FloatingActionButton example with Support Library

So in your build.gradle file, add this:

compile 'com.android.support:design:27.1.1'

AndroidX Note: Google is introducing new AndroidX extension libraries to replace the older Support Libraries. To use AndroidX, first make sure you've updated your gradle.properties file, edited build.gradle to set compileSdkVersion to 28 (or higher), and use the following line instead of the previous compile one.

implementation 'com.google.android.material:material:1.0.0'

Next, in your themes.xml or styles.xml or whatever, make sure you set this- it's your app's accent color-- and the color of your FAB unless you override it (see below):

        <item name="colorAccent">@color/floating_action_button_color</item>

In the layout's XML:

<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"            android:src="@drawable/ic_plus_sign"            app:elevation="4dp"            ... /></RelativeLayout>

Or if you are using the AndroidX material library above, you'd instead use this:

<RelativeLayout ... xmlns:app="http://schemas.android.com/apk/res-auto">       <com.google.android.material.floatingactionbutton.FloatingActionButton            android:id="@+id/myFAB"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:srcCompat="@drawable/ic_plus_sign"            app:elevation="4dp"            ... /></RelativeLayout>

You can see more options in the docs (material docs here) (setRippleColor, etc.), but one of note is:

    app:fabSize="mini"

Another interesting one-- to change the background color of just one FAB, add:

    app:backgroundTint="#FF0000"

(for example to change it to red) to the XML above.

Anyway, in code, after the Activity/Fragment's view is inflated....

    FloatingActionButton myFab = (FloatingActionButton)  myView.findViewById(R.id.myFAB);    myFab.setOnClickListener(new View.OnClickListener() {        public void onClick(View v) {            doMyThing();        }    });

Observations:

• If you have one of those buttons that's on a "seam" splitting two views(using a RelativeLayout, for example) with, say, a negative bottomlayout margin to overlap the border, you'll notice an issue:the FAB's size is actually very different on lollipop vs.pre-lollipop. You can actually see this in AS's visual layout editorwhen you flip between APIs-- it suddenly "puffs out" when you switch topre-lollipop. The reason for the extra size seems to be that theshadow expands the size of the view in every direction. So you have toaccount for this when you're adjusting the FAB's margins if it's close to otherstuff.

• Here's a way to remove orchange the padding if there's too much:

  if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {    RelativeLayout.LayoutParams p = (RelativeLayout.LayoutParams) myFab.getLayoutParams();    p.setMargins(0, 0, 0, 0); // get rid of margins since shadow area is now the margin    myFab.setLayoutParams(p);}

• Also, I was going to programmatically place the FAB on the "seam"between two areas in a RelativeLayout by grabbing the FAB's height,dividing by two, and using that as the margin offset. ButmyFab.getHeight() returned zero, even after the view was inflated, itseemed. Instead I used a ViewTreeObserver to get the height onlyafter it's laid out and then set the position. See this tiphere. It looked like this:

      ViewTreeObserver viewTreeObserver = closeButton.getViewTreeObserver();    if (viewTreeObserver.isAlive()) {        viewTreeObserver.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {            @Override            public void onGlobalLayout() {                if (Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN) {                    closeButton.getViewTreeObserver().removeGlobalOnLayoutListener(this);                } else {                    closeButton.getViewTreeObserver().removeOnGlobalLayoutListener(this);                }                // not sure the above is equivalent, but that's beside the point for this example...                RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams) closeButton.getLayoutParams();                params.setMargins(0, 0, 16, -closeButton.getHeight() / 2); // (int left, int top, int right, int bottom)                closeButton.setLayoutParams(params);            }        });    }

  Not sure if this is the right way to do it, but it seems to work.

• It seems you can make the shadow-space of the button smaller bydecreasing the elevation.

• If you want the FAB on a "seam" you can use layout_anchor and layout_anchorGravity here is an example:

  <android.support.design.widget.FloatingActionButton    android:layout_height="wrap_content"    android:layout_width="wrap_content"    app:layout_anchor="@id/appbar"    app:layout_anchorGravity="bottom|right|end"    android:src="@drawable/ic_discuss"    android:layout_margin="@dimen/fab_margin"    android:clickable="true"/>

Remember that you can automatically have the button jump out of the way when a Snackbar comes up by wrapping it in a CoordinatorLayout.

More:

• Google's Design Support Library Page
• the FloatingActionButton docs
• "Material Now" talk from Google I/O 2015 - Support Design Library introduced at 17m22s
• Design Support Library sample/showcase

I just found some issues on FAB and I want to enhance another answer.

setRippleColor issue

So, the issue will come once you set the ripple color (FAB color on pressed) programmatically through setRippleColor. But, we still have an alternative way to set it, i.e. by calling:

FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);ColorStateList rippleColor = ContextCompat.getColorStateList(context, R.color.fab_ripple_color);fab.setBackgroundTintList(rippleColor);

Your project need to has this structure:

/res/color/fab_ripple_color.xml

And the code from fab_ripple_color.xml is:

<selector xmlns:android="http://schemas.android.com/apk/res/android">    <item android:state_pressed="true" android:color="@color/fab_color_pressed" />    <item android:state_focused="true" android:color="@color/fab_color_pressed" />    <item android:color="@color/fab_color_normal"/></selector>

Finally, alter your FAB slightly:

<android.support.design.widget.FloatingActionButton    android:id="@+id/fab"    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:src="@drawable/ic_action_add"    android:layout_alignParentBottom="true"    android:layout_alignParentRight="true"    app:fabSize="normal"    app:borderWidth="0dp"    app:elevation="6dp"    app:pressedTranslationZ="12dp"    app:rippleColor="@android:color/transparent"/> <!-- set to transparent color -->

For API level 21 and higher, set margin right and bottom to 24dp:

...android:layout_marginRight="24dp"android:layout_marginBottom="24dp" />

FloatingActionButton design guides

As you can see on my FAB xml code above, I set:

        ...        android:layout_alignParentBottom="true"        android:layout_alignParentRight="true"        app:elevation="6dp"        app:pressedTranslationZ="12dp"        ...

• By setting these attributes, you don't need to set layout_marginTop and layout_marginRight again (only on pre-Lollipop). Android will place it automatically on the right corned side of the screen, which the same as normal FAB in Android Lollipop.

      android:layout_alignParentBottom="true"    android:layout_alignParentRight="true"

Or, you can use this in CoordinatorLayout:

        android:layout_gravity="end|bottom"

• You need to have 6dp elevation and 12dp pressedTranslationZ, according to this guide from Google.

FloatingActionButton extends ImageView. So, it's simple as like introducing an ImageView in your layout. Here is an XML sample.

<android.support.design.widget.FloatingActionButton   xmlns:app="http://schemas.android.com/apk/res-auto"    android:id="@+id/fab"    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:src="@drawable/somedrawable"    android:layout_gravity="right|bottom"    app:borderWidth="0dp"    app:rippleColor="#ffffff"/>

app:borderWidth="0dp" is added as a workaround for elevation issues.