Using Animation On A Viewpager And Setfillafter

I have a ViewPager which I need to move as a whole on button press. I use an animation for this. When I press it, I translate the 'x' for it. I use setFillAfter(true) to keep the n

Solution 1:

The main problem seems to be incorrect choice of animation type. You see, View Animation as a tool is not intended to be used with complex interactive objects like ViewPager. It offers only low-cost animation of the drawing place of views. The visual behaivior of the animated ViewPager in response to user-actions is undefined and should not be relied on. Ugly flicks, when you substitute a "gost" with the real object are only natural.

The mechanism, that is intended to use in your case since API 11 is specialized property animator built in Views for optimized performance: ViewPropertyAnimator, or not specialized, but more versatile ObjectAnimator and AnimatorSet.

Property animation makes the View to really change its place and function normally there.

To make project, to use, say, ViewPropertyAnimator, change your listener setting to this:

btn.setOnClickListener(newOnClickListener() {
    boolean b = false;
    @OverridepublicvoidonClick(View v) {
        if(b) {
            myViewPager.animate().translationX(0f).setDuration(700);
        }
        else {
            myViewPager.animate().translationX(300f).setDuration(700);
        }
        b=!b;
    }
});

If you want to use xml configuration only, stick to |ObjectAnimator and AnimatorSet. Read through the above link for further information.

In case, you are anxious to support pre-Honeycomb devices, you can use Jake Warton's NineOldAndroids project. Hope that helps.

Solution 2:

That's because the Animation's setFillAfter(true) doesn't actually change the position or any attributes of the View; all it does is create a Bitmap of the view's drawing cache and leaves it where the animation ends. Once the screen is invalidated again (ie. changing the page in the ViewPager), the bitmap will be removed and it will appear as if the View is returning to it's original position, when in fact it was already there.

If you want the View to retain it's position after the animation has finished, you need to actually adjust the View's LayoutParams to match your desired effect. To achieve this, you can override the onAnimationEnd method of the Animation, and adjust the LayoutParams of the View inside there.

Once you adjust the LayoutParams, you can remove your call to setFillAfter(true) and your View will actually stay where you expect it to.

Solution 3:

Regarding the flicker issue:

I have encountered this issue before, and it stems from the possibility of the onAnimationEnd() call not syncing up with the next layout pass. Animation works by applying a transformation to a View, drawing it relative to its current position.

However, it is possible for a View to be rendered after you have moved it in your onAnimationEnd() method. In this case, the Animation's transformation is still being applied correctly, but the Animation thinks the View has not changed its original position, which means it will be drawn relative to its ENDING position instead of its STARTING position.

My solution was to create a custom subclass of Animation and add a method, changeYOffset(int change), which modifies the y translation that is applied during the Animation's applyTransformation method. I call this new method in my View's onLayout() method, and pass the new y-offset.

Here is some of my code from my Animation, MenuAnimation:

/**
* Signal to this animation that a layout pass has caused the View on which this animation is
* running to have its "top" coordinate changed.
*
* @param change
* the difference in pixels
*/publicvoidchangeYOffset(int change) {
    fromY -= change;
    toY -= change;
}

@OverrideprotectedvoidapplyTransformation(float interpolatedTime, Transformation t) {
    floatreverseTime=1f - interpolatedTime;

    floatdy= (interpolatedTime * toY) + (reverseTime * fromY);
    floatalpha= (interpolatedTime * toAlpha) + (reverseTime * fromAlpha);

    if (alpha > 1f) {
        alpha = 1f;
    }
    elseif (alpha < 0f) {
        alpha = 0f;
    }

    t.setAlpha(alpha);
    t.getMatrix().setTranslate(0f, dy);
}

And from the View class:

privateint lastTop;

// ...@OverrideprotectedvoidonLayout(boolean changed, int left, int top, int right, int bottom) {
    // the animation is expecting that its View will not be moved by the container// during its time period. if this does happen, we need to inform it of the change.Animationanim= getAnimation();
    if (anim != null && anim instanceof MenuAnimation) {
        MenuAnimationanimation= (MenuAnimation) anim;
        animation.changeYOffset(top - lastTop);
    }

    // ...

    lastTop = top;

    super.onLayout(changed, left, top, right, bottom);
}

Solution 4:

Crucero has it right about setFillAfter not adjusting params post invalidation. When the view is re-layed out (which'll happen the pass after it's invalidated), its layout params will be the ones that always applied, so it should go back to the original position.

And Jschools is right about onAnimationEnd. Strongly encourage you to step through the source code with a debugger, where you'll instructively discover that an update is made that affects the drawn position of the view after onAnimationEnd is fired, at which point you've actually applied the layout params, hence the flicker caused by doubled up offset.

But this can be solved quite simply by making sure you relayout at the right time. You want to put your re-positioning logic at the end of the ui message queue at the time of animation end so that it is polled after the animation but before laying out. There's nowhere that suggests doing this, annoyingly, but I've yet find a reason in any release of the SDK reason why (when doing this just once and not incorrectly using ui thread) this shouldn't work.

Also clear the animation due to another issue we found on some older devices.

So, try:

@OverridepublicvoidonAnimationEnd(final Animation animation) {
   myViewPager.post(newRunnable() {
       @Overridepublicpublicvoidrun() {
           final RelativeLayout.LayoutParamslp= (android.widget.RelativeLayout.LayoutParams) myViewPager.getLayoutParams();
           if (!someBooleanIPresume)
               lp.setMargins(300,0,0,0);
           else
               lp.setMargins(0,0,0,0);

           myViewPager.setLayoutParams(lp);
           myViewPager.clearAnimation();
       }
}