How to make “menu” or “manifest” back button to navigate back to the previous activity

Question

I have 3 different activities. I've created menu xml files to build ActionToolbar, buttons etc., but for "back button" I've found a decision to add such code in manifest:

android:parentActivityName=".MainActivity">
        <meta-data
            android:name="android.support.PARENT_ACTIVITY"
            android:value=".MainActivity"/>

The question is how to return on the previous activity which isn't parent activity sometimes. Can I do this with help of menu? I know how to add back button there, but it will be at the end of toolbar's line, not before the activity title.

menu_add_task.xml:

<?xml version="1.0" encoding="utf-8"?>
<menu
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <item
        android:id="@+id/doneTask"
        android:title="@string/doneTask"
        android:icon="@mipmap/ic_done"
        app:showAsAction="ifRoom" />

</menu>

activity_add_task.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="@color/the_darkest_grey">
</android.support.constraint.ConstraintLayout>

AddTaskActivity class: activity, where should be a back button

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;

public class AddTaskActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_add_task);
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        getMenuInflater().inflate(R.menu.menu_add_task, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {

        switch (item.getItemId()){

            case R.id.doneTask:
                finish();
                return true;
        }
        return super.onOptionsItemSelected(item);
    }

}

Answer 1

Gotcha.

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;

public class AddTaskActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_add_task);
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        getMenuInflater().inflate(R.menu.menu_add_task, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {

        switch (item.getItemId()){

            case android.R.id.home:
                finish();
                return true;

            case R.id.doneTask:
                finish();
                return true;
        }
        return super.onOptionsItemSelected(item);
    }

}