问题现象
在Text中显示文本时，如果文本超过一定长度，通常会有超出部分隐藏与显示的需求，例如：当最多显示的行数为2，组件宽度比例为0.4时，该如何实现？
背景知识
measureText方法能够根据文本信息计算文本宽度。
getAllDisplays方法能够获取display对象，display对象的width属性为屏幕的宽度。
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解决方案
首先设定的文本长度计算方式：设定文本长度 = 屏幕宽度 最大行数 组件宽度比例。屏幕宽度可以使用getAllDisplays获取。
然后使用measureText方法测量实际文本宽度，比较“设定文本长度”与“实际文本宽度”进行大小比较，判断是否需要隐藏。
当需要隐藏时，只展示“设定长度”的文本内容，超出部分显示为“...”。当点击“…”时将该文本变为“…收起”，显示隐藏部分内容。
完整示例参考如下：
import { MeasureUtils } from '@kit.ArkUI';
import curves from '@ohos.curves';
import { BusinessError } from '@ohos.base';
import display from '@ohos.display';
@Entry
@Component
struct Index {
// 长文本
longMessage: string = '走在繁华的城市街头，明空感到无比紧张。他的心跳如雷鼓般擂动着胸膛，使得身上的伪装仿佛随时都要被揭开。然而，他仍然保持着冷静，凭借着过人的胆识与智慧，成功地躲过了敌人的层层封锁。\n' +
'\n' +
' 最终，明空来到了敌对帮派的老巢。此时此刻，那里的守卫正沉浸在欢庆的氛围中，丝毫没有察觉到即将来临的危机。明空深吸一口气，压抑住内心的激动，悄然潜入了这座古老的建筑。';
// 最大显示行数
@State lines: number = 2;
// 长文本状态（展开 or 收起）
@State collapseText: string = '...';
// 屏幕宽度（单位px）
screenWidth: number = 0;
// 是否需要显示"展开"字样（注：当文本长度较短时就不需要“展开”）
@State isExpanded: boolean = false;
uiContext: UIContext = this.getUIContext();
uiContextMeasure: MeasureUtils = this.uiContext.getMeasureUtils();
// 测量文本宽度（单位px）
textWidth: number = this.uiContextMeasure.measureText({
textContent: this.longMessage,
fontSize: 20
});
// 获取当前所有的display对象
promise: Promise<Array<display.Display>> = display.getAllDisplays();
aboutToAppear() {
console.info(文本宽度为：${this.textWidth});
this.promise.then((data: Array<display.Display>) => {
console.info(所有的屏幕信息：${JSON.stringify(data)});
// 单位为像素
this.screenWidth = data[0]["width"];
// 屏幕宽度 最大行数 组件宽度比例 和 文字测量宽度
this.isExpanded = this.screenWidth this.lines 0.4 <= this.textWidth;
}).catch((err: BusinessError) => {
console.error(Failed to obtain all the display objects. Code: ${JSON.stringify(err)});
});
}
build() {
Row() {
Column() {
if (this.isExpanded) {
Stack({ alignContent: Alignment.BottomEnd }) {
Text(this.longMessage)
.fontSize(20)
.fontColor(Color.Black)
.maxLines(this.lines)
.width("40%")
Row() {
Text(this.collapseText)
.fontSize(20)
.backgroundColor(Color.White)
}
.justifyContent(FlexAlign.End)
.onClick(() => {
if (this.collapseText == '...') {
this.collapseText = '...收起';
// 展开动画
this.uiContext.animateTo({
duration: 150,
curve: curves.springMotion(0.5, 0.8),
}, () => {
this.lines = -1; // 使得设置的最大行属性无效
});
} else {
this.collapseText = '...';
// 收起动画
this.uiContext.animateTo(
{
duration: 100,
curve: Curve.Friction,
}, () => {
this.lines = 2; // 只显示2行
});
}
})
}
}
else {
Text(this.longMessage)
.fontSize(20)
.fontColor(Color.Black)
}
}
.width('100%')
}
.height('100%')
}
}
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