Differentiating between user scroll and programatic page change in ViewPager

Question

I have a android.support.v4.view.ViewPager in my application and I would like to differentiate between a programmatically-initiated smooth scroll and a user-initiat

Answer 1

You are right about using ViewPager.OnPageChangeListener:

@Override
public void onPageSelected(int arg0) {
    // programmatically-initiated                           
}

@Override
public void onPageScrolled(int arg0, float arg1, int arg2) {

}

@Override
public void onPageScrollStateChanged(int arg0) {
    // user-initiated touch scroll      
}

Alternatively, you can use boolean flags to differentiate between programmatically-initiated smooth scroll and a user-initiated touch scroll. For example, if you use setCurrentItem(int item) to programmatically change the page, try:

boolean progChange = false;

....
....
....

progChange = true;
setCurrentItem(somePageId);     // Set progChange = true every time

....
....
....

Inside your ViewPager.OnPageChangeListener:

@Override
public void onPageSelected(int arg0) {

}

@Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
    if (progChange) {
        // programmatically-initiated
    } else {
        // user-initiated touch scroll
    }

    // Set progChange to false;
    progChange = false;                 
}

@Override
public void onPageScrollStateChanged(int arg0) {

}