java.lang.RuntimeException: Unable to start activity ComponentInfo{}: android.view.InflateException: Binary XML file line #38: Binary XML file line #38: Error inflating class android.widget.RadioButto

原因：RadioButton所在的包没有导入到项目中

解决方法：在build.gradle文件的dependencies中添加 'com.android.support:appcompat-v7:26.0.0'