Develop Reference

Check if Android WebView is consuming touch events

TL;DR
How can I detect whether Android WebView consumed a touch event? onTouchEvent always returns true and WebViewClient's onUnhandledInputEvent is never triggered.
Detailed description
I have multiple WebViews inside a TwoDScrollView. As its name suggests, the TwoDScrollView can be scrolled both vertically and horizontally. The contents of TwoDScrollView can be zoomed in / out. When the user drags his finger or uses pinch-to-zoom, I want to dispatch the touch event to:
WebView if its content is scrollable / zoomable (i.e. only the inside of the WebView will scroll / zoom)
TwoDScrollView if the above condition is false (all contents of the TwoDScrollView will scroll / zoom)
I have partially achieved this by using the canScrollHorizontally and canScrollVertically methods. But these methods only work for "native scrolling". However, in some cases, some JavaScript inside the WebView consumes the touch event, for example Google Maps. In this case, the methods return false. Is there any way to find out whether the WebView's contents consumes the touch events, i.e. is scrollable / zoomable? I cannot change the contents of the WebView, therefore my question is different from this one.
I have considered checking touch handlers by executing some JavaScript inside the Webview by the evaluateJavaScript method, but according to this answer there is no easy way to achieve this and also the page can have some other nested iframes. Any help will be appreciated.
What I've already tried
I overrode WebView's onTouchEvent and read super.onTouchEvent() which always returns true, no matter what.
canScrollHorizontally and canScrollVertically only partially solve this problem, as mentioned above
onScrollChanged isn't useful either
WebViewClient.onUnhandledInputEvent is never triggered
I considered using JavaScript via evaluateJavaScript, but it is a very complicated and ugly solution
I tried to trace the MotionEvent by Debug.startMethodTracing. I found out it is propagated as follows:
android.webkit.WebView.onTouchEvent
com.android.webview.chromium.WebViewChromium.onTouchEvent
com.android.org.chromium.android_webview.AwContents.onTouchEvent
com.android.org.chromium.android_webview.AwContents$AwViewMethodsImpl.onTouchEvent
com.android.org.chromium.content.browser.ContentViewCore.onTouchEventImpl
According to ContentViewCore's source code the touch event ends up in a native method nativeOnTouchEvent and I don't know what further happens with it. Anyway, onTouchEvent always returns true and even if it was possible to find out somewhere whether the event was consumed or not, it would require using private methods which is also quite ugly.
Note
I don't need to know how to intercept touch events sent to WebView, but whether the WebView is consuming them, i.e. is using them for doing anything, such as scrolling, dragging etc.

According to this issue report, not possible.
If the web code is under your control, you can implement some JavaScriptInterface to workaround this. If not, I am afraid there is no solution here.

You can pass all touch events to GestureDetector by overriding onTouchEvent of WebView, so you can know when Android WebView is consuming touch events anywhere, anytime by listening to GestureDetector.
Try like this:
public class MyWebView extends WebView {
private Context context;
private GestureDetector gestDetector;
public MyWebView(Context context) {
super(context);
this.context = context;
gestDetector = new GestureDetector(context, gestListener);
}
#Override
public boolean onTouchEvent(MotionEvent event) {
return gd.onTouchEvent(event);
}
GestureDetector.SimpleOnGestureListener gestListener= new GestureDetector.SimpleOnGestureListener() {
public boolean onDown(MotionEvent event) {
return true;
}
public boolean onFling(MotionEvent event1, MotionEvent event2, float velocityX, float velocityY) {
//if (event1.getRawX() > event2.getRawX()) {
// show_toast("swipe left");
//} else {
// show_toast("swipe right");
//}
//you can trace any touch events here
return true;
}
};
void show_toast(final String text) {
Toast t = Toast.makeText(context, text, Toast.LENGTH_SHORT);
t.show();
}
}
I hope you be inspired.

This code will handle your scrolling events in a webview. This catch the click down and the click up events, and compares the positions of each one. It never minds that the content within the webview is scrollable, just compare the coordinates in the area of webview.
public class MainActivity extends Activity implements View.OnTouchListener, Handler.Callback {
private float x1,x2,y1,y2; //x1, y1 is the start of the event, x2, y2 is the end.
static final int MIN_DISTANCE = 150; //min distance for a scroll event
private static final int CLICK_ON_WEBVIEW = 1;
private static final int CLICK_ON_URL = 2;
private static final int UP_ON_WEBVIEW = 3;
private final Handler handler = new Handler(this);
public WebView webView;
private WebViewClient client;
private WebAppInterface webAppInt = new WebAppInterface(this);
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
webView = (WebView)findViewById(R.id.myWebView);
webView.setOnTouchListener(this);
client = new WebViewClient();
webView.setWebViewClient(client);
webView.loadDataWithBaseURL("file:///android_asset/", "myweb.html", "text/html", "UTF-8", "");
}
//HERE START THE IMPORTANT PART
#Override
public boolean onTouch(View v, MotionEvent event) {
if (v.getId() == R.id.myWebView && event.getAction() == MotionEvent.ACTION_DOWN){
x1 = event.getX();
y1 = event.getY();
handler.sendEmptyMessageDelayed(CLICK_ON_WEBVIEW, 200);
} else if (v.getId() == R.id.myWebView && event.getAction() == MotionEvent.ACTION_UP){
x2 = event.getX();
y2 = event.getY();
handler.sendEmptyMessageDelayed(UP_ON_WEBVIEW, 200);
}
return false;
}
#Override
public boolean handleMessage(Message msg) {
if (msg.what == CLICK_ON_URL){ //if you clic a link in the webview, thats not a scroll
handler.removeMessages(CLICK_ON_WEBVIEW);
handler.removeMessages(UP_ON_WEBVIEW);
return true;
}
if (msg.what == CLICK_ON_WEBVIEW){
//Handle the click in the webview
Toast.makeText(this, "WebView clicked", Toast.LENGTH_SHORT).show();
return true;
}
if (msg.what == UP_ON_WEBVIEW){
float deltaX = x2 - x1; //horizontal move distance
float deltaY = y2 - y1; //vertical move distance
if ((Math.abs(deltaX) > MIN_DISTANCE) && (Math.abs(deltaX) > Math.abs(deltaY)))
{
// Left to Right swipe action
if (x2 > x1)
{
//Handle the left to right swipe
Toast.makeText(this, "Left to Right swipe", Toast.LENGTH_SHORT).show ();
}
// Right to left swipe action
else
{
//Handle the right to left swipe
Toast.makeText(this, "Right to Left swipe", Toast.LENGTH_SHORT).show ();
}
}
else if ((Math.abs(deltaY) > MIN_DISTANCE) && (Math.abs(deltaY) > Math.abs(deltaX)))
{
// Top to Bottom swipe action
if (y2 > y1)
{
//Handle the top to bottom swipe
Toast.makeText(this, "Top to Bottom swipe", Toast.LENGTH_SHORT).show ();
}
// Bottom to top swipe action -- I HIDE MY ACTIONBAR ON SCROLLUP
else
{
getActionBar().hide();
Toast.makeText(this, "Bottom to Top swipe [Hide Bar]", Toast.LENGTH_SHORT).show ();
}
}
return true;
}
return false;
}
}
You can also try to control the speed of the swipe, to detect it as a real swipe or scrolling.
I hope that helps you.

Try to set the android:isClickable="true" in the XML and create an onClickListener in the Java code.

Actually now Touch Actions are not supported for webview. But some workarounds are available;
I am going to show it with a longpress example : I am using Pointoption because i will get the coordinate of element and will use it for longpress.
public void longpress(PointOption po) {
//first you need to switch to native view
driver.switchToNativeView();
TouchAction action = new TouchAction((PerformsTouchActions) driver);
action.longPress(po).waitAction(WaitOptions.waitOptions(Duration.ofSeconds(2)));
action.release();
action.perform();
driver.switchToDefaultWebView();
}
For to get the coordinate of element i designed below methood
public PointOption getElementLocation(WebElement element) {
int elementLocationX;
int elementLocationY;
//get element location in webview
elementLocationX = element.getLocation().getX();
elementLocationY = element.getLocation().getY();
//get the center location of the element
int elementWidthCenter = element.getSize().getWidth() / 2;
int elementHeightCenter = element.getSize().getHeight() / 2;
int elementWidthCenterLocation = elementWidthCenter + elementLocationX;
int elementHeightCenterLocation = elementHeightCenter + elementLocationY;
//calculate the ratio between actual screen dimensions and webview dimensions
float ratioWidth = device.getDeviceScreenWidth() / ((MobileDevice) device)
.getWebViewWidth().intValue();
float ratioHeight = device.getDeviceScreenHeight() / ((MobileDevice) device)
.getWebViewHeight().intValue();
//calculate the actual element location on the screen , if needed you can increase this value,for example i used 115 for one of my mobile devices.
int offset = 0;
float elementCenterActualX = elementWidthCenterLocation * ratioWidth;
float elementCenterActualY = (elementHeightCenterLocation * ratioHeight) + offset;
float[] elementLocation = {elementCenterActualX, elementCenterActualY};
int elementCoordinateX, elementCoordinateY;
elementCoordinateX = (int) Math.round(elementCenterActualX);
elementCoordinateY = (int) Math.round(elementCenterActualY);
PointOption po = PointOption.point(elementCoordinateX, elementCoordinateY);
return po;
}
now you have a longpress(PointOption po) and getElementLocation(Webelement element) methods that gives you po. Now everything is ready and you can use them as below..
longpress(getElementLocation(driver.findElement(By.id("the selector can be any of them(xpath,css,classname,id etc.)")));

Drag and drop in ScrollView

I have some ImageViews inside a HorizontalScrollView.
I would like to be able to drag and drop the ImageViews somewhere else, but still maintain scrolling capability. Dragging should only be activated when the user starts a mostly vertical motion with their finger.
For now, I have drag and drop activate on long-press, but that is not a good solution.
To illustrate:

I had to do exactly this as well. After reading http://techin-android.blogspot.in/2011/11/swipe-event-in-android-scrollview.html I adapted the code as follows:
class MyOnTouchListener implements View.OnTouchListener {
static final int MIN_DISTANCE_Y = 40;
private float downY, upY;
#Override
public boolean onTouch(View view, MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN: {
downY = event.getY();
return true;
}
case MotionEvent.ACTION_MOVE: {
upY = event.getY();
float deltaY = downY - upY;
// swipe vertical?
if (Math.abs(deltaY) > MIN_DISTANCE_Y) {
if (deltaY < 0) {
//Start your drag here if appropriate
return true;
}
if (deltaY > 0) {
//Or start your drag here if appropriate
return true;
}
}
}
}
return false;
}
}
And then set the listener on the ImageViews:
imageView.setOnTouchListener(new MyOnTouchListener());
In this version of the code I am only checking for movement in the vertical direction (I also changed the minimum movement to be 40 instead of 100 as in the original code). If a vertical movement is detected, the specific ImageView can begin to drag or do any other actions you want. If a vertical movement is not detected, the ImageView's MyTouchListener returns false which means the ImageView does not consume the touch event. This allows the parent ScrollView to eventually get the touch event and consume it (for scroll detection). The answers here are helpful for understanding touch events: MotionEvent handling in ScrollView in Android.

SemiClosedSlidingDrawer onClick not dispatched when semi-collapsed

i'm using a SemiClosedSlidingDrawer (http://pastebin.com/FtVyrcEb) and i've added on content part some buttons on the top of slider which are always visibles.
The problems is that they are clickable (or click event is dispatched) only when slider is fully opened... When slider is "semi-opened" click event not seems dispached to button... I have inspected with debugger into onInterceptTouchEvent() and in both cases (opened/semi-collapsed) the following code
#Override
public boolean onInterceptTouchEvent(MotionEvent event) {
if (mLocked) {
return false;
}
final int action = event.getAction();
float x = event.getX();
float y = event.getY();
final Rect frame = mFrame;
final View handle = mHandle;
handle.getHitRect(frame);
//FOLLOWING THE CRITICAL CODE
if (!mTracking && !frame.contains((int) x, (int) y)) {
return false;
}
return false but only when slider is opened event was dispached...
It checks if a (x,y) relative to the click are contained in a rectangle created starting from the HandleButton view of sliding drawer...
final Rect frame = mFrame;
final View handle = mHandle;
handle.getHitRect(frame);
and this is obviously false because i'm clicking on a button contained inside the content part of slidingdrawer and that's ok...
As i said above the problem is that in semi-collapsed state, buttons contained in content part are not receiving the event...
Have you any idea how can i solve this issue?
Can be some state of slidingdrawer that avoid to click childs when collapsed?
Thanks in advance...

Right, I think I've figured out a way to do this.
First you need to modify onInterceptTouchEvent() to return true whenever the user presses the visible content during the semi-opened state. So, for instance, if your SemiClosedSlidingDrawer view is located at the very bottom of the screen, you can use a simple detection algorithm, like this:
public boolean onInterceptTouchEvent(MotionEvent event) {
...
handle.getHitRect(frame);
// NEW: Check if the user pressed on the "semi-open" content (below the handle):
if(!mTracking && (y >= frame.bottom) && action == MotionEvent.ACTION_DOWN) {
return true;
}
if (!mTracking && !frame.contains((int) x, (int) y)) {
...
}
Now the touch events during the user's interaction with the semi-opened content will be dispatched to onTouchEvent(). Now we just need to intercept these events and "manually" redirect them to the right view (note that we also need to offset the coordinates for the child view):
public boolean onTouchEvent(MotionEvent event) {
...
if (mTracking) {
...
}
else
{
// NEW: Dispatch events to the "semi-open" view:
final Rect frame = mFrame;
final View handle = mHandle;
handle.getHitRect(frame);
float x = event.getX();
float y = event.getY() - frame.bottom;
MotionEvent newEvent = MotionEvent.obtain(event);
newEvent.setLocation(x, y);
return mContent.dispatchTouchEvent(newEvent);
}
return mTracking || mAnimating || super.onTouchEvent(event);
}
It's a bit of a messy implementation, but I think the basic concept is right. Let me know how it works for you!

Android View stops receiving touch events when parent scrolls

I have a custom Android view which overrides onTouchEvent(MotionEvent) to handle horizontal scrolling of content within the view. However, when the ScrollView in which this is contained scrolls vertically, the custom view stops receiving touch events. Ideally what I want is for the custom view to continue receiving events so it can handle its own horizontal scrolling, while the containing view hierarchy deals with vertical scrolling.
Is there any way to continue receiving those motion events on scroll? If not, is there any other way to get the touch events I need?

Use requestDisallowInterceptTouchEvent(true) in the childview to prevent from vertical scrolling if you want to continue doing horizontal scrolling and latter reset it when done.
private float downXpos = 0;
private float downYpos = 0;
private boolean touchcaptured = false;
#Override
public boolean onTouchEvent(MotionEvent event) {
switch(event.getAction()) {
case MotionEvent.ACTION_DOWN:
downXpos = event.getX();
downYpos = event.getY();
touchcaptured = false;
break;
case MotionEvent.ACTION_UP:
requestDisallowInterceptTouchEvent(false);
break;
case MotionEvent.ACTION_MOVE:
float xdisplacement = Math.abs(event.getX() - downXpos);
float ydisplacement = Math.abs(event.getY() - downYpos);
if( !touchcaptured && xdisplacement > ydisplacement && xdisplacement > 10) {
requestDisallowInterceptTouchEvent(true);
touchcaptured = true;
}
break;
}
super.onTouchEvent(event);
return true;
}

I'm answering my own question in case anyone else is as bad at Googling for the answer as I apparently was. :P
A workaround for this problem is to extend ScrollView and override the onInterceptTouchEvent method so that it only intercepts touch events where the Y movement is significant (greater than the X movement, according to one suggestion).

HorizontalScrollView within ScrollView Touch Handling

I have a ScrollView that surrounds my entire layout so that the entire screen is scrollable. The first element I have in this ScrollView is a HorizontalScrollView block that has features that can be scrolled through horizontally. I've added an ontouchlistener to the horizontalscrollview to handle touch events and force the view to "snap" to the closest image on the ACTION_UP event.
So the effect I'm going for is like the stock android homescreen where you can scroll from one to the other and it snaps to one screen when you lift your finger.
This all works great except for one problem: I need to swipe left to right almost perfectly horizontally for an ACTION_UP to ever register. If I swipe vertically in the very least (which I think many people tend to do on their phones when swiping side to side), I will receive an ACTION_CANCEL instead of an ACTION_UP. My theory is that this is because the horizontalscrollview is within a scrollview, and the scrollview is hijacking the vertical touch to allow for vertical scrolling.
How can I disable the touch events for the scrollview from just within my horizontal scrollview, but still allow for normal vertical scrolling elsewhere in the scrollview?
Here's a sample of my code:
public class HomeFeatureLayout extends HorizontalScrollView {
private ArrayList<ListItem> items = null;
private GestureDetector gestureDetector;
View.OnTouchListener gestureListener;
private static final int SWIPE_MIN_DISTANCE = 5;
private static final int SWIPE_THRESHOLD_VELOCITY = 300;
private int activeFeature = 0;
public HomeFeatureLayout(Context context, ArrayList<ListItem> items){
super(context);
setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT));
setFadingEdgeLength(0);
this.setHorizontalScrollBarEnabled(false);
this.setVerticalScrollBarEnabled(false);
LinearLayout internalWrapper = new LinearLayout(context);
internalWrapper.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
internalWrapper.setOrientation(LinearLayout.HORIZONTAL);
addView(internalWrapper);
this.items = items;
for(int i = 0; i< items.size();i++){
LinearLayout featureLayout = (LinearLayout) View.inflate(this.getContext(),R.layout.homefeature,null);
TextView header = (TextView) featureLayout.findViewById(R.id.featureheader);
ImageView image = (ImageView) featureLayout.findViewById(R.id.featureimage);
TextView title = (TextView) featureLayout.findViewById(R.id.featuretitle);
title.setTag(items.get(i).GetLinkURL());
TextView date = (TextView) featureLayout.findViewById(R.id.featuredate);
header.setText("FEATURED");
Image cachedImage = new Image(this.getContext(), items.get(i).GetImageURL());
image.setImageDrawable(cachedImage.getImage());
title.setText(items.get(i).GetTitle());
date.setText(items.get(i).GetDate());
internalWrapper.addView(featureLayout);
}
gestureDetector = new GestureDetector(new MyGestureDetector());
setOnTouchListener(new View.OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event) {
if (gestureDetector.onTouchEvent(event)) {
return true;
}
else if(event.getAction() == MotionEvent.ACTION_UP || event.getAction() == MotionEvent.ACTION_CANCEL ){
int scrollX = getScrollX();
int featureWidth = getMeasuredWidth();
activeFeature = ((scrollX + (featureWidth/2))/featureWidth);
int scrollTo = activeFeature*featureWidth;
smoothScrollTo(scrollTo, 0);
return true;
}
else{
return false;
}
}
});
}
class MyGestureDetector extends SimpleOnGestureListener {
#Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
try {
//right to left
if(e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
activeFeature = (activeFeature < (items.size() - 1))? activeFeature + 1:items.size() -1;
smoothScrollTo(activeFeature*getMeasuredWidth(), 0);
return true;
}
//left to right
else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
activeFeature = (activeFeature > 0)? activeFeature - 1:0;
smoothScrollTo(activeFeature*getMeasuredWidth(), 0);
return true;
}
} catch (Exception e) {
// nothing
}
return false;
}
}
}

Update: I figured this out. On my ScrollView, I needed to override the onInterceptTouchEvent method to only intercept the touch event if the Y motion is > the X motion. It seems like the default behavior of a ScrollView is to intercept the touch event whenever there is ANY Y motion. So with the fix, the ScrollView will only intercept the event if the user is deliberately scrolling in the Y direction and in that case pass off the ACTION_CANCEL to the children.
Here is the code for my Scroll View class that contains the HorizontalScrollView:
public class CustomScrollView extends ScrollView {
private GestureDetector mGestureDetector;
public CustomScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
mGestureDetector = new GestureDetector(context, new YScrollDetector());
setFadingEdgeLength(0);
}
#Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
return super.onInterceptTouchEvent(ev) && mGestureDetector.onTouchEvent(ev);
}
// Return false if we're scrolling in the x direction
class YScrollDetector extends SimpleOnGestureListener {
#Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
return Math.abs(distanceY) > Math.abs(distanceX);
}
}
}

Thank you Joel for giving me a clue on how to resolve this problem.
I have simplified the code(without need for a GestureDetector) to achieve the same effect:
public class VerticalScrollView extends ScrollView {
private float xDistance, yDistance, lastX, lastY;
public VerticalScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}
#Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
xDistance = yDistance = 0f;
lastX = ev.getX();
lastY = ev.getY();
break;
case MotionEvent.ACTION_MOVE:
final float curX = ev.getX();
final float curY = ev.getY();
xDistance += Math.abs(curX - lastX);
yDistance += Math.abs(curY - lastY);
lastX = curX;
lastY = curY;
if(xDistance > yDistance)
return false;
}
return super.onInterceptTouchEvent(ev);
}
}

I think I found a simpler solution, only this uses a subclass of ViewPager instead of (its parent) ScrollView.
UPDATE 2013-07-16: I added an override for onTouchEvent as well. It could possibly help with the issues mentioned in the comments, although YMMV.
public class UninterceptableViewPager extends ViewPager {
public UninterceptableViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
#Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
boolean ret = super.onInterceptTouchEvent(ev);
if (ret)
getParent().requestDisallowInterceptTouchEvent(true);
return ret;
}
#Override
public boolean onTouchEvent(MotionEvent ev) {
boolean ret = super.onTouchEvent(ev);
if (ret)
getParent().requestDisallowInterceptTouchEvent(true);
return ret;
}
}
This is similar to the technique used in android.widget.Gallery's onScroll().
It is further explained by the Google I/O 2013 presentation Writing Custom Views for Android.
Update 2013-12-10: A similar approach is also described in a post from Kirill Grouchnikov about the (then) Android Market app.

I've found out that somethimes one ScrollView regains focus and the other loses focus. You can prevent that, by only granting one of the scrollView focus:
scrollView1= (ScrollView) findViewById(R.id.scrollscroll);
scrollView1.setAdapter(adapter);
scrollView1.setOnTouchListener(new View.OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event) {
scrollView1.getParent().requestDisallowInterceptTouchEvent(true);
return false;
}
});

It wasn't working well for me. I changed it and now it works smoothly. If anyone interested.
public class ScrollViewForNesting extends ScrollView {
private final int DIRECTION_VERTICAL = 0;
private final int DIRECTION_HORIZONTAL = 1;
private final int DIRECTION_NO_VALUE = -1;
private final int mTouchSlop;
private int mGestureDirection;
private float mDistanceX;
private float mDistanceY;
private float mLastX;
private float mLastY;
public ScrollViewForNesting(Context context, AttributeSet attrs,
int defStyle) {
super(context, attrs, defStyle);
final ViewConfiguration configuration = ViewConfiguration.get(context);
mTouchSlop = configuration.getScaledTouchSlop();
}
public ScrollViewForNesting(Context context, AttributeSet attrs) {
this(context, attrs,0);
}
public ScrollViewForNesting(Context context) {
this(context,null);
}
#Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
mDistanceY = mDistanceX = 0f;
mLastX = ev.getX();
mLastY = ev.getY();
mGestureDirection = DIRECTION_NO_VALUE;
break;
case MotionEvent.ACTION_MOVE:
final float curX = ev.getX();
final float curY = ev.getY();
mDistanceX += Math.abs(curX - mLastX);
mDistanceY += Math.abs(curY - mLastY);
mLastX = curX;
mLastY = curY;
break;
}
return super.onInterceptTouchEvent(ev) && shouldIntercept();
}
private boolean shouldIntercept(){
if((mDistanceY > mTouchSlop || mDistanceX > mTouchSlop) && mGestureDirection == DIRECTION_NO_VALUE){
if(Math.abs(mDistanceY) > Math.abs(mDistanceX)){
mGestureDirection = DIRECTION_VERTICAL;
}
else{
mGestureDirection = DIRECTION_HORIZONTAL;
}
}
if(mGestureDirection == DIRECTION_VERTICAL){
return true;
}
else{
return false;
}
}
}

Thanks to Neevek his answer worked for me but it doesn't lock the vertical scrolling when user has started scrolling the horizontal view(ViewPager) in horizontal direction and then without lifting the finger scroll vertically it starts to scroll the underlying container view(ScrollView). I fixed it by making a slight change in Neevak's code:
private float xDistance, yDistance, lastX, lastY;
int lastEvent=-1;
boolean isLastEventIntercepted=false;
#Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
xDistance = yDistance = 0f;
lastX = ev.getX();
lastY = ev.getY();
break;
case MotionEvent.ACTION_MOVE:
final float curX = ev.getX();
final float curY = ev.getY();
xDistance += Math.abs(curX - lastX);
yDistance += Math.abs(curY - lastY);
lastX = curX;
lastY = curY;
if(isLastEventIntercepted && lastEvent== MotionEvent.ACTION_MOVE){
return false;
}
if(xDistance > yDistance )
{
isLastEventIntercepted=true;
lastEvent = MotionEvent.ACTION_MOVE;
return false;
}
}
lastEvent=ev.getAction();
isLastEventIntercepted=false;
return super.onInterceptTouchEvent(ev);
}

This finally became a part of support v4 library, NestedScrollView. So, no longer local hacks is needed for most of cases I'd guess.

Neevek's solution works better than Joel's on devices running 3.2 and above. There is a bug in Android that will cause java.lang.IllegalArgumentException: pointerIndex out of range if a gesture detector is used inside a scollview. To duplicate the issue, implement a custom scollview as Joel suggested and put a view pager inside. If you drag (don't lift you figure) to one direction (left/right) and then to the opposite, you will see the crash. Also in Joel's solution, if you drag the view pager by moving your finger diagonally, once your finger leave the view pager's content view area, the pager will spring back to its previous position. All these issues are more to do with Android's internal design or lack of it than Joel's implementation, which itself is a piece of smart and concise code.
http://code.google.com/p/android/issues/detail?id=18990

Date : 2021 - May 12
Looks jibberish..but trust me its worth the time if you wanna scroll any view horizontally in a vertical scrollview butter smooth!!
Works in jetpack compose as well by by making a custom view and extending the view that you wanna scroll horizontally in; inside a vertical scroll view and using that custom view inside AndroidView composable (Right now, "Jetpack Compose is in 1.0.0-beta06"
This is the most optimal solution if you wanna scroll horizontally freely and vertically freely without the vertical scrollbar intercepting ur touch when u are scrolling horizontally and only allowing the vertical scrollbar to intercept the touch when u are scrolling vertically through the horizontal scrolling view :
private class HorizontallyScrollingView #JvmOverloads constructor(
context: Context, attrs: AttributeSet? = null
) : ViewThatYouWannaScrollHorizontally(context, attrs){
override fun onTouchEvent(event: MotionEvent?): Boolean {
// When the user's finger touches the webview and starts moving
if(event?.action == MotionEvent.ACTION_MOVE){
// get the velocity tracker object
val mVelocityTracker = VelocityTracker.obtain();
// connect the velocity tracker object with the event that we are emitting while we are touching the webview
mVelocityTracker.addMovement(event)
// compute the velocity in terms of pixels per 1000 millisecond(i.e 1 second)
mVelocityTracker.computeCurrentVelocity(1000);
// compute the Absolute Velocity in X axis
val xVelocityABS = abs(mVelocityTracker.getXVelocity(event?.getPointerId((event?.actionIndex))));
// compute the Absolute Velocity in Y axis
val yVelocityABS = abs(mVelocityTracker.getYVelocity(event?.getPointerId((event?.actionIndex))));
// If the velocity of x axis is greater than y axis then we'll consider that it's a horizontal scroll and tell the parent layout
// "Hey parent bro! im scrolling horizontally, this has nothing to do with ur scrollview so stop capturing my event and stay the f*** where u are "
if(xVelocityABS > yVelocityABS){
// So, we'll disallow the parent to listen to any touch events until i have moved my fingers off the screen
parent.requestDisallowInterceptTouchEvent(true)
}
} else if (event?.action == MotionEvent.ACTION_CANCEL || event?.action == MotionEvent.ACTION_UP){
// If the touch event has been cancelled or the finger is off the screen then reset it (i.e let the parent capture the touch events on webview as well)
parent.requestDisallowInterceptTouchEvent(false)
}
return super.onTouchEvent(event)
}
}
Here, ViewThatYouWannaScrollHorizontally is the view that you want to scroll horizontally in and when u are scrolling horizontally, you dont want the vertical scrollbar to capture the touch and think that "oh! the user is scrolling vertically so parent.requestDisallowInterceptTouchEvent(true) will basically say the vertical scroll bar "hey you! dont capture any touch coz the user is scrolling horizontally"
And after the user is done scrolling horizontally and tries to scroll vertically through the horizontal scrollbar which is placed inside a vertical scrollbar then it will see that the touch velocity in Y axis is greater than X axis, which shows user is not scrolling horizontally and the horizontal scrolling stuff will say "Hey you! parent, you hear me?..the user is scrolling vertically through me, now u can intercept the touch and show the stuffs present below me in the vertical scroll"