问题1、运行的时候一直报如下错误

Error:Execution failed for task ':app:transformDexArchiveWithExternalLibsDexMergerForApiTestDebug'.
> java.lang.RuntimeException: com.android.builder.dexing.DexArchiveMergerException: Unable to merge dex

然后一遍一遍的检查，发现并没有引用重复的jar包。

最后考虑是不是第三方库引用jar出现的问题，然后就一个一个排查第三方库，最后发现我们用支付用的是

 compile 'com.pingxx:pingpp-alipay:2.1.9' // 使用支付宝时添加

特别注意：引用第三方库在gralde3.0版本是更为严格，要特别注意。

问题2、

AAPT2

AAPT2 将默认启用，如果遇到离奇的问题，可以尝试禁用，只要在 gradle.properties 中加入：

     
      

       
      android.enableAapt2=false
     
      

其他：

应用（app）目录下build.gradle（下面 implementation "com.android.support:design:25.4.0" 切换为 project的统一配置）

apply plugin: 'com.android.application'
apply plugin: 'io.fabric'
apply plugin: 'com.google.gms.google-services'

    android {
        compileSdkVersion 25
        buildToolsVersion "26.0.2"

        defaultConfig {
            multiDexEnabled true
            applicationId "com.example"
            minSdkVersion 21
            targetSdkVersion 23
            versionCode 1
            versionName "1.0"

            renderscriptTargetApi 23
            renderscriptSupportModeEnabled true

        }
        compileOptions {
            sourceCompatibility JavaVersion.VERSION_1_8
			targetCompatibility JavaVersion.VERSION_1_8
        }
        lintOptions {
            quiet true
            abortOnError false
            ignoreWarnings true
            disable 'InvalidPackage'           //Some libraries have issues with this.
            disable 'OldTargetApi'
            //Lint gives this warning but SDK 20 would be Android L Beta.
            disable 'IconDensities'            //For testing purpose. This is safe to remove.
            disable 'IconMissingDensityFolder' //For testing purpose. This is safe to remove.
        }


        dexOptions {
            javaMaxHeapSize "8G"
        }

        packagingOptions {
            exclude 'LICENSE.txt'
            exclude 'META-INF/DEPENDENCIES.txt'
            exclude 'META-INF/LICENSE.txt'
            exclude 'META-INF/NOTICE.txt'
            exclude 'META-INF/NOTICE'
            exclude 'META-INF/LICENSE'
            exclude 'META-INF/DEPENDENCIES'
            exclude 'META-INF/notice.txt'
            exclude 'META-INF/license.txt'
            exclude 'META-INF/dependencies.txt'
            exclude 'META-INF/rxjava.properties'
        }

        sourceSets {
            main.java.srcDirs += 'build/generated/source/apt'
        }
    }

    repositories {
        flatDir {
            dirs 'libs'
        }
    }



    dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])

    implementation project(':library_api')
    implementation project(':library_base')
    implementation project(':library_blur_dialog')
    implementation project(':library_countrycodepicker_dialog')
    implementation project(':library_glow_decorator')
    implementation project(':library_icons')
    implementation project(':library_loopvideo')
    implementation project(':library_section_adaper')
    implementation project(':library_taptargetview')
    implementation project(':library_ucrop')
    implementation project(':library_utils')
    implementation project(':library_utils_picasso')
    implementation project(':library_vector_compat')
    implementation project(':library_view_clock')
    implementation project(':library_view_shimmer_recycler')

    implementation "com.google.android.gms:play-services-cast-framework:11.4.2"
    compileOnly 'com.google.android.wearable:wearable:2.0.3'
    implementation 'com.google.android.support:wearable:2.0.3'
    implementation 'com.google.android.exoplayer:exoplayer:r2.4.1'

    implementation "com.android.support:mediarouter-v7:25.4.0"
    implementation "com.android.support:leanback-v17:25.4.0"
    implementation "com.android.support:design:25.4.0"

    implementation "com.android.support:appcompat-v7:25.4.0"
    implementation "com.android.support:support-v4:25.4.0"
    implementation "com.android.support:gridlayout-v7:25.4.0"
    implementation "com.android.support:cardview-v7:25.4.0"
    implementation "com.android.support:recyclerview-v7:25.4.0"
    implementation "com.android.support:preference-v14:25.4.0"

    // rxjava
    implementation  'io.reactivex:rxjava:1.2.9'
    implementation 'io.reactivex:rxandroid:1.2.1'
    implementation 'com.github.davidmoten:rxjava-extras:0.8.0.6'

    // square
	implementation  "com.squareup.retrofit2:retrofit:2.1.0",
    implementation  "com.squareup.retrofit2:converter-gson:2.1.0"
    implementation "com.squareup.retrofit2:adapter-rxjava:2.1.0"
    implementation "com.squareup.phrase:phrase:1.1.0"

    implementation "com.squareup.okhttp3:okhttp:3.6.0"
    implementation "com.squareup.okhttp3:logging-interceptor:3.6.0"
    implementation "com.squareup.okhttp3:okhttp-urlconnection:3.6.0"

    // picasso
    implementation  "com.squareup.picasso:picasso:2.5.2"
    implementation 'com.jakewharton.picasso:picasso2-okhttp3-downloader:1.1.0'

    // dagger
    implementation "com.google.dagger:dagger:2.10"
    annotationProcessor  "com.google.dagger:dagger-compiler:2.10"
    implementation "javax.annotation:jsr250-api:1.0"
    implementation  "javax.inject:javax.inject:1"


    // jake ftw
    implementation 'com.jakewharton:butterknife:8.8.1'
    annotationProcessor 'com.jakewharton:butterknife-compiler:8.8.1'

    compileOnly 'org.projectlombok:lombok:1.16.16'
    annotationProcessor 'org.projectlombok:lombok:1.16.16'

    // FragmentWithArgs
    implementation   "com.hannesdorfmann.fragmentargs:annotation:3.0.2",
    annotationProcessor "com.hannesdorfmann.fragmentargs:processor:3.0.2",

    implementation "org.parceler:parceler-api:1.1.9",
    annotationProcessor "org.parceler:parceler:1.1.9",
    implementation 'com.hannesdorfmann.fragmentargs:bundler-parceler:3.0.2'

    implementation "com.github.codekidX:storage-chooser:1.0.34"

    implementation 'io.github.yavski:fab-speed-dial:1.0.6'

    implementation('com.crashlytics.sdk.android:crashlytics:[email protected]') {
        transitive = true;
    }

    // intent builder
    implementation         "com.github.marcinmoskala.activitystarter:activitystarter:1.00"
	annotationProcessor  "com.github.marcinmoskala.activitystarter:activitystarter-compiler:1.00"

    implementation 'com.android.support.constraint:constraint-layout:1.0.2'//constraint-layout
    implementation 'org.greenrobot:eventbus:3.0.0'
    //font
    implementation 'uk.co.chrisjenx:calligraphy:2.2.0'
    implementation 'com.github.florent37:expectanim:1.0.6'
    implementation 'com.romandanylyk:pageindicatorview:[email protected]'
    implementation 'com.github.rubensousa:gravitysnaphelper:1.2'
    implementation 'com.flaviofaria:kenburnsview:1.0.7'
    implementation 'com.github.florent37:arclayout:1.0.2'

    implementation 'com.jakewharton.rxbinding:rxbinding:1.0.1'
    implementation 'com.wang.avi:library:2.1.3'
    implementation 'com.flyco.tablayout:FlycoTabLayout_Lib:[email protected]'
    implementation 'com.borax12.materialdaterangepicker:library:1.9'
    implementation 'com.github.scottyab:showhidepasswordedittext:0.8'
    //Location
    implementation "com.google.android.gms:play-services-maps:11.4.2"
    implementation 'pl.charmas.android:android-reactive-location:[email protected]'
    implementation "com.google.android.gms:play-services-location:11.4.2"
    //you can use newer GMS version if you need
    implementation "com.google.android.gms:play-services-places:11.4.2"
    implementation 'com.tbruyelle.rxpermissions:rxpermissions:[email protected]'
    implementation 'commons-validator:commons-validator:1.4.1'
    implementation 'com.balysv:material-ripple:1.0.2'
    implementation 'com.googlecode.libphonenumber:libphonenumber:8.5.2'
    implementation 'ru.egslava:MaskedEditText:1.0.5'
    implementation 'com.futuremind.recyclerfastscroll:fastscroll:0.2.5'

    implementation "com.google.firebase:firebase-core:11.4.2"


    implementation 'com.labo.kaji:swipeawaydialog:0.1.1'
    implementation 'io.supercharge:shimmerlayout:1.0.1'
    implementation 'hanks.xyz:htextview-library:0.1.5'
    implementation 'com.github.castorflex.smoothprogressbar:library:1.1.0'//progressbar for action bar
    implementation 'io.reactivex:rxjava-math:1.0.0'
    implementation 'jp.wasabeef:picasso-transformations:2.1.2'
    implementation 'com.afollestad.material-dialogs:core:0.9.1.0'
    implementation('com.github.ihsanbal:LoggingInterceptor:2.0.2') {
        exclude group: 'org.json', module: 'json'
    }

}

// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {
    repositories {
        maven { url 'http://maven.aliyun.com/nexus/content/groups/public/' }
        maven {
            url 'https://maven.google.com/'
            name 'Google'
        }
        jcenter()
//        maven { url 'http://maven.aliyun.com/nexus/content/repositories/jcenter' }
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.0.1'
        classpath 'com.meituan.android.walle:plugin:1.1.1'
        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        maven { url 'http://maven.aliyun.com/nexus/content/groups/public/' }
//        maven { url 'http://maven.aliyun.com/nexus/content/repositories/jcenter' }
        maven { url "https://jitpack.io" }
        maven { url 'https://maven.google.com' }
        maven { url "https://dl.google.com/dl/android/maven2/"}
        jcenter()
        google()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}


ext {
    targetSdkVersion = 26
    minSdkVersion = 14
    compileSdk = 26
    buildTools = "26.0.2"
    junit = 'junit:junit:4.12'
    recyclerview = 'com.android.support:recyclerview-v7:26.0.2'
    appcompat = 'com.android.support:appcompat-v7:26.0.2'
    design = 'com.android.support:design:26.0.2'
    percent = 'com.android.support:percent:26.0.2'
    glide = 'com.github.bumptech.glide:glide:3.7.0'
    retrofit = 'com.squareup.retrofit:retrofit:1.9.0'
    gson = 'com.google.code.gson:gson:2.8.0'
    okhttp = 'com.squareup.okhttp3:okhttp:3.6.0'
//    converterGson = 'com.squareup.retrofit:converter-gson:2.0.0-beta2'
//    converterJackson = 'com.squareup.retrofit:converter-jackson:1.9.0'
   
    commonsio = 'commons-io:commons-io:2.4'
}

参考资料：

android切换到greale 3.0的官方教程

android 项目使用java8 官方指南