Develop Reference

how to make FloatingActionButtn filled with image?

when I set Image for FloatingActionButton it will be margin at all directions .so I want the ActionButton to be filled with image without any margin.

Use the attribute
android:src="YOUR_DRAWABLE"
in your android.support.design.widget.FloatingActionButton block of XML layout.
Also in you styles.xml, under the style you are using (normally it is AppTheme) use
<item name="colorAccent">#android:color/transparent</item>

I think this is what you want to achieve. Use this code.
<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"
android:fitsSystemWindows="true"
android:cropToPadding="true"
android:background="#android:color/primary_text_dark"
android:src="#drawable/zvam" />
You will get something like this.
http://i.stack.imgur.com/FC4xg.png

Sorry that I do not answer your question directly (I would comment if I could), but I don't think that this is a good idea.
It seems to me that you just want to have a done/check-image on the FAB. If that's the case, you should use the "done" icon from google's material-icons page: https://design.google.com/icons/#ic_done
Also, have a look at google's designguidelines for FABs: https://www.google.com/design/spec/components/buttons-floating-action-button.html.

Android FAB plus sign not present on android drawable

Where can I find the plus sign at the center of a Floating Action Button?
Is it made by Android or do I need to do it by my self?

You can find the plus icon on the Vector Asset Studio.
In Android Studio, open an Android app project.
In the Project window, select the Android view.
Right-click the res folder and select New > Vector Asset.
Click the Android icon Button and look for the plus sign
More info here: https://developer.android.com/studio/write/vector-asset-studio.html#materialicon

You can get the Material Icons:
1.Online - from the Material Design Website. The plus icon is called 'add'. Select the icon, pick a colour & size and download the png or svg resource.
2.From Android Studio - using Vector Asset Studio. Check the link for more information. (as suggested by Wilder Pereira in the post below)

based on #Dagnogo's answer, I found this is the simplest way.
<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"
app:srcCompat="#android:drawable/ic_input_add"
android:tint="#android:color/white"/>
The key is using tint property

If you need to change the color change the tint method on the fab. For example I needed the "white plus" in my fab so I did that :
<android.support.design.widget.FloatingActionButton
android:layout_width="wrap_content"
android:tint="#android:color/white" //put your colors here
android:src="#drawable/ic_add_black_24dp"
android:layout_height="wrap_content" />

I think you are searching for this.
<android.support.design.widget.FloatingActionButton
android:id="#+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="end|bottom"
android:layout_margin="#dimen/fab_margin"
app:srcCompat="#android:drawable/ic_input_add" />

In 2021, if you want to change the colour of the button, then you need to use the app:tint property over android:tint.
Also, I recommend using app:srcCompat over android:src for better support of vectors.
For better accessibility support, it's important to use the android:contentDescription attribute.
Finally, you can use built-in drawables by using the #android:drawable/ prefix.
Putting it all together:
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="32dp"
android:contentDescription="Add a new item"
app:tint="#android:color/white"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:srcCompat="#android:drawable/ic_input_add" />

Android: Set material design elevation for button using AppCompat V7

When following this Android tutorial using AppCompat V7 to get the new Tool Bar work, the android.support.v7.widget.Toolbar supports android:elevation on SDK's < Lollipop. This is because they use android.support.v7.widget.Toolbar and not Toolbar.
Is there equivalent for button? Something like android.support.v7.widget.Button? (This one not exist) Or any other workaround in the kind of overlaying the Button in some view supporting elevation? (I don't want implementation of creating custom shapes with gradients for look & feel of elevation).
Thanks,

You can use the Floating Action Button from support design library .
Use below code to the layout where you want this button.
<android.support.design.widget.FloatingActionButton
android:id="#+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#mipmap/ic_fab"
android:layout_gravity="bottom|end"
app:backgroundTint="#0091b4"
app:elevation="6dp"
app:pressedTranslationZ="12dp"
android:layout_margin="10dp"
android:scaleType="centerCrop" />
Do add design dependency in your project
Add below in the dependency list of build.gradle file
compile 'com.android.support:design:23.0.1'

Unfortunately you will have to do what you do not want. Because there is no support button view yet. (As i know :) perhaps some omniscient person will correct my answer)

How to create a circle button in the right bottom corner on Android 5+?

Is there any standard tools or existing libraries to create a circle button like on Gmail App?

In the android support design support library one of the widgets provided is the Floating Action Button, which is usually added in the bottom right corner(but need not be used only there)
A floating action button is a round button denoting a primary action
on your interface. The Design library’s FloatingActionButton gives you
a single consistent implementation, by default colored using the
colorAccent from your theme.
To get the android design support library in your build.gradle file, add this:
compile 'com.android.support:design:22.2.0'
In your layout file"
<RelativeLayout
...
xmlns:app="http://schemas.android.com/apk/res-auto">
<android.support.design.widget.FloatingActionButton
android:id="#+id/myFAB"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_anchor="#id/appbar"
app:layout_anchorGravity="bottom|right|end"
android:src="#drawable/ic_discuss"
android:layout_margin="10dp"
android:clickable="true"/>
</RelativeLayout>
Details of android design support library here
Also there are many other libraries providing the FAB like
https://github.com/makovkastar/FloatingActionButton
https://github.com/futuresimple/android-floating-action-button

1.First important thing use Android Studio
2.Add as a dependency to your build.gradle:
dependencies {
compile 'com.melnykov:floatingactionbutton:1.3.0'
}
3. Create a layout
<ListView
android:id="#android:id/list"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<com.melnykov.fab.FloatingActionButton
android:id="#+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|right"
android:layout_margin="16dp"
android:src="#drawable/ic_action_content_new"
fab:fab_colorNormal="#color/primary"
fab:fab_colorPressed="#color/primary_pressed"
fab:fab_colorRipple="#color/ripple" />
4.Add the namespace
xmlns:fab="http://schemas.android.com/apk/res-auto"
to your layout file.
You can also Set the button type (normal or mini) via the fab_type xml attribute (default is normal):
fab:fab_type="mini"
or
fab.setType(FloatingActionButton.TYPE_MINI);

Yes, with the new Design Support Library a default implementation of the floating action button is provided here.
In order to have access to the new FAB class you will need to add this dependency to your gradle build file.
compile 'com.android.support:design:22.2.0'

How to add shadow to the FAB provided with the android support design library?

The title is pretty self explaining.
The following code does not render shadow below the Floating Action Button. What can be done to render shadow? Is this feature really not supported even on API 21+?
<android.support.design.widget.FloatingActionButton
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:src="#drawable/ic_add"
android:clickable="true" />
Note: Adding android:elevation does not add shadow on API 21.
Screenshot taken from the example by dandar3:
https://github.com/dandar3/android-support-design

Simply setting app:borderWidth="0dp" resolve this issues for me.
Note: don't forget to add xmlns:app="http://schemas.android.com/apk/res-auto" to your root layout.
This issue should be fixed in next release of android design library.

For API 21+ you need to set app:borderWidth="0dp" and app:elevation="[number]dp". Setting elevation you are giving the size of shadow that you want:
Here is an example of code for API 21+:
<android.support.design.widget.FloatingActionButton
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/locate_user_FAB"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/location_off"
app:elevation="6dp"
app:borderWidth="0dp"
android:layout_above="#+id/take_taxi_FAB"
app:backgroundTint="#color/colorAccentGrey">
One important thing to remember for APIs below to 21 (Android 4), is for terms of compatibility FAB will put a margins around your button to draw the shadow. Then you should do something like that (I'm currently using this code and works):
<android.support.design.widget.FloatingActionButton
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/locate_user_FAB"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/location_off"
app:elevation="6dp"
app:borderWidth="0dp"
android:layout_above="#+id/take_taxi_FAB"
android:layout_alignParentRight="true"
android:layout_marginRight="#dimen/map_FAB_marginRight"
android:layout_marginBottom="#dimen/locate_user_FAB_marginBottom"
app:backgroundTint="#color/colorAccentGrey">
I prefer to put xmlns:app="http://schemas.android.com/apk/res-auto" at the beginning of the XML, but I put there just to remind you ;]

I was experiencing this same issue and I got it to work by deleting this tag from my AndroidManifest.xml.
android:hardwareAccelerated="false"
I initially added it, together with android:largeHeap="true", because I thought I needed it for a HeatMap in which a large number of points where shown, but then I realized it could work just with android:largeHeap="true".

If this still isn't working for some, there is a significant difference between:
app:elevation="6dp"
app:borderWidth="0dp"
and
app:borderWidth="0dp"
app:elevation="6dp"
Order seems to matter for some reason (The first order works, second doesn't) and this is from the support library 23.3.0

Check manifest in project or libraries in Application tag and delete them
android:hardwareAccelerated="false"
android:largeHeap="true"
But if you need these options then shadows and transformation animations will not work

In case it help, I was using
android:tint="#color/myColor"
instead of
android:backgroundTint="#color/myColor".
Replacing tint by backgroundTint brought back the shadow.