const canvas = this.$refs.firstCanvas; 设置宽高无效, 使用 ctx.scale(dpr, dpr); 会导致图片不显示

    methods: {  
        handleGetCanvasFields() {  
            return new Promise((resolve, reject) => {  
                const query = uni.createSelectorQuery().in(this);  
                query.select(`#firstCanvas`).fields({  
                    size: true,  
                }, (res) => {  
                    const width = res.width  
                    const height = res.height  
                    this.canvas = {  
                        width,  
                        height  
                    }  
                    resolve()  
                }).exec()  
            })  
        },  
        handleGetCanvasNode() {  
            const ctx = uni.createCanvasContext("firstCanvas", this);  
            const canvas = this.$refs.firstCanvas; // 获取 canvas 元素  

            // 确保 canvas 元素的物理尺寸设置正确  
            const dpr = uni.getSystemInfoSync().pixelRatio;  
            const width = this.canvas.width * dpr;  
            const height = this.canvas.height * dpr;  

            // 设置 canvas 元素的宽高  
            canvas.width = width;  
            canvas.height = height;  

            // 确保上下文缩放与设备分辨率匹配  
            ctx.setStrokeStyle("#ff0000");  
            ctx.setLineWidth(2);  
            ctx.scale(dpr, dpr); // 缩放使其适配高分辨率设备  

            // 开始绘制图形  
            ctx.beginPath();  
            ctx.moveTo(100, 100);  
            ctx.lineTo(130, 100);  
            ctx.lineTo(140, 70);  
            ctx.stroke();  
            ctx.draw(); // 确保绘制完成  
        }  

    }