Expanding animation.

expandable_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@color/white"
    android:orientation="vertical"
    android:paddingBottom="@dimen/_6">

    <LinearLayout
        android:id="@+id/titleLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/blue_text_color"
        android:clickable="true"
        android:orientation="horizontal">

        <TextView
            android:id="@+id/header_text"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:padding="@dimen/_30"
            android:paddingLeft="@dimen/_61"
            android:paddingTop="@dimen/_30"
            android:textColor="@color/white"
            android:textSize="@dimen/f30"
           />

        <ImageView
            android:id="@+id/arrow"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:paddingLeft="@dimen/_50"
            android:paddingRight="@dimen/_50"
            android:src="@drawable/arrow_white" />
    </LinearLayout>

    <LinearLayout
        android:id="@+id/contentLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:padding="@dimen/_20"
        android:visibility="gone">

    </LinearLayout>

</LinearLayout>

ExpandableLayout.java

import android.content.Context;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewTreeObserver;
import android.view.animation.Animation;
import android.view.animation.AnimationSet;
import android.view.animation.Transformation;
import android.widget.FrameLayout;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;



import butterknife.Bind;
import butterknife.ButterKnife;
import butterknife.OnClick;

/**
 * Created by Kushtrim on 9/3/2015.
 */
public class ExpandableLayout extends FrameLayout {
    public static final int ANIMATION_TIME = 500;
    private final String headerTitle;
    private int targetHeight;

    @Bind(R.id.header_text)
    TextView headerTV;

    @Bind(R.id.arrow)
    ImageView arrow;

    @Bind(R.id.contentLayout)
    LinearLayout contentLayout;


    boolean folded;


    public ExpandableLayout(Context context, final String headerTitle, boolean folded, View... rows) {
        super(context);
        LayoutInflater inflater = LayoutInflater.from(getContext());
        LinearLayout expandableLayout = (LinearLayout) inflater.inflate(R.layout.expandable_layout, this, false);

        addView(expandableLayout, new FrameLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT));
        this.headerTitle = headerTitle;
        ButterKnife.bind(this);
        headerTV.setText(headerTitle);
        for (View row : rows) {
            contentLayout.addView(row);
        }
        contentLayout.setPivotY(0);
        this.folded = folded;

        //get the width
        contentLayout.setVisibility(VISIBLE);
        contentLayout.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {

            @Override
            public void onGlobalLayout() {
                // Ensure you call it only once :
                Utils.removeOnGlobalLayoutListener(contentLayout, this);
                targetHeight = contentLayout.getHeight();
                if (ExpandableLayout.this.folded) {
                    //contentLayout.setScaleY(0f);
                    contentLayout.setVisibility(GONE);
                } else {
                    // contentLayout.setScaleY(1f);
                    contentLayout.setVisibility(VISIBLE);
                }

            }
        });
    }

    @OnClick(R.id.titleLayout)
    public void expandableLayoutClicked() {
        if (folded) {
            arrow.animate().rotation(90).setDuration(ANIMATION_TIME).start();
            expand(contentLayout);
            folded = !folded;

        } else {
            arrow.animate().rotation(0).setDuration(ANIMATION_TIME).start();
            collapse(contentLayout);
            folded = !folded;
        }
    }

    public void expand(final View v) {

        if (v.getLayoutParams().height<=0)
        v.getLayoutParams().height = 1;

        v.setVisibility(View.VISIBLE);

        AnimationSet set = new AnimationSet(false);
        final int startHeight = v.getLayoutParams().height;
        Log.d("startHeight",startHeight+"");
        Animation a = new Animation() {
            @Override
            protected void applyTransformation(float interpolatedTime, Transformation t) {
                v.getLayoutParams().height = (int) ((targetHeight -startHeight) * interpolatedTime + startHeight);
                v.requestLayout();
            }

            @Override
            public boolean willChangeBounds() {
                return true;
            }
        };

        set.addAnimation(a);
        set.setDuration(500);
        v.startAnimation(set);
    }


    public void collapse(final View v) {

        final int startHeight = v.getLayoutParams().height;

        AnimationSet set = new AnimationSet(false);
        Animation a = new Animation() {
            @Override
            protected void applyTransformation(float interpolatedTime, Transformation t) {
                if (interpolatedTime == 1) {
                    v.setVisibility(View.GONE);
                } else {
                    v.getLayoutParams().height = startHeight - (int) (startHeight * interpolatedTime);
                    v.requestLayout();
                }
            }

            @Override
            public boolean willChangeBounds() {
                return true;
            }
        };

        set.addAnimation(a);
        set.setDuration(500);
        v.startAnimation(set);

    }


}

Utils.java

public class Utils {
  
  // ... a bunch of other stuff :P

   @TargetApi(Build.VERSION_CODES.JELLY_BEAN)
    public static void removeOnGlobalLayoutListener(View v, ViewTreeObserver.OnGlobalLayoutListener listener) {
        if (Build.VERSION.SDK_INT < 16) {
            v.getViewTreeObserver().removeGlobalOnLayoutListener(listener);
        } else {
            v.getViewTreeObserver().removeOnGlobalLayoutListener(listener);
        }
    }
    
}