Gradle系列之从init.gradle说起

从maven说起

用过maven的开发都知道，在maven里一些信息可以定义在全局的配置文件中，比如把一些仓库信息定义在用户目录/.m2/setting.xml文件中，这样就不用每个项目都配置这些相同的配置了。对于Andorid开发者来说，使用gradle比使用maven更常见，在开发中说不定你会在每一个项目中配置一遍公司的仓库地址，定义一些相同的配置，那么在gradle中有没有类似maven的这么一个配置文件可以定义一些全局信息呢？

答案当然是有，那就是init.gradle。

init.gradle的作用

先来简单介绍一下init.gradle这个文件的作用。

• 它可以用来建立公司内部的配置,如定义公司内部的仓库地址。
• 它可以用来配置一些全局属性,比如配置持续集成服务器的地址等配置。
• 它可以用来提供构建所需要的用户的个人信息,如仓库或数据库的用户名和密码。
• 它可以用来定义开发者机器的环境,比如定义jdk安装在什么位置，android sdk安装在什么位置等等。
• 最重要的功能之一，它可以用来注册一些监听器。比如监听Gradle事件的发生，做一些额外的操作，例如需要对某个项目构建前和构建后做一些操作，又例如对项目的依赖做检测，检测是否含有snapshot包，在release构建中一般来说是禁止依赖snapshot包的，所以这时候就可以扔出一个异常。
• 重定向日志。我们可以将gradle默认的日志进行重定向，甚至我们可以不输出默认日志，自定义如何输出gradle产生的日志信息。

init.gradle的加载顺序

再来说说init.gradle文件的加载顺序（不一定命名为init.gradle）。Gradle会依次对一些目录进行检测，按照优先级加载这些目录下的文件，如果一个目录下有多个文件被找到，则按照英文字母的顺序依次加载。加载优先级如下：

• 通过 -I 或者 –init-script 参数在构建开始时指定路径，如
gradle --init-script init.gradle clean

gradle --I init.gradle assembleDebug

• 加载USER_HOME/.gradle/init.gradle文件
• 加载USER_HOME/.gradle/init.d/目录下的以.gradle结尾的文件
• 加载GRADLE_HOME/init.d/目录下的以.gradle结尾的文件

那么USER_HOME和GRADLE_HOME可以怎么得到呢，其实USER_HOME一般来说就是当前用户目录下的.gradle目录，而GRADLE_HOME目录一般来说是gradle的可执行目录，如果你配置了环境变量，且你使用的是环境变量中的可执行文件，则这个目录会执向你配置了环境变量的目录，比如，我配置了gradle的环境变量指向/Library/gradle，这两个目录在我电脑上的值为:

gradleHomeDir:/Library/gradle
gradleUserHomeDir:/Users/lizhangqu/.gradle

但是如果我使用项目中的gradlew去执行任务，则这两个值为

gradleHomeDir:/Users/lizhangqu/.gradle/wrapper/dists/gradle-2.10-all/a4w5fzrkeut1ox71xslb49gst/gradle-2.10
gradleUserHomeDir:/Users/lizhangqu/.gradle

我们可以在init.gradle中使用gradle实例来获得这两个目录，甚至可以获得gradle的版本，以及gradle启动时所携带的参数。具体脚本如下：

//gradle的可执行目录
gradle.println "gradleHomeDir:${gradle.gradleHomeDir}"
//gradle的用户目录,用于缓存一些下载好的资源,编译好的构建脚本等
gradle.println "gradleUserHomeDir:${gradle.gradleUserHomeDir}"
//gradle的版本号
gradle.println "gradleVersion:${gradle.gradleVersion}"
//gralde当前构建的启动参数
gradle.println "startParameter:${gradle.startParameter}"

在init.gradle使用三方库

如果我们需要在init.gradle中使用第三方库的功能，比如我需要使用apache的commons-math库中的某个函数，则可以使用initscript定义仓库地址，然后将依赖加入，如下脚本：

initscript {
    //定义init.gradle所需要的仓库地址
    repositories {
        jcenter()
        mavenCentral()
        mavenLocal()
    }
    //加入依赖
    dependencies {
        classpath 'org.apache.commons:commons-math:2.0'
    }
}
//使用函数
println org.apache.commons.math.fraction.Fraction.ONE_FIFTH.multiply(2)

以上代码会输出2/5

在init.gradle中定义全局的仓库

在公司中，我所见到的仓库的定义都是定义在每一个项目中，没有一个全局的仓库配置，这样显得有点冗余，而在init.gradle中就可以定义一个公司的仓库地址，之后所有的gradle项目都可以使用这个仓库。并且对于一些实时在改变的库，我们可以定义其全局的更新策略（虽然这个策略在我的电脑上一直没有生效，但这是gradle官方标准的做法，即使用cacheChangingModulesFor属性，将其时间设为0，没有生效显然是一个bug）。

//init.gralde可以配置一些全局的配置，比如仓库的地址等
import java.util.concurrent.TimeUnit
allprojects { Project project ->
    buildscript {
        repositories {
            maven {
                url "htttp://url/to/maven"
            }
            jcenter()
            mavenCentral()
            mavenLocal()
        }
    }
    repositories {
        maven {
            url "htttp://url/to/maven"
        }
        jcenter()
        mavenCentral()
        mavenLocal()
    }
    configurations.all {
        resolutionStrategy {
            // cache dynamic versions for 10 minutes
            cacheDynamicVersionsFor 10 * 60, TimeUnit.SECONDS
            // don't cache changing modules at all
            cacheChangingModulesFor 0, TimeUnit.SECONDS
        }
    }
}

在init.gradle中自定义插件并使用

在我们的项目中，我们会使用apply plugin来引用一些插件来增强一些功能，当然在init.gradle也可以这么做，我们就以前面定义公司的仓库和依赖的更新策略来做演示，将其修改为一个插件然后使用。如下：

//对于一些仓库的全局定义，也可以使用插件的方式定义，如


apply plugin: EnterpriseRepositoryPlugin

class EnterpriseRepositoryPlugin implements Plugin<Gradle> {
    private static String REPOSITORY_URL = "htttp://url/to/maven"

    void apply(Gradle gradle) {
        gradle.allprojects { project ->
            project.buildscript {
                repositories {
                    maven {
                        url REPOSITORY_URL
                    }
                    jcenter()
                    mavenCentral()
                    mavenLocal()
                }
                dependencies {
                    //可以定义全局的android gradle插件
                    classpath 'com.android.tools.build:gradle:2.1.2'
                }
            }
            project.repositories {
                maven {
                    url REPOSITORY_URL
                }
                jcenter()
                mavenCentral()
                mavenLocal()
            }
            project.configurations.all {
                resolutionStrategy {
                    // cache dynamic versions for 10 minutes
                    cacheDynamicVersionsFor 10 * 60, TimeUnit.SECONDS
                    // don't cache changing modules at all
                    cacheChangingModulesFor 0, TimeUnit.SECONDS
                }
            }
        }
    }
}

使用init.gradle重写日志

默认的如果我使用gradle assembleDebug来执行构建，控制台会输出一系列的log，类似下面的内容

./gradlew --I init.gradle assembleDebug
Incremental java compilation is an incubating feature.
:app:preBuild UP-TO-DATE
:app:preDebugBuild UP-TO-DATE
:app:checkDebugManifest
:app:preReleaseBuild UP-TO-DATE
:app:prepareComAndroidSupportAnimatedVectorDrawable2411Library
:app:prepareComAndroidSupportAppcompatV72411Library
:app:prepareComAndroidSupportSupportV42411Library
:app:prepareComAndroidSupportSupportVectorDrawable2411Library
:app:prepareDebugDependencies
:app:compileDebugAidl
:app:compileDebugRenderscript
:app:generateDebugBuildConfig
:app:mergeDebugShaders
:app:compileDebugShaders
:app:generateDebugAssets
:app:mergeDebugAssets
:app:generateDebugResValues UP-TO-DATE
:app:generateDebugResources
:app:mergeDebugResources
:app:processDebugManifest
:app:processDebugResources
:app:generateDebugSources
:app:incrementalDebugJavaCompilationSafeguard
:app:compileDebugJavaWithJavac
:app:compileDebugJavaWithJavac - is not incremental (e.g. outputs have changed, no previous execution, etc.).
:app:compileDebugNdk UP-TO-DATE
:app:compileDebugSources
:app:prePackageMarkerForDebug
:app:transformClassesWithDexForDebug
Merged dex #1 (5 defs/15.3KiB)
Merged dex #2 (355 defs/574.2KiB)
Merged dex #3 (819 defs/997.1KiB)
Merged dex #4 (17 defs/48.5KiB)
Merged dex #5 (29 defs/89.4KiB)
Merged dex #6 (363 defs/280.8KiB)
Merged dex #7 (46 defs/7.4KiB)
Result is 1634 defs/2438.7KiB. Took 0.5s
:app:mergeDebugJniLibFolders
:app:transformNative_libsWithMergeJniLibsForDebug
:app:processDebugJavaRes UP-TO-DATE
:app:transformResourcesWithMergeJavaResForDebug
:app:validateDebugSigning
:app:packageDebug
:app:zipalignDebug
:app:assembleDebug

BUILD SUCCESSFUL

Total time: 29.62 secs

对于这些log，我们可以使用gradle.useLogger()函数重新定义需要输出什么内容。比如我们让控制台按我们的意思进行输出，则可以定义一个类，实现BuildListener接口和TaskExecutionListener接口。再调用useLogger函数传入这个类的实例，如下：

gradle.useLogger(new CustomEventLogger())

//自定义的log输出
class CustomEventLogger implements BuildListener, TaskExecutionListener {
    @Override
    void buildStarted(Gradle gradle) {
        println "buildStarted"
    }

    @Override
    void settingsEvaluated(Settings settings) {
        println "settingsEvaluated"
    }

    @Override
    void projectsLoaded(Gradle gradle) {
        println "projectsLoaded"
    }

    @Override
    void projectsEvaluated(Gradle gradle) {
        println "projectsEvaluated"
    }

    public void beforeExecute(Task task) {
        println "beforeExecute:[$task.name]"
    }

    public void afterExecute(Task task, TaskState state) {
        println "afterExecute:[$task.name]"
    }

    public void buildFinished(BuildResult result) {
        println 'buildFinished'
        if (result.failure != null) {
            result.failure.printStackTrace()
        }
    }
}

之后控制台的输出就会大变样，变成下面的内容

./gradlew --I init.gradle assembleDebug
settingsEvaluated
projectsLoaded
Incremental java compilation is an incubating feature.
projectsEvaluated
beforeExecute:[preBuild]
afterExecute:[preBuild]
beforeExecute:[preDebugBuild]
afterExecute:[preDebugBuild]
beforeExecute:[checkDebugManifest]
afterExecute:[checkDebugManifest]
beforeExecute:[preReleaseBuild]
afterExecute:[preReleaseBuild]
beforeExecute:[prepareComAndroidSupportAnimatedVectorDrawable2411Library]
afterExecute:[prepareComAndroidSupportAnimatedVectorDrawable2411Library]
beforeExecute:[prepareComAndroidSupportAppcompatV72411Library]
afterExecute:[prepareComAndroidSupportAppcompatV72411Library]
beforeExecute:[prepareComAndroidSupportSupportV42411Library]
afterExecute:[prepareComAndroidSupportSupportV42411Library]
beforeExecute:[prepareComAndroidSupportSupportVectorDrawable2411Library]
afterExecute:[prepareComAndroidSupportSupportVectorDrawable2411Library]
beforeExecute:[prepareDebugDependencies]
afterExecute:[prepareDebugDependencies]
beforeExecute:[compileDebugAidl]
afterExecute:[compileDebugAidl]
beforeExecute:[compileDebugRenderscript]
afterExecute:[compileDebugRenderscript]
beforeExecute:[generateDebugBuildConfig]
afterExecute:[generateDebugBuildConfig]
beforeExecute:[mergeDebugShaders]
afterExecute:[mergeDebugShaders]
beforeExecute:[compileDebugShaders]
afterExecute:[compileDebugShaders]
beforeExecute:[generateDebugAssets]
afterExecute:[generateDebugAssets]
beforeExecute:[mergeDebugAssets]
afterExecute:[mergeDebugAssets]
beforeExecute:[generateDebugResValues]
afterExecute:[generateDebugResValues]
beforeExecute:[generateDebugResources]
afterExecute:[generateDebugResources]
beforeExecute:[mergeDebugResources]
afterExecute:[mergeDebugResources]
beforeExecute:[processDebugManifest]
afterExecute:[processDebugManifest]
beforeExecute:[processDebugResources]
afterExecute:[processDebugResources]
beforeExecute:[generateDebugSources]
afterExecute:[generateDebugSources]
beforeExecute:[incrementalDebugJavaCompilationSafeguard]
afterExecute:[incrementalDebugJavaCompilationSafeguard]
beforeExecute:[compileDebugJavaWithJavac]
:app:compileDebugJavaWithJavac - is not incremental (e.g. outputs have changed, no previous execution, etc.).
afterExecute:[compileDebugJavaWithJavac]
beforeExecute:[compileDebugNdk]
afterExecute:[compileDebugNdk]
beforeExecute:[compileDebugSources]
afterExecute:[compileDebugSources]
beforeExecute:[prePackageMarkerForDebug]
afterExecute:[prePackageMarkerForDebug]
beforeExecute:[transformClassesWithDexForDebug]
Merged dex #1 (5 defs/15.3KiB)
Merged dex #2 (355 defs/574.2KiB)
Merged dex #3 (819 defs/997.1KiB)
Merged dex #4 (17 defs/48.5KiB)
Merged dex #5 (29 defs/89.4KiB)
Merged dex #6 (363 defs/280.8KiB)
Merged dex #7 (46 defs/7.4KiB)
Result is 1634 defs/2438.7KiB. Took 0.7s
afterExecute:[transformClassesWithDexForDebug]
beforeExecute:[mergeDebugJniLibFolders]
afterExecute:[mergeDebugJniLibFolders]
beforeExecute:[transformNative_libsWithMergeJniLibsForDebug]
afterExecute:[transformNative_libsWithMergeJniLibsForDebug]
beforeExecute:[processDebugJavaRes]
afterExecute:[processDebugJavaRes]
beforeExecute:[transformResourcesWithMergeJavaResForDebug]
afterExecute:[transformResourcesWithMergeJavaResForDebug]
beforeExecute:[validateDebugSigning]
afterExecute:[validateDebugSigning]
beforeExecute:[packageDebug]
afterExecute:[packageDebug]
beforeExecute:[zipalignDebug]
afterExecute:[zipalignDebug]
beforeExecute:[assembleDebug]
afterExecute:[assembleDebug]
buildFinished

对于useLogger函数来讲，其传入的参数是一个Object类型，我们让其可以实现任何一个addListener方法传入的参数的接口即可，一旦调用了useLogger方法,默认的gradle事件的日志会被替换,也就是会被替换成我们自定义的日志输出，而这些接口如下：

• org.gradle.BuildListener
• org.gradle.api.execution.TaskExecutionGraphListener
• org.gradle.api.ProjectEvaluationListener
• org.gradle.api.execution.TaskExecutionListener
• org.gradle.api.execution.TaskActionListener
• org.gradle.api.logging.StandardOutputListener
• org.gradle.api.tasks.testing.TestListener
• org.gradle.api.tasks.testing.TestOutputListener
• org.gradle.api.artifacts.DependencyResolutionListener

使用init.gradle注册构建监听

上面我们提到了很多接口，这些接口可以使用gradle.addBuildListener方法或者gradle.addListener方法注册到整个构建过程。

• BuildListener

BuildListener在整个构建过程中的特定点会回调特定的函数，如构建开始时会回调buildStarted，setting.gradle加载和评估完成后会回调settingsEvaluated，所有项目加载进来后会回调projectsLoaded，所有项目配置评估完成会回调projectsEvaluated，构建完成会回调buildFinished，具体例子如下：

//构建监听
gradle.addBuildListener(new BuildListener() {
    @Override
    void buildStarted(Gradle gradle) {
        //init.gradle被执行前,构建已经发生,且buildStarted已经被回调,
        // 因此后续加入的BuildListener都不会再调用buildStarted
        gradle.println("=========BuildListener:buildStarted=========")
    }

    @Override
    void settingsEvaluated(Settings settings) {
        //setting.gradle加载和评估配置阶段完成
        gradle.println("=========BuildListener:settingsEvaluated=========")
    }

    @Override
    void projectsLoaded(Gradle gradle) {
        //项目加载完成
        gradle.println("=========BuildListener:projectsLoaded=========")
    }

    @Override
    void projectsEvaluated(Gradle gradle) {
        //项目评估配置阶段结束
        gradle.println("=========BuildListener:projectsEvaluated=========")
    }

    @Override
    void buildFinished(BuildResult result) {
        //构建完成
        gradle.println("=========BuildListener:buildFinished=========")
    }
})

但是buildStarted这个回调有点特殊，在构建开始后，init.gradle执行前，buildStarted方法就会被回调，因此在init.gradle加入的监听器buildStarted是不会被回调的，只有gradle内部注册的才会回调。这一细节可以从gradle的源码中看到。

import javafx.stage.Stage

private BuildResult doBuild(final Stage upTo) {
    return buildOperationExecutor.run("Run build", new Factory<BuildResult>() {
        @Override
        public BuildResult create() {
            Throwable failure = null;
            try {
                //回调buildStarted，但此时init.gradle没有被执行，时机太早
                buildListener.buildStarted(gradle);
                doBuildStages(upTo);
            } catch (Throwable t) {
                failure = exceptionAnalyser.transform(t);
            }
            BuildResult buildResult = new BuildResult(upTo.name(), gradle, failure);
            buildListener.buildFinished(buildResult);
            if (failure != null) {
                throw new ReportedException(failure);
            }
            return buildResult;
        }
    });
}
private void doBuildStages(Stage upTo) {
//执行init.gradle,此时buildStarted已经被回调，之后都不会再次回调，所以init.gradle中加入的监听器buildStarted都不会被回调
// Evaluate init scripts
    initScriptHandler.executeScripts(gradle);
// Calculate projects
    settingsLoader.findAndLoadSettings(gradle);
// Configure build
    buildOperationExecutor.run("Configure build", new Runnable() {
        @Override
        public void run() {
            buildConfigurer.configure(gradle);
            if (!gradle.getStartParameter().isConfigureOnDemand()) {
                buildListener.projectsEvaluated(gradle);
            }
            modelConfigurationListener.onConfigure(gradle);
        }
    });
    if (upTo == Stage.Configure) {
        return;
    }
// Populate task graph
    buildOperationExecutor.run("Calculate task graph", new Runnable() {
        @Override
        public void run() {
            buildConfigurationActionExecuter.select(gradle);
            if (gradle.getStartParameter().isConfigureOnDemand()) {
                buildListener.projectsEvaluated(gradle);
            }
        }
    });
// Execute build
    buildOperationExecutor.run("Run tasks", new Runnable() {
        @Override
        public void run() {
            buildExecuter.execute(gradle);
        }
    });
    assert upTo == Stage.Build;
}

ProjectEvaluationListener

ProjectEvaluationListener主要用于监听项目的配置评估阶段，配置评估开始前和完成后会回调。如下：

//配置评估监听
gradle.addProjectEvaluationListener(new ProjectEvaluationListener() {
    @Override
    void beforeEvaluate(Project project) {
        //项目配置评估前回调
        gradle.println("=========ProjectEvaluationListener:beforeEvaluate ${project.getName()}=========")
    }

    @Override
    void afterEvaluate(Project project, ProjectState state) {
        //项目配置评估后回调
        //如果失败,则failure不为null
        gradle.println("=========ProjectEvaluationListener:afterEvaluate ${state.executed} ${state.failure}=========")
    }
})

TaskExecutionGraphListener

TaskExecutionGraphListener这个监听器可以在项目评估完成后获得需要构建的任务的所有依赖，比如下面的代码就可以获得我所执行的task的所有依赖。

gradle.addListener(new TaskExecutionGraphListener() {
    @Override
    void graphPopulated(TaskExecutionGraph graph) {
        gradle.println "=========from gradle.addListener graphPopulated========="
        graph.allTasks.each {
            Task task ->
                gradle.println "=========TaskExecutionGraph:${task.getName()}========="
        }
    }
}

输出的内容如下：

./gradlew --I init.gradle assembleDebug
=========from gradle.addListener graphPopulated=========
=========TaskExecutionGraph:preBuild=========
=========TaskExecutionGraph:preDebugBuild=========
=========TaskExecutionGraph:checkDebugManifest=========
=========TaskExecutionGraph:preReleaseBuild=========
=========TaskExecutionGraph:prepareComAndroidSupportAnimatedVectorDrawable2411Library=========
=========TaskExecutionGraph:prepareComAndroidSupportAppcompatV72411Library=========
=========TaskExecutionGraph:prepareComAndroidSupportSupportV42411Library=========
=========TaskExecutionGraph:prepareComAndroidSupportSupportVectorDrawable2411Library=========
=========TaskExecutionGraph:prepareDebugDependencies=========
=========TaskExecutionGraph:compileDebugAidl=========
=========TaskExecutionGraph:compileDebugRenderscript=========
=========TaskExecutionGraph:generateDebugBuildConfig=========
=========TaskExecutionGraph:mergeDebugShaders=========
=========TaskExecutionGraph:compileDebugShaders=========
=========TaskExecutionGraph:generateDebugAssets=========
=========TaskExecutionGraph:mergeDebugAssets=========
=========TaskExecutionGraph:generateDebugResValues=========
=========TaskExecutionGraph:generateDebugResources=========
=========TaskExecutionGraph:mergeDebugResources=========
=========TaskExecutionGraph:processDebugManifest=========
=========TaskExecutionGraph:processDebugResources=========
=========TaskExecutionGraph:generateDebugSources=========
=========TaskExecutionGraph:incrementalDebugJavaCompilationSafeguard=========
=========TaskExecutionGraph:compileDebugJavaWithJavac=========
=========TaskExecutionGraph:compileDebugNdk=========
=========TaskExecutionGraph:compileDebugSources=========
=========TaskExecutionGraph:prePackageMarkerForDebug=========
=========TaskExecutionGraph:transformClassesWithDexForDebug=========
=========TaskExecutionGraph:mergeDebugJniLibFolders=========
=========TaskExecutionGraph:transformNative_libsWithMergeJniLibsForDebug=========
=========TaskExecutionGraph:processDebugJavaRes=========
=========TaskExecutionGraph:transformResourcesWithMergeJavaResForDebug=========
=========TaskExecutionGraph:validateDebugSigning=========
=========TaskExecutionGraph:packageDebug=========
=========TaskExecutionGraph:zipalignDebug=========
=========TaskExecutionGraph:assembleDebug=========

TaskExecutionListener

TaskExecutionListener这个监听器可以用来监听构建过程中所有task构建前和构建后。每一个任务执行前会回调beforeExecute方法，执行完成后会回调afterExecute，执行的结果保存在入参TaskState中。

//等同gradle.taskGraph.addTaskExecutionListener
gradle.addListener(new TaskExecutionListener() {
    @Override
    void beforeExecute(Task task) {
        gradle.println "=========from gradle.addListener beforeExecute========="
        gradle.println "=========TaskExecutionListener:beforeExecute:${task.getName()}========="
    }

    @Override
    void afterExecute(Task task, TaskState state) {
        gradle.println "=========from gradle.addListener afterExecute========="
        gradle.println "=========TaskExecutionListener:afterExecute:${task.getName()}========="
        gradle.println "=========TaskState:[executed]${state.executed}========="
        gradle.println "=========TaskState:[didWork]${state.didWork}========="
        gradle.println "=========TaskState:[failure]${state.failure}========="
        gradle.println "=========TaskState:[skipMessage]${state.skipMessage}========="
        gradle.println "=========TaskState:[skipped]${state.skipped}========="
        gradle.println "=========TaskState:[upToDate]${state.upToDate}========="
    }
})

DependencyResolutionListener

DependencyResolutionListener这个监听器可以用来监听构建过程中依赖的关系，比如可以使用这个监听器来检测release构建中是否包含snapshot包，如果包含则扔出异常停止构建。

//依赖监听
gradle.addListener(new DependencyResolutionListener() {
    @Override
    void beforeResolve(ResolvableDependencies resolvableDependencies) {
        gradle.println "DependencyResolutionListener:beforeResolve:=====${dependencies}====="

    }

    @Override
    void afterResolve(ResolvableDependencies resolvableDependencies) {
        gradle.println "DependencyResolutionListener:afterResolve:=====${dependencies}====="

        def projectPath = resolvableDependencies.path.toLowerCase()

        if (projectPath.contains("releasecompile")) {
            gradle.println "[DependencyResolutionListener] release detect:${resolvableDependencies.path}"
            resolvableDependencies.resolutionResult.allDependencies.each { dependency ->
                if (dependency instanceof org.gradle.api.internal.artifacts.result.DefaultUnresolvedDependencyResult) {
                    gradle.println "DefaultUnresolvedDependencyResult reason: ${dependency.reason}"
                    gradle.println "DefaultUnresolvedDependencyResult failure: ${dependency.failure}"
                } else if (dependency instanceof org.gradle.api.internal.artifacts.result.DefaultResolvedDependencyResult) {
                    String selected = dependency.selected
                    def from = dependency.from
                    gradle.println "[DependencyResolutionListener] current dependency:${selected} which is from:${from}"
                    if (selected != null && (selected.toLowerCase().contains("snapshot") || selected.toLowerCase().contains("beta"))) {
                        String errorMessage = "[DependencyResolutionListener] [Error] ${selected} from ${from} contains a snapshot or beta version. you must fix it."
                        gradle.println errorMessage
                        throw new IllegalStateException(errorMessage)
                    }
                }
            }
        }
    }
})

StandardOutputListener

StandardOutputListener这个监听器可以得到控制台输出的log，除了输出到控制台后，可以对其进行重定向，比如输出到文件中去，如下：

//log输出的监听,可以将log输出到其他文件中去
gradle.addListener(new StandardOutputListener() {
    static File logFile = new File("log.txt");
    static {
        if (logFile.exists()) {
            logFile.delete()
        }
        logFile.createNewFile()
    }

    @Override
    void onOutput(CharSequence output) {
        try {
            FileWriter writer = new FileWriter(logFile, true);
            writer.write(output.toString());
            writer.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
})

TaskActionListener

在一个Task中可能会有很多action，比如我们通过doFirst和doLast加入的闭包都是action，TaskActionListener监听器就可以在这些actions执行前和执行完成后得到回调，如下：

//TaskAction监听器,Task.doFirst,Task.doLast等传入的闭包都是Action
gradle.addListener(new TaskActionListener() {
    @Override
    void beforeActions(Task task) {
        //在所有action执行前回调
        gradle.println "**********beforeActions:${task}**********"
        task.getActions().each {
            Action action ->
                gradle.println "**********${action}**********"
        }
    }

    @Override
    void afterActions(Task task) {
        //在所有action执行后回调
        gradle.println "**********afterActions:${task}**********"
        task.getActions().each {
            Action action ->
                gradle.println "**********${action}**********"
        }
    }
})

TestListener和TestOutputListener

这两个监听器主要是用于执行测试相关的task使用的，比如保存测试报告，但是实际测试中发现TestOutputListener中的方法怎么都不会回调，原因未知，如下脚本：

//测试监听器
gradle.addListener(new TestListener() {
    @Override
    void beforeSuite(TestDescriptor suite) {
        gradle.println "beforeSuite:=====${suite.className} ${suite.name}====="
    }

    @Override
    void afterSuite(TestDescriptor suite, TestResult result) {
        gradle.println "afterSuite:=====${suite.className} ${suite.name} ${result}====="
    }

    @Override
    void beforeTest(TestDescriptor testDescriptor) {
        gradle.println "beforeTest:=====${testDescriptor.className} ${testDescriptor.name}====="
    }

    @Override
    void afterTest(TestDescriptor testDescriptor, TestResult result) {
        gradle.println "afterTest:=====${testDescriptor.className} ${testDescriptor.name} ${result}====="
    }
})
//测试的输出监听,实际测试并没有回调
gradle.addListener(new TestOutputListener() {
    @Override
    void onOutput(TestDescriptor testDescriptor, TestOutputEvent outputEvent) {
        gradle.println "onOutput:=====${testDescriptor} ${outputEvent}====="
        gradle.println "message:${outputEvent.message}"
        gradle.println "destination:${outputEvent.destination}"
    }
})

使用闭包

除了以上监听器之外，我们还可以使用闭包来监听构建的过程中的事件回调，比如我只对构建完成这一事件感兴趣，则可以使用

gradle.buildFinished {
    gradle.println "=========buildFinished========="
}

除了这一闭包，还可以使用其他几个相关的闭包对感兴趣的事件进行注册，注册后对应的事件发生便会回调该闭包。

/**
 * 同上BuildListener和ProjectEvaluationListener
 */
gradle.buildStarted {
    gradle.println "=========buildStarted========="
}
gradle.settingsEvaluated {
    gradle.println "=========settingsEvaluated========="
}
gradle.projectsLoaded {
    gradle.println "=========projectsLoaded========="
}
gradle.projectsEvaluated {
    gradle.println "=========projectsEvaluated========="
}
gradle.buildFinished {
    gradle.println "=========buildFinished========="
}
gradle.beforeProject {
    gradle.println "=========beforeProject========="
}
gradle.afterProject {
    gradle.println "=========afterProject========="
}

其他

对于Task的依赖关系的获得，除了上面的注册TaskExecutionGraphListener监听器，还有其他的方式，即通过gradle.taskGraph来获得，具体的脚步如下：

//当前构建的任务依赖关系图
gradle.taskGraph.whenReady {
    TaskExecutionGraph taskGraph ->
        taskGraph.allTasks.each {
            Task task ->
                gradle.println "=========whenReady:taskGraph:${task.getName()}========="
        }
        taskGraph.beforeTask {
            Task task ->
                gradle.println "=========whenReady:beforeTask:${task.getName()}========="
        }
        taskGraph.afterTask {
            Task task ->
                gradle.println "=========whenReady:afterTask:${task.getName()}========="
        }
}
//等同于上面的whenReady闭包中的内容
gradle.taskGraph.addTaskExecutionGraphListener(new TaskExecutionGraphListener() {
    @Override
    void graphPopulated(TaskExecutionGraph graph) {
        gradle.println "=========TaskExecutionGraphListener:graphPopulated========="
        graph.allTasks.each {
            Task task ->
                gradle.println "=========TaskExecutionGraph:${task.getName()}========="
        }
    }
})
//等同于上面的whenReady闭包中的内容
gradle.taskGraph.addTaskExecutionListener(new TaskExecutionListener() {
    @Override
    void beforeExecute(Task task) {
        gradle.println "=========TaskExecutionListener:beforeExecute:${task.getName()}========="

    }

    @Override
    void afterExecute(Task task, TaskState state) {
        gradle.println "=========TaskExecutionListener:afterExecute:${task.getName()}========="
        gradle.println "=========TaskState:[executed]${state.executed}========="
        gradle.println "=========TaskState:[didWork]${state.didWork}========="
        gradle.println "=========TaskState:[failure]${state.failure}========="
        gradle.println "=========TaskState:[skipMessage]${state.skipMessage}========="
        gradle.println "=========TaskState:[skipped]${state.skipped}========="
        gradle.println "=========TaskState:[upToDate]${state.upToDate}========="
    }
})

//获得root project
gradle.taskGraph.addTaskExecutionGraphListener(new TaskExecutionGraphListener() {
    @Override
    void graphPopulated(TaskExecutionGraph graph) {
        gradle.println "========${gradle.rootProject}========"
    }
})

监听器的应用（构建时间的监听）

对于监听器，我们可以使用它来计算各个task所执行的时间，然后输出控制台，如下:

class TimeListener implements TaskExecutionListener, BuildListener {
    private Clock clock
    private times = []

    @Override
    void beforeExecute(Task task) {
        clock = new org.gradle.util.Clock()
    }

    @Override
    void afterExecute(Task task, TaskState taskState) {
        def ms = clock.timeInMs
        times.add([ms, task.path])
        task.project.logger.warn "${task.path} spend ${ms}ms"
    }

    @Override
    void buildFinished(BuildResult result) {
        println "Task spend time:"
        for (time in times) {
            if (time[0] >= 50) {
                printf "%7sms  %s
", time
            }
        }
    }

    @Override
    void buildStarted(Gradle gradle) {}

    @Override
    void projectsEvaluated(Gradle gradle) {}

    @Override
    void projectsLoaded(Gradle gradle) {}

    @Override
    void settingsEvaluated(Settings settings) {}
}
gradle.addListener(new TimeListener())

监听器的补充 
其实关于监听器，并非一定要在init.gradle中进行注册，我们也可以完全在我们项目中注册监听，只不过在init.gradle中可以注册一些全局的公共功能的监听器，就像上面的构建时间的计算。

总结

Gradle和init.gradle相关的内容大概就这么多，总结起来，其有用的东西就是各种各样的监听器，可用于构建过程中的hook，做一些自己的事情，还有就是可以进行全局的配置等。具体如何使用，可根据自己的需求进行定制。

转载自：https://blog.csdn.net/sbsujjbcy/article/details/52079413