(1) Load keystore:

Let's delete the apk file signed by the first method above. Next, the second signature method is the command line.

Open the graphical interface of the project structure:

In the above figure, select the module app, then switch to the singning tab, click Add, generate the release signature information, and click OK. Then do the following:

In the above figure, switch to the Build Types tab and select Signing config as "release", that is, configure the publishing signature information just generated.

After the operation is completed, we can see that the build.gradle file of the module app has the following code in the red box: