小程序canvas文本换行

drawText: function (ctx, str, leftWidth, initHeight, titleHeight, canvasWidth) {
    var lineWidth = 0;
    var lastSubStrIndex = 0; //每次开始截取的字符串的索引
    for (let i = 0; i < str.length; i++) {
      lineWidth += ctx.measureText(str[i]).width;
      if (lineWidth > canvasWidth) {
        ctx.fillText(str.substring(lastSubStrIndex, i), leftWidth, initHeight); //绘制截取部分
        initHeight += 20; //16为字体的高度
        lineWidth = 0;
        lastSubStrIndex = i;
        titleHeight += 20;
      }
      if (i == str.length - 1) { //绘制剩余部分
        ctx.fillText(str.substring(lastSubStrIndex, i + 1), leftWidth, initHeight);
      }
    }
    // 标题border-bottom 线距顶部距离
    titleHeight = titleHeight + 10;
    return titleHeight
  },

调用方法

that.drawText(ctx, "花时间长多久爱手机单基调是基础",150,220,2,218)