I am investigating Android ViewPager animation in my current project.
I would like to give my users an affordance in relation to my ViewPager.
The effect I am looking for it to "shake" the ViewPager from left to right to partially show the neighbouring pages to the selected page.
When the user selects the first page (F), I would "Shake" between F and F + 1.
When the user selects the last page (L), I would "Shake" between L and L - 1.
Otherwise, when the user selects any other page (X), I would "Shake" between X - 1, X and X + 1.
I have tried the following approaches which have all given unsatisfactory results.
Fake drag using screen density to calculate shake distance and valueAnimator and ObjectAnimator.
Animating ViewPager.PageTransformer.
I am unable to get a satisfactory "Shake" effect.
I would like to achieve a Spring Dampening style of animation.
The FakeDrag was closest, although the effect was not reliable, it seemed to never work correctly the first time I started the animation.
Even the FakeDrag would not give the desired smooth shake between page swipes.
I would like to employ the physics-based animations on my view pager but couldn't see how.
Is it possible to achieve my desired animation?
UPDATE
I have developed this code which gives the desired effect, however its JANKY!
@Override
protected void onResume() {
super.onResume();
final Handler handler = new Handler();
handler.postDelayed(() -> animateViewPager(ANIMATION_OFFSET, ANIMATION_DURATION), ANIMATION_DELAY);
}
/**
* @param offset
* @param duration
*/
private void animateViewPager(final int offset, final int duration) {
if (animator.isRunning()) {
return;
}
animator.removeAllUpdateListeners();
animator.removeAllListeners();
animator.setIntValues(0, -offset);
animator.setDuration(duration);
animator.setRepeatCount(getRepeatCount());
animator.setRepeatMode(ValueAnimator.RESTART);
animator.addUpdateListener(constructUpdateListener());
animator.addListener(constructAnimatorListener());
animator.start();
}
/**
*
* @return
*/
private Animator.AnimatorListener constructAnimatorListener() {
return new AnimatorListenerAdapter() {
@Override
public void onAnimationStart(final Animator animation) {
animFactor = 1;
}
@Override
public void onAnimationEnd(final Animator animation) {
viewPager.endFakeDrag();
if (xAnimation == null) {
xAnimation = createSpringAnimation(viewPager, SpringAnimation.X, 0, SpringForce.STIFFNESS_LOW, SpringForce.DAMPING_RATIO_HIGH_BOUNCY);
} else {
xAnimation.cancel();
}
viewPager.animate().x(viewPager.getWidth() * 0.1f).setDuration(0).start();
xAnimation.start();
}
@Override
public void onAnimationRepeat(final Animator animation) {
animFactor = -1;
}
};
}
/**
* @return
*/
private int getRepeatCount() {
if (isOnlyPage()) {
return 0;
}
if (isFirstListItem()) {
return REPEAT_ONCE;
}
if (isLastListItem()) {
return REPEAT_ONCE;
}
return REPEAT_TWICE;
}
@SuppressWarnings("StatementWithEmptyBody")
private ValueAnimator.AnimatorUpdateListener constructUpdateListener() {
return animation -> {
final Integer value = animFactor * (Integer) animation.getAnimatedValue();
if (viewPager.isFakeDragging()) {
} else {
viewPager.beginFakeDrag();
}
viewPager.fakeDragBy(value);
};
}
/**
* @param view
* @param property
* @param finalPosition
* @param stiffness
* @param dampingRatio
* @return
*/
private SpringAnimation createSpringAnimation(final View view, final DynamicAnimation.ViewProperty property, final float finalPosition, final float stiffness, final float dampingRatio) {
final SpringAnimation animation = new SpringAnimation(view, property);
final SpringForce springForce = new SpringForce(finalPosition);
springForce.setStiffness(stiffness);
springForce.setDampingRatio(dampingRatio);
animation.setSpring(springForce);
return animation;
}
from How to achieve Buttery Smooth ViewPager Shake animation
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