Android 性能优化「黑科技」Baseline Profiles | 开发者说·DTalk

@ExperimentalBaselineProfilesApi@RunWith(AndroidJUnit4::class)class BaselineProfileGenerator {    @get:Rule val baselineProfileRule = BaselineProfileRule()
    @Test    fun startup() =        baselineProfileRule.collectBaselineProfile(packageName = "com.example.app") {            pressHome()            // This block defines the app's critical user journey. Here we are interested in            // optimizing for app startup. But you can also navigate and scroll            // through your most important UI.            startActivityAndWait()        }}

/storage/emulated/0/Android/media/package.name.SampleStartupBenchmark_startup-baseline-prof.txt

implementation "androidx.profileinstaller:profileinstaller:1.2.0-beta02"

<provider   android:name="androidx.startup.InitializationProvider"   android:authorities="${applicationId}.androidx-startup"   android:exported="false"   tools:node="merge">   <meta-data android:name="androidx.profileinstaller.ProfileInstallerInitializer"             tools:node="remove" /></provider>

public class ProfileInstallerInitializer        implements Initializer<ProfileInstallerInitializer.Result> {    private static final int DELAY_MS = 5_000;
    @NonNull    @Override    public Result create(@NonNull Context context) {        if (Build.VERSION.SDK_INT < ProfileVersion.MIN_SUPPORTED_SDK) {            // 小于 7.0 的系统没必要执行            return new Result();        }        // 延迟 5 秒，写入 profile 文件        delayAfterFirstFrame(context.getApplicationContext());            return new Result();        }    }}

@RequiresApi(16)void delayAfterFirstFrame(@NonNull Context appContext) {    // 从第一帧开始算，延迟 5 秒    Choreographer16Impl.postFrameCallback(() -> installAfterDelay(appContext));}
void installAfterDelay(@NonNull Context appContext) {    Handler handler;    if (Build.VERSION.SDK_INT >= 28) {        handler = Handler28Impl.createAsync(Looper.getMainLooper());    } else {        handler = new Handler(Looper.getMainLooper());    }    Random random = new Random();    int extra = random.nextInt(Math.max(DELAY_MS / 5, 1));    // Handler 实现 delay    handler.postDelayed(() -> writeInBackground(appContext), DELAY_MS + extra);}

private static void writeInBackground(@NonNull Context context) {    Executor executor = new ThreadPoolExecutor(            /* corePoolSize = */0,            /* maximumPoolSize = */1,            /* keepAliveTime = */0,            /* unit = */TimeUnit.MILLISECONDS,            /* workQueue = */new LinkedBlockingQueue<>()    );    executor.execute(() -> ProfileInstaller.writeProfile(context));}

static void writeProfile(        @NonNull Context context,        @NonNull Executor executor,        @NonNull DiagnosticsCallback diagnostics,        boolean forceWriteProfile) {    Context appContext = context.getApplicationContext();    String packageName = appContext.getPackageName();    ApplicationInfo appInfo = appContext.getApplicationInfo();    AssetManager assetManager = appContext.getAssets();    String apkName = new File(appInfo.sourceDir).getName();    PackageManager packageManager = context.getPackageManager();    PackageInfo packageInfo;    try {        packageInfo = packageManager.getPackageInfo(packageName, 0);    } catch (PackageManager.NameNotFoundException e) {        diagnostics.onResultReceived(RESULT_IO_EXCEPTION, e);        return;    }    File filesDir = context.getFilesDir();    // 判断是否要写入    if (forceWriteProfile            || !hasAlreadyWrittenProfileForThisInstall(packageInfo, filesDir, diagnostics)) {        transcodeAndWrite(assetManager, packageName, packageInfo, filesDir, apkName, executor,                diagnostics);    }}

private static void transcodeAndWrite(        @NonNull AssetManager assets,        @NonNull String packageName,        @NonNull PackageInfo packageInfo,        @NonNull File filesDir,        @NonNull String apkName,        @NonNull Executor executor,        @NonNull DiagnosticsCallback diagnostics) {    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT) {        result(executor, diagnostics, ProfileInstaller.RESULT_UNSUPPORTED_ART_VERSION, null);        return;    }    File curProfile = new File(new File(PROFILE_BASE_DIR, packageName), PROFILE_FILE);
    DeviceProfileWriter deviceProfileWriter = new DeviceProfileWriter(assets, executor,            diagnostics, apkName, PROFILE_SOURCE_LOCATION, PROFILE_META_LOCATION, curProfile);
    // 是否具备写入权限    if (!deviceProfileWriter.deviceAllowsProfileInstallerAotWrites()) {        return; /* nothing else to do here */    }
    boolean success = deviceProfileWriter.read()            .transcodeIfNeeded()            .write();
    if (success) {        noteProfileWrittenFor(packageInfo, filesDir);    }}
public boolean deviceAllowsProfileInstallerAotWrites() {    if (mDesiredVersion == null) {        result(ProfileInstaller.RESULT_UNSUPPORTED_ART_VERSION, Build.VERSION.SDK_INT);        return false;    }
    if (!mCurProfile.canWrite()) {        // 某些厂商可能不允许写入 Profile 文件        result(ProfileInstaller.RESULT_NOT_WRITABLE, null);        return false;    }
    mDeviceSupportsAotProfile = true;    return true;}