本文主要对eclipse中android项目的编译过程进行分析。
本文只做分析，关于加快eclipse下android项目编译速度请见下一篇博客
Ps：本文中编译过程输出都是以真机（htc g7）作为avd，项目名为AONE，测试项目名为AoneTestProject，api level为8。
1、查看eclipse下android项目的编译过程
选择Window > Preferences > Android > Build > Build output > Verbose. 在console窗口的显示类型（一个显示器样式的图标）选择android。
2、具体编译过程
2.1 如果一个项目未曾修改，第一次在真机运行（即直接Run）输出为
[2012-03-19 15:44:54 - AONE] ------------------------------
[2012-03-19 15:44:54 - AONE] Android Launch!
[2012-03-19 15:44:54 - AONE] adb is running normally.
[2012-03-19 15:44:54 - AONE] Performing com.trinea.sns.activity.AccountManageActivity activity launch
[2012-03-19 15:44:54 - AONE] Automatic Target Mode: using device 'SH135PL00278'
[2012-03-19 15:44:54 - AONE] Uploading AONE.apk onto device 'SH135PL00278'
[2012-03-19 15:44:55 - AONE] Installing AONE.apk...
[2012-03-19 15:45:06 - AONE] Success!
[2012-03-19 15:45:06 - AONE] Starting activity com.trinea.sns.activity.AccountManageActivity on device SH135PL00278
[2012-03-19 15:45:07 - AONE] ActivityManager: Starting: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] cmp=com.trinea.sns.activity/.AccountManageActivity }
从中可以看出install apk过程比较缓慢，但这一步优化的难度过高，而且只会第一次耗时较长优化的必要性不大，暂不作优化。
2.2 对于一般修改，build过程解析
修改一个java文件后保存（已勾选Build Automatically），build信息输出如下：
[2012-03-19 15:50:04 - AONE] Refreshing resource folders. [2012-03-19 15:50:04 - AONE] Starting incremental Pre Compiler: Checking resource changes. [2012-03-19 15:50:04 - AONE] Attribute minSdkVersion (3) is lower than the project target API level (8) [2012-03-19 15:50:04 - AONE] Nothing to pre compile! [2012-03-19 15:50:04 - AONE] Starting incremental Package build: Checking resource changes. [2012-03-19 15:50:04 - AONE] Dx ignored resource D:\Eclipse\google code\AONE\bin\.\.svn\text-base\resources.ap_.svn-base [2012-03-19 15:50:04 - AONE] Dx processing D:\Eclipse\google code\AONE\bin\.\com\trinea\sns\view\AccountView.class... …… [2012-03-19 15:50:19 - AONE] Using default debug key to sign package [2012-03-19 15:50:19 - AONE] Using keystore: C:\Users\Trinea\.android\debug.keystore [2012-03-19 15:50:19 - AONE] Packaging AONE.apk [2012-03-19 15:50:19 - AONE] D:\Eclipse\google code\AONE\bin\resources.ap_: [2012-03-19 15:50:19 - AONE] => res/drawable/aone.png …… [2012-03-19 15:50:19 - AONE] => res/layout/account_manage_list.xml …… [2012-03-19 15:50:19 - AONE] => AndroidManifest.xml [2012-03-19 15:50:19 - AONE] => resources.arsc [2012-03-19 15:50:19 - AONE] D:\Eclipse\google code\AONE\bin\classes.dex => classes.dex [2012-03-19 15:50:20 - AONE] D:\学习\Coding\Android\lib\signpost-commonshttp4-1.2.1.1.jar: …… [2012-03-19 15:50:20 - AONE] => javax/servlet/http/LocalStrings.properties …… [2012-03-19 15:50:20 - AONE] Build Success! [2012-03-19 15:50:21 - AONE] Refreshing resource folders. [2012-03-19 15:50:21 - AONE] Starting incremental Pre Compiler: Checking resource changes. [2012-03-19 15:50:21 - AONE] Attribute minSdkVersion (3) is lower than the project target API level (8) [2012-03-19 15:50:21 - AONE] Nothing to pre compile! [2012-03-19 15:50:21 - AoneTestProject] Starting incremental Package build: Checking resource changes. [2012-03-19 15:50:21 - AoneTestProject] Dx processing D:\Eclipse\google code\AoneTestProject\bin\.\com\trinea\sns\utilImpl\AutoGetDataCacheTest.class... …… [2012-03-19 15:50:29 - AoneTestProject] Using default debug key to sign package [2012-03-19 15:50:29 - AoneTestProject] Using keystore: C:\Users\Trinea\.android\debug.keystore [2012-03-19 15:50:29 - AoneTestProject] Packaging AoneTestProject.apk [2012-03-19 15:50:29 - AoneTestProject] D:\Eclipse\google code\AoneTestProject\bin\resources.ap_: …… [2012-03-19 15:50:29 - AoneTestProject] => resources.arsc [2012-03-19 15:50:29 - AoneTestProject] D:\Eclipse\google code\AoneTestProject\bin\classes.dex => classes.dex [2012-03-19 15:50:29 - AoneTestProject] D:\Eclipse\google code\qqTAndroidSdk\target\QqTAndroidSdk-1.0.0-jar-with-dependencies.jar: [2012-03-19 15:50:29 - AoneTestProject] => org/apache/log4j/lf5/config/defaultconfig.properties …… [2012-03-19 15:50:30 - AoneTestProject] => javax/servlet/http/LocalStrings.properties …… [2012-03-19 15:50:30 - AoneTestProject] D:\学习\Coding\Android\lib\trinea-sina-weibo.jar: …… [2012-03-19 15:50:30 - AoneTestProject] Build Success! [2012-03-19 15:50:30 - AoneTestProject] Refreshing resource folders. [2012-03-19 15:50:30 - AoneTestProject] Starting incremental Pre Compiler: Checking resource changes. [2012-03-19 15:50:30 - AoneTestProject] Nothing to pre compile!
以上省略号表示与上一语句类似
从上面我们可以发现
a. 源项目AONE和测试项目AoneTestProject会同时被编译
b. 源项目和测试项目的编译过程基本包括刷新资源文件、预编译、增量构建、dx class文件、对包进行签名、打包成apk文件。
c. 其中dx class文件过程耗时最长，达到15秒左右。而dx过程不仅编译本项目class文件，同时会编译所有依赖包的class文件，所以会根据项目生成的class文件个数以及依赖个数而变。
由此可见对于优化的重点可以放在dx过程中，android adt提供的dx工具没有缓存上次dx信息，导致每次都需要重新dx所有class，性能表现实在差劲，具体优化可以见加快eclipse下android项目编译速度
参考：http://stackoverflow.com/questions/2883635/android-compilation-is-slow-using-eclipse
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