Android Animations: Expand & Collapse

In reference to my previous post here, this post is regarding some other styles of animation that you can use in your app to make it look more subtle.
As you know Animations in android can add subtle visual cues that notify users about what's going on in your app and improve their mental model of your app's interface. Animations are especially useful when the screen changes state, such as when content loads or new actions become available. Animations can also add a polished look to your app, which gives your app a higher quality feel.

So lets get started now: This tutorial shows you simple way to add Expand & Collapse style animation in your app in just a few steps.
The Expand animation is somewhat like unfolding a view step by step or you can say opening a view from 0 to 100 slowly.
So to add the expand animation in your app just add the following method in your code:

public static void expandAnimation(final View v) {
        v.measure(WindowManager.LayoutParams.MATCH_PARENT, WindowManager.LayoutParams.WRAP_CONTENT);
        final int targetHeight = v.getMeasuredHeight();
        // Older versions of android (pre API 21) cancel animations for views with a height of 0.
        v.getLayoutParams().height = 1;
        v.setVisibility(View.VISIBLE);
        Animation a = new Animation() {
            @Override
            protected void applyTransformation(float interpolatedTime, Transformation t) {
                v.getLayoutParams().height = interpolatedTime == 1
                        ? WindowManager.LayoutParams.WRAP_CONTENT
                        : (int) (targetHeight * interpolatedTime);
                v.requestLayout();
            }
            @Override
            public boolean willChangeBounds() {
                return true;
            }
        };
        // 1dp/ms
        a.setDuration(300);
        v.startAnimation(a);
    }
          

Now to set this animation on any view, just call this method and pass that view which you want to expand, as the parameter to this method as follows:

                    expandAnimation(findViewById(R.id.myview));       

Now after expanding the view you also need to close it or you can say you'll need to collapse it.
Don't worry, closing it is also as simple as expanding it.
Just add the following method in your code to collapse your view.    

public static void collapseAnimation(final View v) {
        final int initialHeight = v.getMeasuredHeight();
        Animation a = new Animation() {
            @Override
            protected void applyTransformation(float interpolatedTime, Transformation t) {
                if (interpolatedTime == 1) {
                    v.setVisibility(View.GONE);
                } else {
                    v.getLayoutParams().height = initialHeight - (int) (initialHeight * interpolatedTime);
                    v.requestLayout();
                }
            }
            @Override
            public boolean willChangeBounds() {
                return true;
            }
        };
        // 1dp/ms
        a.setDuration(300);
        v.startAnimation(a);
    }
        

Now to set this collapse animation on any view, just call this method as you called the method to expand it and pass that view which you want to collapse, as the parameter to this method as follows:

                       collapseAnimation(findViewById(R.id.myview));    

That's all. Use it and have fun.

Comment if any issues and share.