public class TextViewAnimator {

    private TextValueAnimator textValueAnimator;

    public static TextViewAnimator perLetter(TextView textView){

        int steps = textView.getText().length();
        TextViewAnimator textViewAnimator =
                new TextViewAnimator(textView,
                                     new TextEvaluatorPerLetter(),
                                     new TextInterpolator(steps));
        return textViewAnimator;
    }

    public static TextViewAnimator perWord(TextView textView){

        int steps = textView.getText().toString().split(" ").length;

        TextViewAnimator textViewAnimator =
                new TextViewAnimator(textView,
                                     new TextEvaluatorPerWord(),
                                     new TextInterpolator(steps));
        return textViewAnimator;
    }

    public TextViewAnimator(TextView textView,
                            TypeEvaluator typeEvaluator,
                            TextInterpolator textInterpolator){

        this.textValueAnimator = new TextValueAnimator(textView, textView.getText().toString());
        textValueAnimator.setEvaluator(typeEvaluator);
        textValueAnimator.setInterpolator(textInterpolator);
    }

    private static class TextValueAnimator extends ValueAnimator implements ValueAnimator.AnimatorUpdateListener {

        private WeakReference<TextView> weakTextView;

        public TextValueAnimator(TextView textView, String text) {

            weakTextView = new WeakReference<>(textView);
            setObjectValues(text);
            addUpdateListener(this);
        }

        @Override
        public void onAnimationUpdate(ValueAnimator animation) {
            String text = (String) animation.getAnimatedValue();
            TextView textView = weakTextView.get();
            if(textView != null) {
                textView.setText(text);
            }
        }
    }

    private static class TextEvaluatorPerLetter implements TypeEvaluator {

        @Override
        public Object evaluate(float fraction, Object startValue, Object endValue) {
            int step = (int) fraction;
            return ((String) endValue).substring(0, step);
        }
    }

    private static class TextEvaluatorPerWord implements TypeEvaluator {

        private String[] words;
        @Override
        public Object evaluate(float fraction, Object startValue, Object endValue) {

            int step = (int) fraction;
            if(words == null){
                words = ((String) endValue).split(" ");
            }
            String textAtStep = "";
            for (int i = 1; i <= step; i++) {
                textAtStep += words[i-1] + " ";
            }

            return textAtStep;
        }
    }

    private static class TextInterpolator implements TimeInterpolator {

        private int steps;
        public TextInterpolator(int steps) {

            this.steps = steps;
        }
        @Override
        public float getInterpolation(float input) {
            return input * steps;
        }
    }

    public void start(){
        textValueAnimator.start();
    }
    public void cancel(){
        textValueAnimator.cancel();
    }
    public void end(){
        textValueAnimator.end();
    }

    @RequiresApi(19)
    public void pause(){
        textValueAnimator.pause();
    }
    @RequiresApi(19)
    public void resume(){
        textValueAnimator.resume();
    }
    @RequiresApi(19)
    public boolean isStarted(){
        return textValueAnimator.isStarted();
    }
    @RequiresApi(19)
    public float getAnimatedFraction(){
        return textValueAnimator.getAnimatedFraction();
    }
    public void setRepeatCount(int value){
        textValueAnimator.setRepeatCount(value);
    }
    public void setRepeatMode(int repeatMode){
        textValueAnimator.setRepeatMode(repeatMode);
    }
    public void setDuration(long duration){
        textValueAnimator.setDuration(duration);
    }
    public void setStartDelay(long startDelay){
        textValueAnimator.setStartDelay(startDelay);
    }
    public void addUpdateListener(ValueAnimator.AnimatorUpdateListener listener){
        textValueAnimator.addUpdateListener(listener);
    }
    public void removeUpdateListener(ValueAnimator.AnimatorUpdateListener listener){
        textValueAnimator.removeUpdateListener(listener);
    }
    public boolean isRunning(){
        return textValueAnimator.isRunning();
    }
}

public class MainActivity extends AppCompatActivity {

    TextView textView;
    Button button;
    TextViewAnimator textViewAnimator;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        textView = (TextView) findViewById(R.id.text1);

        textViewAnimator = TextViewAnimator.perLetter(textView);
        textViewAnimator.setDuration(5000);
        textViewAnimator.setRepeatCount(2);
        textViewAnimator.setRepeatMode(ValueAnimator.REVERSE);

        button = (Button)findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                textViewAnimator.start();
            }
        });
    }
}

public class Typewriter extends TextView {

    private CharSequence mText;
    private int mIndex;
    private long mDelay = 500; //Default 500ms delay


    public Typewriter(Context context) {
        super(context);
    }

    public Typewriter(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    private Handler mHandler = new Handler();
    private Runnable characterAdder = new Runnable() {
        @Override
        public void run() {
            setText(mText.subSequence(0, mIndex++));
            if(mIndex <= mText.length()) {
                mHandler.postDelayed(characterAdder, mDelay);
            }
        }
    };

    public void animateText(CharSequence text) {
        mText = text;
        mIndex = 0;

        setText("");
        mHandler.removeCallbacks(characterAdder);
        mHandler.postDelayed(characterAdder, mDelay);
    }

    public void setCharacterDelay(long millis) {
        mDelay = millis;
    }
}

<genesysgeneration.pokemaos.Typewriter
        android:id="@+id/meuTxt"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

Typewriter t = (Typewriter) findViewById(R.id.meuTxt);
t.setCharacterDelay(100);
t.animateText("Olha só que legal");

TextAnimatedView textAnimatedView = (TextAnimatedView) findViewById(R.id.tv);
textAnimatedView.setCharacterDelay(150);
textAnimatedView.animPerWord("Desta forma vai funcionar como esperado");

<seu.pacote.TextAnimatedView
    android:id="@+id/tv"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"/>

public class TextAnimatedView extends TextView {

    private Handler handler = new Handler();
    private StringBuilder stringBuilder = new StringBuilder();
    private CharSequence text;
    private String[] arr;
    private int i;
    private long delay = 450;

    public TextAnimatedView(Context context) {
        super(context);
    }

    public TextAnimatedView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    private Runnable runnable = new Runnable() {
        @Override
        public void run() {
            setText(text.subSequence(0, i++));
            if (i <= text.length()) {
                handler.postDelayed(runnable, delay);
            }
        }
    };

    public void animPerLetter(CharSequence text) {
        this.text = text;
        i = 0;

        setText("");
        handler.removeCallbacks(runnable);
        handler.postDelayed(runnable, delay);
    }

    private Runnable runnablePerWord = new Runnable() {
        @Override
        public void run() {

            stringBuilder.append(arr[i++]).append(" ");
            setText(stringBuilder.toString());
            if (i < arr.length) {
                handler.postDelayed(runnablePerWord, delay);
            }
        }
    };

    public void animPerWord(CharSequence text) {
        this.text = text;
        i = 0;

        setText("");
        arr = text.toString().split(" ");
        handler.removeCallbacks(runnablePerWord);
        handler.postDelayed(runnablePerWord, delay);
    }

    public void setCharacterDelay(long delay) {
        this.delay = delay;
    }
}