android{  
//自定義打包時apk名稱  
    applicationVariants.all { variant ->  
        variant.outputs.all { output ->// each 改為 all  
            def fileName = "app_${variant.versionName}.apk"  
            def outFile = output.outputFile  
            if (outFile != null && outFile.name.endsWith('.apk')) {  
                outputFileName = fileName  //  output.outputFile 改為 outputFileName  
            }  
        }  
    }  
}