showFactButton.SetOnClickListener(listener);

package eu.vybafkam.funfactssecondtry;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class FunFactss extends AppCompatActivity {

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

            //Declare our View Variables and assign the Views from the layout file
        final TextView factlabel = (TextView) findViewById(R.id.factsTextView);
        Button showFactButton = (Button) findViewById(R.id.showFactButton);
        View.OnClickListener listener = new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //The button was clicked so update the fact label with a new fact
                String fact = "Ostriches can run faster then horses.";
                factlabel.setText(fact);
            }
        };
        showFactButton.SetOnClickListener(listener);

        }
    }