1、添加网络访问权限

<uses-permission android:name="android.permission.INTERNET" />

developer官方文档关于html5支持视频播放描述如下：In order to support inline HTML5 video in your application, you need to have hardware acceleration turned on, and set a WebChromeClient. For full screen support, implementations of onShowCustomView(View, WebChromeClient.CustomViewCallback) and onHideCustomView() are required, getVideoLoadingProgressView() is optional.

2）重写WebChromeClient的onShowCustomView(View, WebChromeClient.CustomViewCallback)和onHideCustomView()

通过onShowcustomView对大屏的布局进行加载，隐藏小屏布局；在onHideCustomeView中退出全屏播放，重新显示小屏布局

参考：

http://developer.android.com/reference/android/webkit/WebView.html