package android.example.com.visualizerpreferences;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class SettingsActivity extends AppCompatActivity {

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

package android.example.com.visualizerpreferences;

import android.support.v4.app.NavUtils;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MenuItem;

public class SettingsActivity extends AppCompatActivity {

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

        ActionBar actionBar = this.getSupportActionBar();
        if(actionBar != null){
            actionBar.setDisplayHomeAsUpEnabled(true);
        }
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int itemId = item.getItemId();
        if(itemId == android.R.id.home){
            NavUtils.navigateUpFromSameTask(this);
        }
        return super.onOptionsItemSelected(item);
    }
}

Fix up button in T06.01
Fix up button in T06.01
