1、Warning:Conflict with dependency ‘com.google.code.findbugs:jsr305’. Resolved versions for app (3.0.1) and test app (2.0.1) differ. See http://g.co/androidstudio/app-test-app-conflict for details.

这个是库依赖的版本冲突问题，可以使用强制统一依赖版本，在build.gradle中添加如下代码：

android {
    compileSdkVersion 26
    buildToolsVersion "26.0.0"
    defaultConfig {
        applicationId "com.localgo.myapplication2"
        minSdkVersion 15
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

    //强制添加如下代码
    configurations.all {
        resolutionStrategy.force 'com.google.code.findbugs:jsr305:1.3.9'
    }
}

2、所有的后台Java文件的R变成红色，提示“cannot resolve symbol R”

依次点击 Build -> Rebuild Project and then click Tools -> Android -> Sync Project with Gradle Files.

3、Could not find com.android.tools.build3.0.0-alpha1

提示：A problem occurred configuring root project ‘Android-app’. Could not resolve all dependencies for configuration ‘:classpath’. Could not find com.android.tools.build3.0.0-alpha1. Searched in the
following locations:
https://jcenter.bintray.com/com/android/tools/build/gradle/3.0.0-alpha1/gradle-3.0.0-alpha1.pom
https://jcenter.bintray.com/com/android/tools/build/gradle/3.0.0-alpha1/gradle-3.0.0-alpha1.jar
Required by:

更换gradle库地址，在build.gradle中

buildscript {
    repositories {
        jcenter()
        maven { url 'https://maven.google.com' }
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.0.0-alpha2'
        ...
    }
}

allprojects {
    repositories {
        jcenter()
        maven { url 'https://maven.google.com' }
    }
}