A TextView and that expand and contract to show more or less content. Using ellipses with the TextView or the TextUtils to calculate where to ellipsize text can return the wrong result as it doesn't cater for new line characters. This code will consistently returns the correct number of lines.

attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="ExpandableTextView">
        <attr name="etw_maxLines" format="integer"/>
    </declare-styleable>
</resources>

ExpandableTextView.java

import android.content.Context;
import android.content.res.TypedArray;
import android.text.TextUtils;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewTreeObserver;
import android.view.ViewTreeObserver.OnGlobalLayoutListener;
import android.widget.FrameLayout;
import android.widget.TextView;

import java.lang.reflect.Field;

public class ExpandableTextView extends FrameLayout {

    private static final String TAG = ExpandableTextView.class.getSimpleName();
    private static final String mEllipsis = "\u2026";
    private static final String MAXIMUM_VAR_NAME = "mMaximum";

    private TextView mTxtDescription;
    /** if this is true, show the imgExpand ImageView even if the text fits in the textview */
    private boolean mAlwaysShowingImgExpand;

    private boolean mIsExpanded;
    private Integer mMaxLine;
    private CharSequence mOriginalText;
    private ViewTreeObserver mViewTreeObserver;
    private OnGlobalLayoutListener mGlobalLayoutListener;

    /**
     * @param context
     */
    public ExpandableTextView(Context context) {
        super(context);
        init(context, null, 0);
    }

    /**
     * @param context
     * @param attrs
     */
    public ExpandableTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context, attrs, 0);
    }

    /**
     * @param context
     * @param attrs
     * @param defStyle
     */
    public ExpandableTextView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init(context, attrs, defStyle);
    }

    /**
     * @return is expanded or not
     */
    public Boolean isExpanded() {
        return mIsExpanded;
    }

    public void collapse() {
        mIsExpanded = false;
        mTxtDescription.setMaxLines(mMaxLine);
        postInvalidate();
        //The actual change is in onMeasure
    }

    public void expand() {
        mIsExpanded = true;
        if (mMaxLine == null) {
            storeMaxLine();
        }

        mTxtDescription.setEllipsize(null);
        mTxtDescription.setMaxLines(Integer.MAX_VALUE);
        mTxtDescription.setText(mOriginalText);
        postInvalidate();
    }

    public void setText(CharSequence text) {
        setText(text, false);
    }

    public void setText(CharSequence text, final boolean alwaysShowImgExpand) {
        mTxtDescription.setText(text);
        mAlwaysShowingImgExpand = alwaysShowImgExpand;
        if (TextUtils.isEmpty(text)) {
            mTxtDescription.setVisibility(View.GONE);
            mOriginalText = "";
        } else {
            mTxtDescription.setMaxLines(mMaxLine);
            mIsExpanded = false;
            mOriginalText = text;
        }
        hideArrow();
        mTxtDescription.setText(mOriginalText);
        mTxtDescription.requestLayout();
        mTxtDescription.setOnClickListener(null);
        //we need onMeasure() to be called
        requestLayout();
        layoutHelper();
    }

    public void setImgOnClickListener() {
        mTxtDescription.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                toggle();
            }
        });
    }

    private void showArrow(boolean expand) {
        mTxtDescription.setCompoundDrawablesWithIntrinsicBounds(0, 0, 0, (expand ? R.drawable.general_arrow_expand : R.drawable.general_arrow_collapse));
    }

    private void hideArrow() {
        mTxtDescription.setCompoundDrawablesWithIntrinsicBounds(0, 0, 0, 0);
    }

    private void init(Context context, AttributeSet attrs, int defStyle) {
        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.ExpandableTextView, defStyle, 0);

        //get the value of "etw_maxLines" attribute if it has been specified
        int maxLines = 2;
        try {
            maxLines = a.getInt(R.styleable.ExpandableTextView_etw_maxLines, maxLines);
        } finally {
            a.recycle();
        }
        LayoutInflater inflater = LayoutInflater.from(context);
        View view = inflater.inflate(R.layout.view_expandable_text, this);
        mTxtDescription = (TextView) view.findViewById(R.id.txt_description);
        mTxtDescription.setMaxLines(maxLines);

        if (mViewTreeObserver == null) {
            mViewTreeObserver = this.mTxtDescription.getViewTreeObserver();
            mViewTreeObserver.addOnGlobalLayoutListener(mGlobalLayoutListener = new OnGlobalLayoutListener() {

                @Override
                public void onGlobalLayout() {
                    layoutHelper();
                }
            });
        }


        expand();
        collapse();
    }

    private void layoutHelper() {
        if (mTxtDescription.getLineCount() > mMaxLine && !isExpanded()) {
            int lineEndIndex = mTxtDescription.getLayout().getLineEnd(mMaxLine - 1);
            String text = mTxtDescription.getText().subSequence(0, lineEndIndex - 3) + mEllipsis;
            mTxtDescription.setText(text);
            showArrow(true);
            setImgOnClickListener();
        }
        if (mTxtDescription.getLineCount() < mMaxLine) {
            hideArrow();
            mTxtDescription.setOnClickListener(null);

        }
    }

    /**
     * Toggle if it is expanded or not
     */
    public final void toggle() {
        if (isExpanded()) {
            showArrow(true);
            collapse();
        } else {
            showArrow(false);
            expand();
        }
    }

    /**
     * Extract private maxLine from super class
     */
    private void storeMaxLine() {
        Field f;
        try {
            f = mTxtDescription.getClass().getDeclaredField(MAXIMUM_VAR_NAME);
            f.setAccessible(true);
            mMaxLine = f.getInt(mTxtDescription);

            f.setAccessible(false);
        } catch (SecurityException e) {
            Log.e(TAG, e.getMessage(), e);
        } catch (NoSuchFieldException e) {
            Log.e(TAG, e.getMessage(), e);
        } catch (IllegalArgumentException e) {
            Log.e(TAG, e.getMessage(), e);
        } catch (IllegalAccessException e) {
            Log.e(TAG, e.getMessage(), e);
        }
    }

    public TextView getTxtDescription() {
        return mTxtDescription;
    }

    @Override
    protected void onDetachedFromWindow() {
        if (mTxtDescription != null) {
            ViewTreeObserver obs = mTxtDescription.getViewTreeObserver();
            if (mGlobalLayoutListener != null) {
                obs.removeGlobalOnLayoutListener(mGlobalLayoutListener);
            }
        }
        super.onDetachedFromWindow();
    }
}

view_expandable_text.xml

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:android="http://schemas.android.com/apk/res/android">

    <TextView
        android:id="@+id/txt_description"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="This is some text to use for testing\n\nIn order for it to be useful\n\nI will need this text to be really long.\n\nHello World!!!"
        android:drawablePadding="8dp"
        android:textSize="14dp"/>

</RelativeLayout>

The code looks convincing, but the example seems to be wrong.
Can you please help @alphamu ?