最新項(xiàng)目中用到了些Material效果备恤，在此對(duì)自己的學(xué)習(xí)做個(gè)小結(jié)状植。

首先養(yǎng)成良好的學(xué)習(xí)習(xí)慣-----看源碼：

CoordinatorLayout

/**
 * CoordinatorLayout is a super-powered {@link android.widget.FrameLayout FrameLayout}.
 *
 * <p>CoordinatorLayout is intended for two primary use cases:</p> 
 * <ol>
 *     <li>As a top-level application decor or chrome layout</li> 
 *     <li>As a container for a specific interaction with one or more child views</li> 
 * </ol> 
 * 
 * <p>By specifying {@link CoordinatorLayout.Behavior Behaviors} for child views of a 
 * CoordinatorLayout you can provide many different interactions within a single parent and those 
 * views can also interact with one another. View classes can specify a default behavior when 
 * used as a child of a CoordinatorLayout using the 
 * {@link CoordinatorLayout.DefaultBehavior DefaultBehavior} annotation.</p> 
 * 
 * <p>Behaviors may be used to implement a variety of interactions and additional layout 
 * modifications ranging from sliding drawers and panels to swipe-dismissable elements and buttons 
 * that stick to other elements as they move and animate.</p> 
 * 
 * <p>Children of a CoordinatorLayout may have an 
 * {@link CoordinatorLayout.LayoutParams#setAnchorId(int) anchor}. This view id must correspond 
 * to an arbitrary descendant of the CoordinatorLayout, but it may not be the anchored child itself 
 * or a descendant of the anchored child. This can be used to place floating views relative to 
 * other arbitrary content panes.</p> 
 */
public class CoordinatorLayout extends ViewGroup implements NestedScrollingParent {

大概的翻譯如下：

• CoordinateLayout是一個(gè)超級(jí)FrameLayout纺且。
• CoordinateLayout原意是用于以下情況：
  1. 作為頂層布局日丹。
  2. 作為一個(gè)容器铅协，它的子View之間有特殊的相互作用（交互）画机。
• 通過(guò)為CoordinatorLayout的子views指定Behavior盛卡，在同一個(gè)父容器下可以提供不同的交互矗钟，并且那些子view可以和另一個(gè)子view相互作用唆香，相互影響。通過(guò)@DefaultBehavior注釋?zhuān)珻oordinatorLayout的子view可以使用一個(gè)默認(rèn)的behavior吨艇。
• Behavior可以用來(lái)實(shí)現(xiàn)各種交互和 來(lái)自滑動(dòng)抽屜躬它、滑動(dòng)刪除元素和按鈕關(guān)聯(lián)其他元素產(chǎn)生的額外的布局修改。
• CoordinatorLayout的子view也許會(huì)有個(gè)anchor（錨點(diǎn)东涡，即view顯示在哪塊區(qū)域）冯吓，這個(gè)子view必須是CoordinatorLayout的直接子view，不能是孫子輩兒的view - -疮跑！
  通過(guò)看CoordinatorLayout官方注釋文檔组贺，了解到一個(gè)重要信息---Behavior，可以說(shuō)CoordinatorLayout各種炫酷的交互效果祖娘，都是通過(guò)Behavior來(lái)控制的失尖，除此之外，CoordinatorLayout類(lèi)似于FrameLayout渐苏，那么接下來(lái)看重點(diǎn)：

Behavior：

/**
 * Interaction behavior plugin for child views of {@link CoordinatorLayout}. 
 * 
 * <p>A Behavior implements one or more interactions that a user can take on a child view.
 * These interactions may include drags, swipes, flings, or any other gestures.</p>
 *
 * @param <V> The View type that this Behavior operates on
 */
public static abstract class Behavior<V extends View> {

老規(guī)矩：

• CoordinatorLayout的子view的交互行為插件掀潮。
• 一個(gè)Behavior可以實(shí)現(xiàn)一個(gè)或更多的交互，用戶(hù)可以將這些交互用在CoordinatorLayout的子view上琼富，這些交互包括：拖拽胧辽、滑動(dòng)、飛速滑動(dòng)公黑、或者其他任何手勢(shì)。

基本使用：

新建一個(gè)HelloWorld摄咆，選擇BasicActivity凡蚜，可以看到默認(rèn)生成的布局中已經(jīng)包含了CoordinatorLayout，說(shuō)明Goolge官方非常推薦使用這種布局吭从。
官方給出的Behavior實(shí)現(xiàn)類(lèi)有4個(gè)：

• BottomSheetBehavior
• SwipeDismissBehavior
• FloatingActionButton中實(shí)現(xiàn)的Behavior
• ViewOffsetBehavior

Behavior實(shí)現(xiàn)類(lèi)

BottomSheetBehavior

一般用于底部彈出框朝蜘，類(lèi)似于微信支付的效果，使用方法如下：

xml布局

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

    <android.support.v4.widget.NestedScrollView
        android:id="@+id/nestedScrollView"
        android:layout_width="match_parent"
        android:layout_height="350dp"
        android:background="@drawable/mv"
        app:layout_behavior="@string/bottom_sheet_behavior"
        app:behavior_peekHeight="0dp"
        app:behavior_hideable="true">
        <!--中間可以隨意寫(xiě)自己的布局-->
    </android.support.v4.widget.NestedScrollView>

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="@dimen/fab_margin"
        app:layout_behavior="cn.lxf.behaviortext.FloatingBehavior"
        app:srcCompat="@android:drawable/ic_dialog_email" />

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

Activity代碼

scrollView = (NestedScrollView) findViewById(R.id.nestedScrollView);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
     @Override
     public void onClick(View view) {
          BottomSheetBehavior bottomSheetBehavior = BottomSheetBehavior.from(scrollView);
          bottomSheetBehavior.setState(bottomSheetBehavior.getState() == BottomSheetBehavior.STATE_COLLAPSED?BottomSheetBehavior.STATE_EXPANDED:BottomSheetBehavior.STATE_COLLAPSED);
     }
});

效果圖：

bottomSheetBehavior

實(shí)現(xiàn)的關(guān)鍵點(diǎn)：

• 根布局為 CoordinatorLayout涩金；
• 為底部彈出框設(shè)置app:layout_behavior="@string/bottom_sheet_behavior"谱醇；
• 在代碼中得到BottomSheetBehavior，并動(dòng)態(tài)改變它的狀態(tài)步做；
• 至于FloatingActionButton跟隨彈出框移動(dòng)副渴，關(guān)鍵點(diǎn)在于為FloatingActionButton設(shè)置app:layout_behavior="cn.lxf.behaviortext.FloatingBehavior"；這是一個(gè)自定義的Behavior全度，文章后面會(huì)有講解煮剧。

SwipeDismissBehavior

官方實(shí)現(xiàn)為Snackbar，已經(jīng)封裝好，唯一的條件是根布局必須為CoordinatorLayout勉盅，否則沒(méi)有效果佑颇。
??使用方式很簡(jiǎn)單：

Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG).setAction("Action", null).show();

FloatingActionButton.Behavior

FloatingActionButton默認(rèn)使用FloatingActionButton.Behavior，同Snackbar一樣草娜，唯一需要注意的是根布局必須為CoordinatorLayout挑胸。

@CoordinatorLayout.DefaultBehavior(FloatingActionButton.Behavior.class)
public class FloatingActionButton extends VisibilityAwareImageButton {

<android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="@dimen/fab_margin"
        app:srcCompat="@android:drawable/ic_dialog_email" />

Snackbar + FloatingActionButton效果圖

ViewOffsetBehavior

官方實(shí)現(xiàn)為AppBarLayout中的Beihavior。

AppBarLayout官方文檔

挑重點(diǎn)：

• AppBarLayout是一個(gè)實(shí)現(xiàn)了很多Material設(shè)計(jì)風(fēng)格的垂直的LinearLayout宰闰。
• 子view可以通過(guò)設(shè)置layout_scrollFlags來(lái)提供他們所需要的滾動(dòng)方式茬贵。
• 你需要設(shè)置你的Scrolling view的behavior（app:layout_behavior）為AppBarLayout.ScrollingViewBehavior來(lái)提醒AppBarLayout什么時(shí)候滾動(dòng)。
• 最下面為goolgle官方提供的一個(gè)例子议蟆。
  話(huà)說(shuō)第一次看到layout_scrollFlags屬性的萌新必然會(huì)一臉懵逼闷沥，到底應(yīng)該填什么呢（因?yàn)槲耶?dāng)初就是這樣...( ╯□╰ )），這里順便介紹ScrollFlags的幾個(gè)常量：

        /**
         * The view will be scroll in direct relation to scroll events. This flag needs to be
         * set for any of the other flags to take effect. If any sibling views
         * before this one do not have this flag, then this value has no effect.
         */
        public static final int SCROLL_FLAG_SCROLL = 0x1;

        /**
         * When exiting (scrolling off screen) the view will be scrolled until it is
         * 'collapsed'. The collapsed height is defined by the view's minimum height.
         *
         * @see ViewCompat#getMinimumHeight(View)
         * @see View#setMinimumHeight(int)
         */
        public static final int SCROLL_FLAG_EXIT_UNTIL_COLLAPSED = 0x2;

        /**
         * When entering (scrolling on screen) the view will scroll on any downwards
         * scroll event, regardless of whether the scrolling view is also scrolling. This
         * is commonly referred to as the 'quick return' pattern.
         */
        public static final int SCROLL_FLAG_ENTER_ALWAYS = 0x4;

        /**
         * An additional flag for 'enterAlways' which modifies the returning view to
         * only initially scroll back to it's collapsed height. Once the scrolling view has
         * reached the end of it's scroll range, the remainder of this view will be scrolled
         * into view. The collapsed height is defined by the view's minimum height.
         *
         * @see ViewCompat#getMinimumHeight(View)
         * @see View#setMinimumHeight(int)
         */
        public static final int SCROLL_FLAG_ENTER_ALWAYS_COLLAPSED = 0x8;

        /**
         * Upon a scroll ending, if the view is only partially visible then it will be snapped
         * and scrolled to it's closest edge. For example, if the view only has it's bottom 25%
         * displayed, it will be scrolled off screen completely. Conversely, if it's bottom 75%
         * is visible then it will be scrolled fully into view.
         */
        public static final int SCROLL_FLAG_SNAP = 0x10;

• SCROLL_FLAG_SCROLL：對(duì)應(yīng)xml布局中的scroll咐容，如果要設(shè)置其他的滾動(dòng)flag舆逃，這個(gè)flag必須要設(shè)置，否則無(wú)效戳粒。
• SCROLL_FLAG_EXIT_UNTIL_COLLAPSED：對(duì)應(yīng)xml布局中的exitUntilCollapsed路狮，設(shè)置該flag的view在向上滑動(dòng)退出屏幕時(shí)，不會(huì)完全退出蔚约，會(huì)保留collapsed height（minHeight）高度奄妨。
• SCROLL_FLAG_ENTER_ALWAYS：對(duì)應(yīng)xml布局中的enterAlways，只要手指向下滑苹祟，設(shè)置該flag的view就會(huì)直接進(jìn)入屏幕砸抛，不管NestedScrollView是否在滾動(dòng)。
• SCROLL_FLAG_ENTER_ALWAYS_COLLAPSED ：對(duì)應(yīng)xml布局中的enterAlwaysCollapsed树枫，是enterAlways的附加flag直焙，使設(shè)置該flag的view在進(jìn)入屏幕時(shí)最初只滑動(dòng)顯示到它的collapsed height（minHeight），一旦NestedScrollView滑到頂部砂轻，該view再滑動(dòng)顯示剩余的部分奔誓。
• SCROLL_FLAG_SNAP：對(duì)應(yīng)xml布局中的snap，設(shè)置該flag的view在滾動(dòng)停止時(shí)搔涝，如果沒(méi)有完全顯示厨喂，會(huì)自動(dòng)滾到到最近的一個(gè)邊界（頂端、中線和下線）庄呈。

scroll

scroll+exitUntilCollapsed

scroll+enterAlways

scroll+enterAlways+enterAlwaysCollapsed

scroll+enterAlways+snap

自定義Behavior

自定義Behavior一般有兩種情況：

• 某個(gè)view監(jiān)聽(tīng)另一個(gè)view的狀態(tài)變化蜕煌，例如大小、位置诬留、顯示狀態(tài)等幌绍。
• 某個(gè)view監(jiān)聽(tīng)CoordinatorLayout里的滑動(dòng)狀態(tài)颁褂。

上面這兩句話(huà)出自亓斌大神博客，然后我自己在學(xué)習(xí)過(guò)程中做了些實(shí)踐傀广。
??首先看第一種颁独，其實(shí)就是上面那個(gè)例子，F(xiàn)loatingActionButton怎么跟隨自己的布局上下移動(dòng)伪冰？很明顯誓酒，這個(gè)效果類(lèi)似于系統(tǒng)提供的FloatingActionButton+Snackbar的效果，看一下FloatingActionButton.Behavior源碼（只貼了關(guān)鍵部分）:

       /**
         * Determine whether the supplied child view has another specific sibling view as a
         * layout dependency.
         *
         * <p>This method will be called at least once in response to a layout request. If it
         * returns true for a given child and dependency view pair, the parent CoordinatorLayout
         * will:</p>
         * <ol>
         *     <li>Always lay out this child after the dependent child is laid out, regardless
         *     of child order.</li>
         *     <li>Call {@link #onDependentViewChanged} when the dependency view's layout or
         *     position changes.</li>
         * </ol>
         *
         * @param parent the parent view of the given child
         * @param child the child view to test
         * @param dependency the proposed dependency of child
         * @return true if child's layout depends on the proposed dependency's layout,
         *         false otherwise
         *
         * @see #onDependentViewChanged(CoordinatorLayout, android.view.View, android.view.View)
         */
        @Override
        public boolean layoutDependsOn(CoordinatorLayout parent,
                FloatingActionButton child, View dependency) {
            // We're dependent on all SnackbarLayouts (if enabled)
            return SNACKBAR_BEHAVIOR_ENABLED && dependency instanceof Snackbar.SnackbarLayout;
        }

        @Override
        public boolean onDependentViewChanged(CoordinatorLayout parent, FloatingActionButton child,
                View dependency) {
            if (dependency instanceof Snackbar.SnackbarLayout) {
                updateFabTranslationForSnackbar(parent, child, dependency);
            } else if (dependency instanceof AppBarLayout) {
                // If we're depending on an AppBarLayout we will show/hide it automatically
                // if the FAB is anchored to the AppBarLayout
                updateFabVisibility(parent, (AppBarLayout) dependency, child);
            }
            return false;
        }

• layoutDependsOn(parent,child, dependency)：決定一個(gè)child是否有一個(gè)其他特殊的兄弟view（dependency）作為布局依賴(lài)贮聂，聽(tīng)來(lái)比較拗口靠柑，其實(shí)就是指一個(gè)child是否會(huì)根據(jù)另一個(gè)view的參數(shù)和狀態(tài)而改變。這個(gè)方法在初始化布局時(shí)最少會(huì)被調(diào)用一次吓懈，如果返回true歼冰，則父布局(CoordinatorLayout)會(huì)不斷的調(diào)用onDependentViewChanged(parent,child, dependency)來(lái)改變?cè)揷hild的參數(shù)和狀態(tài)。
• 然后系統(tǒng)會(huì)在onDependentViewChanged中判斷dependency的類(lèi)型耻警，進(jìn)而改變Fab的參數(shù)隔嫡、狀態(tài)。
  下面我們來(lái)比葫蘆畫(huà)瓢：

public class FloatingBehavior extends FloatingActionButton.Behavior {

    @Override
    public boolean layoutDependsOn(CoordinatorLayout parent, FloatingActionButton child, View dependency) {
        return super.layoutDependsOn(parent, child, dependency) || dependency instanceof NestedScrollView;
    }

    @Override
    public boolean onDependentViewChanged(CoordinatorLayout parent, FloatingActionButton fab, View dependency) {
        if (dependency instanceof NestedScrollView) {
            CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams) fab.getLayoutParams();
            int fab_BM = lp.bottomMargin;
            int distance = fab.getHeight() + fab_BM;
            fab.setY(dependency.getY() - distance);
        }
        return super.onDependentViewChanged(parent, fab, dependency);
    }
}

為Fab設(shè)置好改behavior后直接運(yùn)行甘穿，發(fā)現(xiàn)報(bào)錯(cuò)：Could not inflate Behavior subclass cn.lxf.behaviortext.FloatingBehavior腮恩，不能實(shí)例化該behavior。一番求證后發(fā)現(xiàn)温兼，自定義behavior時(shí)必須重寫(xiě)那個(gè)帶2個(gè)參數(shù)的構(gòu)造方法秸滴，因?yàn)樵贑oordinatorLayout中是通過(guò)反射這個(gè)構(gòu)造方法來(lái)實(shí)例化behavior的，下面貼完整代碼：

public class FloatingBehavior extends FloatingActionButton.Behavior {

    public FloatingBehavior(Context context, AttributeSet attrs) {

    }

    @Override
    public boolean layoutDependsOn(CoordinatorLayout parent, FloatingActionButton child, View dependency) {
        return super.layoutDependsOn(parent, child, dependency) || dependency instanceof NestedScrollView;
    }

    @Override
    public boolean onDependentViewChanged(CoordinatorLayout parent, FloatingActionButton fab, View dependency) {
        if (dependency instanceof NestedScrollView) {
            CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams) fab.getLayoutParams();
            int fab_BM = lp.bottomMargin;
            int distance = fab.getHeight() + fab_BM ;
            fab.setY(dependency.getY() - distance);
        }
        return super.onDependentViewChanged(parent, fab, dependency);
    }
}

再看第二種情況募判，某個(gè)view監(jiān)聽(tīng)CoordinateLayout中的滑動(dòng)狀態(tài)荡含，這里最好先了解一下android Lollipop版本之后新增的嵌套滑動(dòng)機(jī)制，推薦我學(xué)習(xí)過(guò)的一篇文章https://segmentfault.com/a/1190000002873657届垫。
??對(duì)于監(jiān)聽(tīng)滑動(dòng)狀態(tài)释液，我們需要關(guān)注的總共有以下幾個(gè)方法（由于篇幅原因，官方注釋被我干掉了敦腔，加了簡(jiǎn)單的注解）：

    /**
     * 當(dāng)一個(gè)CoordinatorLayout的子view準(zhǔn)備去開(kāi)始一個(gè)嵌套滑動(dòng)時(shí)調(diào)用
     *
     * @param coordinatorLayout  根布局coordinatorLayout
     * @param child 這個(gè)behavior所關(guān)聯(lián)的coordinatorLayout的子view
     * @param directTargetChild 包含target 嵌套滾動(dòng)操作的coordinatorLayout子view
     * @param target 開(kāi)始嵌套滑動(dòng)的coordinatorLayout子view。
     * @param nestedScrollAxes 嵌套滾動(dòng)的軸線恨溜。See
     *                         {@link ViewCompat#SCROLL_AXIS_HORIZONTAL},
     *                         {@link ViewCompat#SCROLL_AXIS_VERTICAL}
     * @return 如果behavior希望接受這個(gè)嵌套滾動(dòng)符衔，則返回true。
     *
     * @see NestedScrollingParent#onStartNestedScroll(View, View, int)
     */
    public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout,
                                       V child, View directTargetChild, View target, int nestedScrollAxes) {
        return false;
    }

    /**
     * 當(dāng)嵌套滑動(dòng)已經(jīng)被CoordinatorLayout接受時(shí)調(diào)用糟袁。
     *
     * 參數(shù)同上判族。
     * @see NestedScrollingParent#onNestedScrollAccepted(View, View, int)
     */
    public void onNestedScrollAccepted(CoordinatorLayout coordinatorLayout, V child,
                                       View directTargetChild, View target, int nestedScrollAxes) {
        // Do nothing
    }

    /**
     * 嵌套滾動(dòng)結(jié)束時(shí)調(diào)用。
     *
     * 參數(shù)同上项戴。
     *
     * @see NestedScrollingParent#onStopNestedScroll(View)
     */
    public void onStopNestedScroll(CoordinatorLayout coordinatorLayout, V child, View target) {
        // Do nothing
    }

    /**
     * target滑動(dòng)之后調(diào)用
     *
     * @param coordinatorLayout 同上
     * @param child 同上
     * @param target 同上
     * @param dxConsumed 水平方向target滑動(dòng)的距離(消耗的距離px)形帮，左滑大于0，右滑小于0
     * @param dyConsumed 垂直方向target滑動(dòng)的距離(消耗的距離px)，上滑大于0辩撑，下滑小于0
     * @param dxUnconsumed 水平方向target未滑動(dòng)的距離(但是被用戶(hù)請(qǐng)求了)
     * @param dyUnconsumed 垂直方向target未滑動(dòng)的距離(但是被用戶(hù)請(qǐng)求了)
     *
     * @see NestedScrollingParent#onNestedScroll(View, int, int, int, int)
     */
    public void onNestedScroll(CoordinatorLayout coordinatorLayout, V child, View target,
                               int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
        // Do nothing
    }

    /**
     * target準(zhǔn)備滑動(dòng)時(shí)（滑動(dòng)之前）調(diào)用
     *
     * @param coordinatorLayout 同上
     * @param child 同上
     * @param target 同上
     * @param dx 水平方向target想要滑動(dòng)的距離（用戶(hù)請(qǐng)求的）
     * @param dy 垂直方向target想要滑動(dòng)的距離（用戶(hù)請(qǐng)求的）
     * @param consumed 需要我們自己傳入界斜。 consumed[0] 已經(jīng)被消費(fèi)的水平方向滑動(dòng)的距離, consumed[1] 已經(jīng)被消費(fèi)的垂直方向滑動(dòng)的距離
     *
     * @see NestedScrollingParent#onNestedPreScroll(View, int, int, int[])
     */
    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, V child, View target,
                                  int dx, int dy, int[] consumed) {
        // Do nothing
    }

    /**
     * target在fling（飛速滾動(dòng)）之后調(diào)用
     *
     * @param coordinatorLayout 同上
     * @param child 同上
     * @param target 同上
     * @param velocityX 水平方向的速度
     * @param velocityY 垂直方向的速度
     * @param consumed child是否fling了
     * @return behavior是否消費(fèi)了這個(gè)fling
     *
     * @see NestedScrollingParent#onNestedFling(View, float, float, boolean)
     */
    public boolean onNestedFling(CoordinatorLayout coordinatorLayout, V child, View target,
                                 float velocityX, float velocityY, boolean consumed) {
        return false;
    }

    /**
     * target在fling（飛速滾動(dòng)）之前調(diào)用
     *
     * 參數(shù)同onNestedFling方法。
     *
     * @see NestedScrollingParent#onNestedPreFling(View, float, float)
     */
    public boolean onNestedPreFling(CoordinatorLayout coordinatorLayout, V child, View target,
                                    float velocityX, float velocityY) {
        return false;
    }

還是看上面那個(gè)FloatingActionButton的例子合冀，改成上滑消失各薇，下滑顯示，代碼如下：

public class FloatingBehavior extends FloatingActionButton.Behavior {

    private boolean isAniming;

    public FloatingBehavior(Context context, AttributeSet attrs) {

    }

    @Override
    public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, FloatingActionButton child, View directTargetChild, View target, int nestedScrollAxes) {
        return nestedScrollAxes == ViewCompat.SCROLL_AXIS_VERTICAL;
    }

    @Override
    public void onNestedScroll(CoordinatorLayout coordinatorLayout, FloatingActionButton child, View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
        if (dyConsumed > 0 && !isAniming && child.getVisibility() == View.VISIBLE) {
            hide(child);
        } else if (dyConsumed < 0 && !isAniming && child.getVisibility() == View.INVISIBLE) {
            show(child);
        }
    }

    private void show(final View view){
        ValueAnimator animator = ValueAnimator.ofFloat(0,1);
        animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                float f = (float) animation.getAnimatedValue();
                view.setScaleX(f);
                view.setScaleY(f);
            }
        });
        animator.addListener(new Animator.AnimatorListener() {
            @Override
            public void onAnimationStart(Animator animation) {
                view.setVisibility(View.VISIBLE);
                isAniming = true;
            }

            @Override
            public void onAnimationEnd(Animator animation) {
                isAniming = false;
            }

            @Override
            public void onAnimationCancel(Animator animation) {
                isAniming = false;
            }

            @Override
            public void onAnimationRepeat(Animator animation) {

            }
        });
        animator.start();
    }

    private void hide(final View view){
        ValueAnimator animator = ValueAnimator.ofFloat(1,0);
        animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                float f = (float) animation.getAnimatedValue();
                view.setScaleX(f);
                view.setScaleY(f);
            }
        });
        animator.addListener(new Animator.AnimatorListener() {
            @Override
            public void onAnimationStart(Animator animation) {
                isAniming = true;
            }

            @Override
            public void onAnimationEnd(Animator animation) {
                view.setVisibility(View.INVISIBLE);
                isAniming = false;
            }

            @Override
            public void onAnimationCancel(Animator animation) {
                isAniming = false;
            }

            @Override
            public void onAnimationRepeat(Animator animation) {

            }
        });
        animator.start();
    }
}

效果圖：

監(jiān)聽(tīng)CoordinatorLayout中的滑動(dòng)狀態(tài)

Demo地址