在app的build.gradle檔案的android{}目錄下新增

android.applicationVariants.all { variant ->
    variant.outputs.each { output ->
        def outputFile = output.outputFile
if (outputFile != null && outputFile.name.endsWith('.apk')) {
            //這裡修改apk檔名
def fileName = "指定的檔名.apk"
output.outputFile = new 
 
File(outputFile.parent, fileName)
        }
    }
}

gradle 3.0以上版本改用以下程式碼新增

android.applicationVariants.all {
    variant ->
        variant.outputs.all {
            //這裡修改apk檔名
outputFileName = "${variant.name}-v${variant.versionName}.apk"
}
}