1.在已有工程下NEW   NEW Module, 创建 一个android  library.

2.把需要的代码写入library工程里面，提供外部调用类，方法。

3 在buld.gradle 里面

apply plugin: 'com.android.library'

android {
    compileSdkVersion 28



    defaultConfig {
        minSdkVersion 18
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"

    }

    buildTypes {
        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

}

dependencies {
    compile fileTree(include: ['*.jar'], dir: 'libs')
    androidTestCompile('com.android.support.test.espresso:espresso-core:3.0.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:28.0.0'
    compile 'com.android.support.test:runner:1.0.2'
}
tasks.withType(JavaCompile) {
    options.compilerArgs << "-Xlint:unchecked"
}

task makeJar(type: Copy) {
//删除存在的
     delete'build/libs/bleBus.jar'
//设置拷贝的文件
   from('build/intermediates/packaged-classes/release/')
//打进jar包后的文件目录
     into('build/libs/')
//将classes.jar放入build/libs/目录下
//include ,exclude参数来设置过滤
//（我们只关心classes.jar这个文件）
    include('classes.jar')
//重命名
    rename ('classes.jar','bleBus.jar')
}
makeJar.dependsOn(build)

最后一部分 是打包配置。

4.为了代码的安全性，可以加入混淆。

在build.gradle 同目录下， 添加 proguard-rules.pro 文件。

###########################以下是AndroidStudio自带的混淆配置协议###############################

# 表示混淆时不使用大小写混合类名
-dontusemixedcaseclassnames

# 表示不跳过library中的非public的类
-dontskipnonpubliclibraryclasses

# 打印混淆的详细信息
-verbose

# Optimization is turned off by default. Dex does not like code run
# through the ProGuard optimize and preverify steps (and performs some
# of these optimizations on its own).
-dontoptimize

# 表示不进行校验,这个校验作用 在java平台上的
-dontpreverify
# Note that if you want to enable optimization, you cannot just
# include optimization flags in your own project configuration file;
# instead you will need to point to the
# "proguard-android-optimize.txt" file instead of this one from your
# project.properties file.
#使用注解需要添加
-keepattributes *Annotation*
-keep public class com.google.vending.licensing.ILicensingService
-keep public class com.android.vending.licensing.ILicensingService

# For native methods, see http://proguard.sourceforge.net/manual/examples.html#native
#指定不混淆所有的JNI方法
-keepclasseswithmembernames class * {
    native <methods>;
}

# keep setters in Views so that animations can still work.
# see http://proguard.sourceforge.net/manual/examples.html#beans
#所有View的子类及其子类的get、set方法都不进行混淆
-keepclassmembers public class * extends android.view.View {
   void set*(***);
   *** get*();
}

# We want to keep methods in Activity that could be used in the XML attribute onClick
# 不混淆Activity中参数类型为View的所有方法
-keepclassmembers class * extends android.app.Activity {
   public void *(android.view.View);
}

# For enumeration classes, see http://proguard.sourceforge.net/manual/examples.html#enumerations
# 不混淆Enum类型的指定方法
-keepclassmembers enum * {
    public static **[] values();
    public static ** valueOf(java.lang.String);
}

# 不混淆Parcelable和它的子类，还有Creator成员变量
-keepclassmembers class * implements android.os.Parcelable {
  public static final android.os.Parcelable$Creator CREATOR;
}

# 不混淆R类里及其所有内部static类中的所有static变量字段
-keepclassmembers class **.R$* {
    public static <fields>;
}

# The support library contains references to newer platform versions.
# Don't warn about those in case this app is linking against an older
# platform version.  We know about them, and they are safe.
# 不提示兼容库的错误警告
-dontwarn android.support.**

# Understand the @Keep support annotation.
-keep class android.support.annotation.Keep

-keep @android.support.annotation.Keep class * {*;}

-keepclasseswithmembers class * {
    @android.support.annotation.Keep <methods>;
}

-keepclasseswithmembers class * {
    @android.support.annotation.Keep <fields>;
}

-keepclasseswithmembers class * {
    @android.support.annotation.Keep <init>(...);
}


###########################以下是需要手动的混淆配置协议###############################


-libraryjars "C:\Program Files\Java\jdk1.8.0_111\jre\lib\rt.jar"
#-libraryjars "C:\android-sdks\platforms\android-26\android.jar"
# 注意：以上两个路径需要将以上路径是自己jar包的位置，需要根据自己情况进行修改，如果报重复配置的错误，注释掉即可

#代码迭代优化的次数，默认5
-optimizationpasses 5
#混淆时不会产生形形色色的类名
-dontusemixedcaseclassnames


#忽略警告
-ignorewarnings
#以下是不需要混淆的文件
 -keep class cn.hand.blelib.BleBus{
     *;
 }
-keepclassmembers class cn.hand.blelib.BleBus$OnReceiveMsg{
        public *;
}

最后一部分可以自己配置 不需要混淆的文件。