如何在ViewPager和CoordinatorLayout中修复视图的位置

Question

I have an activity with the layout of:

<android.support.design.widget.CoordinatorLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <android.support.design.widget.AppBarLayout
            android:layout_height="wrap_content"
            android:layout_width="match_parent"
            android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_height="56dp"
                android:layout_width="match_parent"
                app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
                app:layout_scrollFlags="scroll|enterAlways"
                app:contentInsetLeft="0dp"
                app:contentInsetStart="0dp"
                app:layout_collapseMode="pin"/>

            <android.support.design.widget.TabLayout
                android:id="@+id/tabs"
                android:layout_width="wrap_content"
                app:tabIndicatorColor="@color/indicator"
                app:tabMode="scrollable"
                android:layout_height="wrap_content" />

        </android.support.design.widget.AppBarLayout>

        <android.support.v4.view.ViewPager
            android:id="@+id/viewpager"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_behavior="@string/appbar_scrolling_view_behavior" />

</android.support.design.widget.CoordinatorLayout>

The fragment loaded in ViewPager has a layout of:

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:android="http://schemas.android.com/apk/res/android">

    <android.support.v4.widget.SwipeRefreshLayout
        android:id="@+id/refresh_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <android.support.v7.widget.RecyclerView
            android:id="@+id/gridView"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:paddingTop="10dp"
            android:scrollbars="vertical" />

    </android.support.v4.widget.SwipeRefreshLayout>

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/download_btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_marginBottom="16dp"
        android:layout_marginLeft="16dp"
        android:src="@drawable/ic_btn_download" />

</RelativeLayout> 

How can I fix the position (prevent scrolling) of the FloatingActionButton inside the fragment (it scrolls with its parent)?

Note that I couldn't move FloatingActionButton to the activity layout.

Answer 1

You should move your floating action button from your view pager to coordinator layout. From there you can set your floating action button position with

android:layout_gravity="end|bottom"

or

app:layout_anchor="@id/yourViewToAnchor"
app:layout_anchorGravity="bottom|right|end"

And don't forget to put your floating action button on the lowermost of your coordinator layout XML to ensure that your floating action button at the top of your layout.

Answer 2

You should use a FAB in activity layout. .If you need different colors or actions you can define FAB in your fragment and set the color or the action for each fragment.