Change ViewPager animation duration when sliding programmatically
I'm changing slide with the following code:
viewPager.setCurrentItem(index++, true);
But it changes too fast. Is there a way to set manually the animation speed?
I've wanted to do myself and have achieved a solution (using reflection, however). I haven't tested it yet but it should work or need minimal modification. Tested on Galaxy Nexus JB 4.2.1. You need to use a ViewPagerCustomDuration in your XML instead of ViewPager, and then you can do this:
ViewPagerCustomDuration vp = (ViewPagerCustomDuration) findViewById(R.id.myPager);
vp.setScrollDurationFactor(2); // make the animation twice as slow
ViewPagerCustomDuration.java:
import android.content.Context;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.view.animation.Interpolator;
import java.lang.reflect.Field;
public class ViewPagerCustomDuration extends ViewPager {
public ViewPagerCustomDuration(Context context) {
super(context);
postInitViewPager();
}
public ViewPagerCustomDuration(Context context, AttributeSet attrs) {
super(context, attrs);
postInitViewPager();
}
private ScrollerCustomDuration mScroller = null;
/**
* Override the Scroller instance with our own class so we can change the
* duration
*/
private void postInitViewPager() {
try {
Field scroller = ViewPager.class.getDeclaredField("mScroller");
scroller.setAccessible(true);
Field interpolator = ViewPager.class.getDeclaredField("sInterpolator");
interpolator.setAccessible(true);
mScroller = new ScrollerCustomDuration(getContext(),
(Interpolator) interpolator.get(null));
scroller.set(this, mScroller);
} catch (Exception e) {
}
}
/**
* Set the factor by which the duration will change
*/
public void setScrollDurationFactor(double scrollFactor) {
mScroller.setScrollDurationFactor(scrollFactor);
}
}
ScrollerCustomDuration.java:
import android.annotation.SuppressLint;
import android.content.Context;
import android.view.animation.Interpolator;
import android.widget.Scroller;
public class ScrollerCustomDuration extends Scroller {
private double mScrollFactor = 1;
public ScrollerCustomDuration(Context context) {
super(context);
}
public ScrollerCustomDuration(Context context, Interpolator interpolator) {
super(context, interpolator);
}
@SuppressLint("NewApi")
public ScrollerCustomDuration(Context context, Interpolator interpolator, boolean flywheel) {
super(context, interpolator, flywheel);
}
/**
* Set the factor by which the duration will change
*/
public void setScrollDurationFactor(double scrollFactor) {
mScrollFactor = scrollFactor;
}
@Override
public void startScroll(int startX, int startY, int dx, int dy, int duration) {
super.startScroll(startX, startY, dx, dy, (int) (duration * mScrollFactor));
}
}
Hope this helps someone!
I have found better solution, based on @df778899's answer and the Android ValueAnimator API. It works fine without reflection and is very flexible. Also there is no need for making custom ViewPager and putting it into android.support.v4.view package. Here is an example:
private void animatePagerTransition(final boolean forward) {
ValueAnimator animator = ValueAnimator.ofInt(0, viewPager.getWidth());
animator.addListener(new Animator.AnimatorListener() {
@Override
public void onAnimationStart(Animator animation) {
}
@Override
public void onAnimationEnd(Animator animation) {
viewPager.endFakeDrag();
}
@Override
public void onAnimationCancel(Animator animation) {
viewPager.endFakeDrag();
}
@Override
public void onAnimationRepeat(Animator animation) {
}
});
animator.setInterpolator(new AccelerateInterpolator());
animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
private int oldDragPosition = 0;
@Override
public void onAnimationUpdate(ValueAnimator animation) {
int dragPosition = (Integer) animation.getAnimatedValue();
int dragOffset = dragPosition - oldDragPosition;
oldDragPosition = dragPosition;
viewPager.fakeDragBy(dragOffset * (forward ? -1 : 1));
}
});
animator.setDuration(AppConstants.PAGER_TRANSITION_DURATION_MS);
if (viewPager.beginFakeDrag()) {
animator.start();
}
}
UPDATE:
Just checked if this solution can be used to swipe several pages at once (for example if first page should be showed after the last one). This is slightly modified code to handle specified page count:
private int oldDragPosition = 0;
private void animatePagerTransition(final boolean forward, int pageCount) {
// if previous animation have not finished we can get exception
if (pagerAnimation != null) {
pagerAnimation.cancel();
}
pagerAnimation = getPagerTransitionAnimation(forward, pageCount);
if (viewPager.beginFakeDrag()) { // checking that started drag correctly
pagerAnimation.start();
}
}
private Animator getPagerTransitionAnimation(final boolean forward, int pageCount) {
ValueAnimator animator = ValueAnimator.ofInt(0, viewPager.getWidth() - 1);
animator.addListener(new Animator.AnimatorListener() {
@Override
public void onAnimationStart(Animator animation) {
}
@Override
public void onAnimationEnd(Animator animation) {
viewPager.endFakeDrag();
}
@Override
public void onAnimationCancel(Animator animation) {
viewPager.endFakeDrag();
}
@Override
public void onAnimationRepeat(Animator animation) {
viewPager.endFakeDrag();
oldDragPosition = 0;
viewPager.beginFakeDrag();
}
});
animator.setInterpolator(new AccelerateInterpolator());
animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
int dragPosition = (Integer) animation.getAnimatedValue();
int dragOffset = dragPosition - oldDragPosition;
oldDragPosition = dragPosition;
viewPager.fakeDragBy(dragOffset * (forward ? -1 : 1));
}
});
animator.setDuration(AppConstants.PAGER_TRANSITION_DURATION_MS / pageCount); // remove divider if you want to make each transition have the same speed as single page transition
animator.setRepeatCount(pageCount);
return animator;
}
public class PresentationViewPager extends ViewPager {
public static final int DEFAULT_SCROLL_DURATION = 250;
public static final int PRESENTATION_MODE_SCROLL_DURATION = 1000;
public PresentationViewPager (Context context) {
super(context);
}
public PresentationViewPager (Context context, AttributeSet attrs) {
super(context, attrs);
}
public void setDurationScroll(int millis) {
try {
Class<?> viewpager = ViewPager.class;
Field scroller = viewpager.getDeclaredField("mScroller");
scroller.setAccessible(true);
scroller.set(this, new OwnScroller(getContext(), millis));
} catch (Exception e) {
e.printStackTrace();
}
}
public class OwnScroller extends Scroller {
private int durationScrollMillis = 1;
public OwnScroller(Context context, int durationScroll) {
super(context, new DecelerateInterpolator());
this.durationScrollMillis = durationScroll;
}
@Override
public void startScroll(int startX, int startY, int dx, int dy, int duration) {
super.startScroll(startX, startY, dx, dy, durationScrollMillis);
}
}
}
Better solution is to simply access the private fields by creating the class in the support package. EDIT This is bound to the MAX_SETTLE_DURATION of 600ms, set by the ViewPagerclass.
package android.support.v4.view;
import android.content.Context;
import android.util.AttributeSet;
public class SlowViewPager extends ViewPager {
// The speed of the scroll used by setCurrentItem()
private static final int VELOCITY = 200;
public SlowViewPager(Context context) {
super(context);
}
public SlowViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
void setCurrentItemInternal(int item, boolean smoothScroll, boolean always) {
setCurrentItemInternal(item, smoothScroll, always, VELOCITY);
}
}
You can, of course, then add a custom attribute so this can be set via XML.