Android彻底去Log，反编译都看不到实现方法

android彻底去log，反编译都看不到实现方法。
当然是由于习惯太好，打了一堆中文log，其实只是想给测试看。然而如果包被反编译，看log基本都能理解流程了，有点尴尬。所以此文主要探究proguard配置，以去除log。

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以下过程示例，来自于这段代码。

public class mainactivity extends appcompatactivity {
 private static final string tag = "mainactivity";

 private string a = "a";
 private string b = "b";

 @override
 protected void oncreate(bundle savedinstancestate) {
  super.oncreate(savedinstancestate);
  setcontentview(r.layout.activity_main);

  log.d(tag, "this is" + a + b);
 }
}

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啥都不配置的情况下，反编译的smali代码如下：

# virtual methods
.method public oncreate(landroid/os/bundle;)v
 .locals 2

 invoke-super {p0, p1}, landroid/support/v7/app/c;->oncreate(landroid/os/bundle;)v

 const p1, 0x7f09001b

 invoke-virtual {p0, p1}, lcom/rentee/logremove/mainactivity;->setcontentview(i)v

 const-string p1, "mainactivity"

 new-instance v0, ljava/lang/stringbuilder;

 const-string v1, "this is"

 invoke-direct {v0, v1}, ljava/lang/stringbuilder;->(ljava/lang/string;)v

 iget-object v1, p0, lcom/rentee/logremove/mainactivity;->m:ljava/lang/string;

 invoke-virtual {v0, v1}, ljava/lang/stringbuilder;->append(ljava/lang/string;)ljava/lang/stringbuilder;

 iget-object v1, p0, lcom/rentee/logremove/mainactivity;->n:ljava/lang/string;

 invoke-virtual {v0, v1}, ljava/lang/stringbuilder;->append(ljava/lang/string;)ljava/lang/stringbuilder;

 invoke-virtual {v0}, ljava/lang/stringbuilder;->tostring()ljava/lang/string;

 move-result-object v0

 invoke-static {p1, v0}, landroid/util/log;->d(ljava/lang/string;ljava/lang/string;)i

 return-void
.end method

很明显，整条字符串拼接过程是由stringbuilder完成的。

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1.在build.gradle配置proguard-android-optimize.txt，因为默认的proguard-android.txt优化开关是关了的，而proguard的assumenosideeffects、assumenoexternalsideeffects配置是需要开启优化开关的。

 buildtypes {
  release {
minifyenabled true
proguardfiles getdefaultproguardfile('proguard-android-optimize.txt'), 'proguard-rules.pro'
  }
 }

在proguard-rules.pro文件中配置assumenosideeffects。这是网上的通用大解。

-assumenosideeffects class android.util.log {
 public static boolean isloggable(java.lang.string, int);
 public static int v(...);
 public static int i(...);
 public static int w(...);
 public static int d(...);
 public static int e(...);
}

不过也的确存在一个问题，就是去除不干净，反编译后，smail如下：

# virtual methods
.method public oncreate(landroid/os/bundle;)v
 .locals 1

 invoke-super {p0, p1}, landroid/support/v7/app/c;->oncreate(landroid/os/bundle;)v

 const p1, 0x7f09001b

 invoke-virtual {p0, p1}, lcom/rentee/logremove/mainactivity;->setcontentview(i)v

 new-instance p1, ljava/lang/stringbuilder;

 const-string v0, "this is"

 invoke-direct {p1, v0}, ljava/lang/stringbuilder;->(ljava/lang/string;)v

 iget-object v0, p0, lcom/rentee/logremove/mainactivity;->m:ljava/lang/string;

 invoke-virtual {p1, v0}, ljava/lang/stringbuilder;->append(ljava/lang/string;)ljava/lang/stringbuilder;

 iget-object v0, p0, lcom/rentee/logremove/mainactivity;->n:ljava/lang/string;

 invoke-virtual {p1, v0}, ljava/lang/stringbuilder;->append(ljava/lang/string;)ljava/lang/stringbuilder;

 return-void
.end method

log的相关代码没了，但是还是有stringbuilder的拼接过程在，这个从根本上解决不了问题。

2.进化版，proguard 6.0以上版本新增了assumenoexternalsideeffects和assumenoexternalreturnvalues，这两个属性6.0才引入，android自带proguard-gradle插件并没有这么新，所以要在工程项目根目录配置如下strategy，强制将progurad指定到6.0以上版本。

buildscript {
 configurations.all {
  resolutionstrategy {
force "net.sf.proguard:proguard-gradle:6.0.3"
  }
 }
}

然后在progaurd-rules.txt文件中增加如下配置：

-assumenoexternalsideeffects class java.lang.stringbuilder {
 public java.lang.stringbuilder();
 public java.lang.stringbuilder(int);
 public java.lang.stringbuilder(java.lang.string);
 public java.lang.stringbuilder append(java.lang.object);
 public java.lang.stringbuilder append(java.lang.string);
 public java.lang.stringbuilder append(java.lang.stringbuffer);
 public java.lang.stringbuilder append(char[]);
 public java.lang.stringbuilder append(char[], int, int);
 public java.lang.stringbuilder append(boolean);
 public java.lang.stringbuilder append(char);
 public java.lang.stringbuilder append(int);
 public java.lang.stringbuilder append(long);
 public java.lang.stringbuilder append(float);
 public java.lang.stringbuilder append(double);
 public java.lang.string tostring();
}

-assumenoexternalreturnvalues public final class java.lang.stringbuilder {
 public java.lang.stringbuilder append(java.lang.object);
 public java.lang.stringbuilder append(java.lang.string);
 public java.lang.stringbuilder append(java.lang.stringbuffer);
 public java.lang.stringbuilder append(char[]);
 public java.lang.stringbuilder append(char[], int, int);
 public java.lang.stringbuilder append(boolean);
 public java.lang.stringbuilder append(char);
 public java.lang.stringbuilder append(int);
 public java.lang.stringbuilder append(long);
 public java.lang.stringbuilder append(float);
 public java.lang.stringbuilder append(double);
}

这段配置的作用是，去除返回值无用的stringbuilder的相关操作，由于在第2点配置后，log相关代码被去除，所以log中的字符串拼接也是无用的，会被去除。配置后smali代码是：

# virtual methods
.method public oncreate(landroid/os/bundle;)v
 .locals 0

 invoke-super {p0, p1}, landroid/support/v7/app/c;->oncreate(landroid/os/bundle;)v

 const p1, 0x7f09001b

 invoke-virtual {p0, p1}, lcom/rentee/logremove/mainactivity;->setcontentview(i)v

 return-void
.end method