无法在iOS的ontouchstart中打开文件对话框？

Question

我正在研究React。以下组件是一个示例。当我在IOS上打开页面时，只有touchend可以触发文件对话框，但不能触发touchstart。但是，onmousedown / onmouseup都可以在桌面浏览器上触发它。 ontouchstart有什么特别之处吗？

class Sub extends React.Component {
    componentDidMount() {
        this.refs.test.ontouchstart = function(e) {
            e.preventDefault()
            const fileSelector = document.createElement('input');
            fileSelector.setAttribute('type', 'file');
            fileSelector.click()
            console.log('this file dialog fails to open')
        }

        this.refs.test.ontouchend = function(e) {
            e.preventDefault()
            const fileSelector = document.createElement('input');
            fileSelector.setAttribute('type', 'file');
            fileSelector.click()
            console.log('this file dialog opens')
        }


        this.refs.test.onmousemove = function(e) {
            e.preventDefault()
        }


        this.refs.test.onmouseup = function(e) {
            e.preventDefault()
        }
        this.refs.test.onmouseout = this.refs.test.onmouseup
        this.refs.test.ontouchmove = this.refs.test.onmousemove
    }
    render() {
        let canvas_style = { border: '2px solid black' }
        return (
            <div>
            <canvas ref='test' style={canvas_style}/>
            </div>
        )
    }
}