Possible causes of interface errors during redirection

I wrote a new section and found that the default class is correct. The newly created class is correct, and no error is reported on both interfaces.

Previously programmed,
 

Android. content. ActivityNotFoundException: Unable to find explicit activity class {life. xuexi. dierci/life. xuexi. dierci. rgb}; have you declared this activity in your AndroidManifest. xml?

I felt that I did not write any error, and I checked it and did not know where the problem was. (I found that I would not read LogCat)
In fact, no errors have been found on the java interface and the interfaces in rec, but an error occurs when a VM is run.

In fact, you only need to go to the project directory, and the last and third file is AndroidManifest. xml.

Add a line of code
<Application android: icon = "@ drawable/ic_launcher" android: label = "@ string/app_name"> <activity android: name = ". dierciActivity "android: label =" @ string/app_name "> <intent-filter> <action android: name =" android. intent. action. MAIN "/> <category android: name =" android. intent. category. LAUNCHER "/> </intent-filter> </activity> [here] </application>

In the last application, that is, the code for the location difference [here] marked by me:
<Activity android: name = "mmmm"/> among them, mmmm is the class name of the interface to jump.