HarmonyOS 鸿蒙Next Text组件如何知道可以展示的文本长度

可以使用maxLines设置文本的最大行数

https://developer.huawei.com/consumer/cn/doc/harmonyos-references-V5/ts-basic-components-text-V5#textalign

或者当大于一定高度或行数的时候显示展开和收起

参考代码：

import inspector from '@ohos.arkui.inspector';
import componentUtils from '@ohos.arkui.componentUtils';
import measure from '@ohos.measure'

@Entry
@Component
export struct TextButton {
  @State content: string = '#限定的校服，限定的青春！那群陪你度过青涩阳光的人，你还记得他们吗？12月15日中午12点，一起来重拾回忆'
  @State maxLines: number = Infinity
  @State isCollapse: boolean = true; // true收起 false展开
  @State collapseTxt: string = '…[展开]';
  private subTxt: string = '';
  @State flag: boolean = false; // 是否需要展开收起

  build() {
    Row() {
      Column() {
        Text() {
          if (this.flag) {
            Span(this.collapseTxt)
              .onClick(() => {
                if (this.isCollapse) {
                  this.maxLines = Infinity;
                  this.content = this.measureText;
                  this.isCollapse = false;
                  this.collapseTxt = '[收起]';
                } else {
                  this.isCollapse = true;
                  this.collapseTxt = '…[展开]';
                  this.content = this.subTxt;
                }
              })
          }
        }
        .textOverflow({ overflow: TextOverflow.Ellipsis })
        .maxLines(this.maxLines)
        .fontSize(24)
        .width(300)
        .backgroundColor(Color.White)
        .key('txt_info')
      }
      .width('100%')
    }
    .height('100%')
  }

  listener: inspector.ComponentObserver = inspector.createComponentObserver('txt_info')
  aboutToAppear() {
    let onLayoutComplete: () => void = (): void => {
      if (this.isCollapse) {
        this.getComponentRect('txt_info');
      }
    }
    let onDrawComplete: () => void = (): void => {
      if (this.isCollapse) {
        this.subTxt = this.content;
      }
    }
    let FuncLayout = onLayoutComplete
    let FuncDraw = onDrawComplete
    this.listener.on('layout', FuncLayout)
    this.listener.on('draw', FuncDraw)
  }

  private getComponentRect(key: string) {
    let modePosition = componentUtils.getRectangleById(key);
    let localOffsetHeight = modePosition.size.height;
    const textSize: SizeOptions =
      measure.measureTextSize({ textContent: this.content, fontSize: 24, constraintWidth: 300 })
    const textSize2: SizeOptions = measure.measureTextSize({
      textContent: this.content,
      fontSize: 24,
      maxLines: 3,
      constraintWidth: 300
    })
    if ((textSize.height || 0) > (textSize2.height || 0)) {
      this.flag = true;
    }
    console.info(`localOffsetHeight ${localOffsetHeight} textSize${textSize.height} textSize2 ${textSize2.height}`)
    if (localOffsetHeight > (textSize2.height || 300)) {
      this.content = this.content.substring(0, this.content.length - 2);
      this.isCollapse = true;
    }
  }
}