FloatingActionButton example with Support Library

Question

Recently, I read these posts:

Android Design Support Library

Android Support Library, revision 22.2.0

FloatingActionButton

But, none of them give me a detail example about creating a new

FloatingActionButton

. So hard to understand, I ask this question.

Can anyone give me an example about it?

Any help much be appreciated. Thanks in advance.

EDIT

I just found some issues on

FloatingActionButton

(FAB), and I want to improve another answer. See my answer below.

Answer 1

So in your build.gradle file, add this:

compile 'com.android.support:design:24.0.0'

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>

(Note: In version 22.2.0, app:borderWidth="0dp" was also required to address a bug where shadows would not appear in Lollipop/M without it. Thanks to the explanation for the fix here. This bug was corrected in version 22.2.1.)

You can see more options in the docs (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 bottom layout 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 editor when you flip between APIs-- it suddenly "puffs out" when you switch to pre-lollipop. The reason for the extra size seems to be that the shadow expands the size of the view in every direction. So you have to account for this when you're adjusting the FAB's margins if it's close to other stuff.

Here's a way to remove or change 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. But myFab.getHeight() returned zero, even after the view was inflated, it seemed. Instead I used a ViewTreeObserver to get the height only after it's laid out and then set the position. See this tip here. 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 by decreasing 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

FloatingActionButton example with Support Library

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