異常信息：
Caused by: java.lang.IllegalStateException: This Activity already has an action bar supplied by the window decor. Do not request Window.FEATURE_SUPPORT_ACTION_BAR and set windowActionBar to false in your theme to use a Toolbar instead.
問題原因：
當在activity中調用了setSupportActionBar(toolbar);
同時，AndroidManifest.xml 對應的Activity標簽的android:theme為
同時，AndroidManifest.xml 對應的Activity標簽的android:theme為
android:theme="@style/AppTheme" >
且，style資源文件中的parent為
parent="Theme.AppCompat.Light.DarkActionBar
就會報這個異常。
問題分析：
Using Theme.AppCompat.Light tells Android that you want the framework to provide an ActionBar for you. However, you are creating your own ActionBar (a Toolbar), so you are giving the framework mixed signals as to where you want the ActionBar to come from.
解決方法：
在style.xml中加入：
在Manifest.xml中，修改theme
