使用CoordinatorLayout

Design Support Library是在Google I/O2015上发布的一个全新兼容函数库，主要包括：

• Snackbar
• TextInputLayout
• TabLayout
• FloatingActionButton
• Navigation View

• CoordinatorLayout

• CoordinatorLayout继承ViewGroup，是Design Support Library中的布局，可以使不同视图组件直接相互作用，并协调动画效果。
  看如下效果对比：
  

右图使用的是CoordinatorLayout，可以看出动画效果要比左图更和谐。

布局文件代码:

<?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"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context="com.tlkg.welcome.coordinatorlayoutdemo.MainActivity">    <android.support.design.widget.FloatingActionButton        android:id="@+id/fab"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_gravity="bottom|right|end"        android:layout_margin="16dp"        android:src="@mipmap/ic_launcher_round" /></android.support.design.widget.CoordinatorLayout>

MainActivity代码：

public class MainActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);        fab.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Snackbar.make(v, "Hello", Snackbar.LENGTH_SHORT).show();            }        });    }}

在CoordinatorLayout有一个onStartNestedScroll方法

    @Override    public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {        boolean handled = false;        final int childCount = getChildCount();        for (int i = 0; i < childCount; i++) {            final View view = getChildAt(i);            if (view.getVisibility() == View.GONE) {                // If it's GONE, don't dispatch                continue;            }            final LayoutParams lp = (LayoutParams) view.getLayoutParams();            final Behavior viewBehavior = lp.getBehavior();            if (viewBehavior != null) {                final boolean accepted = viewBehavior.onStartNestedScroll(this, view, child, target,                        nestedScrollAxes);                handled |= accepted;                lp.acceptNestedScroll(accepted);            } else {                lp.acceptNestedScroll(false);            }        }        return handled;    }

会遍历子View,如果childView隐藏，跳过，获取Behavior对象，Behavior继承自View，调用Behavior对象的onStartNestedScroll方法来实现scroll效果，有兴趣的可以看下源码。