Android Floating Action Button doesn't get fixed at the bottom

问题

I have a fragment wich renders a recycleview with an floating action buttom. The problem is that when the list is empty, the fab keeps on the right top, when the list has few items, the fab keeps bellow the list but not at the bottom, and it only keeps totatly at the bottom when the list fill the screen with items. Could somebody help me please? Bellow is my code:

<?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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.app.juninho.financeapp.activity.FuncionarioActivity">

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

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/btn_add_func"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|right|end"
        android:layout_alignParentBottom="true"
        android:layout_alignParentEnd="true"
        android:layout_alignParentRight="true"
        android:layout_margin="16dp"
        android:src="@drawable/ic_menu_send"
        app:layout_behavior="com.app.juninho.financeapp.utils.ScrollAwareFABBehavior" />

回答1:

The problem is your FAB attribute: app:layout_behavior="com.app.juninho.financeapp.utils.ScrollAwareFABBehavior".

#. You don't need to add this with your FAB. Just remove this attribute and add attribute app:layout_anchor="@id/funcionario_recycler_view" and app:layout_anchorGravity="bottom|right|end" to FAB to anchor it with RecyclerView.

Update your layout as below:

<?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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.app.juninho.financeapp.activity.FuncionarioActivity">

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

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/btn_add_func"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|right|end"
        android:layout_alignParentBottom="true"
        android:layout_alignParentEnd="true"
        android:layout_alignParentRight="true"
        android:layout_margin="16dp"
        android:src="@drawable/ic_menu_send"
        app:layout_anchor="@id/funcionario_recycler_view"
        app:layout_anchorGravity="bottom|right|end" />
</android.support.design.widget.CoordinatorLayout>

#. If you want to hide/show FAB when scrolling RecyclerView, then you can do it pragmatically in your java code as below:

RecyclerView recyclerView = (RecyclerView) findViewById(R.id.funcionario_recycler_view);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.btn_add_func); 

recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener()
{
    @Override
    public void onScrolled(RecyclerView recyclerView, int dx, int dy)
    {
        if (dy > 0 ||dy<0 && fab.isShown())
        {
            fab.hide();
        }
    }

    @Override
    public void onScrollStateChanged(RecyclerView recyclerView, int newState)
    {
        if (newState == RecyclerView.SCROLL_STATE_IDLE)
        {
            fab.show();
        }

        super.onScrollStateChanged(recyclerView, newState);
    }
});

Hope this will help~

来源：https://stackoverflow.com/questions/44013537/android-floating-action-button-doesnt-get-fixed-at-the-bottom