1、給webVeiw注冊長按事件

val webview=findViewById(R.id.web_view)
registerForContextMenu(webView)

2、捕獲WebView組件中長按事件,重寫 Activity子類的onCreateContextMenu函數(shù)

override fun onCreateContextMenu(menu: ContextMenu, view: View, menuInfo: ContextMenu.ContextMenuInfo?) {
        webView!!.hitTestResult?.let {
            when (it.type) {//判斷所長按的類型，如果是圖片->
                WebView.HitTestResult.IMAGE_TYPE,
                WebView.HitTestResult.SRC_IMAGE_ANCHOR_TYPE -> {
                    Logger.d("viewtype",it.type.toString())
                    menu.setHeaderTitle("Image Options")
                    menu.add(0, 1, 0, "Download")
                }
                else -> Logger.d("App does not yet handle target type: ${it.type}")
            }
        }
        super.onCreateContextMenu(menu, view, menuInfo)
        Logger.d("oncreatemune","長按了")

    }

3、重寫onContextItemSelected函數(shù)，當(dāng)2中add的菜單項(xiàng)被點(diǎn)擊時(shí)調(diào)用，因?yàn)橹惶砑恿艘粋€(gè)菜單項(xiàng)，所有下面沒有對點(diǎn)擊的哪一項(xiàng)進(jìn)行判斷

override fun onContextItemSelected(item: MenuItem): Boolean {
        webView!!.hitTestResult?.let {
            when (it.type) {
                WebView.HitTestResult.IMAGE_TYPE,
                WebView.HitTestResult.SRC_IMAGE_ANCHOR_TYPE -> {//如果是圖片就調(diào)用自己寫的downloadFile()函數(shù)下載圖片
                    val path=Environment.getExternalStorageDirectory().getPath()+"/DCIM"
                    downloadFile(imgSrc!!,path)
                }
                else -> Logger.d("App does not yet handle target type: ${it.type}")
            }
        }
        return super.onContextItemSelected(item)
    }

4、downloadFile函數(shù)：參數(shù)分別為圖片的下載地址和要存儲(chǔ)到的路徑
使用DownloadManager進(jìn)行下載

private fun downloadFile(url:String,path:String) {
        val uri = Uri.parse(url)
        val guessedFileName = URLUtil.guessFileName(url, null, null)
        val request = DownloadManager.Request(uri).apply {
            allowScanningByMediaScanner()
            setDestinationInExternalPublicDir(path, guessedFileName)
            setNotificationVisibility(VISIBILITY_VISIBLE_NOTIFY_COMPLETED)//通知欄的下載條，VISIBILITY_VISIBLE_NOTIFY_COMPLETED是個(gè)常量，表示在下載過程中通知欄會(huì)一直顯示該下載的Notification
        }
        val manager = getSystemService(Context.DOWNLOAD_SERVICE) as DownloadManager
        manager.enqueue(request)

        //下面的代碼是發(fā)送廣播，刷新Media庫更新相冊
        val contentUri = Uri.fromFile(File(path+File.separator+guessedFileName))
        val mediaScanIntent = Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE,contentUri)
        sendBroadcast(mediaScanIntent)

    }

5、注意事項(xiàng)
（1）onCreateContextMenu不要與setOnLongClickListener同時(shí)使用
（2）設(shè)置圖片的儲(chǔ)存路徑時(shí)，有些路徑手機(jī)的系統(tǒng)不會(huì)識(shí)別，我這里設(shè)置的根目錄+/DCIM，我在用小米手機(jī)進(jìn)行測試時(shí)，發(fā)現(xiàn)生成的相冊會(huì)被屏蔽，需要在相冊設(shè)置中打開“顯示被屏蔽的相冊”