底部有固定按钮，带有RecyclerView和CollapsingToolbar

Question

当用户滚动RecyclerView时，我试图将按钮固定在底部。这就是我试过的：

<?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=".AddProduct">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/product_app_bar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#ffffff"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/main.collapsing"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:expandedTitleMarginEnd="64dp"
            app:expandedTitleMarginStart="48dp"
            app:layout_scrollFlags="scroll|enterAlwaysCollapsed">

            <android.support.constraint.ConstraintLayout
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_marginBottom="16dp"
                android:orientation="vertical">

                <TextView
                    android:id="@+id/tv_name"
                    android:layout_width="0dp"
                    android:layout_height="wrap_content"
                    android:layout_marginEnd="8dp"
                    android:layout_marginStart="8dp"
                    android:layout_marginTop="16dp"
                    android:text="teste"
                    android:textColor="#161616"
                    android:textSize="22sp"
                    app:layout_constraintEnd_toEndOf="parent"
                    app:layout_constraintStart_toStartOf="parent"
                    app:layout_constraintTop_toTopOf="parent" />


            </android.support.constraint.ConstraintLayout>

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

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


    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior">

        <android.support.v7.widget.RecyclerView
            app:layout_behavior="@string/appbar_scrolling_view_behavior"
            android:id="@+id/rv_test"
            android:layout_width="match_parent"
            android:layout_height="match_parent"></android.support.v7.widget.RecyclerView>

        <Button
            android:id="@+id/btn_product_add_product"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:layout_marginBottom="138dp"
            android:background="@color/colorPrimary"
            android:text="Test button"
            android:textColor="@color/textColorPrimary" />

    </RelativeLayout>

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

然后我根据用户滚动使用AppBarLayout.OnOffsetChangedListener来调整按钮边距。

虽然有效，但如果用户滚动得快一点，它就无法很好地调整边距，并且按钮似乎没有固定。它不可靠。

那么，最好的方法是怎样做的？

Answer 1

也许您可以使用ConstraintLayout代替RelativeLayout，如下所示：

<android.support.constraint.ConstraintLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior">

    <android.support.v7.widget.RecyclerView
        app:layout_behavior="@string/appbar_scrolling_view_behavior"
        android:id="@+id/rv_test"
        android:layout_width="0dp"
        android:layout_height="0dp" 
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toTopOf="@+id/btn_product_add_product"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent" />

    <Button
        android:id="@+id/btn_product_add_product"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        android:background="@color/colorPrimary"
        android:text="Test button"
        android:textColor="@color/textColorPrimary" />

</android.support.constraint.ConstraintLayout>