CollapsingToolbarLayout

效果图

代码实现

这里我们主要用到CollapsingToolbarLayout
CollapsingToolbarLayout包裹 Toolbar 的时候提供一个可折叠的 Toolbar，一般作为AppbarLayout的子视图使用。

<android.support.design.widget.CoordinatorLayout 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"
    >
    <android.support.design.widget.AppBarLayout
        android:id="@+id/appbar"
        android:background="#00ff99"
        android:layout_width="match_parent"
        android:layout_height="160dp">
        <android.support.design.widget.CollapsingToolbarLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            //标题放大后距离右边的距离
            app:expandedTitleMarginEnd="64dp"
            //Toolbar被折叠到顶部固定时的背景
            app:contentScrim="?attr/colorPrimary"
            //标题放大后距离左边的距离
            app:expandedTitleMarginStart="48dp"
            //状态栏的背景
            app:statusBarScrim="?attr/colorPrimary"
    //设置北京，滚动退出屏幕，最后折叠在顶端            app:layout_scrollFlags="scroll|exitUntilCollapsed"
            >
            <ImageView
                android:id="@+id/image"
//CollapsingToolbarLayout滑动时，子视图的视觉差                app:layout_collapseParallaxMultiplier="0.6"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:scaleType="fitXY"
                android:src="@drawable/ym2"
                //折叠模式
                app:layout_collapseMode="parallax" />
    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        //Toolbar的高度必须是固定的，否则不起效果
        android:layout_height="?attr/actionBarSize"
        app:layout_collapseMode="pin"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
        ></android.support.v7.widget.Toolbar>
        </android.support.design.widget.CollapsingToolbarLayout>
    </android.support.design.widget.AppBarLayout>

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
//要滑动的View必须设置这个        app:layout_behavior="@string/appbar_scrolling_view_behavior"
        ></android.support.v7.widget.RecyclerView>
    <android.support.design.widget.FloatingActionButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:fabSize="normal"
        android:src="@drawable/ym1"
        android:scaleType="fitXY"
        android:layout_gravity="bottom|end"
        //设置锚点
        app:layout_anchor="@+id/appbar"
        app:layout_anchorGravity="bottom|end|right"
        />
</android.support.design.widget.CoordinatorLayout>

接着我们来修改ToolBar折叠到顶端的背景颜色，上面是白色的，重点就在这句代码

app:contentScrim="?attr/colorPrimary"

我们把颜色改成黄色

app:contentScrim="#ff8c00"

public class MainActivity extends AppCompatActivity{
    private List<String> datas;
    private RecyclerView recyclerView;
    private AppBarLayout appBarLayout;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        recyclerView = (RecyclerView) findViewById(R.id.recview);
        appBarLayout = (AppBarLayout) findViewById(R.id.appbar);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        toolbar.setNavigationIcon(R.mipmap.ic_launcher);
        initData();
        CustomAdapter adapter = new CustomAdapter(this,datas);
        RecyclerView.LayoutManager manager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(manager);
        recyclerView.setAdapter(adapter);
    }

    public void initData() {
        datas = new ArrayList<>();
        for (int i = 'A'; i < 'K'; i++) {
            datas.add(""+(char)i);
        }
    }

}

public class CustomAdapter extends RecyclerView.Adapter<CustomAdapter.MyViewHolder> {
    private Context context;
    private List<String> data;
    public CustomAdapter(Context context, List<String> data){
        this.context = context;
        this.data = data;
    }
    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemView = View.inflate(context, R.layout.item_view, null);
        MyViewHolder holder = new MyViewHolder(itemView);
        return holder;
    }

    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
            holder.textView.setText(data.get(position));
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public int getItemCount() {
        return data.size();
    }
    class MyViewHolder extends RecyclerView.ViewHolder {

        private final TextView textView;

        public MyViewHolder(View itemView) {
            super(itemView);
            textView = (TextView) itemView.findViewById(R.id.tv_item);
        }
    }
}

效果二

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

    <android.support.design.widget.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="180dp"
        android:background="#00ff99">

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/collap"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:contentScrim="#FA7199"
            app:expandedTitleMarginEnd="64dp"
            app:expandedTitleMarginStart="48dp"
            app:layout_scrollFlags="scroll|exitUntilCollapsed"
            app:statusBarScrim="?attr/colorPrimary">

            <ImageView
                android:id="@+id/image"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:scaleType="fitXY"
                android:src="@drawable/ym2"
                app:layout_collapseMode="parallax"
                app:layout_collapseParallaxMultiplier="0.9" />

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                app:layout_collapseMode="pin"
                app:popupTheme="@style/ThemeOverlay.AppCompat.Light">
                <android.support.v7.widget.ButtonBarLayout
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:gravity="center"
                    >
                    <TextView
                        android:id="@+id/tv_play"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:textColor="#ffffff"
                        android:text="立即播放"
                        android:textSize="20sp"
                        android:layout_gravity="center_vertical"
                        />
                </android.support.v7.widget.ButtonBarLayout>
            </android.support.v7.widget.Toolbar>

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

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

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

然后我们需要监听AppBarLayout的状态

public abstract class AppBarStateChangeListener implements AppBarLayout.OnOffsetChangedListener {

    public enum State {
        EXPANDED,
        COLLAPSED,
        IDLE
    }

    private State mCurrentState = State.IDLE;

    @Override
    public final void onOffsetChanged(AppBarLayout appBarLayout, int i) {
        if (i == 0) {
            if (mCurrentState != State.EXPANDED) {
                onStateChanged(appBarLayout, State.EXPANDED);
            }
            mCurrentState = State.EXPANDED;
        } else if (Math.abs(i) >= appBarLayout.getTotalScrollRange()) {
            if (mCurrentState != State.COLLAPSED) {
                onStateChanged(appBarLayout, State.COLLAPSED);
            }
            mCurrentState = State.COLLAPSED;
        } else {
            if (mCurrentState != State.IDLE) {
                onStateChanged(appBarLayout, State.IDLE);
            }
            mCurrentState = State.IDLE;
        }
    }

    public abstract void onStateChanged(AppBarLayout appBarLayout, State state);
}

public class MainActivity extends AppCompatActivity {
    private List<String> datas;
    private RecyclerView recyclerView;
    private AppBarLayout appBarLayout;
    private CollapsingToolbarLayout collapsingToolbarLayout;
    private TextView tvPlay;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        recyclerView = (RecyclerView) findViewById(R.id.recview);
        appBarLayout = (AppBarLayout) findViewById(R.id.appbar);
        collapsingToolbarLayout = (CollapsingToolbarLayout) findViewById(R.id.collap);
        tvPlay = (TextView) findViewById(R.id.tv_play);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        initData();
        CustomAdapter adapter = new CustomAdapter(this,datas);
        RecyclerView.LayoutManager manager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(manager);
        recyclerView.setAdapter(adapter);
        appBarLayout.addOnOffsetChangedListener(new AppBarStateChangeListener() {
            @Override
            public void onStateChanged(AppBarLayout appBarLayout, State state) {
                if(state == State.EXPANDED){
                    tvPlay.setText("");
                }else if(state == State.COLLAPSED){
                    tvPlay.setText("立即播放");
                }else{
                    tvPlay.setText("");
                }
            }

        });
    }

    public void initData() {
        datas = new ArrayList<>();
        for (int i = 'A'; i < 'Z'; i++) {
            datas.add(""+(char)i);
        }
    }

}