Android项目构建报错：Failed to resolve: com.android.support:appcompat-v7:27.+

Hey there, let’s work through this dependency resolution error step by step. This issue pops up when Gradle can’t locate the specified support library, and it’s usually tied to missing repository configurations or incomplete SDK setup. Here’s how to fix it:

1. Add Google Maven Repository to Your Root Build.gradle #

Starting with Android Support Library 26, Google moved these libraries to their own Maven repository. Your old setup might be missing this, so update your project’s root build.gradle file to include it:

buildscript {
    repositories {
        jcenter()
        // Add Google Maven repository here for build tools
        maven { url 'https://maven.google.com' }
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:4.6'
    }
}

allprojects {
    repositories {
        jcenter()
        // This is critical for finding 27+ support libraries
        maven { url 'https://maven.google.com' }
    }
}

Note: IntelliJ 2017.2 might not recognize the shorthand google() syntax, so using the full URL is safer here.

2. Verify SDK Components Are Installed #

Make sure you have all required SDK components for API 27:

• Open IntelliJ’s SDK Manager (File → Project Structure → SDKs → Android SDK)
• Go to the SDK Platforms tab and ensure "Android 8.1 (API 27)" is checked and installed
• Switch to the SDK Tools tab, check "Android Support Repository" and the latest "Android Support Library" (version 27.x.x)
• Click "Apply" to install any missing components

3. Match Support Library Version to Compile SDK #

In your app module’s build.gradle, ensure your compileSdkVersion matches the support library version, and avoid using dynamic versions like 27.+ (they cause instability):

android {
    compileSdkVersion 27 // Must match the support library's major version
    defaultConfig {
        targetSdkVersion 27
        // ... other configs like applicationId, minSdkVersion
    }
}

dependencies {
    // Use a specific version instead of 27.+ for consistent builds
    implementation 'com.android.support:appcompat-v7:27.1.1'
}

4. Sync and Clean Your Project #

• Click File → Sync Project with Gradle Files to apply the configuration changes
• Then run Build → Clean Project followed by Build → Rebuild Project to clear any cached build artifacts

5. Disable Gradle Offline Mode #

If Gradle is in offline mode, it can’t download new dependencies:

• Go to File → Settings → Build, Execution, Deployment → Build Tools → Gradle
• Uncheck the "Offline work" option and click "OK"

After following these steps, your project should resolve the appcompat-v7 dependency successfully.

内容的提问来源于stack exchange，提问作者Nikolay Baranenko