title: How to add a back button to action bar / toolbar
body: <p>I have written a piece of code as part of an app where I want to implement a back button on the action bar/tool bar such that when the button is pressed, the previous page (the page/fragment immediately before the current page/fragment) will be displayed.</p>
  
  <p>This is the code for the ToolBar, DrawerLayout, NavigationView and getSupportActionBar():</p>
  
  <pre><code>final DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
  final NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
  
  android.support.v7.widget.Toolbar toolbar = (android.support.v7.widget.Toolbar) findViewById(R.id.toolbar);
  setSupportActionBar(toolbar);
  toolbar.setVisibility(View.VISIBLE);
  getSupportActionBar().setDisplayHomeAsUpEnabled(true);
  getSupportActionBar().setLogo(R.mipmap.ic_launcher);
  getSupportActionBar().setDisplayUseLogoEnabled(true);
  getSupportActionBar().setHomeButtonEnabled(true);
  </code></pre>
  
  <p>I am unable to use ActionBar. For some reason (I don't know why), my Android studio/ program, will not allow me to use the ActionBar. So I am substituting that with the set/getSupportActionBar().</p>
  
  <p>The function used in relation to this are:</p>
  
  <pre><code>@Override
  public boolean onCreateOptionsMenu(Menu menu) {
       MenuInflater inflater = getMenuInflater();
       inflater.inflate(R.menu.menu_settings, menu);
       return true;
  }        
  
  @Override
  public boolean onOptionsItemSelected(MenuItem item) {
  
       // Handle action bar item clicks here. The action bar will
       // automatically handle clicks on the Home/Up button, so long
       // as you specify a parent activity in AndroidManifest.xml.
  
       int id = item.getItemId();
  
       switch (id) {
           case android.R.id.home:
               onBackPressed();
               return true;
           default:
               return super.onOptionsItemSelected(item);
           }
      }        
  
  @Override
  public void onBackPressed() {
  
      DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
      if (drawer.isDrawerOpen(GravityCompat.START)) {
          drawer.closeDrawer(GravityCompat.START);
      } else {
          super.onBackPressed();        
      }
  }
  </code></pre>
  
  <p>My activity_main.xml file is:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;LinearLayout
      xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"
      xmlns:tools="http://schemas.android.com/tools"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:fitsSystemWindows="true"
      android:id="@+id/activity_main"
      android:orientation="vertical"
      tools:openDrawer="start"
      tools:context="com.example.albin.settings_menu.SettingsActivity"&gt;
  
      &lt;RelativeLayout
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:background="#fff"&gt;
  
      &lt;android.support.v7.widget.Toolbar
              xmlns:android="http://schemas.android.com/apk/res/android"
              xmlns:app="http://schemas.android.com/apk/res-auto"
              android:id="@+id/toolbar"
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:background="?attr/colorPrimary"
              app:popupTheme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
              app:title="Settings"/&gt;
  
      &lt;android.support.v4.widget.DrawerLayout
              xmlns:android="http://schemas.android.com/apk/res/android"
              xmlns:app="http://schemas.android.com/apk/res-auto"
              xmlns:tools="http://schemas.android.com/tools"
              android:id="@+id/drawer_layout"
              android:layout_width="match_parent"
              android:layout_height="match_parent"&gt;
  
          &lt;FrameLayout
          android:id="@+id/frame"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_below="@+id/toolbar"&gt;
  
          &lt;/FrameLayout&gt;
  
              &lt;android.support.design.widget.NavigationView
                  xmlns:android="http://schemas.android.com/apk/res/android"
                  xmlns:app="http://schemas.android.com/apk/res-auto"
                  android:id="@+id/nav_view"
                  android:layout_width="wrap_content"
                  android:layout_height="match_parent"
                  android:layout_gravity="start"
                  android:fitsSystemWindows="true"
                  android:layout_marginTop="-24dp"
                  app:menu="@menu/options_menu" /&gt;
  
  
          &lt;/android.support.v4.widget.DrawerLayout&gt;
  
      &lt;/RelativeLayout&gt;
      &lt;/LinearLayout&gt;
  </code></pre>
  
  <p>The problem is that I don't know which is the useful code, which is the useless code and how to mix/join/(add additional codes to) these (codes, methods, variables/objects, fragments, xml layouts) to get the desired outcome, that is, the application of a back button on the action bar/tool bar.</p>
  
  <p>Most of the code above is implemented for the up button, not the back button. I have read at several places that up and back buttons are not the same.</p>
  
  <p>I tried several links on internet as well as on this site, but none of them has just what I need.</p>
  
  <p>Hope someone can give me an  clear answer...</p>