diff --git a/src/background/actions.ts b/src/background/actions.ts
index cc1b0e9..946cfd8 100644
--- a/src/background/actions.ts
+++ b/src/background/actions.ts
@@ -1,5 +1,6 @@
 import { Actions, Request } from "../common";
 import { sendMessage } from "./messaging";
+import { logger } from "./common";
 
 /**
  * redirect tab to url.
@@ -41,7 +42,7 @@ export function redirectTab(tab: chrome.tabs.Tab, url: string) {
  * @param {Array<string>} fieldSelectors fields selectors for selecting fields (data columns) under each item
  * @returns {Promise<string[]>} a promise of extracted data
  */
-export function extractTabData(tab, itemsSelector, fieldSelectors) {
+export function extractTabData(tab: chrome.tabs.Tab, itemsSelector: string, fieldSelectors: string[], askOnfail?: boolean) {
     let req = {
         action: Actions.EXTRACT,
         itemsSelector: itemsSelector,
@@ -49,7 +50,13 @@ export function extractTabData(tab, itemsSelector, fieldSelectors) {
     }
     let checker = (result, err, tryCount) => {
         if (!result || !result.length) {
-            if (tryCount % 20 == 0 && confirm('No data found in current page. \n\nContinue to next page?')) {
+            if (
+                tryCount % 20 == 0 && (
+                    !askOnfail ||
+                    confirm('No data found in current page. \n\nContinue to next page?')
+                )
+            ) {
+                logger.warn(`Failed after ${tryCount} tries: ${tab.url}`)
                 return [];
             } else {
                 return undefined;
@@ -135,6 +142,25 @@ export async function findIncognitoWindow(): Promise<chrome.windows.Window> {
     });
 }
 
+export async function getCurrentWindow(): Promise<chrome.windows.Window> {
+    return new Promise((resolve, reject) => {
+        chrome.windows.getCurrent(
+            (windows: chrome.windows.Window) => {
+                return resolve(windows);
+            }
+        );
+    });
+}
+
+export async function getWindowByID(id: number) {
+    return new Promise<chrome.windows.Window>((resolve, reject) => {
+        chrome.windows.get(id, function (window) {
+            chrome.runtime.lastError;
+            resolve(window);
+        })
+    })
+}
+
 export async function CreateIncognitoWindow() {
     return new Promise((resolve, reject) => {
         chrome.windows.create(
diff --git a/src/background/messaging.ts b/src/background/messaging.ts
index 59ac0ca..dbcb79c 100644
--- a/src/background/messaging.ts
+++ b/src/background/messaging.ts
@@ -31,7 +31,7 @@ export function sendMessage<T>(
         loop();
 
         async function loop() {
-            logger.debug("Request for", req.action);
+            logger.debug("Request for", Actions[req.action]);
             let tabAvailable = await getTabByID(tab.id);
             if (!tabAvailable) {
                 reject("Task interrupted due to the target tab is closed.");
diff --git a/src/background/task.ts b/src/background/task.ts
index d77a37f..3b8b99d 100644
--- a/src/background/task.ts
+++ b/src/background/task.ts
@@ -1,5 +1,5 @@
 import { parseUrls } from "./tools";
-import { queryUrl, redirectTab, scrollToBottom, extractTabData } from "./actions";
+import { queryUrl, redirectTab, scrollToBottom, extractTabData, findIncognitoWindow, getCurrentWindow, getWindowByID } from "./actions";
 import { testArgs, signitures } from "./signiture";
 import { ExtractResult } from "./result";
 import { messageSubscribers, ActionSubscriber } from "./messaging";
@@ -14,6 +14,7 @@ export class Task {
     private _fieldSelectors: string[];
     private _urls: string[] = [];
     private _running = false;
+    private _listeners: ActionSubscriber[] = [];
 
     constructor(options: any, ...arg: any);
     constructor(options: any, itemsSelector: string, fieldSelectors: string[]);
@@ -56,15 +57,46 @@ export class Task {
     }
     stop() {
         this._running = false;
-        messageSubscribers.removeListener(Actions.REPORT_NEW_PAGE, this.listener);
+        let listener: ActionSubscriber;
+        while (listener = this._listeners.pop()) {
+            messageSubscribers.removeListener(Actions.REPORT_NEW_PAGE, listener);
+        }
     }
-    watch() {
+    async watch() {
         if (this._running) {
             logger.info("The task is running. Please wait...");
             return;
         }
         this._running = true;
-        messageSubscribers.addListener(Actions.REPORT_NEW_PAGE, this.listener);
+        let window = await findIncognitoWindow() || await getCurrentWindow();
+        if (!window) {
+            logger.info("No window to watch...");
+            return;
+        }
+        let listener: ActionSubscriber = async (request, sender, sendResponse) => {
+            let findWindow = await getWindowByID(window.id);
+            if (!findWindow) {
+                // stop watch on window close.
+                messageSubscribers.removeListener(Actions.REPORT_NEW_PAGE, listener);
+                return;
+            }
+            // only watch current window.
+            if (sender.tab.windowId != window.id) return;
+            let pm = this.makeOptionalTasks(sender.tab);
+            return pm.then(
+                () => extractTabData(sender.tab, this._itemsSelector, this._fieldSelectors, false)
+            ).then(
+                results => {
+                    if (results && results.length) {
+                        this.saveResult(results, sender.tab.url);
+                    }
+                }
+            ).catch(
+                e => logger.error(e)
+            )
+        }
+        this._listeners.push(listener);
+        messageSubscribers.addListener(Actions.REPORT_NEW_PAGE, listener);
     }
     async execute(tab: chrome.tabs.Tab, upstreamData?: ExtractResult): Promise<void> {
         if (!tab) return Promise.reject("No tab to execute the task.");
@@ -108,21 +140,6 @@ export class Task {
             }
         );
     }
-    private listener: ActionSubscriber = (request, sender, sendResponse) => {
-        sendResponse('recieved!');
-        let pm = this.makeOptionalTasks(sender.tab);
-        return pm.then(
-            () => extractTabData(sender.tab, this._itemsSelector, this._fieldSelectors)
-        ).then(
-            results => {
-                if (results && results.length) {
-                    this.saveResult(results, sender.tab.url);
-                }
-            }
-        ).catch(
-            e => logger.error(e)
-        )
-    }
     private makeOptionalTasks(tab: chrome.tabs.Tab): Promise<any> {
         let pm: Promise<any>;
         if (this._options["scrollToBottom"]) {