How to know viewpager is scroll left or right?

Question

I am using ViewPager (support library). I want to know every time the ViewPager change the visible page, it is scrolling left or right.

Please give me a solution. Any recommend is welcome also.

Thanks

Answer 1

set setOnPageChangeListener to your ViewPager

keep a variable global as

private int lastPosition = 0; 

and in

@Override public void onPageSelected(int arg0) {     if (lastPosition > position) {          System.out.println("Left");       }else if (lastPosition < position) {          System.out.println("Right");       }       lastPosition = position; } 

Answer 2

It's not a perfect solution but here's a way to check the swipe direction when you start swiping:

new ViewPager.OnPageChangeListener() {              private static final float thresholdOffset = 0.5f;             private boolean scrollStarted, checkDirection;              @Override             public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {                 if (checkDirection) {                     if (thresholdOffset > positionOffset) {                         Log.i(C.TAG, "going left");                     } else {                         Log.i(C.TAG, "going right");                     }                     checkDirection = false;                 }             }              @Override             public void onPageSelected(int position) {}              @Override             public void onPageScrollStateChanged(int state) {                 if (!scrollStarted && state == ViewPager.SCROLL_STATE_DRAGGING) {                     scrollStarted = true;                     checkDirection = true;                 } else {                     scrollStarted = false;                 }             }         }); 

EDIT: there's a more elegant approach that involves using a ViewPager.PageTransformer and checking it's position intervals:

... myViewPager.setPageTransformer(true, new PageTransformer()); ...  public class PageTransformer implements ViewPager.PageTransformer {     public void transformPage(View view, float position) {          if (position < -1) {              // [-00,-1): the page is way off-screen to the left.         } else if (position <= 1) {              // [-1,1]: the page is "centered"         } else {              // (1,+00]: the page is way off-screen to the right.                    }     } } 

You can learn more from: Using ViewPager for Screen Slides