急急急canvasToTempFilePath: fail canvas is empty？
canvas作为自定义组件，保存画布提示canvasToTempFilePath: fail canvas is empty？
在页面里面直接写是OK的，封装到组件内部就不能用
const that = this
setTimeout(()=>{
Taro.canvasToTempFilePath({
canvasId: 'measure-angle',
success(result) {
console.log(111, result)
},
fail(result) {
console.log(222, result)
}
}, that)
}, 500)
