Cannot set the value of read-only property 'outputFile' for ApkVariantOutputImpl_Decorated{apkData=M

gradle打包的时候，自定义apk名称的时候，遇到这个问题：

Cannot set the value of read-only property 'outputFile' for ApkVariantOutputImpl_Decorated{apkData=Main{type=MAIN, fullName=debug, filters=[]}} of type com.android.build.gradle.internal.api.ApkVariantOutputImpl. Ope

搜到一个答案，解决了问题：

//**Use all() instead of each() 
//Use outputFileName instead of output.outputFile if you change only file name (that is your case)**

// 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 = "xxx.apk"
                }
            }

答案出处：https://blog.csdn.net/CHITTY1993/article/details/78667069

我原来的方法是这样的：

 //修改生成的文件名
        applicationVariants.all { variant ->
            variant.outputs.each { output ->
                def outputFile = output.outputFile
                def buildName
                variant.productFlavors.each { product ->
                    buildName = product.name
                }
                //这里修改文件名
                def fileName = "XXX" + "_" + buildName + "_" + variant.buildType.name + "_" +
                        "${defaultConfig.versionName}_${releaseDate()}.apk"
                output.outputFile = new File(outputFile.parent, fileName)
            }
        }