1<?xml version="1.0" encoding="utf-8"?>2<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"3    xmlns:app="http://schemas.android.com/apk/res-auto"4    xmlns:tools="http://schemas.android.com/tools"5    android:layout_width="match_parent"6    android:layout_height="match_parent">7 8    <com.google.android.material.appbar.AppBarLayout9        android:id="@+id/abl_bar_layout"10        android:layout_width="match_parent"11        android:layout_height="wrap_content"12        android:fitsSystemWindows="true"13        android:minHeight="0dp"14        app:liftOnScrollTargetViewId="@+id/rv_recyclerview">15 16        <com.google.android.material.appbar.CollapsingToolbarLayout17            android:id="@+id/collapsing_Toolbar"18            android:layout_width="match_parent"19            android:layout_height="wrap_content"20            app:layout_scrollFlags="scroll|exitUntilCollapsed">21 22            <androidx.appcompat.widget.AppCompatImageView23                android:layout_width="match_parent"24                android:layout_height="300dp"25                android:scaleType="centerCrop"26                android:src="@mipmap/cover_01"27                app:layout_collapseMode="parallax"28                app:layout_collapseParallaxMultiplier="0.7" />29 30            <com.google.android.material.textview.MaterialTextView31                android:id="@+id/tv_mode"32                android:layout_width="match_parent"33                android:layout_height="wrap_content"34                android:layout_gravity="bottom"35                android:layout_marginBottom="56dp"36                android:paddingHorizontal="16dp"37                android:textColor="@color/white"38                android:textAppearance="?attr/textAppearanceTitleMedium" />39 40            <com.google.android.material.appbar.MaterialToolbar41                android:id="@+id/toolbar"42                android:layout_width="match_parent"43                android:layout_height="?attr/actionBarSize"44                android:background="#20ff0000"45                app:layout_collapseMode="pin"46                app:title="ToolBar" />47 48        </com.google.android.material.appbar.CollapsingToolbarLayout>49    </com.google.android.material.appbar.AppBarLayout>50 51    <androidx.core.widget.NestedScrollView52        android:layout_width="match_parent"53        android:layout_height="match_parent"54        app:layout_behavior="@string/appbar_scrolling_view_behavior">55 56        <TextView57            android:layout_width="wrap_content"58            android:layout_height="wrap_content"59            android:layout_margin="@dimen/text_margin"60            android:text="@string/large_text" />61 62    </androidx.core.widget.NestedScrollView>63 64</androidx.coordinatorlayout.widget.CoordinatorLayout>

1open class ExtendedFAB @JvmOverloads constructor(2    context: Context,3    attributeSet: AttributeSet? = null,4) : ExtendedFloatingActionButton(context, attributeSet) {5 6    private val fabBehavior = ExtendedFABBehavior(context, attributeSet)7 8    override fun getBehavior(): CoordinatorLayout.Behavior<ExtendedFloatingActionButton> {9        return fabBehavior10    }11 12    /**13     * 自定义 Behavior14     */15    protected class ExtendedFABBehavior(16        context: Context,17        attributeSet: AttributeSet?18    ) : ExtendedFloatingActionButtonBehavior<ExtendedFloatingActionButton>(context, attributeSet) {19 20     21        /**22         * 因为实现了 Behavior 接口，CoordinatorLayout 始终会调用该视图的 onLayoutChild。23         * 在这里自定义或修改布局，以代替默认的子布局行为。24         */25        @SuppressLint("RestrictedApi")26        override fun onLayoutChild(parent: CoordinatorLayout, child: ExtendedFloatingActionButton, layoutDirection: Int): Boolean {27            val paramsCompat = child.layoutParams as ViewGroup.MarginLayoutParams28            height = child.measuredHeight + paramsCompat.bottomMargin29            return super.onLayoutChild(parent, child, layoutDirection)30        }31 32        /**33         * 当依赖的视图发生变化时调用，可以在这里处理子视图的位置或大小变化。34         */35        override fun onDependentViewChanged(parent: CoordinatorLayout, child: ExtendedFloatingActionButton, dependency: View): Boolean {36            return super.onDependentViewChanged(parent, child, dependency)37        }38 39        /**40         * 用于确定一个视图是否依赖于另一个视图，返回true表示依赖，false表示不依赖。41         */42        override fun layoutDependsOn(parent: CoordinatorLayout, child: ExtendedFloatingActionButton, dependency: View): Boolean {43            return super.layoutDependsOn(parent, child, dependency)44        }45 46        /**47         * 用于处理滚动事件，可以在这里响应滚动事件并调整子视图的位置或大小。48         */49        override fun onStartNestedScroll(50            coordinatorLayout: CoordinatorLayout,51            child: ExtendedFloatingActionButton,52            directTargetChild: View,53            target: View,54            axes: Int,55            type: Int56        ): Boolean {57            return axes == ViewCompat.SCROLL_AXIS_VERTICAL58        }59 60        /**61         * 用于处理滚动事件，可以在这里响应滚动事件并调整子视图的位置或大小。62         */63        override fun onNestedScroll(64            coordinatorLayout: CoordinatorLayout,65            child: ExtendedFloatingActionButton,66            target: View,67            dxConsumed: Int,68            dyConsumed: Int,69            dxUnconsumed: Int,70            dyUnconsumed: Int,71            type: Int,72            consumed: IntArray73        ) {74            if (dyConsumed > 0) {75                shrink(child)76                slideDown(child)77            } else {78                extend(child)79                if (dyConsumed < 0) {80                    slideUp(child)81                }82            }83        }84    }85}