Flutter插件中引用aar

背景

最近需要制作一个基于aar的Flutter插件，但遇到了一些问题。我们假设插件名称叫作my_plugin。以前我的解决方案是把aar文件导入my_plugin/android/libs中，然后在my_plugin/android/build.gradle做如下修改：

grovvy 复制代码

rootProject.allprojects {
    repositories {
        google()
        jcenter()
        flatDir {
            dirs project(':my_plugin').file('libs')
        }
    }
}

dependencies {
    implementation fileTree(include: ['*.aar'], dir: 'libs')
}

但我很快发现，这条路现在行不通：

sql 复制代码

Execution failed for task 'xxxx'.
> Direct local .aar file dependencies are not supported when building an AAR. 
The resulting AAR would be broken because the classes and Android resources from any local .aar 
file dependencies would not be packaged in the resulting AAR. Previous versions of the Android 
Gradle Plugin produce broken AARs in this case too (despite not throwing this error). The 
following direct local .aar file dependencies of the xxxx project caused this error: 
______.aar

很快我又换了一个姿势，同样使用flatDir，但这次我改用了compileOnly

scss 复制代码

```groovy
rootProject.allprojects {
    repositories {
        google()
        mavenCentral()
        flatDir {
            dirs project(':my_plugin').file('libs')
        }
    }
}

dependencies {
    compileOnly fileTree(include: ['*.aar'], dir: 'libs')
}

但也引起了一个小小的麻烦，这种方式需要在宿主app中把aar文件再次导入到对应的libs文件下，然后又要在build.gradle中添加 implementation fileTree(include: ['*.aar'], dir: 'libs')。对于使用者来说不友好，而且flatDir这种形式官方其实是不太推荐的（你会在控制台看到一些警告）。所以怎么相对优雅地解决这个问题？最快的方法当然是发布到远程maven之类的仓库了。谁都能想得到，但很实际开发中并不具备发布到远程maven的条件。

既然远程maven不行，那本地的maven是不是就可以了？

姿势一

第一种方式是直接借用maven-publish插件了。在my_plugin/android/build.gradle写点代码：

groovy 复制代码

//define this
String mavenLocalPath = project(":my_plugin").mkdir("m2repository").absolutePath


rootProject.allprojects {
    repositories {
        google()
        mavenCentral()
        maven {
            url mavenLocalPath
        }
    }
}


//apply plugin
apply plugin: "maven-publish"


publishing {
  publications {
    release(MavenPublication) {
            groupId = 'com.my-company'
            artifactId = 'my-library'
            version = '1.0'
            artifact "path/to/aar"
    }
  }
  repositories {
    maven {
      name = 'myrepo'
      url = mavenLocalPath
    }
  }
}

dependencies {
    implementation "com.my-company:my-library:1.0"
}

然后使用gradle运行publish任务即可：

shell 复制代码

./gradlew publish

//or 
gradle publish

然后你会发现在my_plugin/m2repository目录下生成了相关文件，大功告成！当有新版本时，我们只需再次publish即可。

姿势二

第一种方是借用了maven-publish插件，当然我们也可以手搓一个类似功能的，假设我们把aar放到了my_plugin/android/libs下：

groovy 复制代码

import java.security.MessageDigest
import java.security.NoSuchAlgorithmException

//define this
String mavenLocalPath = project(":my_plugin").mkdir("m2repository").absolutePath


rootProject.allprojects {
    repositories {
        google()
        mavenCentral()
        maven {
            url mavenLocalPath
        }
    }
}

task useAar {
    File file = project.file("libs")
    if (file.exists() && file.isDirectory()) {
        file.listFiles(new FileFilter() {
            @Override
            boolean accept(File pathname) {
                return pathname.name.endsWith(".aar")
            }
        }).each { item ->
            String aarName = item.name.substring(0, item.name.length() - 4)
            String[] aarInfo = aarName.split("-")
            String sha1 = getFileSha1(item)
            String md5 = getFileMD5(item)
            String fromStr = item.path
            String intoStr = aarPath + "/" + aarInfo[0].replace(".", "/") + "/" + aarInfo[1] + "/" + aarInfo[2]
            String newName = aarInfo[1] + "-" + aarInfo[2] + ".aar"

            project.copy {
                from fromStr
                into intoStr
                rename(item.name, newName)
            }

            project.file(intoStr + "/" + newName + ".md5").write(md5)
            project.file(intoStr + "/" + newName + ".sha1").write(sha1)

            String pomPath = intoStr + "/" + newName.substring(0, newName.length() - 4) + ".pom"
            project.file(pomPath).write(createPomStr(aarInfo[0], aarInfo[1], aarInfo[2]))
            project.file(pomPath + ".md5").write(getFileMD5(project.file(pomPath)))
            project.file(pomPath + ".sha1").write(getFileSha1(project.file(pomPath)))

            String metadataPath = project.file(intoStr).getParentFile().path + "/maven-metadata.xml"
            project.file(metadataPath).write(createMetadataStr(aarInfo[0], aarInfo[1], aarInfo[2]))
            project.file(metadataPath + ".md5").write(getFileMD5(project.file(metadataPath)))
            project.file(metadataPath + ".sha1").write(getFileSha1(project.file(metadataPath)))
            dependencies {
                implementation "${aarInfo[0]}:${aarInfo[1]}:${aarInfo[2]}"
            }
        }
    }
}

public static String createMetadataStr(String groupId, String artifactId, String version) {
    return "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" +
            "<metadata>\n" +
            "  <groupId>$groupId</groupId>\n" +
            "  <artifactId>$artifactId</artifactId>\n" +
            "  <versioning>\n" +
            "    <release>$version</release>\n" +
            "    <versions>\n" +
            "      <version>$version</version>\n" +
            "    </versions>\n" +
            "    <lastUpdated>${new Date().format('yyyyMMdd')}000000</lastUpdated>\n" +
            "  </versioning>\n" +
            "</metadata>\n"
}

public static String createPomStr(String groupId, String artifactId, String version) {
    return "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" +
            "<project xsi:schemaLocation=\"http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd\" xmlns=\"http://maven.apache.org/POM/4.0.0\"\n" +
            "    xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\">\n" +
            "  <modelVersion>4.0.0</modelVersion>\n" +
            "  <groupId>$groupId</groupId>\n" +
            "  <artifactId>$artifactId</artifactId>\n" +
            "  <version>$version</version>\n" +
            "  <packaging>aar</packaging>\n" +
            "</project>\n"
}

public static String getFileSha1(File file) {
    FileInputStream input = null;
    try {
        input = new FileInputStream(file);
        MessageDigest digest = MessageDigest.getInstance("SHA-1");
        byte[] buffer = new byte[1024 * 1024 * 10];

        int len = 0;
        while ((len = input.read(buffer)) > 0) {
            digest.update(buffer, 0, len);
        }
        String sha1 = new BigInteger(1, digest.digest()).toString(16);
        int length = 40 - sha1.length();
        if (length > 0) {
            for (int i = 0; i < length; i++) {
                sha1 = "0" + sha1;
            }
        }
        return sha1;
    }
    catch (IOException e) {
        System.out.println(e);
    }
    catch (NoSuchAlgorithmException e) {
        System.out.println(e);
    }
    finally {
        try {
            if (input != null) {
                input.close();
            }
        }
        catch (IOException e) {
            System.out.println(e);
        }
    }
}

public static String getFileMD5(File file) {
    FileInputStream input = null;
    try {
        input = new FileInputStream(file);
        MessageDigest digest = MessageDigest.getInstance("MD5");
        byte[] buffer = new byte[1024 * 1024 * 10];

        int len = 0;
        while ((len = input.read(buffer)) > 0) {
            digest.update(buffer, 0, len);
        }
        String md5 = new BigInteger(1, digest.digest()).toString(16);
        int length = 32 - md5.length();
        if (length > 0) {
            for (int i = 0; i < length; i++) {
                md5 = "0" + md5;
            }
        }
        return md5;
    }
    catch (IOException e) {
        System.out.println(e);
    }
    catch (NoSuchAlgorithmException e) {
        System.out.println(e);
    }
    finally {
        try {
            if (input != null) {
                input.close();
            }
        }
        catch (IOException e) {
            System.out.println(e);
        }
    }
}

结束语

当然方式可能有很多，最后我也只用了第一种方式，如果大家有更好的招，欢迎指出~