Android Material Design：基于CoordinatorLayout实现向上滚动导航条ToolBar滚出、向下滚动导航条滚出

Android Material Design：基于CoordinatorLayout实现向上滚动导航条ToolBar滚出、向下滚动导航条滚出

要实现的效果：
一个导航条和一个ToolBar，初始状态：

手指在屏幕向上滑动时候的效果，ToolBar滚出：

当手指在屏幕向下滑动时候，ToolBar又滚出：

实现上述效果要使用Android Material Design引入的CoordinatorLayout。关键地方有两点：

（1）设置app:layout_scrollFlags="scroll|enterAlways"。
如果打算将某个View实现滑入滑出，则需要在此View的属性中定义。在本例中是ToolBar。
（2）同时要设置触发（1）View的滚动组件的一个属性app:layout_behavior="@string/appbar_scrolling_view_behavior"
比如在本例中，ToolBar下方是一个TabLayout，TabLayout下方是是一个RecyclerView，意图是RecyclerView在向上、向下滚动时候，自动触发ToolBar滚出或者滚入。

现在给出完整例子加以说明。
MainActivity.java :

package zhangphil.view;

import android.app.Activity;
import android.os.Bundle;
import android.support.design.widget.TabLayout;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.TextView;

public class MainActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		Toolbar mToolbar = (Toolbar) findViewById(R.id.toolBar);
		mToolbar.setLogo(R.drawable.ic_launcher);
		mToolbar.setNavigationIcon(android.R.drawable.ic_menu_delete);
		mToolbar.setTitle("zhangphil");
		mToolbar.setSubtitle("zhangphil副标题");

		TabLayout tabLayout = (TabLayout) findViewById(R.id.tabLayout);
		for (int i = 0; i < 10; i++)
			tabLayout.addTab(tabLayout.newTab().setText("选项卡槽" + i));
		tabLayout.setTabMode(TabLayout.MODE_SCROLLABLE);

		RecyclerView mRecyclerView = (RecyclerView) findViewById(R.id.recyclerView);
		LinearLayoutManager mLayoutManager = new LinearLayoutManager(this);
		mLayoutManager.setOrientation(LinearLayout.VERTICAL);
		mRecyclerView.setLayoutManager(mLayoutManager);
		RecyclerView.Adapter mAdapter = new MyRecyclerViewAdapter(this);
		mRecyclerView.setAdapter(mAdapter);
	}

	public class MyRecyclerViewAdapter extends RecyclerView.Adapter<MyViewHolder> {

		private	LayoutInflater mLayoutInflater;
		
		public MyRecyclerViewAdapter(Activity activity) {
			super();
			mLayoutInflater=activity.getLayoutInflater();
		}

		@Override
		public MyViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {

			View v = mLayoutInflater.inflate(android.R.layout.simple_list_item_1, null);
			MyViewHolder holder = new MyViewHolder(v);
			return holder;
		}

		@Override
		public void onBindViewHolder(MyViewHolder viewHolder, int pos) {
			viewHolder.text.setText("数据" + pos);
		}

		@Override
		public int getItemCount() {
			return 100;
		}
	}

	private class MyViewHolder extends RecyclerView.ViewHolder {
		public TextView text;

		public MyViewHolder(View itemView) {
			super(itemView);
			text=(TextView) itemView.findViewById(android.R.id.text1);
		}
	}
}

MainActivity.java的布局文件activity_main.xml :

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/main_content"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true" >

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

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolBar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            app:layout_scrollFlags="scroll|enterAlways"
            android:background="#2196f3"
            android:minHeight="?attr/actionBarSize" >

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="一个TextView" />
        </android.support.v7.widget.Toolbar>

        <android.support.design.widget.TabLayout
            android:id="@+id/tabLayout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="#e0e0e0"
            app:tabIndicatorColor="#ef5350"
            app:tabSelectedTextColor="#1976d2"
            app:tabTextColor="#90caf9" />
    </android.support.design.widget.AppBarLayout>

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

    <android.support.design.widget.FloatingActionButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:src="@drawable/ic_launcher" />

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

代码运行结果本文开始的三张图示内容。