Develop Reference

Android map under transparent system bar

I have a fairly simple layout:
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<com.mapbox.mapboxsdk.maps.MapView
android:id="#+id/mapView"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<android.support.design.widget.FloatingActionButton
android:id="#+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|end"
android:layout_margin="#dimen/fab_margin" />
</FrameLayout>
I want the map to appear under the completly transparent system bars (navigation bar and status bar). To accieve this, I set the status and navigation bar color to android:color/transparent:
<style name="Theme.Lab.Map">
<item name="android:statusBarColor">#android:color/transparent</item>
<item name="android:navigationBarColor">#android:color/transparent</item>
<item name="android:fitsSystemWindows">false</item>
</style>
But unfortunatly, the map does not appear under the system bars. Instead, the default activity backgound color is visible.
I set fitSystemWindows to false as it helped when I set android:translucentStatusBar to true. The problem with translucentStatusBar is, that the status bar is only semi translucent, not completly transparent as I want it to be.
I somehow have to tell the map - or the activity - that it can expand underneath the systembars.
EDIT
It could also be possible to use translucentStatusBar but change the transparency/opacity of the status bar. I just didn't find a way to do this.

Translucent/Transparent status bar + CoordinatorLayout + Toolbar + Fragment

I have following setup:
I'm using AppCompat
MainActivity, that holds a fragment and has a toolbar, that's hiding when scrolling down
Fragment with RecyclerView
all views that should fit the screen have the according android:fitsSystemWindows="true" in the xml layout
The problem is, I can't get the statusbar transparent in this case. What I do is following:
Create the activity and call setContent
Then I try to adjust the activity to programmatically get a translucent toolbar like following:
#TargetApi(Build.VERSION_CODES.LOLLIPOP)
public void themeNavAndStatusBar(Activity activity)
{
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP)
return;
Window w = activity.getWindow();
w.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);
w.setFlags(
WindowManager.LayoutParams.FLAG_TRANSLUCENT_NAVIGATION,
WindowManager.LayoutParams.FLAG_TRANSLUCENT_NAVIGATION);
w.setFlags(
WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS,
WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
w.setNavigationBarColor(activity.getResources().getColor(android.R.color.transparent));
w.setStatusBarColor(activity.getResources().getColor(android.R.color.transparent));
}
Replace the placeholder in the activity (#+id/frame_container) with the fragment
The statusbar is solid colored in this case, and the views are not drawn underneath it... Why?
What I want
I want a toolbar, that is scrolled of the screen and hiding completely while the content underneath this toolbar should fitScreen and be drawn behind the transparent nav bar.
Layouts
Here's my main activity:
<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/clMain"
android:fitsSystemWindows="true"
android:background="?attr/main_background_color"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.AppBarLayout
android:id="#+id/appBarLayout"
android:fitsSystemWindows="true"
android:background="#null"
app:elevation="0dp"
app:contentInsetLeft="0dp"
app:contentInsetStart="0dp"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
android:elevation="4dp"
android:theme="?actionBarThemeStyle"
app:popupTheme="?actionBarPopupThemeStyle"
app:layout_scrollFlags="scroll|enterAlways">
<LinearLayout
android:orientation="vertical"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<LinearLayout
android:orientation="horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<ImageView
android:id="#+id/ivToolbarDataSource"
android:layout_gravity="center_vertical"
android:layout_marginRight="2dp"
android:layout_width="24dp"
android:layout_height="24dp" />
<TextView
android:id="#+id/tvToolbarTitle"
style="#style/TextAppearance.AppCompat.Widget.ActionBar.Title"
android:theme="?actionBarThemeStyle"
android:layout_gravity="center_vertical"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
<TextView
android:id="#+id/tvToolbarSubTitle"
style="#style/TextAppearance.AppCompat.Widget.ActionBar.Subtitle"
android:theme="?actionBarThemeStyle"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
</android.support.v7.widget.Toolbar>
<!-- BUG: http://stackoverflow.com/questions/30541409/coordinatorlayoutappbarlayout-does-not-draw-toolbar-properly -->
<View
android:layout_width="fill_parent"
android:layout_height="1dp"/>
</android.support.design.widget.AppBarLayout>
<FrameLayout
android:id="#+id/frame_container"
android:fitsSystemWindows="true"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior" />
<android.support.design.widget.FloatingActionButton
android:id="#+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|right"
android:layout_margin="32dp"
android:src="#drawable/ic_local_offer_white_24dp"
app:backgroundTint="?attr/colorPrimary"
app:borderWidth="0dp"
app:fabSize="normal"
app:rippleColor="?attr/colorPrimaryDark"
app:layout_anchorGravity="bottom|right|end"
app:layout_behavior="com.test.classes.ScrollAwareFABBehavior"/>
</android.support.design.widget.CoordinatorLayout>
And here is my fragment, that will be placed in the main activity:
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:fitsSystemWindows="true"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v4.widget.SwipeRefreshLayout
android:id="#+id/srlImages"
android:fitsSystemWindows="true"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.RecyclerView
android:id="#+id/rvImages"
android:fitsSystemWindows="true"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</android.support.v4.widget.SwipeRefreshLayout>
<TextView
android:id="#+id/tvEmpty"
android:gravity="center"
android:layout_centerInParent="true"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</RelativeLayout>
EDIT - Screenshots
I use a light/dark base theme and theme everything by hand (because the user can select any color as primary/accent color), so don't mind that the toolbar is white (it's the default's theme background color and primary color). I added a black border as well so that you see where the activity ends...
First Screenshot: Shows the toolbar, nothing is scrolled
Second Screenshot: I just started scrolling => the toolbar now should scroll away
Third Screenshot: the main content should now scroll underneath the nav bar...
In the end, I'll of course make the toolbar and navbar semi transparent for a better visual effect...

tl;dr Set android:fitsSystemWindows="false" at least to the root CoordinatorLayout and to the inner fragment container, #frame_container.
This might not be the final solution (i.e. there might be other fitsSystemWindows to change) so tell me if you have any problems.
why
When it comes to status bar, I think of fitsSystemWindows like so:
fitsSystemWindows="false" : draws the view normally, under the status bar because of the window flags you have set.
fitsSystemWindows="true" : draws the view normally, under the status bar because of the window flags you have set, but adds a top padding so that content is drawn below the status bar and they don't overlap.
In fact, in my opinion, the white you see is not the status bar color, but rather your CoordinatorLayout background. That is due to fitsSystemWindows="true" on the coordinator: it draws the background to the whole window, but adds top padding to the content so inner views are not covered by status bar.
This is not what you want. Your inner content must be covered by the status bar, and so you have to set fitsSystemWindows="false" to the coordinator (so it won't apply top padding) and probably to the content itself.
Once you get how it works, it is easy to debug and achieve the effect you are looking for. Actually, it is not. Years pass, but I still spend hours trying to figure out the right fitsSystemWindows combination, because most Views (in the support libraries at least) override the default behavior that I stated above, in ways that are mostly not intuitive. See this post for a small guide on how to use it.

Edit your styles.xml (v21) , add the following style
<style name="AppTheme.Home" parent="AppTheme.Base">
<!-- Customize your theme here. -->
<item name="android:windowTranslucentStatus">true</item>
<item name="android:windowDrawsSystemBarBackgrounds">true</item>
<item name="android:windowTranslucentNavigation">true</item>
</style>
You can change parent theme as per your liking, but now declare this theme in your AndroidManifest.xml file for a particular activity like this :
<activity
android:theme="#style/AppTheme.Home"
android:name=".HomeActivity"
android:launchMode="singleTop"
android:screenOrientation="portrait" />
This will let your content visible under the transparent actionbar.
Now use the following to align your toolbar below the StatusBar properly, call this in your oncreate:
toolbar.setPadding(0, getStatusBarHeight(), 0, 0);
Get statusbar height using following :
public int getStatusBarHeight() {
int result = 0;
int resourceId = getResources().getIdentifier("status_bar_height", "dimen", "android");
if (resourceId > 0) {
result = getResources().getDimensionPixelSize(resourceId);
}
return result;
}
Remove the following from your coordinator layout tags :
android:fitsSystemWindows="true"
Now in order to collapse your toolbar or hide it you may refer to this tutorial
Make sure you are using following version of design support library, as it is bug free :
compile 'com.android.support:design:23.1.0'

After reading your descriptions about your question, I thought styles of Google Photos matches your requirement.
OK, there are just some tips for your question. After my test, it works.
If you want to show content behind status bar, you need add <item name="android:windowTranslucentStatus">true</item> into your
style when Android version level is larger than 19(namely KitKat)
If you want to show content behind navigation bar, you need add
<item name="android:windowTranslucentNavigation">true</item> into your
style when Android version level is larger than 19(namely KitKat)
If you want to hide Toolbar smoothly when content is scrolled up
and to show Toolbar smoothly when content is scrolled down, you
need to add app:layout_collapseMode="parallax" into your
Toolbar's attributes based on your current codes.Of course, you
need coordinate Toolbar with CollapsingToolbarLayout
CoordinatorLayout and AppBarLayout.

as some users said, by setting android:fitsSystemWindows="false", the layout overlapped below statusbar.
I solved it by setting android:fitsSystemWindows="true" and in CoordinatorLayout tag setting app:statusBarBackground="#android:color/transparent".

For me, the reason was not that it did not work per se, but that I use the material drawer library from Mike Penz and this library does use fullscreen + offset + custom background behind the toolbar so I had to solve the problem respecting that special setup...
I'll reward the points to the in my opinion most informative answer though...

I had the same issue and my solution was add android:fitsSystemWindows="true" to the DrawerLayout
<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"
android:fitsSystemWindows="true">
....
</android.support.v4.widget.DrawerLayout>

I had relevant issues depend on android:fitsSystemWindows setting.
Once false:
Snacks was drawn under the Navigation bar
Once true:
Status bar had none transparent background
Solution was really simple...
Just to add android:layout_marginBottom="48dp". to CoordinatorLayout like that:
just to add <android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:map="http://schemas.android.com/apk/res-auto"
tools:context=".MapsActivity"
android:id="#+id/coordinatorLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="false"
android:layout_marginBottom="48dp">
Theoretically Navigation bar should have fixed size "48dp", but in future releases potentially it may change (like Status bar got slimmer by 1dp in Marshmallow), so I wouldn't rely on fixed size.
Better additionally get it and apply on run time.
If You are using Google Map like me You may want to know ActionBar/Toolbar size and the navigation bar in run time:
in onCreate use this code:
final TypedArray styledAttributes = MapsActivity.this.getTheme().obtainStyledAttributes(
new int[]{android.R.attr.actionBarSize});
mToolbarHeight = (int) styledAttributes.getDimension(0, 0);
styledAttributes.recycle();
// translucent bars code. Will not fire below Lollipop
// Ask NavigationBar Height
ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.coordinatorLayout),
new OnApplyWindowInsetsListener() { // setContentView() must be fired already
#Override
public WindowInsetsCompat onApplyWindowInsets(View v, WindowInsetsCompat insets) {
statusBar = insets.getSystemWindowInsetTop(); // You may also need this value
mNavBarHeight = insets.getSystemWindowInsetBottom();
if (mMap != null)
mMap.setPadding(0, mToolbarHeight, 0, mNavBarHeight);
// else will be set in onMapReady()
SharedPreferences.Editor editor = mSharedPref.edit();
editor
.putInt(NAVBAR_HEIGHT_KEY, mNavBarHeight)
.commit(); // Save the results in flash memory and run the code just once on app first run instead of doing it every run
return insets;
}
}
);
And what's important. If You got some additional layers like drawer etc put them encapsulating the CoordinatorLayout inside rather than outside as otherwise it will make other views inside shorter by the marginBottom

Here's what I did to have the toolbar have the same color as the status bar, by getting the status bar transparent:
build.gradle
...
implementation 'androidx.core:core-ktx:1.2.0'
implementation 'androidx.appcompat:appcompat:1.1.0'
implementation 'com.google.android.material:material:1.1.0'
**ScrollingActivity.kt**
```kt
class ScrollingActivity : AppCompatActivity(R.layout.activity_scrolling) {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setSupportActionBar(toolbar)
}
}
activity_scrolling.xml
<androidx.coordinatorlayout.widget.CoordinatorLayout 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"
tools:context=".ScrollingActivity">
<com.google.android.material.appbar.AppBarLayout
android:id="#+id/app_bar" android:layout_width="match_parent" android:layout_height="wrap_content"
android:background="#f00" android:fitsSystemWindows="true" android:theme="#style/AppTheme.AppBarOverlay">
<com.google.android.material.appbar.MaterialToolbar
android:id="#+id/toolbar" android:layout_width="match_parent" android:layout_height="?attr/actionBarSize"
app:popupTheme="#style/AppTheme.PopupOverlay" />
</com.google.android.material.appbar.AppBarLayout>
<androidx.core.widget.NestedScrollView
android:layout_width="match_parent" android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior">
<TextView
android:layout_width="wrap_content" android:layout_height="wrap_content"
android:layout_margin="#dimen/text_margin" android:text="#string/large_text" />
</androidx.core.widget.NestedScrollView>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
styles.xml
<resources>
<style name="AppTheme" parent="Theme.MaterialComponents.DayNight.DarkActionBar">
<item name="colorPrimary">#color/colorPrimary</item>
<item name="colorPrimaryDark">#color/colorPrimaryDark</item>
<item name="colorAccent">#color/colorAccent</item>
</style>
<style name="AppTheme.NoActionBar">
<item name="windowActionBar">false</item>
<item name="windowNoTitle">true</item>
<item name="android:statusBarColor">#android:color/transparent</item>
</style>
<style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.AppCompat.Dark.ActionBar" />
<style name="AppTheme.PopupOverlay" parent="ThemeOverlay.AppCompat.Light" />
</resources>
manifest
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.lb.myapplication">
<application
android:allowBackup="true" android:icon="#mipmap/ic_launcher" android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round" android:supportsRtl="true" android:theme="#style/AppTheme">
<activity
android:name=".ScrollingActivity" android:label="#string/app_name"
android:theme="#style/AppTheme.NoActionBar">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>

You should add the following code to your theme, this code will make the status bar transparent:
<item name="android:windowTranslucentStatus" tools:targetApi="kitkat">true</item>
Additionally, add scroll behavior to your top app bar. The following example shows the top app bar disappearing upon scrolling up, and appearing upon scrolling down:
<androidx.coordinatorlayout.widget.CoordinatorLayout
...>
<com.google.android.material.appbar.AppBarLayout
...>
<com.google.android.material.appbar.MaterialToolbar
...
app:layout_scrollFlags="scroll|enterAlways|snap"
/>
</com.google.android.material.appbar.AppBarLayout>
...
</androidx.coordinatorlayout.widget.CoordinatorLayout>

First add this code to AppBarLayout:
app:liftOnScroll="true"
Then update your "app:layout_scrollFlags" in your toolbar:
app:layout_scrollFlags="scroll|enterAlways|snap"
This will work, I am pretty sure.

Setting the shadow on android's TabLayout

I want to remove the shadow below TabLayout. I Tried setting this feature as a theme, but it doesn't work:
<item name="android:windowContentOverlay">#null<item/>
Or
<item name="windowContentOverlay">#null<item/>
I was wandering if there's another way to do this, from the XML declaration or from code behind on the TabLayout instance.
I'm aware of this solution, which doesn't work for me.
Getting rid of the gradient at the top of an Activity (Android)
Please, don't suggest the theme fix, I know it's the best android-way to go here, but it's not an option for me.
This is my XML declaration :
<android.support.design.widget.TabLayout xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/sliding_tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:background="#android:color/white"
app:backgroundTint="#android:color/transparent"
app:tabIndicatorColor="#android:color/transparent"
app:tabMode="scrollable"
app:tabSelectedTextColor="#color/tab_on_state"
app:tabTextColor="#color/tab_off_state" />

Shadow is not cast by the TabLayout but the container in which it resides.
If you are using TabLayout in ActionBar then set the background of ActionBar to solid colour to remove the shadow.
I have tried it on ActionBar but i guess it should work fine for other pattern like AppBarLayout

How to center toolbar back button?

I'm having a problem trying to center the back button on the support toolbar.
I'm using it inside an ActionBarActivity.
<android.support.v7.widget.Toolbar xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:toolbar="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"
android:minHeight="?attr/actionBarSize"
toolbar:popupTheme="#style/ThemeOverlay.AppCompat.Light"
toolbar:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar" />
And set the up navigation inside the Activity's onCreate() like this:
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setTitle(R.string.title_activity_scanner);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
However, what I'm getting is this:
As you can see the back button is misplaced
Edit:
The problem seems to lie in a custom value for ?attr/actionBarSize set to 40dp, however, it turns out now, that it's the title that is misplaced instead.

From the developer.android.com :
Toolbar supports a more focused feature set than ActionBar. From start
to end, a toolbar may contain a combination of the following optional
elements:
A navigation button. This may be an Up arrow, navigation menu toggle,
close, collapse, done or another glyph of the app's choosing. This
button should always be used to access other navigational destinations
within the container of the Toolbar and its signified content or
otherwise leave the current context signified by the Toolbar. The
navigation button is vertically aligned within the Toolbar's minimum
height, if set.
So if you set minHeight attribute the same as your toolbar height (layout_height ), the back arrow will be centered vertically.

(2020)
In case you have a non-standard toolbar height, to center the back button nowadays (2k20) with androidx Toolbar you can just use the buttonGravity property.
This allows you to use wrap_content instead of a specific height (minHeight doesn't allow you to do so):
<androidx.appcompat.widget.Toolbar
app:buttonGravity="center_vertical"
android:layout_height="wrap_content"
... />

Inside ActionBarActivity
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBat().setTitle("Hello World");
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setHomeButtonEnabled(true);
Layout code :
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="#color/primary"
app:theme="#style/ToolbarTheme"
app:popupTheme="#style/Theme.AppCompat"/>
And style :
<style name="AppTheme.Base" parent="Theme.AppCompat.Light">
<item name="colorPrimary">#color/primary</item>
<item name="colorPrimaryDark">#color/primaryDark</item>
<item name="android:windowNoTitle">true</item>
<item name="android:windowActionBar">false</item>
<item name="windowActionBar">false</item>
</style>
<style name="AppTheme" parent="AppTheme.Base">
Remember that toolbar is just viewgroup, so u can style it in any way u like.
Here is image link : Toolbar sample
Hope it helps.

Best way to achieve this is remove regular Back button from the toolbar and add a custom ImageButton in your XML layout and set image to it. You can place this ImageButtton wherever you want on the toolbar.
Your activity layout code should be something like this.
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<include
android:id="#+id/toolbar"
layout="#layout/toolbar" />
<ImageButton
android:layout_width="60dp"
android:layout_height="60dp"
android:id="#+id/button"
android:src="#drawable/attach_icon"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true" />
</RelativeLayout>

For me, none of the solutions worked. In my case the problem was the margin I applied:
<android.support.v7.widget.Toolbar
android:layout_width="match_parent"
android:layout_height="wrap_content"
... >
<View
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="10dp"
android:layout_marginTop="10dp" />
</android.support.v7.widget.Toolbar>
After applying it to the toolbar directly, the button was centered vertically:
<android.support.v7.widget.Toolbar
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="10dp"
android:layout_marginTop="10dp"
... >
<View
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</android.support.v7.widget.Toolbar>

Piggybacking off of #Rick Sanchez answer - if you know the size of the Toolbar's minHeight attribute you can then use:
android:gravity="top"
app:titleMarginTop="#dimen/margin_to_center"
in the Toolbar to center the text. If you are using android:minHeight="?actionBarSize" then this would be about 13p

#Rick Sanchez answer is work,setup Toolbar's layout_height the same as minHeight
I found in Toolbar constructor have a field can setup button gravity,
mButtonGravity = a.getInteger(R.styleable.Toolbar_buttonGravity, Gravity.TOP);
,but v7 support Toolbar can not setup,
mButtonGravity = Gravity.TOP;

make your button size 56dp and set scaleType to center with no margins on Appbar
Make sure your icon is 24x24 dimensions

I was using
<style name="MyActionBar" parent="#style/Widget.AppCompat.ActionBar">
when I should've been using
<style name="MyActionBar" parent="#style/Widget.AppCompat.Toolbar">

Appcompat v21 Toolbar elevation pre-lollipop

First off, I know that this question has been asked before, but it hasn't been answered before. I hope someone can give me an answer.
In my application, I use the Toolbar from Appcompat_v7 (API 21). This is my code:
<android.support.v7.widget.Toolbar
style="#style/DarkActionbarStyle"
android:id="#+id/toolBar"
android:layout_width="match_parent"
android:layout_height="#dimen/actionbar_height" />
And this is the ToolBar style I use:
<style name="DarkActionbarStyle" parent="#style/Widget.AppCompat.Toolbar">
<item name="android:background">?attr/colorPrimary</item>
<item name="titleTextAppearance">#style/ActionBarTitle</item>
<item name="android:elevation">2dp</item>
<item name="popupTheme">#style/ThemeOverlay.AppCompat.Light</item>
<item name="theme">#style/ThemeActionBarDark</item>
</style>
<style name="ThemeActionBarDark" parent="#style/ThemeOverlay.AppCompat.Dark.ActionBar">
<item name="actionBarItemBackground">#drawable/btn_dark_orange</item>
<item name="selectableItemBackground">#drawable/btn_dark_orange</item>
</style>
The problem is, that elevation doesn't work pre-lollipop. So my question is: Is it possible to have a shadow under the ToolBar on pre-lollipop devices?

This worked for me very well:
<android.support.v7.widget.CardView
xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/primary"
card_view:cardElevation="4dp"
card_view:cardCornerRadius="0dp">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/primary"
android:minHeight="?attr/actionBarSize" />
</android.support.v7.widget.CardView>

Using CardView container for toolbar is a bad idea.
CardView is heavy, especially for low end devices.
The best way is to put a gradient Shadow view below the toolbar. Shadow view must be a direct child to the coordinator layout. ie. The appbar which contains toolbar and shadow View must be siblings.
Add this view component to your layout.
<View
android:id="#+id/gradientShadow"
android:layout_width="match_parent"
android:layout_height="5dp"
android:background="#drawable/toolbar_shadow"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
app:layout_collapseMode="pin"/>
The drawable toolbar_shadow.xml
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<gradient
android:angle="90"
android:endColor="#33333333"
android:startColor="#android:color/transparent"/>
</shape>
This will solve the problems in pre-lollipop devices. But we don't want this shadow in lollipop and above devices so make visibility to gone in devices with lollipop and above.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
findViewById(R.id.gradientShadow).setVisibility(View.GONE);
}
Done.

You can add the shadow (elevation) back by using a FrameLayout with foreground="?android:windowContentOverlay". The elevation attribute is not supported pre-Lollipop. So if you are using FrameLayout like fragment container just add foreground attribute to it.

As I've had issues with the CardView widget method, I've used the FrameLayout method as mentioned by #Sniper; it is working perfectly!
I just wanted to share the code snippet you'll have to use.
Just put this directly under the toolbar where your main content starts:
<FrameLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:foreground="?android:windowContentOverlay">
And don't forget to close with:
</FrameLayout>

It's possible to have real shadows - animated and generated. The method used by Lollipop is available since Froyo. Hardware acceleration used for shadow generation is available since Honeycomb I guess. Here's how it works:
draw your view to an off-screen bitmap with LightingColorFilter set to 0,0
blur the black shape (the off-screen bitmap) using the ScriptIntrinsicBlur class and elevation value as radius
draw the bitmap beneath the view
It requires adding custom elevation attributes, custom views capable of rendering shadows, and using render script and the compatibility library (for older devices). I'm not going to dive into the details, because there's a lot of them including issues with compilation and minor performance optimisations. But it's possible.
Why there's no shadows in the official support library?
it would require changes in the UI framework as it's impossible to freely draw outside view bounds
smooth animation requires a quite good GPU
See:
https://www.youtube.com/watch?v=jbU4SXblO5s
https://androidreclib.wordpress.com/2014/11/25/lollipops-shadows-on-gingerbread/
https://github.com/ZieIony/Carbon

I'm using this answer:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical">
<android.support.v7.widget.Toolbar xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/orange"
android:titleTextAppearance="#color/White"
app:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar" />
<View
android:layout_width="match_parent"
android:layout_height="5dp"
android:background="#drawable/toolbar_shadow" />
</LinearLayout>
toolbar_shadow.xml:
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
<gradient
android:startColor="#3f3f3f"
android:endColor="#android:color/transparent"
android:angle="270" />
</shape>

You can't use the elevation attribute before API 21 (Android Lollipop).
You can however add the shadow programmatically, for example using a custom view placed below the Toolbar.
For example:
<ImageView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="#+id/toolbar"
android:background="#drawable/shadow"/>
Where the shadow is a drawable with a black gradient.

To show shadow under your toolbar please use AppBarLayout available in Google Android Design Support Library. Here is an example of how it should be used.
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<android.support.v7.widget.Toolbar
android:layout_height="?attr/actionBarSize"
android:layout_width="match_parent"/>
</android.support.design.widget.AppBarLayout>
To use Google Android Design Support Library enter following into your build.gradle file:
compile 'com.android.support:design:22.2.0'

The solution with a view to add a shadow manually would work as long as there are no action bar menus. If so, the shadow view would stop before the action bar icons.
i think it is easier to have a vertical linear layout with appbar on the top and a view for shadow below it as the next linear layout item or in my case, it is
<LinearLayout Vertical>
<v7 toolbar/>
<RelativeLayout>
<View for shadow with alignParent_top= true/>
....
</RelativeLayout>
</LinearLayout>
I really hope the near future appCompat would fix this.