renameapk

// in your android.applicationVariants.all { variant ->
// or in your android.libraryVariants.all { variant ->
// code block put this:
if (variant.productFlavors[0] == null){
                variant.outputs[0].outputFile = new File(variant.outputs[0].outputFile.parent,
                        project.ext.ourProjectName + "_"
                                + variant.buildType.name + "_"
                                + android.defaultConfig.versionCode + "_"
                                + android.defaultConfig.versionName + ".apk")
            }else{
                variant.outputs[0].outputFile = new File(variant.outputs[0].outputFile.parent,
                        project.ext.ourProjectName + "_"
                                + variant.productFlavors[0].name + "_"
                                + variant.buildType.name + "_"
                                + variant.mergedFlavor.versionCode + "_"
                                + variant.mergedFlavor.versionName + ".apk")
            }
//works for all use cases:
//     app without productFlavors
//  app with productFlavors and even flavorDimensions