({ left: 3, top: 4 })// .width(100)// .height(100).borderWidth(1).border({ radius: 4 }).padding(5).textAlign(TextAlign.Center)// .offset({ x: 10, y: 20 })})}build() {Column() {Column() {CustomTagView({ buildTagView: this.TagViewChildren })}.backgroundColor(Color.Pink).margin({ top: 2 })}.width('100%').height('100%').alignItems(HorizontalAlign.Start)}
}

好了，具体的可以参考下 demo 啦，有疑问的可以一起交流。