BaseScannerActivity

public class BaseScannerActivity extends AppCompatActivity {

    public void setupToolbar() {
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        final ActionBar ab = getSupportActionBar();
        if (ab != null) {
            ab.setDisplayHomeAsUpEnabled(true);
        }
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                finish();
                return true;
        }
        return super.onOptionsItemSelected(item);
    }

}