他的问题在这里，移除它

compile 'com.google.android.gms:play-services:11.8.0'

why?

注意:不要使用组合play-services目标。它带来了几十个库，使您的应用程序变得臃肿。相反，只指定应用程序使用的特定谷歌Play服务api。

使用你所需要的https://developers.google.com/android/guides/setup

比如位置服务

com.google.android.gms:play-services-location:11.8.0

对于云消息传递

com.google.android.gms:play-services-gcm:11.8.0

修改应用程序或模块的build.gradle

android {
    defaultConfig {
        ...
        minSdkVersion 21 <----- *here
        targetSdkVersion 26
        multiDexEnabled true <------ *here
    }
    ...
}

根据官方文件

Multidex support for Android 5.0 and higher Android 5.0 (API level 21) and higher uses a runtime called ART which natively supports loading multiple DEX files from APK files. ART performs pre-compilation at app install time which scans for classesN.dex files and compiles them into a single .oat file for execution by the Android device. Therefore, if your minSdkVersion is 21 or higher, you do not need the multidex support library. For more information on the Android 5.0 runtime, read ART and Dalvik.

https://developer.android.com/studio/build/multidex

我所要做的就是在文件>项目结构>应用>口味中将最低SDK版本设置为21

在构建应用程序

apply plugin: 'com.android.application'
android {
compileSdkVersion 28
defaultConfig {
    applicationId "com.proyecto.marketdillo"
    minSdkVersion 14
    targetSdkVersion 28
    versionCode 1
    versionName "1.0"
    testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    multiDexEnabled true
}
buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
    }
  }
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'com.android.support:appcompat-v7:28.0.0-rc02'
implementation 'com.google.firebase:firebase-core:16.0.7'
implementation 'com.android.support.constraint:constraint-layout:1.1.3'
implementation 'com.android.support:support-v4:28.0.0-rc02'
implementation 'com.android.support:design:28.0.0-rc02'
implementation 'com.google.firebase:firebase-auth:16.1.0'
implementation 'com.squareup.picasso:picasso:2.5.2'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.2'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
implementation 'com.google.firebase:firebase-firestore:17.1.5'
implementation 'com.android.support:multidex:1.0.3'
}
apply plugin: 'com.google.gms.google-services'

你的方法太多了。 Android dex文件有65536个方法的限制。

对于初学者来说，如果你不需要谷歌播放服务API，只需要位置，请替换

compile 'com.google.android.gms:play-services:11.8.0'

with

compile 'com.google.android.gms:play-services-location:11.8.0'

你可以参考本页的方法来避免它，或者如果需要允许更多: https://developer.android.com/studio/build/multidex.html

在Gradle构建文件中添加依赖项:

implementation 'com.android.support:multidex:1.0.2'

or

implementation 'com.android.support:multidex:1.0.3'

or

implementation 'com.android.support:multidex:2.0.0'

然后在“defaultConfig”部分，添加:

multiDexEnabled true

在targetSdkVersion

minSdkVersion 17
targetSdkVersion 27
multiDexEnabled true

如果你遇到这个错误

错误:Failed to resolve: multidex-instrumentation Open File

您需要将gradle更改为3.0.1

classpath 'com.android.tools.build:gradle:3.0.1'

并将以下代码放入gradle-wrapper.properties文件中

- 4.1 - all.zip distributionUrl = https://services.gradle.org/distributions/gradle

最后

在项目中添加类application并将其引入到AndroidManifest中 哪个是从MultiDexApplication扩展过来的

public class App extends MultiDexApplication {

    @Override
    public void onCreate( ) {
        super.onCreate( );
    }
}

首先运行项目以创建错误，然后清除项目

最后，重新启动项目并享受它