Android - 读取类内的 build.gradle 属性

我希望能够访问 build.gradle 属性，以便我可以自动化应用程序中的某些流程。

这是我目前的结构：

根项目/build.gradle

buildscript {
    ext {
        buildTools = "25.0.2"
        minSdk = 16
        compileSdk = 23
        targetSdk = 23

        versions = [supportLib         : '25.0.0',
                    multidex           : '1.0.1',
                    playServices       : '10.0.1']
        libs = [appcompat            : "com.android.support:appcompat-v7:$versions.supportLib",
               design               : "com.android.support:design:$versions.supportLib"]

        .... Other libraries and setup....

    }
}

rootProject/app/build.gradle

...
dependencies {
    // Support libraries
    compile libs.appcompat
    compile libs.design
    .....
}

我想在 Java 和 build.gradle 端访问属性version and libs变量。我怎样才能实现这个目标？

你可以做这样的事情，但是outside the buildscript block

ext {
    // Version
    supportVersion = '26.0.0'

    // Support Libraries dependencies
    supportDependencies = [
            design:            "com.android.support:design:${supportVersion}",
            recyclerView:      "com.android.support:recyclerview-v7:${supportVersion}",
            cardView:          "com.android.support:cardview-v7:${supportVersion}",
            appCompat:         "com.android.support:appcompat-v7:${supportVersion}",
            supportAnnotation: "com.android.support:support-annotations:${supportVersion}",
    ]

    firebaseVersion = '11.0.2';

    firebaseDependencies = [
            core:         "com.google.firebase:firebase-core:${firebaseVersion}",
            database:     "com.google.firebase:firebase-database:${firebaseVersion}",
            storage:      "com.google.firebase:firebase-storage:${firebaseVersion}",
            crash:        "com.google.firebase:firebase-crash:${firebaseVersion}",
            auth:         "com.google.firebase:firebase-auth:${firebaseVersion}",
            messaging:    "com.google.firebase:firebase-messaging:${firebaseVersion}",
            remoteConfig: "com.google.firebase:firebase-config:${firebaseVersion}",
            invites:      "com.google.firebase:firebase-invites:${firebaseVersion}",
            adMod:        "com.google.firebase:firebase-ads:${firebaseVersion}",
            appIndexing:  "com.google.android.gms:play-services-appindexing:${firebaseVersion}",
    ];
}


// Module build file
dependencies {
    // ...
    compile supportDependencies.appCompat
    compile supportDependencies.design
    compile firebaseDependencies.crash
}

在java中你无法访问build.gradle文件，因为它们仅在构建时使用。但是您可以将相同的值放入BuildConfig文件。在此文件中，有一些预先构建的值，例如BuildConfig.VERSION_NAME或者您可以使用一些自定义键，例如：

android {
    ...
    defaultConfig {
        ...
        // defining the build date
        buildConfigField "long", "BUILD_DATE", System.currentTimeMillis() + "L"
        // define whether this build is a production build
        buildConfigField "boolean", "IS_PRODUCTION", "false"
        // note that to define a string you need to escape it
        buildConfigField "String", "API_KEY", "\"my_api_key\""
    }
}

自动生成的<package_name>.BuildConfig.java将包含基于上述指令的以下字段：

public class BuildConfig {
    // ... other generated fields ...
    public static final long BUILD_DATE = 1469504547000L;
    public static final boolean IS_PRODUCTION = false;
    public static final String API_KEY = "my_api_key";
}