java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.view.ViewGroup.dispatchTouchEvent(android.view.MotionEvent)' on a null object reference

[ngokhongkn]

07-10 08:43:55.768 32514-32514/de.zweidenker.rheinwerk_reader E/AndroidRuntime: FATAL EXCEPTION: main
Process: de.zweidenker.rheinwerk_reader, PID: 32514
java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.view.ViewGroup.dispatchTouchEvent(android.view.MotionEvent)' on a null object reference
at com.folioreader.view.FolioWebView.computeHorizontalScroll(FolioWebView.java:121)
at com.folioreader.view.FolioWebView.onTouchEvent(FolioWebView.java:108)
at android.view.View.dispatchTouchEvent(View.java:10779)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2859)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2535)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2865)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2492)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2865)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2492)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2865)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2492)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2865)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2492)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2865)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2492)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2865)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2492)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2865)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2492)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2865)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2492)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2865)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2492)
at com.android.internal.policy.DecorView.superDispatchTouchEvent(DecorView.java:582)
at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1885)
at android.app.Activity.dispatchTouchEvent(Activity.java:3240)
at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:71)

[udfvirus]

Add to FolioWebView.java if (webViewPager! = Null) webViewPager.dispatchTouchEvent (event);

[hrishikesh-kadam]

@ngokhongkn Can you please share EPUB file with us so that we can investigate?

@javavirys the solution you proposed would not make the Horizontal scrolling feature work. It would be helpful if you can share EPUB file with us.

This generally happens when JS Horizontal pagination code doesn't give callback to Java code -

FolioReader-Android/folioreader/src/main/assets/js/Bridge.js

Lines 486 to 523 in 1545995

	function postInitHorizontalDirection() {
	var htmlElement = document.getElementsByTagName('html')[0];
	var bodyElement = document.getElementsByTagName('body')[0];
	var bodyStyle = bodyElement.currentStyle || window.getComputedStyle(bodyElement);
	var paddingTop = parseInt(bodyStyle.paddingTop, 10);
	var paddingRight = parseInt(bodyStyle.paddingRight, 10);
	var paddingBottom = parseInt(bodyStyle.paddingBottom, 10);
	var paddingLeft = parseInt(bodyStyle.paddingLeft, 10);
	var clientWidth = document.documentElement.clientWidth;
	var scrollWidth = document.documentElement.scrollWidth;
	//console.log("-> document.documentElement.offsetWidth = " + document.documentElement.offsetWidth);
	if (scrollWidth > clientWidth
	&& scrollWidth > document.documentElement.offsetWidth) {
	scrollWidth += paddingRight;
	}
	var newBodyWidth = scrollWidth - (paddingLeft + paddingRight);
	window.scrollWidth = scrollWidth;
	htmlElement.style.width = scrollWidth + 'px';
	bodyElement.style.width = newBodyWidth + 'px';
	// pageCount deliberately rounded instead of ceiling to avoid any unexpected error
	var pageCount = Math.round(scrollWidth / clientWidth);
	var pageCountFloat = scrollWidth / clientWidth;
	if (pageCount != pageCountFloat) {
	console.warn("-> pageCount = " + pageCount + ", pageCountFloat = " + pageCountFloat
	+ ", Something wrong in pageCount calculation");
	}
	//console.log("-> scrollWidth = " + scrollWidth);
	//console.log("-> newBodyWidth = " + newBodyWidth);
	//console.log("-> pageCount = " + pageCount);
	FolioPageFragment.setHorizontalPageCount(pageCount);
	}

FolioReader-Android/folioreader/src/main/java/com/folioreader/ui/folio/fragment/FolioPageFragment.java

Lines 742 to 749 in 1545995

	@SuppressWarnings("unused")
	@JavascriptInterface
	public void setHorizontalPageCount(int horizontalPageCount) {
	Log.v(LOG_TAG, "-> setHorizontalPageCount = " + horizontalPageCount
	+ " -> " + spineItem.originalHref);
	mWebview.setHorizontalPageCount(horizontalPageCount);
	}

FolioReader-Android/folioreader/src/main/java/com/folioreader/view/FolioWebView.java

Lines 154 to 166 in 1545995

	public void setHorizontalPageCount(int horizontalPageCount) {
	this.horizontalPageCount = horizontalPageCount;
	handler.post(new Runnable() {
	@Override
	public void run() {
	if (webViewPager == null)
	webViewPager = ((View) getParent()).findViewById(R.id.webViewPager);
	webViewPager.setHorizontalPageCount(FolioWebView.this.horizontalPageCount);
	}
	});
	}

[udfvirus]

Here's the epub
pub.zip

[hrishikesh-kadam]

@javavirys I am unable to reproduce the issue.
Can you please give me exact steps?

[ngokhongkn]

Hi everybody
When I switch very fast, this error occurs.
In my project, I use folioreader to open each html page and not use it to open the epub.
thanks everyone. I fixed it by check null

[hrishikesh-kadam]

@mahavir155 I think this bug still exists due to the limitation of nanohttpd. Fast swiping between chapters leads to some connection problem between client and server.

Let's keep it open.