1. 这个优化是做什么的其实就是一种让App启动更快滑动更流畅。原理是在你的工程里放一个配置文件列出用户一打开就会用到的代码系统在安装的时候把这些代码提前编译好。这样用户第一次打开就不用等JIT边跑边编译了。支持Android7.0及以上性能大概提升15% - 30%低端机比较明显。2. 他的编译方式有什么不同常见的三种编译方式标题功能优点缺点纯JIT边运行边编译节省空间第一次打开慢全量AOT安装时编译所有代码启动快安装慢体积大Baseline Profile预编译热点代码兼顾了性能安装效率与体积3. Baseline实现具体步骤Benchmark1.创建benchmark模拟启动和生成baseline可以通过创建benchmark实现。创建StartupBenchmark类模拟启动和首次的交互等。为了对比差异数据使用CompilationMode.None()表示使用JIT模式编译用CompilationMode.Partial()表示使用baseline的方式一会看查看测试数据。//benchmark - StartupBenchmark.ktsRunWith(AndroidJUnit4::class)classStartupBenchmark{get:RulevalbenchmarkRuleMacrobenchmarkRule()TestfunstartupCompilationNone()startup(CompilationMode.None())TestfunstartupCompilationPartial()startup(CompilationMode.Partial())funstartup(compilationMode:CompilationMode)benchmarkRule.measureRepeated(packageNamecom.jettx.empty,metricslistOf(StartupTimingMetric()),iterations5,compilationModecompilationMode,startupModeStartupMode.COLD){pressHome()startActivityAndWait()}}//benchmark - BaselineProfileGenerator.ktsRunWith(AndroidJUnit4::class)classBaselineProfileGenerator{get:RulevalbaselineProfileRuleBaselineProfileRule()Testfungenerate()baselineProfileRule.collect(packageNamecom.jettx.empty,includeInStartupProfiletrue){// 定义关键用户旅程pressHome()startActivityAndWait()// 可添加滑动、点击等交互// val recyclerView device.findObject(By.res(recycler_view))// recyclerView.waitForExists(5000)// recyclerView.fling(androidx.test.uiautomator.Direction.DOWN)}}2. 运行生成./gradlew :benchmark:AndroidTest -P android.testInstrumentationRunnerArguments.androidx.benchmark.enableRulesBaselineProfile我是在模拟器上运行的建议在真机上运行模拟器上运行需要配置支持。//benchmark - build.gradle defaultConfig { testInstrumentationRunnerArguments[androidx.benchmark.suppressErrors] EMULATOR }生成后把/benchmark/build/outputs/connected_android_test_additional_output/benchmark/connected/Pixel8Api34(AVD) - 14/BaselineProfileGenerator_generate-startup-prof.txt重命名为baseline-prof.txt放入/app/src/main/目录中。3. 编译打包App查看生成后的APK会有合入的baseline4. 测试运行StartupBenchmark纯JIT编译和Baseline编译冷启动各5次后的数据StartupBenchmark_startupCompilationPartial timeToInitialDisplayMs min 1,694.4, median 1,873.2, max 2,458.6 Traces: Iteration 0 1 2 3 4 Pixel8Api34(AVD) - 14 Tests 1/2 completed. (0 skipped) (0 failed) Timed out waiting for process (com.jettx.empty) to appear on Pixel8Api34 [emulator-5554]. WARNING: Running on Emulator Benchmark is running on an emulator, which is not representative of real user devices. Use a physical device to benchmark. Emulator benchmark improvements might not carry over to a real users experience (or even regress real device performance). StartupBenchmark_startupCompilationNone timeToInitialDisplayMs min 1,593.7, median 2,602.0, max 51,479.6 Traces: Iteration 0 1 2 3 4 Finished 2 tests on Pixel8Api34(AVD) - 14从median来看优化了729ms。4 .参考文件https://developer.android.com/topic/performance/baselineprofiles/overview