FloatingActionButton(悬浮按钮)使用学习<一>

 

FloatingActionButton简称FAB。

 

一. 对于App或某个页面中是否要使用FloatingActionButton必要性：

    FAB代表一个App或一个页面中最主要的操作，如果一个App的每个页面都有FAB,则通常表示该App最主要的功能是通过该FAB操作的。

    为了突出FAB的重要性，一个页面最好只有一个FAB。

二. FloatingActionButton大小

    通常有两种尺寸

    1. 56 * 56dp ：默认的大小，最常用的尺寸。

    2. 40 * 40 dp ：Mini版。

    当然也可以改它的大小。

    FAB中间的图标，google推荐的大小是：24 * 24dp

三. 哪些操作推荐使用FloatingActionButton

   如： 添加，收藏，编辑，分享，导航等，如下图：

   

   而如：删除，警告，错误，剪切等操作，则不推荐使用FloatingActionButton。

 

 

 

四. FAB的使用

　Android 5.0 中引入Material Design，FAB为Android Design Support Library支持包中的中Material Design控件，要使用FAB，先要引入Design Support Library包，如：在build.gradle中加入: compile 'com.android.support:design:X.X.X'，X为支持包版本号，如下图：

　FAB的继承关系：

    

　FAB的XMl属性除了继承自View,ImageView的属性外，Android 5.0后引入的常用新属性如下：

    注：使用下面属性，先要引入命名空间：xmlns:app="http://schemas.android.com/apk/res-auto"

    　　1>   app:elevation="50dp"：阴影的高度，elevation是Android 5.0中引入的新属性，设置该属性使控件有一个阴影，感觉该控件像是“浮”起来一样，这样达到3D效果。对应的方法：setCompatElevation(float)

    　　2>   app:fabSize="normal"：FAB的大小，为normal时，大小为：56 * 56dp ，为mini时，大小为： 40 * 40 dp。

   　　3>  app:backgroundTint="#31bfcf"：FAB的背景颜色。

   　　4>  app:rippleColor="#e7d16b"：点击FAB时，形成的波纹颜色。

    <一> 使用例子1： 简单使用FAB

     点击“+”悬浮按钮，弹出悬浮按钮菜单，效果如下：

     代码如下：

     XMl布局：

 <?xml version="1.0" encoding="utf-8"?>
 <RelativeLayout
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     >
     <CheckBox
         android:id="@+id/cbDelay"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="delay"
         android:layout_marginTop="10dp"
         android:layout_marginLeft="10dp"
         />
     <RelativeLayout
         android:id="@+id/rlAddBill"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:background="#80000000"
         android:visibility="gone"
         >
             <LinearLayout
                 android:id="@+id/ll01"
                 android:layout_width="match_parent"
                 android:layout_height="wrap_content"
                 android:layout_alignParentBottom="true"
                 android:layout_marginBottom="100dp"
                 android:orientation="horizontal"
                 >
                     <TextView
                         android:layout_toLeftOf="@+id/miniFab01"
                         android:layout_width="0dp"
                         android:layout_height="wrap_content"
                         android:layout_weight="1"
                         android:text="销售单"
                         android:textSize="15sp"
                         android:textColor="@android:color/white"
                         android:layout_gravity="center_vertical"
                         android:gravity="right"
                         android:paddingBottom="5dp"
                        />
                     <android.support.design.widget.FloatingActionButton
                         android:id="@+id/miniFab01"
                         android:layout_width="wrap_content"
                         android:layout_height="wrap_content"
                         android:src="@mipmap/ic_list_white_24dp"
                         android:layout_marginRight="25dp"
                         app:fabSize="mini"
                         app:elevation="5dp"
                         app:backgroundTint="@color/color_XSD"
                         />
             </LinearLayout>
            <LinearLayout
                 android:id="@+id/ll02"
                 android:layout_width="match_parent"
                 android:layout_height="wrap_content"
                 android:orientation="horizontal"
                 android:layout_above="@+id/ll01"
                 >
             <TextView
                 android:layout_toLeftOf="@+id/miniFab02"
                 android:layout_width="0dp"
                 android:layout_height="wrap_content"
                 android:layout_weight="1"
                 android:text="销售退货"
                 android:textSize="15sp"
                 android:textColor="@android:color/white"
                 android:layout_gravity="center_vertical"
                 android:gravity="right"
                 android:paddingBottom="5dp"
                 />
             <android.support.design.widget.FloatingActionButton
                 android:id="@+id/miniFab02"
                 android:layout_width="wrap_content"
                 android:layout_height="wrap_content"
                 android:src="@mipmap/ic_list_white_24dp"
                 android:layout_marginRight="25dp"
                 app:fabSize="mini"
                 app:elevation="5dp"
                 app:backgroundTint="@color/color_XSTH"
                 />
         </LinearLayout>
         <LinearLayout
             android:id="@+id/ll03"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
             android:orientation="horizontal"
             android:layout_above="@+id/ll02"
             >
             <TextView
                 android:layout_toLeftOf="@+id/miniFab02"
                 android:layout_width="0dp"
                 android:layout_height="wrap_content"
                 android:layout_weight="1"
                 android:text="收款单"
                 android:textSize="15sp"
                 android:textColor="@android:color/white"
                 android:layout_gravity="center_vertical"
                 android:gravity="right"
                 android:paddingBottom="5dp"
                 />
             <android.support.design.widget.FloatingActionButton
                 android:id="@+id/miniFab03"
                 android:layout_width="wrap_content"
                 android:layout_height="wrap_content"
                 android:src="@mipmap/ic_list_white_24dp"
                 android:layout_marginRight="25dp"
                 app:fabSize="mini"
                 app:elevation="5dp"
                 app:backgroundTint="@color/color_SKD"
                 />
         </LinearLayout>
         <LinearLayout
             android:id="@+id/ll04"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
             android:orientation="horizontal"
             android:layout_above="@+id/ll03"
             >
             <TextView
                 android:layout_toLeftOf="@+id/miniFab02"
                 android:layout_width="0dp"
                 android:layout_height="wrap_content"
                 android:layout_weight="1"
                 android:text="进货单"
                 android:textSize="15sp"
                 android:textColor="@android:color/white"
                 android:layout_gravity="center_vertical"
                 android:gravity="right"
                 android:paddingBottom="5dp"
                 />
             <android.support.design.widget.FloatingActionButton
                 android:id="@+id/miniFab04"
                 android:layout_width="wrap_content"
                 android:layout_height="wrap_content"
                 android:src="@mipmap/ic_list_white_24dp"
                 android:layout_marginRight="25dp"
                 app:fabSize="mini"
                 app:elevation="5dp"
                 app:backgroundTint="@color/color_JHD"
                 />
         </LinearLayout>
         <LinearLayout
             android:id="@+id/ll05"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
             android:orientation="horizontal"
             android:layout_above="@+id/ll04"
             >
             <TextView
                 android:layout_toLeftOf="@+id/miniFab02"
                 android:layout_width="0dp"
                 android:layout_height="wrap_content"
                 android:layout_weight="1"
                 android:text="采购退货"
                 android:textSize="15sp"
                 android:textColor="@android:color/white"
                 android:layout_gravity="center_vertical"
                 android:gravity="right"
                 android:paddingBottom="5dp"
                 />
             <android.support.design.widget.FloatingActionButton
                 android:id="@+id/miniFab05"
                 android:layout_width="wrap_content"
                 android:layout_height="wrap_content"
                 android:src="@mipmap/ic_list_white_24dp"
                 android:layout_marginRight="25dp"
                 app:fabSize="mini"
                 app:elevation="5dp"
                 app:backgroundTint="@color/color_CGTH"
                 />
         </LinearLayout>
         <LinearLayout
             android:id="@+id/ll06"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
             android:orientation="horizontal"
             android:layout_above="@+id/ll05"
             >
             <TextView
                 android:layout_toLeftOf="@+id/miniFab02"
                 android:layout_width="0dp"
                 android:layout_height="wrap_content"
                 android:layout_weight="1"
                 android:text="付款单"
                 android:textSize="15sp"
                 android:textColor="@android:color/white"
                 android:layout_gravity="center_vertical"
                 android:gravity="right"
                 android:paddingBottom="5dp"
                 />
             <android.support.design.widget.FloatingActionButton
                 android:id="@+id/miniFab06"
                 android:layout_width="wrap_content"
                 android:layout_height="wrap_content"
                 android:src="@mipmap/ic_list_white_24dp"
                 android:layout_marginRight="25dp"
                 app:fabSize="mini"
                 app:elevation="5dp"
                 app:backgroundTint="@color/color_FKD"
                 />
         </LinearLayout>
     </RelativeLayout>
     <android.support.design.widget.FloatingActionButton
         android:id="@+id/fab01Add"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentRight="true"
         android:layout_alignParentBottom="true"
         android:src="@mipmap/ic_add_white_24dp"
         android:layout_marginRight="15dp"
         android:layout_marginBottom="20dp"
         app:fabSize="normal"
         app:elevation="5dp"
         app:backgroundTint="#31bfcf"
         app:rippleColor="#e7d161"
         />
 </RelativeLayout>

　　Java代码：

 package com.zst.floatactionbutton;
 import android.animation.Animator;
 import android.animation.AnimatorInflater;
 import android.animation.AnimatorSet;
 import android.content.Intent;
 import android.content.res.ColorStateList;
 import android.os.Bundle;
 import android.support.annotation.Nullable;
 import android.support.design.widget.FloatingActionButton;
 import android.support.v7.app.AppCompatActivity;
 import android.view.View;
 import android.view.WindowManager;
 import android.widget.CheckBox;
 import android.widget.LinearLayout;
 import android.widget.RelativeLayout;
 /**
  * Created by shengtao_zeng on 2016/11/10.
  */
 public class BasicFABActivity extends AppCompatActivity implements View.OnClickListener{
     private CheckBox cbDelay;
     private FloatingActionButton fab01Add;
     private boolean isAdd = false;
     private RelativeLayout rlAddBill;
     private int[] llId = new int[]{R.id.ll01,R.id.ll02,R.id.ll03,R.id.ll04,R.id.ll05,R.id.ll06};
     private LinearLayout[] ll = new LinearLayout[llId.length];
     private int[] fabId = new int[]{R.id.miniFab01,R.id.miniFab02,R.id.miniFab03,R.id.miniFab04,R.id.miniFab05,R.id.miniFab06};
     private FloatingActionButton[] fab = new FloatingActionButton[fabId.length];
     private AnimatorSet addBillTranslate1;
     private AnimatorSet addBillTranslate2;
     private AnimatorSet addBillTranslate3;
     private AnimatorSet addBillTranslate4;
     private AnimatorSet addBillTranslate5;
     private AnimatorSet addBillTranslate6;
     @Override
     protected void onCreate(@Nullable Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.basic_fab_activity);
         initView();
         setDefaultValues();
         bindEvents();
     }
     private void initView(){
         cbDelay  = (CheckBox)findViewById(R.id.cbDelay);
         fab01Add = (FloatingActionButton)findViewById(R.id.fab01Add);
         rlAddBill = (RelativeLayout)findViewById(R.id.rlAddBill);
         for (int i = 0; i < llId.length;i++){
             ll[i] = (LinearLayout)findViewById(llId[i]);
         }
         for (int i = 0;i < fabId.length; i++){
             fab[i] = (FloatingActionButton)findViewById(fabId[i]);
         }
     }
     private void setDefaultValues(){
         addBillTranslate1 = (AnimatorSet) AnimatorInflater.loadAnimator(this,R.animator.add_bill_anim);
         addBillTranslate2 = (AnimatorSet) AnimatorInflater.loadAnimator(this,R.animator.add_bill_anim);
         addBillTranslate3 = (AnimatorSet) AnimatorInflater.loadAnimator(this,R.animator.add_bill_anim);
         addBillTranslate4 = (AnimatorSet) AnimatorInflater.loadAnimator(this,R.animator.add_bill_anim);
         addBillTranslate5 = (AnimatorSet) AnimatorInflater.loadAnimator(this,R.animator.add_bill_anim);
         addBillTranslate6 = (AnimatorSet) AnimatorInflater.loadAnimator(this,R.animator.add_bill_anim);
     }
     private void bindEvents(){
         fab01Add.setOnClickListener(this);
         for (int i = 0;i < fabId.length; i++){
             fab[i].setOnClickListener(this);
         }
     }
     @Override
     public void onClick(View v) {
         switch (v.getId()) {
             case R.id.fab01Add:
                 fab01Add.setImageResource(isAdd ? R.mipmap.ic_add_white_24dp:R.mipmap.ic_close_white_24dp);
                 isAdd = !isAdd;
                 rlAddBill.setVisibility(isAdd ? View.VISIBLE : View.GONE);
                 if (isAdd) {
                     addBillTranslate1.setTarget(ll[0]);
                     addBillTranslate1.start();
                     addBillTranslate2.setTarget(ll[1]);
                     addBillTranslate2.setStartDelay(cbDelay.isChecked() ? 150 : 0);
                     addBillTranslate2.start();
                     addBillTranslate3.setTarget(ll[2]);
                     addBillTranslate3.setStartDelay(cbDelay.isChecked() ? 200 : 0);
                     addBillTranslate3.start();
                     addBillTranslate4.setTarget(ll[3]);
                     addBillTranslate4.setStartDelay(cbDelay.isChecked() ? 250 : 0);
                     addBillTranslate4.start();
                     addBillTranslate5.setTarget(ll[4]);
                     addBillTranslate5.setStartDelay(cbDelay.isChecked() ? 300 : 0);
                     addBillTranslate5.start();
                     addBillTranslate6.setTarget(ll[5]);
                     addBillTranslate6.setStartDelay(cbDelay.isChecked() ? 350 : 0);
                     addBillTranslate6.start();
                 }
                 break;
             case R.id.miniFab01:
                 hideFABMenu();
                 break;
             case R.id.miniFab02:
                 hideFABMenu();
                 break;
             case R.id.miniFab03:
                 hideFABMenu();
                 break;
             case R.id.miniFab04:
                 hideFABMenu();
                 break;
             case R.id.miniFab05:
                 hideFABMenu();
                 break;
             case R.id.miniFab06:
                 hideFABMenu();
                 break;
             default:
                 break;
         }
     }
     private void hideFABMenu(){
         rlAddBill.setVisibility(View.GONE);
         fab01Add.setImageResource(R.mipmap.ic_add_white_24dp);
         isAdd = false;
     }
 }

　　Property Animation定义：

 <?xml version="1.0" encoding="utf-8"?>
 <set xmlns:android="http://schemas.android.com/apk/res/android"
     android:ordering="sequentially"
     >
     <set
         android:ordering="together"
         >
         <objectAnimator
             android:propertyName="translationY"
             android:valueFrom="100.00"
             android:valueTo="-50.00"
             android:duration="100"
             android:startOffset="0"
             android:repeatCount="0"
             android:valueType="floatType"
             />
         <objectAnimator
             android:propertyName="alpha"
             android:valueFrom="0.00"
             android:valueTo="1.00"
             android:duration="100"
             android:startOffset="0"
             android:valueType="floatType"
             android:repeatCount="0"
             />
         <objectAnimator
             android:propertyName="scaleY"
             android:valueFrom="0.00"
             android:valueTo="1.50"
             android:duration="100"
             android:startOffset="0"
             android:valueType="floatType"
             android:repeatCount="0"
             />
     </set>
     <set
         android:ordering="together"
         >
         <objectAnimator
             android:propertyName="translationY"
             android:valueTo="0.00"
             android:duration="100"
             android:startOffset="0"
             android:repeatCount="0"
             android:valueType="floatType"
             />
         <objectAnimator
             android:propertyName="scaleY"
             android:valueTo="1.0"
             android:duration="100"
             android:startOffset="0"
             android:valueType="floatType"
             android:repeatCount="0"
             />
     </set>
 </set>

    <二> 使用例子2： FAB和ListView 的结合使用

           效果如下：

                        

                            a>  ListView向下滚动时，添加联系人的悬浮按钮隐藏。

                            b>  ListView向上滚动时，添加联系人的悬浮按钮显示。

                            c>  ListView向下滚动1/4时，会显示“回到顶部”的悬浮按钮，点击该按钮，ListView显示的顶部Item返回到第一个Item。

       ListView滚动和FAB的隐藏/显示的关系逻辑如下图：

                            

     代码如下：

      XML布局：

 <?xml version="1.0" encoding="utf-8"?>
 <RelativeLayout
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     >
     <ListView
         android:id="@+id/lvContacts"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:divider="#80000000"
         android:dividerHeight="1px"
         >
     </ListView>
     <android.support.design.widget.FloatingActionButton
         android:id="@+id/fabAddContact"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginBottom="16dp"
         android:layout_marginRight="8dp"
         android:src="@mipmap/ic_person_add_white_24dp"
         app:fabSize="normal"
         android:layout_alignParentBottom="true"
         android:layout_alignParentRight="true"
         />
     <android.support.design.widget.FloatingActionButton
         android:id="@+id/fabUp"
         android:layout_above="@+id/fabAddContact"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginBottom="16dp"
         android:layout_marginRight="20dp"
         android:src="@mipmap/ic_keyboard_arrow_up_white_24dp"
         app:fabSize="mini"
         android:layout_alignParentRight="true"
         app:backgroundTint="#92be0a"
         android:visibility="gone"
         />
 </RelativeLayout>

    主逻辑代码：

 package com.zst.floatactionbutton;
 import android.animation.AnimatorInflater;
 import android.animation.AnimatorSet;
 import android.content.Context;
 import android.os.Bundle;
 import android.support.annotation.Nullable;
 import android.support.design.widget.FloatingActionButton;
 import android.support.v7.app.AppCompatActivity;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.AbsListView;
 import android.widget.BaseAdapter;
 import android.widget.ListView;
 import android.widget.TextView;
 import java.util.ArrayList;
 import java.util.List;

 public class FABInListViewActivity extends AppCompatActivity implements View.OnClickListener{
     private ListView lvContacts;
     private ContactsAdapter adapter;
     private List<String> list = new ArrayList<>();
     private long  mNumber = 13812007799L;
     private FloatingActionButton fabAddContact;
     private FloatingActionButton fabUp;
     private AnimatorSet mHideFAB;
     private AnimatorSet mShowFAB;
     private boolean FAB_VISIBLE = true;
     private int mPreviousFirstVisibleItem;   //记录前面第一个Item
     private int mLastScrollY;            //记录ListView中最上面的Item(View)的上一次顶部Y坐标()
     private int mScrollThreshold = 2;   //阈值：单位px
     @Override
     protected void onCreate(@Nullable Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.fab_in_listview_activity);
         initView();
         setDefaultValues();
         bindEvents();
     }
     private void initView(){
         lvContacts = (ListView)findViewById(R.id.lvContacts);
         fabAddContact = (FloatingActionButton)findViewById(R.id.fabAddContact);
         fabUp = (FloatingActionButton)findViewById(R.id.fabUp);
     }
     private void setDefaultValues(){
         for (int i = 0; i < 100;i++){
             list.add("Contact" + i + "+" + (mNumber + i));
         }
         adapter = new ContactsAdapter(this,list);
         lvContacts.setAdapter(adapter);
         initAnimation();
     }
     private void initAnimation(){
         mHideFAB = (AnimatorSet)AnimatorInflater.loadAnimator(this,R.animator.scroll_hide_fab);
         mShowFAB = (AnimatorSet)AnimatorInflater.loadAnimator(this,R.animator.scroll_show_fab);
         mHideFAB.setTarget(fabAddContact);
         mShowFAB.setTarget(fabAddContact);
     }
     private void bindEvents(){
         fabUp.setOnClickListener(this);
         lvContacts.setOnScrollListener(new AbsListView.OnScrollListener() {
             @Override
             public void onScrollStateChanged(AbsListView view, int scrollState) {
 //                if(scrollState == AbsListView.OnScrollListener.SCROLL_STATE_IDLE) {  //停止滚动
                     //showFAB();
 //                }
             }
             @Override
             public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
                 if(totalItemCount == 0) {
                     showFAB();
                     return;
                 }
                 //滚动过程中：ListView中最上面一个Item还是同一个Item
                 if(isSameRow(firstVisibleItem)) {
                     int newScrollY = getTopItemScrollY();
                     boolean isExceedThreshold = Math.abs(mLastScrollY - newScrollY) > mScrollThreshold;
                     if (isExceedThreshold) {
                         if (mLastScrollY > newScrollY && FAB_VISIBLE == true) {
                             FAB_VISIBLE = false;
                             hideFAB();
                         } else if(mLastScrollY < newScrollY && FAB_VISIBLE == false){
                             FAB_VISIBLE = true;
                             showFAB();
                         }
                     }
                     mLastScrollY = newScrollY;
                 } else {
                     if (firstVisibleItem > mPreviousFirstVisibleItem && FAB_VISIBLE == true){  //向下滚动
                         FAB_VISIBLE = false;
                         hideFAB();
                     } else if(firstVisibleItem < mPreviousFirstVisibleItem && FAB_VISIBLE == false){ //向上滚动
                         FAB_VISIBLE = true;
                         showFAB();
                     }
                     mLastScrollY = getTopItemScrollY();
                     mPreviousFirstVisibleItem = firstVisibleItem;
                 }
                 if (firstVisibleItem > (totalItemCount/4)) {
                     fabUp.setVisibility(View.VISIBLE);
                 } else {
                     fabUp.setVisibility(View.GONE);
                 }
             }
         });
     }
     private boolean isSameRow(int firstVisisbleItem){
         return mPreviousFirstVisibleItem == firstVisisbleItem;
     }
     /**
      * 滚动过程中，获得当前ListView中最上面的Item(View)的顶部的Y坐标(以px为单位)
      * @return
      */
     private int getTopItemScrollY() {
         if (lvContacts == null || lvContacts.getChildAt(0) == null) return 0;
         View topChild = lvContacts.getChildAt(0);
         return topChild.getTop();
     }
     @Override
     public void onClick(View v) {
         switch (v.getId()) {
             case R.id.fabUp:
                 lvContacts.setSelection(0);
                 fabUp.setVisibility(View.GONE);
                 break;
             default:
                 break;
         }
     }
     private void hideFAB() {
         mHideFAB.start();
     }
     private void showFAB(){
         mShowFAB.start();
     }
     class ContactsAdapter extends BaseAdapter {
         private Context mContext;
         private List<String> list;
         public ContactsAdapter(Context mContext,List<String> list) {
             this.mContext = mContext;
             this.list = list;
         }
         @Override
         public int getCount() {
             return list.size();
         }
         @Override
         public Object getItem(int position) {
             return list.get(position);
         }
         @Override
         public long getItemId(int position) {
             return position;
         }
         @Override
         public View getView(int position, View convertView, ViewGroup parent) {
             convertView = LayoutInflater.from(mContext).inflate(R.layout.contacts_item,null);
             TextView tvName = (TextView)convertView.findViewById(R.id.tvName);
             TextView tvNumber = (TextView)convertView.findViewById(R.id.tvNumber);
             tvName.setText((list.get(position).split("\\+"))[0]);
             tvNumber.setText((list.get(position).split("\\+"))[1]);
             return convertView;
         }
     }
 }

Property Animation定义如下：

   scroll_hide_fab.xml：

 <?xml version="1.0" encoding="utf-8"?>
 <set xmlns:android="http://schemas.android.com/apk/res/android"
     android:ordering="together"
     >
     <objectAnimator
         android:propertyName="translationY"
         android:valueTo="500.00"
         android:duration="200"
         android:startOffset="0"
         android:repeatCount="0"
         android:valueType="floatType"
         />
     <objectAnimator
         android:propertyName="alpha"
         android:valueFrom="1.00"
         android:valueTo="0.00"
         android:duration="200"
         android:startOffset="0"
         android:valueType="floatType"
         android:repeatCount="0"
         />
 </set>

　scroll_show_fab.xml:　

 <?xml version="1.0" encoding="utf-8"?>
 <set xmlns:android="http://schemas.android.com/apk/res/android"
     android:ordering="together"
     >
     <objectAnimator
         android:propertyName="translationY"
         android:valueTo="0.0"
         android:duration="100"
         android:startOffset="0"
         android:repeatCount="0"
         android:valueType="floatType"
         />
     <objectAnimator
         android:propertyName="alpha"
         android:valueFrom="0.00"
         android:valueTo="1.00"
         android:duration="100"
         android:startOffset="0"
         android:valueType="floatType"
         android:repeatCount="0"
         />
 </set>

来自为知笔记(Wiz)