- showAsAction 不能正常配置
If your app is using the Support Library for compatibility on versions as low as Android 2.1, the showAsAction attribute is not available from the android: namespace. Instead this attribute is provided by the Support Library and you must define your own XML namespace and use that namespace as the attribute prefix. (A custom XML namespace should be based on your app name, but it can be any name you want and is only accessible within the scope of the file in which you declare it.)
appname: xml namespace
Using a logo instead of an icon
By default, the system uses your application icon in the action bar, as specified by the icon attribute in the
or element. However, if you also specify the logo attribute, then the action bar uses the logo image instead of the icon. A logo should usually be wider than the icon, but should not include unnecessary text. You should generally use a logo only when it represents your brand in a traditional format that users recognize. A good example is the YouTube app's logo—the logo represents the expected user brand, whereas the app's icon is a modified version that conforms to the square requirement for the launcher icon.