android - 如何阻止 PDF 查看应用程序将以前的 PDF 保存在堆栈中？

Question

当我从 WebView 成功下载 PDF 时，我可以使用 VIEW 意图打开 PDF。当我按下后退按钮时，我会返回到我自己的应用程序。但是，当我下载并打开另一个 PDF 时，第一个 PDF 似乎仍在堆栈中。我必须按两次后退按钮才能返回我的应用程序。无论我使用主导航返回按钮还是 PDF 查看活动的标题栏中的按钮，这都是正确的。

我需要更改什么以确保只有我打开的 PDF 在堆栈上？

            setDownloadListener { url, _, _, mimetype, _ ->
                val downloadUri = Uri.parse(url)
                val downloadRequest = DownloadManager.Request(downloadUri).apply {
                    setTitle("Title")
                    setDescription("Downloading file")
                    setDestinationInExternalFilesDir(context, Environment.DIRECTORY_DOWNLOADS, downloadUri.lastPathSegment)
                    addRequestHeader("Cookie", CookieManager.getInstance().getCookie(url))
                }

                val manager: DownloadManager = getSystemService(Context.DOWNLOAD_SERVICE) as DownloadManager
                val downloadId = manager.enqueue(downloadRequest)

                registerReceiver(
                    object: BroadcastReceiver() {
                        override fun onReceive(context: Context?, intent: Intent?) {
                            Log.w("onReceive", "${intent?.action}")
                            if (intent !== null && DownloadManager.ACTION_DOWNLOAD_COMPLETE == intent.action) {
                                val cursor = manager.query(DownloadManager.Query().apply{ setFilterById(downloadId) })

                                if (cursor.moveToFirst()) {
                                    val downloadStatus = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_STATUS))
                                    val downloadLocalUri = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI))
                                    val downloadMimeType = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_MEDIA_TYPE))
                                    if (downloadStatus == DownloadManager.STATUS_SUCCESSFUL && downloadLocalUri !== null) {
                                        val viewIntent = Intent(Intent.ACTION_VIEW).apply {
                                            this.setDataAndType(Uri.parse(downloadLocalUri), downloadMimeType)
                                            this.flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK
                                        }
                                        if (viewIntent.resolveActivity(packageManager) !== null) {
                                            startActivity(
                                                Intent.createChooser(viewIntent, "Choose app")
                                            )
                                        } else {
                                            Toast.makeText(context, "No app available that can open file", Toast.LENGTH_SHORT).show()
                                        }
                                    } else {
                                        Toast.makeText(context, "Unable to download file", Toast.LENGTH_SHORT).show()
                                        Log.w("onReceive", "failure reason ${cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_REASON))}, ${cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_STATUS))}")
                                    }
                                }


                            }
                        }
                    },
                    IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE)
                )
            }

标签： androidandroid-webview