先直接上图看效果:

WeChat_20170916214217_20170916214334.gif

项目需求:

滑动的时候标题渐变颜色，并且左右两边的图片渐变切换。并且Toolbar能够悬浮置顶，查阅了一些资料有用ScrollView实现 有用CoordinatorLayout +AppBarLayout +CollapsingToolbarLayout +Toolbar 实现，没错我用的就是后者，其实实现了也就是这么回事，蛮简单的。

所以写下博客，一个是帮助其他小伙伴，另外一个是记录下自己的菜鸟成长之路吧。也决定之后有空了,把自己过去在项目中遇到的问题都记录下来，做成笔记。

实现原理：

为什么要用CoordinatorLayout CollapsingToolbarLayout是用来对Toolbar进行再次包装的ViewGroup，主要是用于实现折叠（其实就是看起来像伸缩~）的App Bar效果。它需要放在AppBarLayout布局里面，并且作为AppBarLayout的直接子View。就不做过多解释了不懂的可以看下这边文章 玩转AppBarLayout更酷炫的顶部栏

贴上代码:

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>

        <variable
            name="ShopDetailsAcitvity"
            type="com.example.youjia.shopping.MainActivity" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <android.support.design.widget.CoordinatorLayout
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1">

            <android.support.design.widget.AppBarLayout
                android:id="@+id/app_bar"
                android:layout_width="match_parent"
                android:layout_height="wrap_content">

                <android.support.design.widget.CollapsingToolbarLayout
                    android:id="@+id/toolbar_layout"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:background="#f7f7f7"
                    app:contentScrim="?attr/colorPrimary"
                    app:layout_scrollFlags="scroll|exitUntilCollapsed">


                    <RelativeLayout
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:background="@color/view"
                        android:orientation="vertical">


                        <RelativeLayout
                            android:id="@+id/banner_layout"
                            android:layout_width="match_parent"
                            android:layout_height="264dp"
                            android:orientation="vertical">

                            <com.youth.banner.Banner
                                android:id="@+id/banner"
                                android:layout_width="match_parent"
                                android:layout_height="match_parent"
                                app:image_scale_type="center_crop"
                                app:indicator_drawable_selected="@mipmap/banner_red"
                                app:indicator_drawable_unselected="@mipmap/banner_grey"
                                app:indicator_height="9dp"
                                app:indicator_margin="3dp"
                                app:indicator_width="9dp"
                                app:is_auto_play="true" />

                            <View
                                style="@style/View"
                                android:layout_alignParentBottom="true" />
                        </RelativeLayout>

                        <RelativeLayout
                            android:id="@+id/relativelayout_goods"
                            android:layout_width="match_parent"
                            android:layout_height="wrap_content"
                            android:layout_below="@+id/banner_layout"
                            android:background="@color/white"
                            android:gravity="center_vertical"
                            android:paddingBottom="12dp"
                            android:paddingLeft="13.3dp"
                            android:paddingRight="13.3dp"
                            android:paddingTop="12dp">

                            <TextView
                                android:text="禄福来精品翡翠"
                                android:id="@+id/shop_details_1"
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:lineSpacingExtra="5dp"
                                android:textColor="#282828"
                                android:textSize="16sp" />

                            <TextView
                                android:text="￥399.00"
                                android:id="@+id/shop_details_2"
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_below="@+id/shop_details_1"
                                android:layout_marginTop="10dp"
                                android:textColor="#e75446"
                                android:textSize="16sp" />

                            <TextView
                                android:text="原价￥500.00"
                                android:id="@+id/shop_details_3"
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_below="@+id/shop_details_2"
                                android:layout_marginTop="10dp"
                                android:textColor="#999999"
                                android:textSize="12sp" />
                            <!--android:layout_alignBottom="@+id/shop_details_2"-->
                            <TextView
                                android:text="月销8238笔"
                                android:id="@+id/sumSotre"
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_alignParentBottom="true"
                                android:layout_alignParentRight="true"
                                android:textColor="#656565"
                                android:textSize="14sp" />


                        </RelativeLayout>



                        <LinearLayout
                            android:id="@+id/linearLayout_goods"
                            android:layout_width="match_parent"
                            android:layout_height="46.3dp"
                            android:layout_alignParentStart="true"
                            android:layout_below="@+id/relativelayout_goods"
                            android:layout_marginTop="19dp"
                            android:background="@drawable/ripple_item_white_bg"
                            android:gravity="center_vertical"
                            android:orientation="vertical">

                            <TextView
                                android:layout_width="wrap_content"
                                android:layout_height="wrap_content"
                                android:layout_marginLeft="13dp"
                                android:layout_weight="1"
                                android:gravity="center_vertical"
                                android:text="选择：商品规格"
                                android:textColor="#282828"
                                android:textSize="15.3sp" />

                            <View style="@style/View" />

                        </LinearLayout>


                    </RelativeLayout>
                    <android.support.v7.widget.Toolbar
                        android:id="@+id/toolbaretail"
                        android:layout_width="match_parent"
                        android:layout_height="70dp"
                        app:layout_collapseMode="pin"
                        android:fitsSystemWindows="true"
                        android:paddingTop="15dp"
                        app:popupTheme="@style/ThemeOverlay.AppCompat.Dark" >

                        <ImageView
                            android:src="@mipmap/share_shop"
                            android:id="@+id/share_img"
                            android:layout_gravity="center|right"
                            android:layout_marginRight="15dp"
                            android:layout_marginTop="5dp"
                            android:layout_width="wrap_content"
                            android:layout_height="match_parent" />
                    </android.support.v7.widget.Toolbar>
                </android.support.design.widget.CollapsingToolbarLayout>

                <android.support.design.widget.TabLayout
                    android:id="@+id/infoPhoneTabLayou"
                    app:tabTextColor="#989898"
                    app:tabSelectedTextColor="#e91b04"
                    app:tabIndicatorColor="@color/tablayout"
                    app:tabBackground="@drawable/ripple_tab_bg"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"  >

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

                <View
                    android:background="@color/view"
                    android:layout_width="match_parent"
                    android:layout_height="1dp"/>
            </android.support.design.widget.AppBarLayout>


            <android.support.v4.widget.NestedScrollView
                android:id="@+id/NestedScrollView"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:overScrollMode="always"
                app:layout_behavior="@string/appbar_scrolling_view_behavior">



                    <com.example.youjia.shopping.WrapContentHeightViewPager
                        android:id="@+id/infoPhone_Fragment_pager"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        />


            </android.support.v4.widget.NestedScrollView>


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

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="50dp"
            android:layout_alignParentBottom="true"
            android:background="@color/white"
            android:gravity="center_vertical"
            android:orientation="horizontal">

            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_weight="1.2"
                android:background="@drawable/ripple_item_white_bg"
                android:drawablePadding="2dp"
                android:drawableTop="@mipmap/shop_details_3"
                android:gravity="center_horizontal"
                android:text="店铺"
                android:textColor="#656565"
                android:textSize="10sp" />

            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_weight="1.2"
                android:background="@drawable/ripple_item_white_bg"
                android:drawablePadding="2dp"
                android:drawableTop="@mipmap/shop_details_4"
                android:gravity="center_horizontal"
                android:text="进货单"
                android:textColor="#656565"
                android:textSize="10sp" />

            <TextView
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_gravity="center_vertical"
                android:layout_weight="1"
                android:background="#ff6554"
                android:drawablePadding="5dp"
                android:gravity="center"
                android:text="加入进货单"
                android:textColor="#ffffff" />

            <TextView
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_gravity="center_vertical"
                android:layout_weight="1"
                android:background="#ff334c"
                android:drawablePadding="5dp"
                android:gravity="center"
                android:text="立即采购"
                android:textColor="#ffffff" />
        </LinearLayout>
    </LinearLayout>
</layout>

package com.example.youjia.shopping;

import android.databinding.DataBindingUtil;
import android.graphics.Color;
import android.graphics.Paint;
import android.support.design.widget.AppBarLayout;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Gravity;


import com.example.youjia.shopping.databinding.ActivityMainBinding;

import java.util.ArrayList;
import java.util.List;


public class MainActivity extends AppCompatActivity {
    private ActivityMainBinding mBinding;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
         mBinding  = DataBindingUtil.setContentView(this,R.layout.activity_main);
        mBinding.setShopDetailsAcitvity(this);
        mBinding.shopDetails3.getPaint().setFlags(Paint. STRIKE_THRU_TEXT_FLAG);
        TabLayout();
        initBanner();
        setToolBar();
    }

    /**
     * 初始化轮播图
     */
    private void initBanner() {
        List<Integer> integers = new ArrayList<>();
        integers.add(R.drawable.img1);
        integers.add(R.drawable.img2);
        integers.add(R.drawable.img3);
//        integers.add(R.drawable.img4);
//        integers.add(R.drawable.img5);
//        integers.add(R.drawable.img6);
//        integers.add(R.drawable.img7);

        mBinding.banner.startAutoPlay();
        mBinding.banner.setDelayTime(2000);
        mBinding.banner.setImages(integers).setImageLoader(new GlideImageLoader()).start();
    }

    /**
     * 初始化setToolBar
     */
    private void setToolBar(){
        setSupportActionBar(mBinding.toolbaretail);
        mBinding.toolbaretail.setTitleTextColor(Color.WHITE);
        mBinding.toolbarLayout.setTitleEnabled(false);
        mBinding.toolbarLayout.setExpandedTitleGravity(Gravity.CENTER);//设置展开后标题的位置
        mBinding.toolbarLayout.setCollapsedTitleGravity(Gravity.CENTER);//设置收缩后标题的位置
        mBinding.toolbarLayout.setExpandedTitleColor(Color.WHITE);//设置展开后标题的颜色
        mBinding.toolbarLayout.setCollapsedTitleTextColor(Color.WHITE);//设置收缩后标题的颜色
        mBinding.appBar.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
            @Override
            public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
                //verticalOffset  当前偏移量 appBarLayout.getTotalScrollRange() 最大高度 便宜值
                int Offset = Math.abs(verticalOffset); //目的是将负数转换为绝对正数；
                //标题栏的渐变
                mBinding.toolbaretail.setBackgroundColor(changeAlpha(getResources().getColor(R.color.redcustom)
                        , Math.abs(verticalOffset * 1.0f) / appBarLayout.getTotalScrollRange()));

                /**
                 * 当前最大高度便宜值除以2 在减去已偏移值 获取浮动 先显示在隐藏
                 */
                if (Offset < appBarLayout.getTotalScrollRange() / 2) {
                    mBinding.toolbaretail.setTitle("");
                    mBinding.toolbaretail.setAlpha((appBarLayout.getTotalScrollRange() / 2 - Offset * 1.0f) / (appBarLayout.getTotalScrollRange() / 2));
                    mBinding.shareImg.setAlpha((appBarLayout.getTotalScrollRange() / 2 - Offset * 1.0f) / (appBarLayout.getTotalScrollRange() / 2));
                    mBinding.shareImg.setImageDrawable(getResources().getDrawable(R.mipmap.share_shop));
                    mBinding.toolbaretail.setNavigationIcon(R.mipmap.shop_details_2);
                    /**
                     * 从最低浮动开始渐显 当前 Offset就是  appBarLayout.getTotalScrollRange() / 2
                     * 所以 Offset - appBarLayout.getTotalScrollRange() / 2
                     */
                } else if (Offset > appBarLayout.getTotalScrollRange() / 2) {
                    float floate = (Offset - appBarLayout.getTotalScrollRange() / 2) * 1.0f / (appBarLayout.getTotalScrollRange() / 2);
                    mBinding.toolbaretail.setAlpha(floate);
                    mBinding.shareImg.setAlpha(floate);
                    mBinding.toolbaretail.setNavigationIcon(R.mipmap.image_left);
                    mBinding.shareImg.setImageDrawable(getResources().getDrawable(R.mipmap.img_share));
                    mBinding.toolbaretail.setTitle("禄福来精品翡翠");
                    mBinding.toolbaretail.setAlpha(floate);
                }
            }
        });
    }

    /**
     * 根据百分比改变颜色透明度
     */
    public int changeAlpha(int color, float fraction) {
        int alpha = (int) (Color.alpha(color) * fraction);
        return Color.argb(alpha, 0, 128, 0);
    }

    /**TabLayout
     * 初始化
     */
    private void TabLayout(){
        List<String>list_Title = new ArrayList<>();
        list_Title.add("图文详情");
        list_Title.add("规格参数");

        List<Fragment> fragmentList = new ArrayList<>();
        fragmentList.add(new Fragment1());
        fragmentList.add(new Fragment2());

        mBinding.infoPhoneFragmentPager.setAdapter(new HomeFragmentPageAdapter(getSupportFragmentManager(),fragmentList,list_Title,2));
        mBinding.infoPhoneTabLayou.setTabMode(TabLayout.MODE_FIXED);
        mBinding.infoPhoneTabLayou.setupWithViewPager(mBinding.infoPhoneFragmentPager);
    }
}

渐变核心实现AppBarLayout.addOnOffsetChangedListener监听
通过verticalOffset 拿到当前的当前偏移量,appBarLayout.getTotalScrollRange() 是最大高度 偏移值 有了这两个参数我们就可以计算 浮度

是不是感觉很简单呢到此就结束了，在此奉上源码点击下载
有更好的方式或者需要改进的地方请给我留言，大家共同学习进步。
图片是一个做微商朋友提供的，要是需要玉的话可以给我留言。就当给他推广推广啦