App keeps crashing

@Override
public void onCreate(Bundle savedInstanceState) {
    final String[] facts= {
            "Ants stretch when they wake up in the morning.",
            "Ostriches can run faster than horses.",
            "Olympic gold medals are actually made mostly of silver.",
            "You are born with 300 bones; by the time you are an adult you will have 206.",
            "It takes about 8 minutes for light from the Sun to reach Earth.",
            "Some bamboo plants can grow almost a meter in just one day.",
            "The state of Florida is bigger than England.",
            "Some penguins can leap 2-3 meters out of the water.",
            "On average, it takes 66 days to form a new habit.",
            "Mammoths still walked the earth when the Great Pyramid was being built." };

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_fun_facts);

    // Declare our View variables and assign the the Views from the layout file
    final TextView factLabel = (TextView) findViewById(R.id.factTextView);
    Button showFactButton = (Button) findViewById(R.id.showFactButton);
    View.OnClickListener listener = new View.OnClickListener() {
        @Override
        public void onClick(View view) {
             // The button was clicked so update the fact label with a new fact
            String fact = "";

            //Randomly select a fact.
            Random randomGenerator = new Random(); //construct a new number generator
            int randomNumber = randomGenerator.nextInt(fact.length());

           fact = facts[randomNumber];

            //Update the label with our dynamic fact.
            factLabel.setText(fact);
        }
    };
    showFactButton.setOnClickListener(listener);


}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.fun_facts, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}