packages/flutter_tools/lib/src/android/android_sdk.dart - mirrors/flutter - Git at Google

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 import 'dart:convert';

 import 'package:meta/meta.dart';

 import '../base/common.dart';
 import '../base/context.dart';
 import '../base/file_system.dart';
 import '../base/io.dart' show ProcessResult;
 import '../base/os.dart';
 import '../base/platform.dart';
 import '../base/process.dart';
 import '../base/process_manager.dart';
 import '../base/version.dart';
 import '../globals.dart';
 import 'android_studio.dart' as android_studio;

 AndroidSdk get androidSdk => context[AndroidSdk];

 const String kAndroidHome = 'ANDROID_HOME';

 // Android SDK layout:

 // $ANDROID_HOME/platform-tools/adb

 // $ANDROID_HOME/build-tools/19.1.0/aapt, dx, zipalign
 // $ANDROID_HOME/build-tools/22.0.1/aapt
 // $ANDROID_HOME/build-tools/23.0.2/aapt
 // $ANDROID_HOME/build-tools/24.0.0-preview/aapt
 // $ANDROID_HOME/build-tools/25.0.2/apksigner

 // $ANDROID_HOME/platforms/android-22/android.jar
 // $ANDROID_HOME/platforms/android-23/android.jar
 // $ANDROID_HOME/platforms/android-N/android.jar

 final RegExp _numberedAndroidPlatformRe = new RegExp(r'^android-([0-9]+)$');
 final RegExp _sdkVersionRe = new RegExp(r'^ro.build.version.sdk=([0-9]+)$');

 /// The minimum Android SDK version we support.
 const int minimumAndroidSdkVersion = 25;

 /// Locate ADB. Prefer to use one from an Android SDK, if we can locate that.
 /// This should be used over accessing androidSdk.adbPath directly because it
 /// will work for those users who have Android Platform Tools installed but
 /// not the full SDK.
 String getAdbPath([AndroidSdk existingSdk]) {
   if (existingSdk?.adbPath != null)
     return existingSdk.adbPath;

   final AndroidSdk sdk = AndroidSdk.locateAndroidSdk();

   if (sdk?.latestVersion == null) {
     return os.which('adb')?.path;
   } else {
     return sdk.adbPath;
   }
 }

 /// Locate 'emulator'. Prefer to use one from an Android SDK, if we can locate that.
 /// This should be used over accessing androidSdk.emulatorPath directly because it
 /// will work for those users who have Android Tools installed but
 /// not the full SDK.
 String getEmulatorPath([AndroidSdk existingSdk]) {
   return existingSdk?.emulatorPath ??
     AndroidSdk.locateAndroidSdk()?.emulatorPath;
 }

 /// Locate the path for storing AVD emulator images. Returns null if none found.
 String getAvdPath() {

   final List<String> searchPaths = <String>[
     platform.environment['ANDROID_AVD_HOME']
   ];

   if (platform.environment['HOME'] != null)
     searchPaths.add(fs.path.join(platform.environment['HOME'], '.android', 'avd'));

   if (platform.isWindows) {
     final String homeDrive = platform.environment['HOMEDRIVE'];
     final String homePath = platform.environment['HOMEPATH'];

     if (homeDrive != null && homePath != null) {
       // Can't use path.join for HOMEDRIVE/HOMEPATH
       // https://github.com/dart-lang/path/issues/37
       final String home = homeDrive + homePath;
       searchPaths.add(fs.path.join(home, '.android', 'avd'));
     }
   }

   return searchPaths.where((String p) => p != null).firstWhere(
     (String p) => fs.directory(p).existsSync(),
     orElse: () => null,
   );
 }

 /// Locate 'avdmanager'. Prefer to use one from an Android SDK, if we can locate that.
 /// This should be used over accessing androidSdk.avdManagerPath directly because it
 /// will work for those users who have Android Tools installed but
 /// not the full SDK.
 String getAvdManagerPath([AndroidSdk existingSdk]) {
   return existingSdk?.avdManagerPath ??
     AndroidSdk.locateAndroidSdk()?.avdManagerPath;
 }

 class AndroidNdkSearchError {
   AndroidNdkSearchError(this.reason);

   /// The message explaining why NDK was not found.
   final String reason;
 }

 class AndroidNdk {
   AndroidNdk._(this.directory, this.compiler, this.compilerArgs);

   /// The path to the NDK.
   final String directory;

   /// The path to the NDK compiler.
   final String compiler;

   /// The mandatory arguments to the NDK compiler.
   final List<String> compilerArgs;

   /// Locate NDK within the given SDK or throw [AndroidNdkSearchError].
   static AndroidNdk locateNdk(String androidHomeDir) {
     if (androidHomeDir == null) {
       throw new AndroidNdkSearchError('Can not locate NDK because no SDK is found');
     }

     String findBundle(String androidHomeDir) {
       final String ndkDirectory = fs.path.join(androidHomeDir, 'ndk-bundle');
       if (!fs.isDirectorySync(ndkDirectory)) {
         throw new AndroidNdkSearchError('Can not locate ndk-bundle, tried: $ndkDirectory');
       }
       return ndkDirectory;
     }

     String findCompiler(String ndkDirectory) {
       String directory;
       if (platform.isLinux) {
         directory = 'linux-x86_64';
       } else if (platform.isMacOS) {
         directory = 'darwin-x86_64';
       } else {
         throw new AndroidNdkSearchError('Only Linux and macOS are supported');
       }

       final String ndkCompiler = fs.path.join(ndkDirectory,
           'toolchains', 'arm-linux-androideabi-4.9', 'prebuilt', directory,
           'bin', 'arm-linux-androideabi-gcc');
       if (!fs.isFileSync(ndkCompiler)) {
         throw new AndroidNdkSearchError('Can not locate GCC binary, tried $ndkCompiler');
       }

       return ndkCompiler;
     }

     List<String> findSysroot(String ndkDirectory) {
       // If entity represents directory with name android-<version> that
       // contains arch-arm subdirectory then returns version, otherwise
       // returns null.
       int toPlatformVersion(FileSystemEntity entry) {
         if (entry is! Directory) {
           return null;
         }

         if (!fs.isDirectorySync(fs.path.join(entry.path, 'arch-arm'))) {
           return null;
         }

         final String name = fs.path.basename(entry.path);

         const String platformPrefix = 'android-';
         if (!name.startsWith(platformPrefix)) {
           return null;
         }

         return int.tryParse(name.substring(platformPrefix.length));
       }

       final String platformsDir = fs.path.join(ndkDirectory, 'platforms');
       final List<int> versions = fs
           .directory(platformsDir)
           .listSync()
           .map(toPlatformVersion)
           .where((int version) => version != null)
           .toList(growable: false);
       versions.sort();

       final int suitableVersion = versions
           .firstWhere((int version) => version >= 9, orElse: () => null);
       if (suitableVersion == null) {
         throw new AndroidNdkSearchError('Can not locate a suitable platform ARM sysroot (need android-9 or newer), tried to look in $platformsDir');
       }

       final String armPlatform = fs.path.join(ndkDirectory, 'platforms',
           'android-$suitableVersion', 'arch-arm');
       return <String>['--sysroot', armPlatform];
     }

     final String ndkDir = findBundle(androidHomeDir);
     final String ndkCompiler = findCompiler(ndkDir);
     final List<String> ndkCompilerArgs = findSysroot(ndkDir);
     return new AndroidNdk._(ndkDir, ndkCompiler, ndkCompilerArgs);
   }

   /// Returns a descriptive message explaining why NDK can not be found within
   /// the given SDK.
   static String explainMissingNdk(String androidHomeDir) {
     try {
       locateNdk(androidHomeDir);
       return 'Unexpected error: found NDK on the second try';
     } on AndroidNdkSearchError catch (e) {
       return e.reason;
     }
   }
 }

 class AndroidSdk {
   AndroidSdk(this.directory, [this.ndk]) {
     _init();
   }

   static const String _javaHomeEnvironmentVariable = 'JAVA_HOME';
   static const String _javaExecutable = 'java';

   /// The path to the Android SDK.
   final String directory;

   /// Android NDK (can be `null`).
   final AndroidNdk ndk;

   List<AndroidSdkVersion> _sdkVersions;
   AndroidSdkVersion _latestVersion;

   static AndroidSdk locateAndroidSdk() {
     String findAndroidHomeDir() {
       String androidHomeDir;
       if (config.containsKey('android-sdk')) {
         androidHomeDir = config.getValue('android-sdk');
       } else if (platform.environment.containsKey(kAndroidHome)) {
         androidHomeDir = platform.environment[kAndroidHome];
       } else if (platform.isLinux) {
         if (homeDirPath != null)
           androidHomeDir = fs.path.join(homeDirPath, 'Android', 'Sdk');
       } else if (platform.isMacOS) {
         if (homeDirPath != null)
           androidHomeDir = fs.path.join(homeDirPath, 'Library', 'Android', 'sdk');
       } else if (platform.isWindows) {
         if (homeDirPath != null)
           androidHomeDir = fs.path.join(homeDirPath, 'AppData', 'Local', 'Android', 'sdk');
       }

       if (androidHomeDir != null) {
         if (validSdkDirectory(androidHomeDir))
           return androidHomeDir;
         if (validSdkDirectory(fs.path.join(androidHomeDir, 'sdk')))
           return fs.path.join(androidHomeDir, 'sdk');
       }

       // in build-tools/$version/aapt
       final List<File> aaptBins = os.whichAll('aapt');
       for (File aaptBin in aaptBins) {
         // Make sure we're using the aapt from the SDK.
         aaptBin = fs.file(aaptBin.resolveSymbolicLinksSync());
         final String dir = aaptBin.parent.parent.parent.path;
         if (validSdkDirectory(dir))
           return dir;
       }

       // in platform-tools/adb
       final List<File> adbBins = os.whichAll('adb');
       for (File adbBin in adbBins) {
         // Make sure we're using the adb from the SDK.
         adbBin = fs.file(adbBin.resolveSymbolicLinksSync());
         final String dir = adbBin.parent.parent.path;
         if (validSdkDirectory(dir))
           return dir;
       }

       return null;
     }

     final String androidHomeDir = findAndroidHomeDir();
     if (androidHomeDir == null) {
       // No dice.
       printTrace('Unable to locate an Android SDK.');
       return null;
     }

     // Try to find the NDK compiler. If we can't find it, it's also ok.
     AndroidNdk ndk;
     try {
       ndk = AndroidNdk.locateNdk(androidHomeDir);
     } on AndroidNdkSearchError {
       // Ignore AndroidNdkSearchError's but don't ignore any other
       // exceptions.
     }

     return new AndroidSdk(androidHomeDir, ndk);
   }

   static bool validSdkDirectory(String dir) {
     return fs.isDirectorySync(fs.path.join(dir, 'platform-tools'));
   }

   List<AndroidSdkVersion> get sdkVersions => _sdkVersions;

   AndroidSdkVersion get latestVersion => _latestVersion;

   String get adbPath => getPlatformToolsPath('adb');

   String get emulatorPath => getEmulatorPath();

   String get avdManagerPath => getAvdManagerPath();

   /// Validate the Android SDK. This returns an empty list if there are no
   /// issues; otherwise, it returns a list of issues found.
   List<String> validateSdkWellFormed() {
     if (!processManager.canRun(adbPath))
       return <String>['Android SDK file not found: $adbPath.'];

     if (sdkVersions.isEmpty || latestVersion == null)
       return <String>['Android SDK is missing command line tools; download from https://goo.gl/XxQghQ'];

     return latestVersion.validateSdkWellFormed();
   }

   String getPlatformToolsPath(String binaryName) {
     return fs.path.join(directory, 'platform-tools', binaryName);
   }

   String getEmulatorPath() {
     final String binaryName = platform.isWindows ? 'emulator.exe' : 'emulator';
     // Emulator now lives inside "emulator" but used to live inside "tools" so
     // try both.
     final List<String> searchFolders = <String>['emulator', 'tools'];
     for (final String folder in searchFolders) {
       final String path = fs.path.join(directory, folder, binaryName);
       if (fs.file(path).existsSync())
         return path;
     }
     return null;
   }

   String getAvdManagerPath() {
     final String binaryName = platform.isWindows ? 'avdmanager.bat' : 'avdmanager';
     final String path = fs.path.join(directory, 'tools', 'bin', binaryName);
     if (fs.file(path).existsSync())
       return path;
     return null;
   }

   void _init() {
     Iterable<Directory> platforms = <Directory>[]; // android-22, ...

     final Directory platformsDir = fs.directory(fs.path.join(directory, 'platforms'));
     if (platformsDir.existsSync()) {
       platforms = platformsDir
         .listSync()
         .where((FileSystemEntity entity) => entity is Directory)
         .map<Directory>((FileSystemEntity entity) {
           final Directory dir = entity;
           return dir;
         });
     }

     List<Version> buildTools = <Version>[]; // 19.1.0, 22.0.1, ...

     final Directory buildToolsDir = fs.directory(fs.path.join(directory, 'build-tools'));
     if (buildToolsDir.existsSync()) {
       buildTools = buildToolsDir
         .listSync()
         .map((FileSystemEntity entity) {
           try {
             return new Version.parse(entity.basename);
           } catch (error) {
             return null;
           }
         })
         .where((Version version) => version != null)
         .toList();
     }

     // Match up platforms with the best corresponding build-tools.
     _sdkVersions = platforms.map((Directory platformDir) {
       final String platformName = platformDir.basename;
       int platformVersion;

       try {
         final Match numberedVersion = _numberedAndroidPlatformRe.firstMatch(platformName);
         if (numberedVersion != null) {
           platformVersion = int.parse(numberedVersion.group(1));
         } else {
           final String buildProps = platformDir.childFile('build.prop').readAsStringSync();
           final String versionString = const LineSplitter()
               .convert(buildProps)
               .map(_sdkVersionRe.firstMatch)
               .firstWhere((Match match) => match != null)
               .group(1);
           platformVersion = int.parse(versionString);
         }
       } catch (error) {
         return null;
       }

       Version buildToolsVersion = Version.primary(buildTools.where((Version version) {
         return version.major == platformVersion;
       }).toList());

       buildToolsVersion ??= Version.primary(buildTools);

       if (buildToolsVersion == null)
         return null;

       return new AndroidSdkVersion._(
         this,
         sdkLevel: platformVersion,
         platformName: platformName,
         buildToolsVersion: buildToolsVersion,
       );
     }).where((AndroidSdkVersion version) => version != null).toList();

     _sdkVersions.sort();

     _latestVersion = _sdkVersions.isEmpty ? null : _sdkVersions.last;
   }

   /// Returns the filesystem path of the Android SDK manager tool or null if not found.
   String get sdkManagerPath {
     return fs.path.join(directory, 'tools', 'bin', 'sdkmanager');
   }

   /// First try Java bundled with Android Studio, then sniff JAVA_HOME, then fallback to PATH.
   static String findJavaBinary() {

     if (android_studio.javaPath != null)
       return fs.path.join(android_studio.javaPath, 'bin', 'java');

     final String javaHomeEnv = platform.environment[_javaHomeEnvironmentVariable];
     if (javaHomeEnv != null) {
       // Trust JAVA_HOME.
       return fs.path.join(javaHomeEnv, 'bin', 'java');
     }

     // MacOS specific logic to avoid popping up a dialog window.
     // See: http://stackoverflow.com/questions/14292698/how-do-i-check-if-the-java-jdk-is-installed-on-mac.
     if (platform.isMacOS) {
       try {
         final String javaHomeOutput = runCheckedSync(<String>['/usr/libexec/java_home'], hideStdout: true);
         if (javaHomeOutput != null) {
           final List<String> javaHomeOutputSplit = javaHomeOutput.split('\n');
           if ((javaHomeOutputSplit != null) && (javaHomeOutputSplit.isNotEmpty)) {
             final String javaHome = javaHomeOutputSplit[0].trim();
             return fs.path.join(javaHome, 'bin', 'java');
           }
         }
       } catch (_) { /* ignore */ }
     }

     // Fallback to PATH based lookup.
     return os.which(_javaExecutable)?.path;
   }

   Map<String, String> _sdkManagerEnv;
   Map<String, String> get sdkManagerEnv {
     if (_sdkManagerEnv == null) {
       // If we can locate Java, then add it to the path used to run the Android SDK manager.
       _sdkManagerEnv = <String, String>{};
       final String javaBinary = findJavaBinary();
       if (javaBinary != null) {
         _sdkManagerEnv['PATH'] =
             fs.path.dirname(javaBinary) + os.pathVarSeparator + platform.environment['PATH'];
       }
     }
     return _sdkManagerEnv;
   }

   /// Returns the version of the Android SDK manager tool or null if not found.
   String get sdkManagerVersion {
     if (!processManager.canRun(sdkManagerPath))
       throwToolExit('Android sdkmanager not found. Update to the latest Android SDK to resolve this.');
     final ProcessResult result = processManager.runSync(<String>[sdkManagerPath, '--version'], environment: sdkManagerEnv);
     if (result.exitCode != 0) {
       printTrace('sdkmanager --version failed: exitCode: ${result.exitCode} stdout: ${result.stdout} stderr: ${result.stderr}');
       return null;
     }
     return result.stdout.trim();
   }

   @override
   String toString() => 'AndroidSdk: $directory';
 }

 class AndroidSdkVersion implements Comparable<AndroidSdkVersion> {
   AndroidSdkVersion._(this.sdk, {
     @required this.sdkLevel,
     @required this.platformName,
     @required this.buildToolsVersion,
   }) : assert(sdkLevel != null),
        assert(platformName != null),
        assert(buildToolsVersion != null);

   final AndroidSdk sdk;
   final int sdkLevel;
   final String platformName;
   final Version buildToolsVersion;

   String get buildToolsVersionName => buildToolsVersion.toString();

   String get androidJarPath => getPlatformsPath('android.jar');

   String get aaptPath => getBuildToolsPath('aapt');

   List<String> validateSdkWellFormed() {
     if (_exists(androidJarPath) != null)
       return <String>[_exists(androidJarPath)];

     if (_canRun(aaptPath) != null)
       return <String>[_canRun(aaptPath)];

     return <String>[];
   }

   String getPlatformsPath(String itemName) {
     return fs.path.join(sdk.directory, 'platforms', platformName, itemName);
   }

   String getBuildToolsPath(String binaryName) {
     return fs.path.join(sdk.directory, 'build-tools', buildToolsVersionName, binaryName);
   }

   @override
   int compareTo(AndroidSdkVersion other) => sdkLevel - other.sdkLevel;

   @override
   String toString() => '[${sdk.directory}, SDK version $sdkLevel, build-tools $buildToolsVersionName]';

   String _exists(String path) {
     if (!fs.isFileSync(path))
       return 'Android SDK file not found: $path.';
     return null;
   }

   String _canRun(String path) {
     if (!processManager.canRun(path))
       return 'Android SDK file not found: $path.';
     return null;
   }
 }
	// Copyright 2016 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	import 'dart:convert';

	import 'package:meta/meta.dart';

	import '../base/common.dart';
	import '../base/context.dart';
	import '../base/file_system.dart';
	import '../base/io.dart' show ProcessResult;
	import '../base/os.dart';
	import '../base/platform.dart';
	import '../base/process.dart';
	import '../base/process_manager.dart';
	import '../base/version.dart';
	import '../globals.dart';
	import 'android_studio.dart' as android_studio;

	AndroidSdk get androidSdk => context[AndroidSdk];

	const String kAndroidHome = 'ANDROID_HOME';

	// Android SDK layout:

	// $ANDROID_HOME/platform-tools/adb

	// $ANDROID_HOME/build-tools/19.1.0/aapt, dx, zipalign
	// $ANDROID_HOME/build-tools/22.0.1/aapt
	// $ANDROID_HOME/build-tools/23.0.2/aapt
	// $ANDROID_HOME/build-tools/24.0.0-preview/aapt
	// $ANDROID_HOME/build-tools/25.0.2/apksigner

	// $ANDROID_HOME/platforms/android-22/android.jar
	// $ANDROID_HOME/platforms/android-23/android.jar
	// $ANDROID_HOME/platforms/android-N/android.jar

	final RegExp _numberedAndroidPlatformRe = new RegExp(r'^android-([0-9]+)$');
	final RegExp _sdkVersionRe = new RegExp(r'^ro.build.version.sdk=([0-9]+)$');

	/// The minimum Android SDK version we support.
	const int minimumAndroidSdkVersion = 25;

	/// Locate ADB. Prefer to use one from an Android SDK, if we can locate that.
	/// This should be used over accessing androidSdk.adbPath directly because it
	/// will work for those users who have Android Platform Tools installed but
	/// not the full SDK.
	String getAdbPath([AndroidSdk existingSdk]) {
	if (existingSdk?.adbPath != null)
	return existingSdk.adbPath;

	final AndroidSdk sdk = AndroidSdk.locateAndroidSdk();

	if (sdk?.latestVersion == null) {
	return os.which('adb')?.path;
	} else {
	return sdk.adbPath;
	}
	}

	/// Locate 'emulator'. Prefer to use one from an Android SDK, if we can locate that.
	/// This should be used over accessing androidSdk.emulatorPath directly because it
	/// will work for those users who have Android Tools installed but
	/// not the full SDK.
	String getEmulatorPath([AndroidSdk existingSdk]) {
	return existingSdk?.emulatorPath ??
	AndroidSdk.locateAndroidSdk()?.emulatorPath;
	}

	/// Locate the path for storing AVD emulator images. Returns null if none found.
	String getAvdPath() {

	final List<String> searchPaths = <String>[
	platform.environment['ANDROID_AVD_HOME']
	];

	if (platform.environment['HOME'] != null)
	searchPaths.add(fs.path.join(platform.environment['HOME'], '.android', 'avd'));

	if (platform.isWindows) {
	final String homeDrive = platform.environment['HOMEDRIVE'];
	final String homePath = platform.environment['HOMEPATH'];

	if (homeDrive != null && homePath != null) {
	// Can't use path.join for HOMEDRIVE/HOMEPATH
	// https://github.com/dart-lang/path/issues/37
	final String home = homeDrive + homePath;
	searchPaths.add(fs.path.join(home, '.android', 'avd'));
	}
	}

	return searchPaths.where((String p) => p != null).firstWhere(
	(String p) => fs.directory(p).existsSync(),
	orElse: () => null,
	);
	}

	/// Locate 'avdmanager'. Prefer to use one from an Android SDK, if we can locate that.
	/// This should be used over accessing androidSdk.avdManagerPath directly because it
	/// will work for those users who have Android Tools installed but
	/// not the full SDK.
	String getAvdManagerPath([AndroidSdk existingSdk]) {
	return existingSdk?.avdManagerPath ??
	AndroidSdk.locateAndroidSdk()?.avdManagerPath;
	}

	class AndroidNdkSearchError {
	AndroidNdkSearchError(this.reason);

	/// The message explaining why NDK was not found.
	final String reason;
	}

	class AndroidNdk {
	AndroidNdk._(this.directory, this.compiler, this.compilerArgs);

	/// The path to the NDK.
	final String directory;

	/// The path to the NDK compiler.
	final String compiler;

	/// The mandatory arguments to the NDK compiler.
	final List<String> compilerArgs;

	/// Locate NDK within the given SDK or throw [AndroidNdkSearchError].
	static AndroidNdk locateNdk(String androidHomeDir) {
	if (androidHomeDir == null) {
	throw new AndroidNdkSearchError('Can not locate NDK because no SDK is found');
	}

	String findBundle(String androidHomeDir) {
	final String ndkDirectory = fs.path.join(androidHomeDir, 'ndk-bundle');
	if (!fs.isDirectorySync(ndkDirectory)) {
	throw new AndroidNdkSearchError('Can not locate ndk-bundle, tried: $ndkDirectory');
	}
	return ndkDirectory;
	}

	String findCompiler(String ndkDirectory) {
	String directory;
	if (platform.isLinux) {
	directory = 'linux-x86_64';
	} else if (platform.isMacOS) {
	directory = 'darwin-x86_64';
	} else {
	throw new AndroidNdkSearchError('Only Linux and macOS are supported');
	}

	final String ndkCompiler = fs.path.join(ndkDirectory,
	'toolchains', 'arm-linux-androideabi-4.9', 'prebuilt', directory,
	'bin', 'arm-linux-androideabi-gcc');
	if (!fs.isFileSync(ndkCompiler)) {
	throw new AndroidNdkSearchError('Can not locate GCC binary, tried $ndkCompiler');
	}

	return ndkCompiler;
	}

	List<String> findSysroot(String ndkDirectory) {
	// If entity represents directory with name android-<version> that
	// contains arch-arm subdirectory then returns version, otherwise
	// returns null.
	int toPlatformVersion(FileSystemEntity entry) {
	if (entry is! Directory) {
	return null;
	}

	if (!fs.isDirectorySync(fs.path.join(entry.path, 'arch-arm'))) {
	return null;
	}

	final String name = fs.path.basename(entry.path);

	const String platformPrefix = 'android-';
	if (!name.startsWith(platformPrefix)) {
	return null;
	}

	return int.tryParse(name.substring(platformPrefix.length));
	}

	final String platformsDir = fs.path.join(ndkDirectory, 'platforms');
	final List<int> versions = fs
	.directory(platformsDir)
	.listSync()
	.map(toPlatformVersion)
	.where((int version) => version != null)
	.toList(growable: false);
	versions.sort();

	final int suitableVersion = versions
	.firstWhere((int version) => version >= 9, orElse: () => null);
	if (suitableVersion == null) {
	throw new AndroidNdkSearchError('Can not locate a suitable platform ARM sysroot (need android-9 or newer), tried to look in $platformsDir');
	}

	final String armPlatform = fs.path.join(ndkDirectory, 'platforms',
	'android-$suitableVersion', 'arch-arm');
	return <String>['--sysroot', armPlatform];
	}

	final String ndkDir = findBundle(androidHomeDir);
	final String ndkCompiler = findCompiler(ndkDir);
	final List<String> ndkCompilerArgs = findSysroot(ndkDir);
	return new AndroidNdk._(ndkDir, ndkCompiler, ndkCompilerArgs);
	}

	/// Returns a descriptive message explaining why NDK can not be found within
	/// the given SDK.
	static String explainMissingNdk(String androidHomeDir) {
	try {
	locateNdk(androidHomeDir);
	return 'Unexpected error: found NDK on the second try';
	} on AndroidNdkSearchError catch (e) {
	return e.reason;
	}
	}
	}

	class AndroidSdk {
	AndroidSdk(this.directory, [this.ndk]) {
	_init();
	}

	static const String _javaHomeEnvironmentVariable = 'JAVA_HOME';
	static const String _javaExecutable = 'java';

	/// The path to the Android SDK.
	final String directory;

	/// Android NDK (can be `null`).
	final AndroidNdk ndk;

	List<AndroidSdkVersion> _sdkVersions;
	AndroidSdkVersion _latestVersion;

	static AndroidSdk locateAndroidSdk() {
	String findAndroidHomeDir() {
	String androidHomeDir;
	if (config.containsKey('android-sdk')) {
	androidHomeDir = config.getValue('android-sdk');
	} else if (platform.environment.containsKey(kAndroidHome)) {
	androidHomeDir = platform.environment[kAndroidHome];
	} else if (platform.isLinux) {
	if (homeDirPath != null)
	androidHomeDir = fs.path.join(homeDirPath, 'Android', 'Sdk');
	} else if (platform.isMacOS) {
	if (homeDirPath != null)
	androidHomeDir = fs.path.join(homeDirPath, 'Library', 'Android', 'sdk');
	} else if (platform.isWindows) {
	if (homeDirPath != null)
	androidHomeDir = fs.path.join(homeDirPath, 'AppData', 'Local', 'Android', 'sdk');
	}

	if (androidHomeDir != null) {
	if (validSdkDirectory(androidHomeDir))
	return androidHomeDir;
	if (validSdkDirectory(fs.path.join(androidHomeDir, 'sdk')))
	return fs.path.join(androidHomeDir, 'sdk');
	}

	// in build-tools/$version/aapt
	final List<File> aaptBins = os.whichAll('aapt');
	for (File aaptBin in aaptBins) {
	// Make sure we're using the aapt from the SDK.
	aaptBin = fs.file(aaptBin.resolveSymbolicLinksSync());
	final String dir = aaptBin.parent.parent.parent.path;
	if (validSdkDirectory(dir))
	return dir;
	}

	// in platform-tools/adb
	final List<File> adbBins = os.whichAll('adb');
	for (File adbBin in adbBins) {
	// Make sure we're using the adb from the SDK.
	adbBin = fs.file(adbBin.resolveSymbolicLinksSync());
	final String dir = adbBin.parent.parent.path;
	if (validSdkDirectory(dir))
	return dir;
	}

	return null;
	}

	final String androidHomeDir = findAndroidHomeDir();
	if (androidHomeDir == null) {
	// No dice.
	printTrace('Unable to locate an Android SDK.');
	return null;
	}

	// Try to find the NDK compiler. If we can't find it, it's also ok.
	AndroidNdk ndk;
	try {
	ndk = AndroidNdk.locateNdk(androidHomeDir);
	} on AndroidNdkSearchError {
	// Ignore AndroidNdkSearchError's but don't ignore any other
	// exceptions.
	}

	return new AndroidSdk(androidHomeDir, ndk);
	}

	static bool validSdkDirectory(String dir) {
	return fs.isDirectorySync(fs.path.join(dir, 'platform-tools'));
	}

	List<AndroidSdkVersion> get sdkVersions => _sdkVersions;

	AndroidSdkVersion get latestVersion => _latestVersion;

	String get adbPath => getPlatformToolsPath('adb');

	String get emulatorPath => getEmulatorPath();

	String get avdManagerPath => getAvdManagerPath();

	/// Validate the Android SDK. This returns an empty list if there are no
	/// issues; otherwise, it returns a list of issues found.
	List<String> validateSdkWellFormed() {
	if (!processManager.canRun(adbPath))
	return <String>['Android SDK file not found: $adbPath.'];

	if (sdkVersions.isEmpty \|\| latestVersion == null)
	return <String>['Android SDK is missing command line tools; download from https://goo.gl/XxQghQ'];

	return latestVersion.validateSdkWellFormed();
	}

	String getPlatformToolsPath(String binaryName) {
	return fs.path.join(directory, 'platform-tools', binaryName);
	}

	String getEmulatorPath() {
	final String binaryName = platform.isWindows ? 'emulator.exe' : 'emulator';
	// Emulator now lives inside "emulator" but used to live inside "tools" so
	// try both.
	final List<String> searchFolders = <String>['emulator', 'tools'];
	for (final String folder in searchFolders) {
	final String path = fs.path.join(directory, folder, binaryName);
	if (fs.file(path).existsSync())
	return path;
	}
	return null;
	}

	String getAvdManagerPath() {
	final String binaryName = platform.isWindows ? 'avdmanager.bat' : 'avdmanager';
	final String path = fs.path.join(directory, 'tools', 'bin', binaryName);
	if (fs.file(path).existsSync())
	return path;
	return null;
	}

	void _init() {
	Iterable<Directory> platforms = <Directory>[]; // android-22, ...

	final Directory platformsDir = fs.directory(fs.path.join(directory, 'platforms'));
	if (platformsDir.existsSync()) {
	platforms = platformsDir
	.listSync()
	.where((FileSystemEntity entity) => entity is Directory)
	.map<Directory>((FileSystemEntity entity) {
	final Directory dir = entity;
	return dir;
	});
	}

	List<Version> buildTools = <Version>[]; // 19.1.0, 22.0.1, ...

	final Directory buildToolsDir = fs.directory(fs.path.join(directory, 'build-tools'));
	if (buildToolsDir.existsSync()) {
	buildTools = buildToolsDir
	.listSync()
	.map((FileSystemEntity entity) {
	try {
	return new Version.parse(entity.basename);
	} catch (error) {
	return null;
	}
	})
	.where((Version version) => version != null)
	.toList();
	}

	// Match up platforms with the best corresponding build-tools.
	_sdkVersions = platforms.map((Directory platformDir) {
	final String platformName = platformDir.basename;
	int platformVersion;

	try {
	final Match numberedVersion = _numberedAndroidPlatformRe.firstMatch(platformName);
	if (numberedVersion != null) {
	platformVersion = int.parse(numberedVersion.group(1));
	} else {
	final String buildProps = platformDir.childFile('build.prop').readAsStringSync();
	final String versionString = const LineSplitter()
	.convert(buildProps)
	.map(_sdkVersionRe.firstMatch)
	.firstWhere((Match match) => match != null)
	.group(1);
	platformVersion = int.parse(versionString);
	}
	} catch (error) {
	return null;
	}

	Version buildToolsVersion = Version.primary(buildTools.where((Version version) {
	return version.major == platformVersion;
	}).toList());

	buildToolsVersion ??= Version.primary(buildTools);

	if (buildToolsVersion == null)
	return null;

	return new AndroidSdkVersion._(
	this,
	sdkLevel: platformVersion,
	platformName: platformName,
	buildToolsVersion: buildToolsVersion,
	);
	}).where((AndroidSdkVersion version) => version != null).toList();

	_sdkVersions.sort();

	_latestVersion = _sdkVersions.isEmpty ? null : _sdkVersions.last;
	}

	/// Returns the filesystem path of the Android SDK manager tool or null if not found.
	String get sdkManagerPath {
	return fs.path.join(directory, 'tools', 'bin', 'sdkmanager');
	}

	/// First try Java bundled with Android Studio, then sniff JAVA_HOME, then fallback to PATH.
	static String findJavaBinary() {

	if (android_studio.javaPath != null)
	return fs.path.join(android_studio.javaPath, 'bin', 'java');

	final String javaHomeEnv = platform.environment[_javaHomeEnvironmentVariable];
	if (javaHomeEnv != null) {
	// Trust JAVA_HOME.
	return fs.path.join(javaHomeEnv, 'bin', 'java');
	}

	// MacOS specific logic to avoid popping up a dialog window.
	// See: http://stackoverflow.com/questions/14292698/how-do-i-check-if-the-java-jdk-is-installed-on-mac.
	if (platform.isMacOS) {
	try {
	final String javaHomeOutput = runCheckedSync(<String>['/usr/libexec/java_home'], hideStdout: true);
	if (javaHomeOutput != null) {
	final List<String> javaHomeOutputSplit = javaHomeOutput.split('\n');
	if ((javaHomeOutputSplit != null) && (javaHomeOutputSplit.isNotEmpty)) {
	final String javaHome = javaHomeOutputSplit[0].trim();
	return fs.path.join(javaHome, 'bin', 'java');
	}
	}
	} catch (_) { /* ignore */ }
	}

	// Fallback to PATH based lookup.
	return os.which(_javaExecutable)?.path;
	}

	Map<String, String> _sdkManagerEnv;
	Map<String, String> get sdkManagerEnv {
	if (_sdkManagerEnv == null) {
	// If we can locate Java, then add it to the path used to run the Android SDK manager.
	_sdkManagerEnv = <String, String>{};
	final String javaBinary = findJavaBinary();
	if (javaBinary != null) {
	_sdkManagerEnv['PATH'] =
	fs.path.dirname(javaBinary) + os.pathVarSeparator + platform.environment['PATH'];
	}
	}
	return _sdkManagerEnv;
	}

	/// Returns the version of the Android SDK manager tool or null if not found.
	String get sdkManagerVersion {
	if (!processManager.canRun(sdkManagerPath))
	throwToolExit('Android sdkmanager not found. Update to the latest Android SDK to resolve this.');
	final ProcessResult result = processManager.runSync(<String>[sdkManagerPath, '--version'], environment: sdkManagerEnv);
	if (result.exitCode != 0) {
	printTrace('sdkmanager --version failed: exitCode: ${result.exitCode} stdout: ${result.stdout} stderr: ${result.stderr}');
	return null;
	}
	return result.stdout.trim();
	}

	@override
	String toString() => 'AndroidSdk: $directory';
	}

	class AndroidSdkVersion implements Comparable<AndroidSdkVersion> {
	AndroidSdkVersion._(this.sdk, {
	@required this.sdkLevel,
	@required this.platformName,
	@required this.buildToolsVersion,
	}) : assert(sdkLevel != null),
	assert(platformName != null),
	assert(buildToolsVersion != null);

	final AndroidSdk sdk;
	final int sdkLevel;
	final String platformName;
	final Version buildToolsVersion;

	String get buildToolsVersionName => buildToolsVersion.toString();

	String get androidJarPath => getPlatformsPath('android.jar');

	String get aaptPath => getBuildToolsPath('aapt');

	List<String> validateSdkWellFormed() {
	if (_exists(androidJarPath) != null)
	return <String>[_exists(androidJarPath)];

	if (_canRun(aaptPath) != null)
	return <String>[_canRun(aaptPath)];

	return <String>[];
	}

	String getPlatformsPath(String itemName) {
	return fs.path.join(sdk.directory, 'platforms', platformName, itemName);
	}

	String getBuildToolsPath(String binaryName) {
	return fs.path.join(sdk.directory, 'build-tools', buildToolsVersionName, binaryName);
	}

	@override
	int compareTo(AndroidSdkVersion other) => sdkLevel - other.sdkLevel;

	@override
	String toString() => '[${sdk.directory}, SDK version $sdkLevel, build-tools $buildToolsVersionName]';

	String _exists(String path) {
	if (!fs.isFileSync(path))
	return 'Android SDK file not found: $path.';
	return null;
	}

	String _canRun(String path) {
	if (!processManager.canRun(path))
	return 'Android SDK file not found: $path.';
	return null;
	}
	}