gradle 统一 常量/依赖库 管理方式（二）

(you module-level)build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion rootProject.ext.compileSdkVersion
    //在project-level 定义的常量,编译时会默认,所以不必指定'ext'
    buildToolsVersion rootProject.buildToolsVersion
    
    defaultConfig {
        .....
    }
    
    buildTypes {
        debug {
            .....
        }
        
        prod{
            ......
        }
    }
    
}

/*
 Dependency versions are defined in the top level build.gradle file. This helps keeping track of
 all versions in a single place. This improves readability and helps managing project complexity.
 这里开始 引用 project-leve build.gradle 中定义的常量
 */
dependencies {
    // App's dependencies, including test
    compile "com.android.support:appcompat-v7:$rootProject.ext.supportLibraryVersion"
    //不用添加'ext'也可以(理由同上)
    compile "com.android.support:cardview-v7:$rootProject.supportLibraryVersion"
    //Q:不用添加'$'符号也可以? 
    compile "com.android.support:support-v4:rootProject.supportLibraryVersion"
    compile "com.google.guava:guava:$rootProject.guavaVersion"
}

(you project-level)build.gradle

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.2.0'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        jcenter()
    }
}

// Define versions in a single place 
//需要使用的依赖库版本  和 编译工具的版本 统一定义如下
ext {
    // Sdk and tools
    minSdkVersion = 10
    targetSdkVersion = 24
    compileSdkVersion = 24
    buildToolsVersion = '24.0.2'

    // App dependencies
    supportLibraryVersion = '24.2.0'
    guavaVersion = '18.0'
   
}