How to reduce the gap between navigation icon and toolbar title?

Add

app:contentInsetLeft="0dp"
app:contentInsetStart="0dp"
app:contentInsetStartWithNavigation="0dp"

to the ToolBar.

Complete Code :

<android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        app:titleTextAppearance="@style/Toolbar.TitleText"
        app:popupTheme="@style/AppTheme.PopupOverlay"
        app:contentInsetLeft="0dp"
        app:contentInsetStart="0dp"
        app:contentInsetStartWithNavigation="0dp" />

With the MaterialToolbar and the androidx.appcompat.widget.Toolbar you can use these attributes:

• contentInsetStartWithNavigation: Minimum inset for content views within a bar when a navigation button is present, such as the Up button (default value=72dp).

• contentInsetStart: Minimum inset for content views within a bar. Navigation buttons and menu views are excepted (default value = 16dp)

• titleMarginStart: specifies extra space on the start side of the toolbar's title. If both this attribute and titleMargin are specified, then this attribute takes precedence. Margin values should be positive.

Just use in your layout:

    <com.google.android.material.appbar.MaterialToolbar
        app:contentInsetStartWithNavigation="0dp"
        app:titleMarginStart="0dp"
        ..>

Default:

With app:contentInsetStartWithNavigation="0dp":

With app:contentInsetStartWithNavigation="0dp" and app:titleMarginStart="0dp":

You can also define a custom style:

<style name="MyToolbar" parent="....">
    <item name="titleMarginStart">0dp</item>
    <item name="contentInsetStart">..dp</item>
    <item name="contentInsetStartWithNavigation">..dp</item>
</style>

Add app:contentInsetStartWithNavigation="0dp" in toolbar

Add this line app:contentInsetStartWithNavigation="0dp"

 <android.support.v7.widget.Toolbar
                android:id="@+id/share"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                app:navigationIcon="@drawable/action_back"
                app:popupTheme="@style/AppTheme.PopupOverlay"
                app:title="@{title}"
                android:background="4855b5"
                app:titleTextColor="ffffff"
                style="@style/TextAppearance.AppCompat.Widget.ActionBar.Title"
                app:titleTextAppearance="@style/Toolbar.TitleText"
                app:contentInsetStartWithNavigation="0dp" />