XML : Android toolbar home button not showing

I am trying to create a toolbar which also have the Home icon/button so that the user can go back to home with it.

This is my code:

AndroidManifest.xml

  <activity              android:name=".SettingsActivity"              android:noHistory="true"              android:theme="@style/AppTheme">          <meta-data                  android:name="android.support.PARENT_ACTIVITY"                  android:value=".MainActivity"/>  </activity>    

toolbar.xml:

  <android.support.v7.widget.Toolbar      xmlns:android="http://schemas.android.com/apk/res/android"      android:layout_height="wrap_content"      android:layout_width="match_parent"      android:background="@color/ColorPrimary"      android:elevation="2dp"      android:theme="@style/Base.ThemeOverlay.AppCompat.Dark"/>    

settings_activity.xml:

  <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"            android:orientation="vertical"            android:layout_width="match_parent"            android:layout_height="match_parent">    <include          android:id="@+id/tool_bar"          layout="@layout/toolbar"          android:layout_height="wrap_content"          android:layout_width="match_parent"/>  </LinearLayout    

SettingsActivity.java

  @Override  public void onCreate(Bundle savedInstanceState) {      super.onCreate(savedInstanceState);      setContentView(R.layout.settings_activity);        toolbar = (android.support.v7.widget.Toolbar) findViewById(R.id.tool_bar);      setSupportActionBar(toolbar);      getSupportActionBar().setDefaultDisplayHomeAsUpEnabled(true);      getSupportActionBar().setHomeButtonEnabled(true);  }  @Override  public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {  }    @Override  public void onNothingSelected(AdapterView<?> adapterView) {  }    

However all I see is the name of my application and no UP/Home button at all?

Can you help me please