问题现象
在HarmonyOS开发中，由于Span组件本身不支持设置margin、padding等布局属性，开发者可以通过属性字符串（StyledString）实现类似效果。
背景知识
ArkUI提供轻量的UI元素复用机制@Builder，其内部UI结构固定，仅与使用方进行数据传递。开发者可将重复使用的UI元素抽象成函数，在build函数中调用。
将StyledString应用到文本组件上，可以采用多种方式修改文本，包括调整字号、添加字体颜色、使文本具备可点击性，以及通过自定义方式绘制文本等。
解决方案
可以通过以下几点达成最终效果：
路径计算：定义calculateArcPoints方法，该方法用于生成圆弧边框的路径坐标点，确保边框形状符合预期。
自定义Span绘制：绘制边框与文本，在onDraw方法中调用canvas.drawPath绘制边框路径，并同步渲染文本内容。
样式绑定：将生成的styledString通过setStyledString方法设置到Text组件。
具体代码实现如下：
import { DrawContext } from '@ohos.arkui.node';
import { drawing } from '@kit.ArkGraphics2D';
interface Point {
x: number;
y: number;
}
function calculateArcPoints(
start: Point,
end: Point,
center: Point,
numPoints: number = 20
): Point[] {
const startVec: Point = {
x: start.x - center.x,
y: start.y - center.y
};
const endVec: Point = {
x: end.x - center.x,
y: end.y - center.y
};
const radius = Math.hypot(startVec.x, startVec.y);
let thetaStart = Math.atan2(startVec.y, startVec.x);
let thetaEnd = Math.atan2(endVec.y, endVec.x);
if (thetaEnd < thetaStart) {
thetaEnd += 2 * Math.PI;
}
const angleDiff = thetaEnd - thetaStart;
const angles = Array.from({ length: numPoints + 1 }, (item: undefined, i) =>
thetaStart + angleDiff (i / numPoints)
);
let arr: Point[] = [];
angles.forEach(item => {
arr.push({
x: center.x + radius Math.cos(item),
y: center.y + radius * Math.sin(item)
});
});
return arr;
}
class MyCustomSpan extends CustomSpan {
width: number = 300;
word: string = '';
height: number = 300;
strokeWidth: number = 5;
uiContext: UIContext | undefined = undefined;
constructor(uiContext: UIContext, word: string, width: number, height: number, strokeWidth: number) {
super();
this.word = word;
this.width = width;
this.height = height;
this.strokeWidth = strokeWidth;
this.uiContext = uiContext;
}
onMeasure(): CustomSpanMetrics {
return { width: this.width, height: this.height };
}
onDraw(context: DrawContext) {
const canvas = context.canvas;
const pen = new drawing.Pen();
pen.setStrokeWidth(this.strokeWidth);
pen.setColor({
alpha: 255,
red: 255,
green: 0,
blue: 0
});
let path = new drawing.Path();
path.moveTo(this.uiContext?.vp2px(15), this.uiContext?.vp2px(5));
let rightTopArr =
calculateArcPoints({ x: this.width - 15, y: 5 }, { x: this.width - 10, y: 10 }, { x: this.width - 15, y: 10 });
rightTopArr.forEach(item => {
path.lineTo(this.uiContext?.vp2px(item.x), this.uiContext?.vp2px(item.y));
});
let rightBottomArr =
calculateArcPoints({ x: this.width - 10, y: 20 }, { x: this.width - 15, y: 25 }, { x: this.width - 15, y: 20 });
rightBottomArr.forEach(item => {
path.lineTo(this.uiContext?.vp2px(item.x), this.uiContext?.vp2px(item.y));
});
let leftBottomArr = calculateArcPoints({ x: 15, y: 25 }, { x: 10, y: 20 }, { x: 15, y: 20 });
leftBottomArr.forEach(item => {
path.lineTo(this.uiContext?.vp2px(item.x), this.uiContext?.vp2px(item.y));
});
let leftTopArr = calculateArcPoints({ x: 10, y: 10 }, { x: 15, y: 5 }, { x: 15, y: 10 });
leftTopArr.forEach(item => {
path.lineTo(this.uiContext?.vp2px(item.x), this.uiContext?.vp2px(item.y));
});
path.close();
canvas.attachPen(pen);
canvas.drawPath(path);
const font = new drawing.Font();
font.setSize(45);
const textBlob =
drawing.TextBlob.makeFromString(this.word, font, drawing.TextEncoding.TEXT_ENCODING_UTF8);
canvas.drawTextBlob(textBlob, 50, 65);
canvas.detachPen(); }
}
@Entry
@Component
struct StyledStringWithBorder {
message: string = 'TESTING';
strokeWidth: number = 5;
borderW: number = 100;
uiContext: UIContext = this.getUIContext();
customSpan: MyCustomSpan = new MyCustomSpan(this.uiContext, this.message, 100, 30, 5);
style: MutableStyledString = new MutableStyledString(this.customSpan);
textController: TextController = new TextController();
controller: TextInputController = new TextInputController();
@Builder
customInput(title: string, upValue: string, type: number) {
Row() {
Text(title)
.width('25%')
.height(40)
.textAlign(TextAlign.Center)
.margin(10);
TextInput({ text: upValue!!, placeholder: 'input your word...', controller: this.controller })
.placeholderColor(Color.Grey)
.placeholderFont({ size: 14, weight: 400 })
.caretColor(Color.Blue)
.width('60%')
.height(40)
.margin(10)
.fontSize(14)
.fontColor(Color.Black)
.onChange((value) => {
if (type === 1) {
this.message = value;
} else if (type === 2) {
this.strokeWidth = parseInt(value);
} else if (type === 3) {
this.borderW = parseInt(value);
}
})
.inputFilter(type === 1 ? '*' : '[0-9]', (e) => {
console.info(JSON.stringify(e));
});
}
.width('75%');
}
build() {
Column() {
Row() {
Text(undefined, { controller: this.textController })
.copyOption(CopyOptions.InApp);
}
.height('20%');
this.customInput('输入文本', this.message, 1);
this.customInput('画笔线宽', this.strokeWidth + '', 2);
this.customInput('标签总长', this.borderW + '', 3);
Button('属性字符串生成')
.margin(10)
.onClick(() => {
this.customSpan = new MyCustomSpan(this.uiContext, this.message, this.borderW, 30, this.strokeWidth);
this.style = new MutableStyledString(this.customSpan);
this.textController.setStyledString(this.style);
});
}
.height('100%')
.width('100%'); }
}
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