Android Studio默认主题AppTheme不显示预览画面

设计页面右上角有个红色圆圈，里面一个感叹号，点开它查看错误信息：

The following classes could not be instantiated:
   - android.support.v7.widget.ActionBarContainer (Open Class, Show Exception, Clear Cache)
   - android.support.v7.widget.ActionBarContextView (Open Class, Show Exception, Clear Cache)
   - android.support.v7.app.WindowDecorActionBar (Open Class, Show Exception, Clear Cache)
 Tip: Use View.isInEditMode() in your custom views to skip code or show sample data when shown in the IDE.  

If this is an unexpected error you can also try to build the project, then manually refresh the layout.  

Exception Details

java.lang.ClassNotFoundException: android.view.View$OnUnhandledKeyEventListener

这是由于插件版本与SDK版本不符引起的，解决办法是打开Project-%工程名%-app-build.gradle，修改这几行:

compileSdkVersion 28  改为compileSdkVersion 27

targetSdkVersion 28   改为targetSdkVersion 27

implementation 'com.android.support:appcompat-v7:28.0.0-alpha3'改为

implementation 'com.android.support:appcompat-v7:27.1.1'

然后点击右上角的Sync Now进行同步

同步完成，构建完成后回到设计界面，预览图可以正常显示。