title: Toolbar navigation icon can't be center inside
body: <p>I want to set the navigation icon for my toolbar ,and get into the problem that <strong>the icon isn't center inside by default</strong> it looks like:</p>
  <hr />
  <p><a href="https://i.stack.imgur.com/k8OV9.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/k8OV9.png" alt="enter image description here" /></a></p>
  <p>and the code is:</p>
  <hr />
  <pre><code>    setSupportActionBar(toolbar);
      ActionBar actionBar = getSupportActionBar();
      actionBar.setHomeButtonEnabled(true); 
      actionBar.setDisplayHomeAsUpEnabled(true);
      actionBar.setDisplayShowTitleEnabled(false);
      toolbar.setNavigationIcon(R.drawable.ic_arrow_back_white_48dp);
  </code></pre>
  <hr />
  <p>and the theme.xml is:</p>
  <hr />
  <pre><code>    &lt;style name=&quot;AppTheme&quot; parent=&quot;Theme.AppCompat.NoActionBar&quot;&gt;
      &lt;!-- Customize your theme here. --&gt;
      &lt;item name=&quot;android:windowTranslucentStatus&quot;&gt;true&lt;/item&gt;
      &lt;item name=&quot;android:navigationBarColor&quot;&gt;@color/colorPrimaryDark&lt;/item&gt;
      &lt;item name=&quot;android:windowContentTransitions&quot;&gt;true&lt;/item&gt;
      &lt;item name=&quot;android:windowAllowEnterTransitionOverlap&quot;&gt;true&lt;/item&gt;
      &lt;item name=&quot;android:windowAllowReturnTransitionOverlap&quot;&gt;true&lt;/item&gt;
  </code></pre>
  <p>and the layout xml is:</p>
  <hr />
  <pre><code>&lt;android.support.v7.widget.Toolbar     
  xmlns:android=&quot;http://schemas.android.com/apk/res/android&quot;
  android:id=&quot;@+id/toolbar&quot;
  android:layout_width=&quot;match_parent&quot;
  android:layout_height=&quot;@dimen/toolbar_height&quot;
  /&gt;
  </code></pre>
  <p>I think I have tried everything I know but I just can't figure it out.I used to set the navigation icon for toolbar then it will be center inside  and now.Any help will save my day!</p>
  <p>Eidted: of course I tried different size of icons
  <a href="https://i.stack.imgur.com/wZFSo.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/wZFSo.png" alt="24dp" /></a>
  <a href="https://i.stack.imgur.com/xl6S4.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/xl6S4.png" alt="32dp" /></a>
  and I konw I could add a custom layout in toolbar or customize a layout like (which is a Linearlayout I write about)</p>
  <hr />
  <p><a href="https://i.stack.imgur.com/9X09M.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/9X09M.png" alt="enter image description here" /></a></p>
  <hr />
  <p>But I just don't why I can't set the navigation icon like before,it will automatically be center inside....I think maybe I should change the theme or define something like navigationButttonStyle in the attributes....</p>