Animate layout change of bottom sheet

user_2047987 0
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In my application I use a bottom sheet (from the support library) which works great. Now I would like to animate a layout change while the sheet is dragged up. For this I have created a subclass of BottomSheetCallback (this is normaly an inner class of a Fragment so not all objects used in this calss are initialized here):

public class MyBehavior extends BottomSheetBehavior.BottomSheetCallback {

    Transition transition;
    float lastOffset = 0;
    Scene scene;

    public PlayerBehavior() {
        TransitionInflater inflater = TransitionInflater.from(getContext());
        transition = inflater.inflateTransition(R.transition.player);
        //transition.setDuration(300);

        scene = fullLayout;

        transition.setInterpolator(new Interpolator() {
            @Override
            public float getInterpolation(float v) {
                return lastOffset;
            }
        });
    }

    @Override
    public void onStateChanged(@NonNull View bottomSheet, int newState) {
        if(newState == BottomSheetBehavior.STATE_DRAGGING) {
            TransitionManager.go(scene, transition);
        }
    }

    @Override
    public void onSlide(View bottomSheet, final float slideOffset) {
        scene = (slideOffset > lastOffset) ? smallLayout : fullLayout;
        lastOffset = slideOffset;
    }
}

As you can see I also created two Scene from different layout files and a custom Transition to animate between the scenes with the TransitionManager. My problem is that the Transition should be based on the slideOffset parameter (in range of 0-1) but the TransitionManager uses the Animation class in the background which is normally time based in Android.

I tried to create the custom Intapolator but this does not work properly. So how can I create a Transition which is based on an external variable and not on time?

android-transitions android-animation android
4 Answers
## Translation Animation ##
<?xml version="1.0" encoding="utf-8"?>
<set
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:interpolator="@android:anim/accelerate_decelerate_interpolator"
    android:fillAfter="true"
    >
    <translate
        android:fromYDelta="100%p"
        android:toYDelta="-30%p"
        android:duration="900" />
</set>

## Main Activity ##

@Override
protected void onResume() {
    super.onResume();
    Animation am= AnimationUtils.loadAnimation(this,R.anim.fadeout);
    tv5.startAnimation(am);
    Animation myanim= AnimationUtils.loadAnimation(this,R.anim.translate);
    tv1.startAnimation(myanim);
    myanim.setStartOffset(500);
    Animation animation= AnimationUtils.loadAnimation(this,R.anim.translate);
    animation.setStartOffset(1000);
    tv2.startAnimation(animation);
    Animation an= AnimationUtils.loadAnimation(this,R.anim.translate);
    an.setStartOffset(1500);
    tv3.startAnimation(an);
    Animation ab= AnimationUtils.loadAnimation(this,R.anim.translate);
    ab.setStartOffset(2000);
    tv4.startAnimation(ab);
    Animation ac= AnimationUtils.loadAnimation(this,R.anim.fadein);
    ac.setStartOffset(2500);
    btn1.startAnimation(ac);
}
user_86446360

To easily slide something off the bottom of the screen, you can use code such as:

final int activityHeight = findViewById(android.R.id.content).getHeight();
cardContainer.animate().yBy(activityHeight - cardContainer.getY()).setDuration(SLIDE_OUT_DURATION);

where cardContainer is the view you are trying to slide off the screen.

See this blog post for the complete example. Note that you can also use translationY instead of yBy. Another, more generic way of doing it is with this code:

public static ViewPropertyAnimator slideOutToBottom(Context ctx, View view) {
    final int screenHeight = ctx.getResources().getDisplayMetrics().heightPixels;
    int[] coords = new int[2];
    view.getLocationOnScreen(coords);
    return view.animate().translationY(screenHeight - coords[Y_INDEX]).setDuration(SLIDE_OUT_DURATION);
}

public static ViewPropertyAnimator slideInFromBottom(Context ctx, View view) {
    final int screenHeight = ctx.getResources().getDisplayMetrics().heightPixels;
    int[] coords = new int[2];
    view.getLocationOnScreen(coords);
    view.setTranslationY(screenHeight - coords[Y_INDEX]);
    return view.animate().translationY(0).setDuration(SLIDE_IN_DURATION).setInterpolator(new OvershootInterpolator(1f));
}
user_7294150
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