Gradle:如何在android-library中使用BuildConfig,并在应用程序中设置一个标志

Question

我的(gradle 1.10和gradle插件0.8)基于android的项目包含一个大的android-library,它是3个不同的android-app的依赖

在我的图书馆,我希望能够使用这样的结构

if (BuildConfig.SOME_FLAG) {
    callToBigLibraries()
}

因为proguard可以根据SOME_FLAG的最终值减小生成的apk的大小

但我无法想象如何用gradle做到:

* the BuildConfig produced by the library doesn't have the same package name than the app
* I have to import the BuildConfig with the library package in the library
* The apk of an apps includes the BuildConfig with the package of the app but not the one with the package of the library.

我尝试使用BuildTypes和类似的东西没有成功

release {
    // packageNameSuffix "library"
    buildConfigField "boolean", "SOME_FLAG", "true"
}
debug {
    //packageNameSuffix "library"
    buildConfigField "boolean", "SOME_FLAG", "true"
}

为我的库和我的应用程序构建共享BuildConfig的正确方法是什么,其标志将在应用程序中构建时被覆盖？

Answer 1

作为一种变通方法,您可以使用此方法,该方法使用反射从应用程序(而不是库)获取字段值:

/**
 * Gets a field from the project's BuildConfig. This is useful when, for example, flavors
 * are used at the project level to set custom fields.
 * @param context       Used to find the correct file
 * @param fieldName     The name of the field-to-access
 * @return              The value of the field, or {@code null} if the field is not found.
 */
public static Object getBuildConfigValue(Context context, String fieldName) {
    try {
        Class<?> clazz = Class.forName(context.getPackageName() + ".BuildConfig");
        Field field = clazz.getField(fieldName);
        return field.get(null);
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (NoSuchFieldException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    }
    return null;
}

DEBUG例如,要获得该字段,只需从您的Activity:

boolean debug = (Boolean) getBuildConfigValue(this, "DEBUG");

我也在AOSP问题跟踪器上分享了这个解决方案.

Answer 2

以下解决方案/解决方法适用于我.它是由谷歌问题跟踪器中的一些人发布的:

尝试设置publishNonDefault到true在库项目:

android {
    ...
    publishNonDefault true
    ...
}

并将以下依赖项添加到使用该库的应用程序项目:

dependencies {
    releaseCompile project(path: ':library', configuration: 'release')
    debugCompile project(path: ':library', configuration: 'debug')
}

这样,使用该库的项目包括库的正确构建类型.

Answer 3

你无法做你想做的事,因为BuildConfig.SOME_FLAG它不会被正确地传播到你的图书馆; 构建类型本身不会传播到库 - 它们总是构建为RELEASE.这是错误https://code.google.com/p/android/issues/detail?id=52962

要解决这个问题:如果您可以控制所有库模块,那么您可以确保所有涉及的代码callToBigLibraries()都在可以使用ProGuard完全切割的类和包中,然后使用反射以便您可以访问它们.如果不存在,它们就会存在并优雅地降级.你基本上做了同样的事情,但是你在运行时进行检查而不是编译时间,这有点困难.

如果你在弄清楚如何做到这一点,请告诉我.如果需要,我可以提供样品.

Answer 4

我在应用程序和库中都使用了静态 BuildConfigHelper 类，这样我就可以将 BuildConfig 包设置为库中的最终静态变量。

在应用程序中，放置一个这样的类：

package com.yourbase;

import com.your.application.BuildConfig;

public final class BuildConfigHelper {

    public static final boolean DEBUG = BuildConfig.DEBUG;
    public static final String APPLICATION_ID = BuildConfig.APPLICATION_ID;
    public static final String BUILD_TYPE = BuildConfig.BUILD_TYPE;
    public static final String FLAVOR = BuildConfig.FLAVOR;
    public static final int VERSION_CODE = BuildConfig.VERSION_CODE;
    public static final String VERSION_NAME = BuildConfig.VERSION_NAME;

}

在图书馆：

package com.your.library;

import android.support.annotation.Nullable;

import java.lang.reflect.Field;

public class BuildConfigHelper {

    private static final String BUILD_CONFIG = "com.yourbase.BuildConfigHelper";

    public static final boolean DEBUG = getDebug();
    public static final String APPLICATION_ID = (String) getBuildConfigValue("APPLICATION_ID");
    public static final String BUILD_TYPE = (String) getBuildConfigValue("BUILD_TYPE");
    public static final String FLAVOR = (String) getBuildConfigValue("FLAVOR");
    public static final int VERSION_CODE = getVersionCode();
    public static final String VERSION_NAME = (String) getBuildConfigValue("VERSION_NAME");

    private static boolean getDebug() {
        Object o = getBuildConfigValue("DEBUG");
        if (o != null && o instanceof Boolean) {
            return (Boolean) o;
        } else {
            return false;
        }
    }

    private static int getVersionCode() {
        Object o = getBuildConfigValue("VERSION_CODE");
        if (o != null && o instanceof Integer) {
            return (Integer) o;
        } else {
            return Integer.MIN_VALUE;
        }
    }

    @Nullable
    private static Object getBuildConfigValue(String fieldName) {
        try {
            Class c = Class.forName(BUILD_CONFIG);
            Field f = c.getDeclaredField(fieldName);
            f.setAccessible(true);
            return f.get(null);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

}

然后，在您想要检查 BuildConfig.DEBUG 的库中的任何地方，您都可以检查 BuildConfigHelper.DEBUG 并从任何没有上下文的地方访问它，其他属性也是如此。我这样做是为了使库可以与我的所有应用程序一起使用，而无需以其他方式传入上下文或设置包名称，并且应用程序类只需要更改导入行以适应将其添加到新的应用

编辑：我想重申一下，这是从所有应用程序获取要分配给库中最终静态变量的值的最简单（此处仅列出一种）方法，无需上下文或硬编码某处的包名，这几乎和在默认库 BuildConfig 中的值一样好，对于在每个应用程序中更改导入行的最小维护。

Answer 5

For the case where the applicationId is not the same as the package (i.e. multiple applicationIds per project) AND you want to access from a library project:

Use Gradle to store the base package in resources.

In main/AndroidManifest.xml:

android {
    applicationId "com.company.myappbase"
    // note: using ${applicationId} here will be exactly as above
    // and so NOT necessarily the applicationId of the generated APK
    resValue "string", "build_config_package", "${applicationId}"
}

In Java:

android {
    applicationId "com.company.myappbase"
    // note: using ${applicationId} here will be exactly as above
    // and so NOT necessarily the applicationId of the generated APK
    resValue "string", "build_config_package", "${applicationId}"
}