使用android studio创建jar包工程，并导出jar

    1、打开android studio选择File->New->New Module...

         选择Android Library，创建一个Android Library的jar包工程

2、打开工程中的build.gradle

在文件末尾添加如下脚本

task deleteOldJar(type:Delete) {
    delete 'build/libs/APPTest.jar'
}

task exportJar(type:Copy) {
    from('build/intermediates/bundles/default/')
    into('build/libs')
    include('classes.jar')
    rename('classes.jar','APPTest.jar')
}

exportJar.dependsOn(deleteOldJar,build)

APPTest.jar为要生成的jar文件名，生成的jar路径在工程中的build/libs目录下

完整文件如下：

apply plugin: 'com.android.library'

android {
    compileSdkVersion 22
    buildToolsVersion "25.0.3"

    defaultConfig {
        minSdkVersion 19
        targetSdkVersion 22
        versionCode 1
        versionName "1.0"

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

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

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:22.2.1'
    testCompile 'junit:junit:4.12'
}

task deleteOldJar(type:Delete) {
    delete 'build/libs/APPTest.jar'
}

task exportJar(type:Copy) {
    from('build/intermediates/bundles/default/')
    into('build/libs')
    include('classes.jar')
    rename('classes.jar','APPTest.jar')
}

exportJar.dependsOn(deleteOldJar,build)

3、在Android Studio中选择Gradle projects->APPTest工程->Tasks->other->exportJar，双击exportJar生成jar包。