使用ADT 16.0或者以上版本时，用户定义一个ImageView，会提示[Accessibility] Missing contentDescription attribute on image，虽说这个警告可以忽略不计，但总让人感觉不舒服。
其实，这是ADT 16.0的新特性，在一些没有文本显示的控件里，如imageView和imageButton等，ADT会提示你添加一个android:contentDescription属性，用来描述这个控件的作用。（而且值引用strings.xml文件中的，否则又会有提示。）
英文原文如下:
Resolved this warning by setting attribute android:contentDescription for my ImageView
android:contentDescription="@string/desc"
Android Lint support in ADT 16 throws this warning to ensure that image widgets provide a contentDescription
This defines text that briefly describes content of the view. This property is used primarily for accessibility. Since some views do not have textual representation this attribute can be used for providing such.
Non-textual widgets like ImageViews and ImageButtons should use the contentDescription attribute to specify a textual description of the widget such that screen readers and other accessibility tools can adequately describe the user interface.
