MainActivity.java

package id.binarykitchen.gemarbelajar;

import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    private static final String TAG = MainActivity.class.getSimpleName();

    private TextView tvHelloWorld;

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

        tvHelloWorld = (TextView) findViewById(R.id.tv_hello_world);

        tvHelloWorld.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Toast.makeText(MainActivity.this, "HI!", Toast.LENGTH_SHORT).show();
            }
        });
    }
}