” app-release.apk” how to change this default generated apk name

Yes we can change that but with some more attention

Now add this in your build.gradle in your project while make sure you have checked the build variant of your project like release or Debug
so here I have set my build variant as release but you may select as Debug as well.

    buildTypes {
            release {
                minifyEnabled false
                proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
                signingConfig getSigningConfig()
                applicationVariants.all { variant ->
                    variant.outputs.each { output ->
                        def date = new Date();
                        def formattedDate = date.format('yyyyMMddHHmmss')
                        output.outputFile = new File(output.outputFile.parent,
                                output.outputFile.name.replace("-release", "-" + formattedDate)
    //for Debug use output.outputFile = new File(output.outputFile.parent,
   //                             output.outputFile.name.replace("-debug", "-" + formattedDate)
                        )
                    }
                }
            }
        }

You may Do it With different Approach Like this

 defaultConfig {
        applicationId "com.myapp.status"
        minSdkVersion 16
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
        setProperty("archivesBaseName", "COMU-$versionName")
    }

Using Set property method in build.gradle
and Don’t forget to sync the gradle before running the projects
Hope It will solve your problem 🙂

A New approach to handle this added recently by google update
You may now rename your build according to flavor or Variant output
//Below source is from developer android documentation
For more details follow the above documentation link
Using the Variant API to manipulate variant outputs is broken with the new plugin. It still works for simple tasks, such as changing the APK name during build time, as shown below:

// If you use each() to iterate through the variant objects,
// you need to start using all(). That's because each() iterates
// through only the objects that already exist during configuration time—
// but those object don't exist at configuration time with the new model.
// However, all() adapts to the new model by picking up object as they are
// added during execution.
android.applicationVariants.all { variant ->
    variant.outputs.all {
        outputFileName = "${variant.name}-${variant.versionName}.apk"
    }
}

Renaming .aab bundle
This is nicely answered by David Medenjak

tasks.whenTaskAdded { task ->
    if (task.name.startsWith("bundle")) {
        def renameTaskName = "rename${task.name.capitalize()}Aab"
        def flavor = task.name.substring("bundle".length()).uncapitalize()
        tasks.create(renameTaskName, Copy) {
            def path = "${buildDir}/outputs/bundle/${flavor}/"
            from(path)
            include "app.aab"
            destinationDir file("${buildDir}/outputs/renamedBundle/")
            rename "app.aab", "${flavor}.aab"
        }

        task.finalizedBy(renameTaskName)
    }
//@credit to David Medenjak for this block of code
}

Is there need of above code

What I have observed in the latest version of the android studio 3.3.1

The rename of .aab bundle is done by the previous code there don’t require any task rename at all.

Hope it will help you guys. 🙂