随着项目越来越大，android应用不得不面对64k方法数限制的问题，说真的，这个问题很头疼，虽然网上已经有了多种解决方案，multidex，dynamicApk，代码混淆，业务逻辑用c实现然后用jni调用等等，dynamicApk需要工程模块化，高度解耦，修改量极大；代码混淆，已经做了，治标不治本；业务逻辑用c实现然后用jni调用，技术不到家是一种，各种依赖包的添加才是方法数爆棚的罪魁祸首，作用不大；multidex，虽然解了燃眉之急，但仍感到忧心忡忡，不是长久之计，还有各种坑等着你跳。

问题预防，检测方法数

虽然目前还没有一劳永逸的方案，只能走一步算一步，避免使用一些方法数较多的库，时时刻刻意识到这问题，让它慢一点到来，做我们能做的事，哦弥陀佛。

使用dexcount-gradle-plugin 计算apk方法数

用法
在app/build.gradle添加

buildscript {
    repositories {
        mavenCentral() // or jcenter()
    }

    dependencies {
        classpath 'com.getkeepsafe.dexcount:dexcount-gradle-plugin:0.3.0'
    }
}

apply plugin: 'com.getkeepsafe.dexcount'

简单输出

> ./gradlew assembleDebug

...buildspam...
:app:compileDebugSources
:app:preDexDebug UP-TO-DATE
:app:dexDebug
:app:packageDebug
:app:zipalignDebug
:app:assembleDebug
Total methods in MyApp-debug-5.3.14.apk: 56538

BUILD SUCCESSFUL

Total time: 33.017 secs

更多查看dexcount-gradle-plugin

使用dex-method-count计算单个dex方法数

解压apk文件可以看到classes.dex文件，如果使用了multidex可能会看到多个classses.dex,classes2.dex等。
这里使用了网上找的一个脚本，很早之前看到的，找不到出处了，贴出来

printhex.ps1

<#
.SYNOPSIS
Outputs the number of methods in a dex file.

.PARAMETER Path
Specifies the path to a file. Wildcards are not permitted.

#>
param(
  [parameter(Position=0,Mandatory=$TRUE)]
    [String] $Path
)

if ( -not (test-path -literalpath $Path) ) {
  write-error "Path '$Path' not found." -category ObjectNotFound
  exit
}

$item = get-item -literalpath $Path -force
if ( -not ($? -and ($item -is [System.IO.FileInfo])) ) {
  write-error "'$Path' is not a file in the file system." -category InvalidType
  exit
}

if ( $item.Length -gt [UInt32]::MaxValue ) {
  write-error "'$Path' is too large." -category OpenError
  exit
}

$stream = [System.IO.File]::OpenRead($item.FullName)
$buffer = new-object Byte[] 2
$stream.Position = 88
$bytesread = $stream.Read($buffer, 0, 2)
$output = $buffer[0..1] 
#("{1:X2} {0:X2}") -f $output
$outputdec = $buffer[1]*256 + $buffer[0]
"Number of methods is " + $outputdec
$stream.Close() 

dex-method-count.bat

@ECHO OFF

IF "%1"=="" GOTO MissingFileNameError

IF EXIST "%1" (GOTO ContinueProcessing) ELSE (GOTO FileDoesntExist)



:ContinueProcessing

set FileNameToProcess=%1

set FileNameForDx=%~n1.dex

IF "%~x1"==".dex" GOTO ProcessWithPowerShell



REM preprocess Jar with dx

IF "%~x1"==".jar" (

   ECHO Processing Jar %FileNameToProcess% with DX!

   CALL dx --dex --output=%FileNameForDx% %FileNameToProcess%

   set FileNameToProcess=%FileNameForDx%

   IF ERRORLEVEL 1 GOTO DxProcessingError

)



:ProcessWithPowerShell

ECHO Counting methods in DEX file %FileNameToProcess%

CALL powershell -noexit -executionpolicy bypass "& ".\printhex.ps1" %FileNameToProcess%

GOTO End



:MissingFileNameError

@ECHO Missing filename for processing

GOTO End



:DxProcessingError

@ECHO Error processing file %1% with dx!

GOTO End



:FileDoesntExist

@ECHO File %1% doesn't exist!

GOTO End



:End

用法：
将上面两个文件拷贝到电脑（windows），文件名字和后缀都不要变，且放在同一个目录下，需要检测的dex文件也放在同一级目录，就像这样

QQ截图20151116174811.png

打开命令行并切到当前目录下，运行命令

dex-method-count.bat classes.dex

运行结果：Number of methods is 64595

QQ截图20151116175052.png

计算开源库方法数的网站

http://www.methodscount.com/
感谢Razerdp提供