求指教The following classes could not be found: - DatePicker
使用eclipse在做安卓的界面布局时,拉控件DatePicker到Activity_main.xml的窗口后,
在窗口下方提示:The following classes could not be found: - DatePicker(Change to android.widget.DatePicker, Fix Build Path, Edit XML).
请问怎么解决!(用的android4.1.2)