Develop Reference

Android navigation bar and status bar elevation/shadows

I would like to set my navigation bar and my status bar like in the example in the image in the link below.
How could I do that
see the example

you can do this simply by setting style attributes like this:
<resources xmlns:android="http://schemas.android.com/apk/res/android">
<style name="Theme" parent="android:Theme.Material.Wallpaper.NoTitleBar">
<item name="android:statusBarColor">set_your_color</item>
<item name="android:navigationBarColor">set_your_color</item>
<item name="android:windowTranslucentStatus">true</item>
<item name="android:windowTranslucentNavigation">true</item>
</style>
</resources>
Hope it will help you!!

If you want to remove elevation and shadow of toolbar add app:elevation="0dp" in toolbar like below:
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:elevation="0dp"
android:theme="#style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="#+id/custom_toolbar"
android:layout_width="match_parent"
android:elevation="0dp"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
android:popupTheme="#style/AppTheme.PopupOverlay" />
</android.support.design.widget.AppBarLayout>

How to make colorPrimary not show as toolbar background

I am trying to make the toolbar background color transparent however, the colorPrimary theme seems to be showing instead. When I set the background of the toolbar to a standard color, it overrides colorPrimary and work as intended, but is there a way for me to get rid of it completely as to make the toolbar background transparent? The reason that I still want colorPrimary is because of the recent apps tab color, I just want it to not show in the toolbar. Thank you.
Toolbar
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="#android:color/transparent" />
Style
<style name="AppTheme1" parent="Theme.AppCompat.Light.NoActionBar">
<item name="colorPrimary">#color/colorPrimary</item>
<item name="colorPrimaryDark">#android:color/transparent</item>
<item name="colorAccent">#color/colorPrimary</item>
<item name="android:windowLightStatusBar">true</item>
<item name="android:windowContentOverlay">#null</item>
<item name="android:elevation">0dp</item>
<item name="elevation">0dp</item>
<item name="drawerArrowStyle">#style/DrawerArrowStyle</item>
<item name="android:textColorSecondary">#color/colorPrimary</item>
</style>

use the code instead of only toolbar
<android.support.design.widget.AppBarLayout
android:id="#+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingTop="8dp"
android:background="#android:color/transparent"
android:theme="#style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="#android:color/transparent"
app:layout_scrollFlags="scroll|enterAlways"
app:popupTheme="#style/AppTheme.PopupOverlay">
</android.support.v7.widget.Toolbar>
</android.support.design.widget.AppBarLayout>

use this
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.Toolbar
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/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="#drawable/background_toolbar_translucent" />
background_toolbar_translucent.xml
<?xml version="1.0" encoding="utf-8"?>
<gradient
android:angle="270"
android:endColor="#android:color/transparent"
android:startColor="#color/black_alpha_40"/>
colors.xml
<color name="black_alpha_40">#66000000</color>

make toolbar.xml inside layout folder. Use below code:
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.Toolbar xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:local="http://schemas.android.com/apk/res-auto"
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:minHeight="?attr/actionBarSize"
android:background="#android:color/transparent"
local:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar"
local:popupTheme="#style/ThemeOverlay.AppCompat.Light" />
And use this toolbar in your activity's xml. This way you will have a transparent toolbar.

Status Bar (notification bar) is disappearing on scroll with CoordinatorLayout

I am using the CoordinatorLayout using the default templates in Android Studio.
However when I scroll down, the notification bar (status bar) is scrolling off screen. The effect can be seen in this video.
https://youtu.be/1oAqEpg7N4I
I have included the relevant parts, but the rest of the code is available here:
https://github.com/vidia/MaterialDiningCourts/blob/master/app/src/main/res/layout/activity_meal_view.xml
In the demo (cheesesquare) the behavior is what I expect, to leave the notification bar in place and the Toolbar scrolls out underneath it. I have scoured those layouts and made changes in my code to match them, but haven't been able to find the necessary change.
What is causing the notification bar to scroll off the page, and why does the sample in Android Studio have this incorrect behavior?
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.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:id="#+id/main_content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context=".MealViewActivity">
<android.support.v4.view.ViewPager
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior" />
<android.support.design.widget.AppBarLayout
android:id="#+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:layout_scrollFlags="scroll|enterAlways|snap"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:popupTheme="#style/ThemeOverlay.AppCompat.Light">
<Spinner
android:id="#+id/meal_chooser_spinner"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
</android.support.v7.widget.Toolbar>
<android.support.design.widget.TabLayout
android:id="#+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="#style/AppTabLayout"
android:foregroundGravity="top"
app:tabIndicatorColor="#color/tabSelectedIndicatorColor"/>
</android.support.design.widget.AppBarLayout>
And styles.xml, though I have removed my custom themes from this file and it doesnt help the issue.
<resources>
<!-- Base application theme. -->
<style name="AppTheme" parent="#style/Theme.AppCompat.Light">
<!-- Customize your theme here. -->
<item name="colorPrimary">#color/colorPrimary</item>
<item name="colorPrimaryDark">#color/colorPrimaryDark</item>
<item name="colorAccent">#color/colorAccent</item>
<!-- Required from http://stackoverflow.com/a/29014475/2193387 -->
<item name="android:datePickerDialogTheme">#style/dateDialogTheme</item>
</style>
<style name="AppTheme.NoActionBar">
<item name="windowActionBar">false</item>
<item name="windowNoTitle">true</item>
</style>
<style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.AppCompat.Dark.ActionBar" />
<style name="AppTheme.PopupOverlay" parent="ThemeOverlay.AppCompat.Light" />
<style name="AppTabLayout" parent="Widget.Design.TabLayout">
<!--<item name="tabMaxWidth">#dimen/tab_max_width</item>-->
<item name="tabIndicatorColor">#color/tabIndicatorColor</item>
<item name="tabIndicatorHeight">4dp</item>
<!--<item name="tabPaddingStart">6dp</item>-->
<!--<item name="tabPaddingEnd">6dp</item>-->
<!--<item name="tabBackground">?attr/selectableItemBackground</item>-->
<item name="tabTextAppearance">#style/AppTabTextAppearance</item>
<item name="tabSelectedTextColor">#color/white</item>
</style>
<style name="AppTabTextAppearance" parent="TextAppearance.Design.Tab">
<item name="android:textSize">12sp</item>
<item name="android:textColor">#color/tabUnselectedTextColor</item>
<item name="textAllCaps">true</item>
</style>
<!-- TODO: Change to use AppCompat rather than Material -->
<style name="dateDialogTheme" parent="android:Theme.Material.Light.Dialog">
<!-- Required from http://stackoverflow.com/a/29014475/2193387 -->
<item name="colorPrimary">#color/colorPrimary</item>
<item name="colorPrimaryDark">#color/colorPrimaryDark</item>
<item name="colorAccent">#color/colorAccent</item>
</style>

The disappearing status bar effect is the result of these definitions in values-21/styles.xml:
<item name="android:windowDrawsSystemBarBackgrounds">true</item>
<item name="android:statusBarColor">#android:color/transparent</item>
With these definitions, the system no longer draws system bar background. What you see as status bar background is actually drawn by CoordinatingLayout, beyond the now-transparent system bar. Now, when you scroll, CoordinatedLayout scrolls AppBarLayout up, and its content is visible through the transparent system bar.
You have two options to fix this:
Make the status bar opaque
Additionally use CollapsingToolbarLayout, and set status bar scrim

I was also running into this issue and after some time I figured out, that I had to remove
android:fitsSystemWindows="true"
from CoordinatorLayout
I'm not quite sure why, but I think it is only required for the NavigationDrawer, because according to material design guidlines it overlays the status bar and there I needed to set this tag true.
Hope this is also working for you.

Add this to your CoordinatorLayout:
android:fitsSystemWindows="true"
or try with this:
<android.support.design.widget.CoordinatorLayout
...
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true">
<android.support.v4.view.ViewPager
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior" />
<android.support.design.widget.AppBarLayout
android:id="#+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar" >
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_height="?attr/actionBarSize"
android:layout_width="match_parent"
android:minHeight="?attr/actionBarSize"
android:background="#color/colorPrimary"
app:layout_scrollFlags="scroll|enterAlways|snap"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:popupTheme="#style/ThemeOverlay.AppCompat.Light">
...
</android.support.v7.widget.Toolbar>
<android.support.design.widget.TabLayout
android:id="#+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:foregroundGravity="top"
... />
</android.support.design.widget.AppBarLayout>
</android.support.design.widget.CoordinatorLayout>

To solve it you have to remove this line:
android:fitsSystemWindows="true"
It solves the problem for me.

I managed to get rid of this behaviour by removing the line below in the toolbar inside CoordinatorLayout:
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:layout_scrollFlags="scroll|enterAlways" << this one
app:popupTheme="#style/AppTheme.PopupOverlay">

Android Toolbar color not being set by colorPrimary

according to the google docs, I should be able to set the color of Toolbar background using colorPrimary in the theme, but it's not working. Here's what I have:
styles.xml:
<resources>
<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
<!-- Customize your theme here. -->
<item name="colorPrimary">#color/light_purple</item>
<!-- colorPrimaryDark is used for the status bar -->
<item name="colorPrimaryDark">#color/dark_purple</item>
<!-- colorAccent is used as the default value for colorControlActivated,
which is used to tint widgets -->
<item name="colorAccent">#color/dark_purple</item>
<item name="colorSwitchThumbNormal">#color/light_purple</item>
</style>
</resources>
activity layout:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:minHeight="?attr/actionBarSize"
android:theme="#style/AppTheme"
tools:showIn="#layout/activity_main">
<TextView
android:id="#+id/pivot_title_image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="toolbar text view" />
</android.support.v7.widget.Toolbar>
...
</LinearLayout>
Activity:
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
}
I have set my app theme to AppTheme in the manifest: android:theme="#style/AppTheme" >
I have setup android support appcompat in build.gradle
compile 'com.android.support:appcompat-v7:22.1.0'
But my toolbar, is still not colored.
I know I can manually set the toolbar background color manually in the layout file, but shouldn't it get its color from the theme? as you can see the accent colors are working.

Toolbar will not get primary color from your theme. You have to set the following xml property of the toolbar
android:background="#color/primary"
This is my working implementation of toolbar.
<?xml version="1.0" encoding="utf-8"?>
<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/primary"
android:minHeight="?actionBarSize">
</android.support.v7.widget.Toolbar>
Hope it works for you too.

Style and theme are different.
The style is local to the Toolbar view, for example the background color.
The theme is instead global to all ui elements inflated in the Toolbar, for example the color of the title and icons.
More info here.
With Material Components Library:
the android:background attribute in the layout:
<com.google.android.material.appbar.MaterialToolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
apply the default style: style="#style/Widget.MaterialComponents.Toolbar.Primary" or customize the style inheriting from it:
<com.google.android.material.appbar.MaterialToolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
style="#style/Widget.MaterialComponents.Toolbar.Primary"
override the default color using the android:theme attribute:
<com.google.android.material.appbar.MaterialToolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:theme="#style/MyThemeOverlay_Toolbar"
with:
<style name="MyThemeOverlay_Toolbar" parent="ThemeOverlay.MaterialComponents.Toolbar.Primary">
<item name="android:textColorPrimary">....</item>
<item name="colorPrimary">#color/.....
<item name="colorOnPrimary">#color/....</item>
</style>
With design support library:
<android.support.v7.widget.Toolbar
style="#style/HeaderBar"/>
where:
<style name="HeaderBar">
<item name="android:background">?colorPrimary</item>
</style>
Otherwise you can define the background for your Toolbar.
<android.support.v7.widget.Toolbar
android:background="?attr/colorPrimary">

You have to use android: prefixed attributes in the theme for android 5+, as the non-prefixed variant is only for the app compat parts for versions < android 5.
So you should have one values/styles.xml for pre-android 5 and one values-v21/styles.xml for android 5+.
In the v21 styles you define your theme as following:
<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
<item name="android:colorPrimary">#color/light_purple</item>
<item name="android:colorPrimaryDark">#color/dark_purple</item>
<item name="android:colorAccent">#color/dark_purple</item>
</style>
As you now define the colorPrimary attribute once simply as colorPrimary for pre-Lollipop and once as android:colorPrimary for Lollipop devices, you can no longer directly use ?attr/colorPrimary. Instead, like others here said before, you should define your own style for the toolbar, but for both variations:
values/styles.xml:
<style name="Toolbar">
<item name="android:background">?attr/colorPrimary</item>
</style>
values-v21/styles.xml:
<style name="Toolbar">
<item name="android:background">?android:attr/colorPrimary</item>
</style>
And use the style for your toolbar:
<android.support.v7.widget.Toolbar
style="#style/Toolbar"
Like this the background color and other styles can be set on all versions and is still changeable by the colorPrimary that is set in the theme(s).

Try to set background color to toolbar
This worked for me
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar_main"
android:layout_width="match_parent"
android:layout_height="?actionBarSize"
android:background="#color/primary_color"
android:gravity="right"
app:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar">
<ProgressBar
android:id="#+id/pb_loading_news"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="right"
android:visibility="gone" />
</android.support.v7.widget.Toolbar>

How to make Toolbar transparent?

It is self Q&A post
I have transparent ActionBar which overlays layout. After migration to the latest support library I have been forced to get rid off the ActionBar in favor of the Toolbar. The old ways to make it transparent and overlay that layout doesn't work anymore.
<style name="CustomActionBarTheme" parent="#android:style/Theme.AppCompat">
<item name="android:windowActionBarOverlay">true</item>
<item name="windowActionBarOverlay">true</item>
<item name="android:actionBarStyle">#style/TransparentActionBar</item>
</style>
<style name="TransparentActionBar" parent="#android:style/Widget.Holo.Light.ActionBar">
<item name="android:background">#android:color/transparent</item>
</style>

Create your toolbar.xml file with background of AppBarLayout is #null
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.AppBarLayout
android:id="#+id/general_appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#null"
xmlns:android="http://schemas.android.com/apk/res/android">
<android.support.v7.widget.Toolbar
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
android:text="Login"
android:textSize="20sp"/>
</android.support.v7.widget.Toolbar>
</android.support.design.widget.AppBarLayout>
and here is result:

All you need to is to define theme which hide action bar, define action bar style with transparent background and set this style to the toolbar widget. Please note that toolbar should be drawen as last view (over all view tree)
<style name="Theme.Custom" parent="#android:style/Theme.AppCompat">
<item name="windowActionBar">false</item>
<item name="windowActionBarOverlay">true</item>
<item name="android:windowActionBarOverlay">true</item>
</style>
<style name="CustomActionBar" parent="#style/ThemeOverlay.AppCompat.Dark.ActionBar">
<item name="android:windowActionBarOverlay">true</item>
<!-- Support library compatibility -->
<item name="windowActionBarOverlay">true</item>
</style>
Layout:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- Toolbar should be above content-->
<include layout="#layout/toolbar" />
</RelativeLayout>
Toolbar layout:
<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"
app:theme="#style/CustomActionBar"/>

Checking Google's example Source Code I found out how to make the toolbar completely transparent. It was simpler than I thought. We just have to create a simple Shape drawable like this.
The name of the drawable is toolbar_bg
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" >
<gradient
android:angle="90"
android:startColor="#android:color/transparent"
android:endColor="#android:color/transparent"
android:type="linear" />
</shape>
And then in the fragment or activity.. Add the toolbar like this.
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:background="#drawable/toolbar_bg"
android:popupTheme="#style/ThemeOverlay.AppCompat.Light"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar"/>
And here we will have a fully transparent toolbar.
Don't add the <android.support.design.widget.AppBarLayout > if you do, this won't work.
Note: If you need the AppBarLayout, set the elevation to 0 so it doesn't draw its shadow.

The Toolbar works like a View, so the answer it's very simple.
toolbar.getBackground().setAlpha(0);

Only this worked for me (AndroidX support library):
<com.google.android.material.appbar.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#null"
android:theme="#style/AppTheme.AppBarOverlay"
android:translationZ="0.1dp"
app:elevation="0dp">
<androidx.appcompat.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="#null"
app:popupTheme="#style/AppTheme.PopupOverlay" />
</com.google.android.material.appbar.AppBarLayout>
This code removes background in all necessary views and also removes shadow from AppBarLayout (which was a problem)
Answer was found here: remove shadow below AppBarLayout widget android

Add the following line in style.xml
<style name="Base.Theme.AppTheme" parent="Theme.AppCompat.DayNight.NoActionBar">
<item name="colorPrimary">#color/colorPrimary</item>
<item name="colorPrimaryDark">#color/colorPrimaryDark</item>
<item name="colorAccent">#color/colorAccent</item>
</style>
<style name="AppTheme" parent="Base.Theme.AppTheme">
</style>
Now add the following line in style-v21,
<style name="AppTheme" parent="Base.Theme.AppTheme">
<item name="android:windowDrawsSystemBarBackgrounds">true</item>
<item name="android:statusBarColor">#android:color/transparent</item>
</style>
and set the theme as
android:theme="#style/AppTheme"
It will make the status bar transparent.

Just add android:background="#android:color/transparent" like below in your appbar layout
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#android:color/transparent">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
app:popupTheme="#style/AppTheme.PopupOverlay" />
</android.support.design.widget.AppBarLayout>`

Just use the following xml code:
Code for the layout:
<android.support.v7.widget.Toolbar
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/def_toolbar"
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:minHeight="?attr/actionBarSize"
android:background="#color/toolbarTransparent"
android:layout_alignParentTop="true" />
And add the following code in the colors.xml:
<color name="toolbarTransparent">#00FFFFFF</color>
This will give you the desired output.

Perhaps you need to take a look at this post transparent Actionbar with AppCompat-v7 21
Points that the post suggest are
Just ensure that you use RelativeLayout to lay Toolbar and the body.
Put the Toolbar in the last.
Put transparent color for android:background attribute of the Toolbar
This should solve the problem without too much hassle.

The simplest way to put a Toolbar transparent is to define a opacity in #colors section, define a TransparentTheme in #styles section and then put these defines in your toolbar.
#colors.xml
<color name="actionbar_opacity">#33000000</color>
#styles.xml
<style name="TransparentToolbar" parent="#style/ThemeOverlay.AppCompat.Dark.ActionBar">
<item name="android:windowActionBarOverlay">true</item>
<item name="windowActionBarOverlay">true</item>
</style>
#activity_main.xml
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:background="#color/actionbar_opacity"
app:theme="#style/TransparentToolbar"
android:layout_height="?attr/actionBarSize"/>
That's the result:
Screenshot transparent toolbar

I implemented translucent Toolbar by creating two Theme.AppCompat.Light.NoActionBar themes and setting colorPrimary attribute to transparent color.
1) Create one theme for opaque Toolbar:
<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
<!-- Toolbar background color -->
<item name="colorPrimary">#ff212cff</item>
</style>
Second theme for transparent/overlay Toolbar:
<style name="AppTheme.Overlay" parent="AppTheme">
<item name="colorPrimary">#color/transparent</item>
</style>
2) In your activity layout, put Toolbar behind content so it can be displayed in front of it:
<RelativeLayout
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:orientation="vertical">
<fragment
android:id="#+id/container"
android:name="com.test.CustomFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="?attr/colorPrimary"
android:minHeight="?attr/actionBarSize"
app:popupTheme="#style/ThemeOverlay.AppCompat.Light"
app:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar"/>
</RelativeLayout>
3)
Apply the transparent theme to your acivity in AndroidManifest.xml
<activity
android:name="com.test.TransparentActivity"
android:parentActivityName="com.test.HomeActivity"
android:theme="#style/AppTheme.Overlay" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.test.HomeActivity" />
</activity>

I know am late for the party. I've created a simple class to manage the Toolbar transparency.
import android.annotation.SuppressLint;
import android.graphics.drawable.ColorDrawable;
import android.support.v7.widget.Toolbar;
public class TransparentToolbarManager {
private Toolbar mToolbar;
private ColorDrawable colorDrawable;
public static final int MAX_ALPHA = 255, MIN_ALPHA = 0;
public TransparentToolbarManager(Toolbar mToolbar) {
this.mToolbar = mToolbar;
this.colorDrawable = new ColorDrawable(mToolbar.getContext().getResources().getColor(R.color.colorPrimary));
}
public TransparentToolbarManager(Toolbar mToolbar, ColorDrawable colorDrawable) {
this.mToolbar = mToolbar;
this.colorDrawable = colorDrawable;
}
//Fading toolbar
public void manageFadingToolbar(int scrollDistance) {
if (mToolbar != null && colorDrawable != null) {
//FadeinAndOut according to the horizontal scrollValue
if (scrollDistance <= MAX_ALPHA && scrollDistance >= MIN_ALPHA) {
setToolbarAlpha(scrollDistance);
} else if (scrollDistance > MAX_ALPHA) {
setToolbarAlpha(MAX_ALPHA);
}
}
}
#SuppressLint("NewApi")
public void setToolbarAlpha(int i) {
colorDrawable.setAlpha(i);
if (CommonHelper.isSupport(16)) {
mToolbar.setBackground(colorDrawable);
} else {
mToolbar.setBackgroundDrawable(colorDrawable);
}
}
}
and the CommonHelper.isSupport()
public static boolean isSupport(int apiLevel) {
return Build.VERSION.SDK_INT >= apiLevel;
}

Just Add android:background="#10000000" in your AppBarLayout tag It works

https://stackoverflow.com/a/37672153/2914140 helped me.
I made this layout for an activity:
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
>
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/transparent" <- Add transparent color in AppBarLayout.
android:theme="#style/AppTheme.AppBarOverlay"
>
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?android:attr/actionBarSize"
android:theme="#style/ToolbarTheme"
app:popupTheme="#style/AppTheme.PopupOverlay"
app:theme="#style/ToolbarTheme"
/>
</android.support.design.widget.AppBarLayout>
<FrameLayout
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
<- Remove app:layout_behavior=...
/>
</android.support.design.widget.CoordinatorLayout>
If this doesn't work, in onCreate() of the activity write (where toolbar is #+id/toolbar):
toolbar.background.alpha = 0
If you want to set a semi-transparent color (like #30ff00ff), then set toolbar.setBackgroundColor(color). Or even set a background color of AppBarLayout.
In my case styles of AppBarLayout and Toolbar didn't play role.

try below code
<android.support.design.widget.AppBarLayout
android:id="#+id/app_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="#style/AppTheme.Transparent"
>
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
app:popupTheme="#style/AppTheme.PopupOverlay" />
</android.support.design.widget.AppBarLayout>
style.xml
<style name="AppTheme.Transparent" parent="ThemeOverlay.AppCompat.Light">
<item name="colorPrimary">#android:color/transparent</item>
<item name="colorControlActivated">#color/colorWhite</item>
<item name="colorControlNormal">#color/colorWhite</item>
</style>

for Support Toolbar v7 android.support.v7.widget.Toolbar:
code
toolbar.setBackground(null);
// or
toolbar.setBackgroundColor(ContextCompat.getColor(getContext(), android.R.color.transparent));
xml (android:background="#null" or android:background="#android:color/transparent")
<android.support.v7.widget.Toolbar
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:background="#null"
android:minHeight="?attr/actionBarSize"
android:theme="#style/Theme.AppCompat.Light.DarkActionBar">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textColor="#android:color/white"
android:ellipsize="start"
android:singleLine="true"
android:textAppearance="#style/TextAppearance.AppCompat.Widget.ActionBar.Title"/>
</android.support.v7.widget.Toolbar>
if Title is invisible, set textColor

Add below code to styles.xml file
<style name="LayoutPageTheme" parent="#style/Theme.AppCompat.Light.NoActionBar">
<item name="android:windowActionBarOverlay">true</item>
<!-- Support library compatibility -->
<item name="windowActionBarOverlay">true</item>
<item name="android:actionBarStyle">#style/TransparentActionBar</item>
</style>
<!-- ActionBar styles -->
<style name="TransparentActionBar"
parent="#android:style/Widget.Holo.Light.ActionBar">
<item name="android:background">#android:color/transparent</item>
</style>
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="#android:color/transparent"
app:popupTheme="#style/AppTheme.PopupOverlay" />
Don't forget to write: android:background="#android:color/transparent"

Go to res package and open color.xml.
Set color primary to #00000000.