Expand-Collapse animation

ExpandCollapseAnimationHelper.java

public class ExpandCollapseAnimationHelper {

    private final static int DURATION = 300;

    ValueAnimator valueAnimator;

    ViewGroup contentLayout;

    public ExpandCollapseAnimationHelper(ViewGroup contentLayout) {
        this.contentLayout = contentLayout;

        init();
    }

    private void init() {
        contentLayout.getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
            @Override
            public boolean onPreDraw() {
				
                contentLayout.getViewTreeObserver().removeOnPreDrawListener(this);
                contentLayout.setVisibility(View.GONE);
                
		final int widthSpec = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
		final int heightSpec = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
		contentLayout.measure(widthSpec, heightSpec);

                valueAnimator = slideAnimator(0, contentLayout.getHeight());
                return true;
            }
        });
    }

    public void collapse() {

        ValueAnimator mAnimator = slideAnimator(contentLayout.getHeight(), 0);

        mAnimator.addListener(new Animator.AnimatorListener() {
            @Override
            public void onAnimationStart(Animator animation) {
            }

            @Override
            public void onAnimationEnd(Animator animation) {
                contentLayout.setVisibility(View.GONE);
            }

            @Override
            public void onAnimationCancel(Animator animation) {
            }

            @Override
            public void onAnimationRepeat(Animator animation) {
            }
        });

        mAnimator.start();
    }

    public void expand() {
        contentLayout.setVisibility(View.VISIBLE);
        valueAnimator.start();
    }
    
    public void toggle() {
	if (contentLayout.isShown()) {
	    collapse();
	} else {
	    expand();
	}
    }

    private ValueAnimator slideAnimator(int start, int end) {

        ValueAnimator animator = ValueAnimator.ofInt(start, end);
        animator.setDuration(DURATION);

        animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator valueAnimator) {
                int value = (Integer) valueAnimator.getAnimatedValue();

                ViewGroup.LayoutParams layoutParams = contentLayout.getLayoutParams();
                layoutParams.height = value;

                contentLayout.setLayoutParams(layoutParams);
                contentLayout.invalidate();
            }
        });

        return animator;
    }
}

How to use?

LinearLayout contentLayout; // ViewGroup that contains all your child views that should be hidden/shown
ExpandCollapseAnimationHelper mExpandCollapseAnimationHelper;

mExpandCollapseAnimationHelper = new ExpandCollapseAnimationHelper(contentLayout);

// toggle visibility
mExpandCollapseAnimationHelper.toggle();

layout_example.xml

<LinearLayout
        android:id="@+id/contentLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:visibility="gone"
        android:background="@color/accent">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="New Text"
            android:id="@+id/textView"

            android:layout_margin="20dp"/>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceLarge"
            android:text="Large Text"
            android:id="@+id/textView2"
            android:layout_margin="20dp"/>

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/imageView2"
            android:src="@mipmap/ic_launcher"
            android:layout_margin="20dp"/>
    </LinearLayout>