看着Hitesh Sahu和kam C答案,我得到了解决方案。
在API 21中,它引发了一个异常:“ android.util.AndroidRuntimeException:从Activity上下文外部调用startActivity()需要FLAG_ACTIVITY_NEW_TASK标志。这真的是您想要的吗?”。
正如diyism所注意到的,也可能找不到活动。因此,我处理了这些情况。
class MyWebViewClient : WebViewClient() {
    @Suppress("DEPRECATION")
    override fun shouldOverrideUrlLoading(view: WebView?, url: String?): Boolean {
        if (view != null && url != null) {
            return resolveUri(view.context, Uri.parse(url))
        }
        return super.shouldOverrideUrlLoading(view, url)
    }
    @TargetApi(Build.VERSION_CODES.N)
    override fun shouldOverrideUrlLoading(view: WebView?, request: WebResourceRequest?): Boolean {
        val uri = request?.url
        if (view != null && uri != null) {
            return resolveUri(view.context, uri)
        }
        return super.shouldOverrideUrlLoading(view, request)
    }
    private fun resolveUri(context: Context, uri: Uri): Boolean {
        val url = uri.toString()
        URL_SCHEMES.forEach {
            if (url.startsWith(it)) {
                val intent = Intent(Intent.ACTION_VIEW).apply {
                    data = uri
                    addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
                }
                try {
                    context.startActivity(intent)
                } catch (e: ActivityNotFoundException) {
                }
                return true
            }
        }
        return false
    }
    companion object {
        private val URL_SCHEMES = arrayOf(WebView.SCHEME_TEL,
            WebView.SCHEME_MAILTO, WebView.SCHEME_GEO, "sms:", "smsto:", "mms:", "mmsto:")
    }
}