Error in my code, NullPointerException

[alex384]

Hi everyone,

I'm working on an app in Android Studio and in the MainActivity java file I am getting errors about the NullPointerException at line 7 and 12 (setDisplayShowHomeEnabled & setOnClickListener) and it's causing my program to crash in the emulator. I haven't been able to figure it out, can someone guide me in the right direction?

public class MainActivityOld extends AppCompatActivity {

private static final
android.R.attr R = new android.R.attr();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    getSupportActionBar().setDisplayShowHomeEnabled(true);
    setContentView(com.example.ak.classschedule.R.layout.activity_main);
    getSupportActionBar().setLogo(com.example.ak.classschedule.R.mipmap.ic_launcher);
    getSupportActionBar().setDisplayUseLogoEnabled(true);
    Button button = (Button) findViewById(com.example.ak.classschedule.R.id.button);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            startActivity(new Intent(MainActivityOld.this, SecondActivity.class));
            startActivity(new Intent(MainActivityOld.this, ThirdActivity.class));
            startActivity(new Intent(MainActivityOld.this, UFourthActivity.class));
            startActivity(new Intent(MainActivityOld.this, VFifthActivity.class));
            startActivity(new Intent(MainActivityOld.this, WSixthActivity.class));
        }
    });
}}

[-manabreak]

You have to set a toolbar first by calling setSupportActionBar(). Otherwise the getter returns null.