LeakCanary 2.0源码分析

根据How LeakCanary works我们可以知道LeakCanary工作流程大致分为4个阶段：

• 检测持有对象
• 存储堆信息
• 分析堆信息
• 对泄露进行分类

LeakCanary2.0的安装流程

LeakCanary1.0需要手动在Application进行安装，2.0不需要任何手动安装的代码。AppWatcherInstaller继承ContentProvider,AppWatcherInstaller的onCreate方法会调用安装方法。

  override fun onCreate(): Boolean {
    val application = context!!.applicationContext as Application
    //安装
    AppWatcher.manualInstall(application)
    return true
  }

AppWatcher的manualInstall方法。

  fun manualInstall(application: Application) {
    InternalAppWatcher.install(application)
  }

InternalAppWatcher的install方法

  //创建ObjectWatcher
  val objectWatcher = ObjectWatcher(
      clock = clock,
      checkRetainedExecutor = checkRetainedExecutor,
      isEnabled = { true }
  )

  fun install(application: Application) {
    checkMainThread()
    if (this::application.isInitialized) {
      return
    }
    SharkLog.logger = DefaultCanaryLog()
    InternalAppWatcher.application = application
    //获取配置
    val configProvider = { AppWatcher.config }
    ActivityDestroyWatcher.install(application, objectWatcher, configProvider)
    FragmentDestroyWatcher.install(application, objectWatcher, configProvider)
    onAppWatcherInstalled(application)
  }

ActivityDestroyWatcher

internal class ActivityDestroyWatcher private constructor(
  private val objectWatcher: ObjectWatcher,
  private val configProvider: () -> Config
) {

  private val lifecycleCallbacks =
    object : Application.ActivityLifecycleCallbacks by noOpDelegate() {
      override fun onActivityDestroyed(activity: Activity) {
        if (configProvider().watchActivities) {
          //调用watch观察
          objectWatcher.watch(
              activity, "${activity::class.java.name} received Activity#onDestroy() callback"
          )
        }
      }
    }

  companion object {
    fun install(
      application: Application,
      objectWatcher: ObjectWatcher,
      configProvider: () -> Config
    ) {
      val activityDestroyWatcher =
        ActivityDestroyWatcher(objectWatcher, configProvider)
      application.registerActivityLifecycleCallbacks(activityDestroyWatcher.lifecycleCallbacks)
    }
  }
}

检测持有对象

InternalAppWatcher的init代码块

  init {
    //创建InternalLeakCanary实例
    val internalLeakCanary = try {
      val leakCanaryListener = Class.forName("leakcanary.internal.InternalLeakCanary")
      leakCanaryListener.getDeclaredField("INSTANCE")
          .get(null)
    } catch (ignored: Throwable) {
      NoLeakCanary
    }
    @kotlin.Suppress("UNCHECKED_CAST")
    onAppWatcherInstalled = internalLeakCanary as (Application) -> Unit
  }

InternalLeakCanary实现OnObjectRetainedListener接口，并继承一个函数对象。

  override fun invoke(application: Application) {
    _application = application

    checkRunningInDebuggableBuild()
    //添加持有对象监听
    AppWatcher.objectWatcher.addOnObjectRetainedListener(this)
    //创建AndroidHeapDumper
    val heapDumper = AndroidHeapDumper(application, createLeakDirectoryProvider(application))
    //Gc触发器
    val gcTrigger = GcTrigger.Default

    val configProvider = { LeakCanary.config }

    val handlerThread = HandlerThread(LEAK_CANARY_THREAD_NAME)
    handlerThread.start()
    val backgroundHandler = Handler(handlerThread.looper)
    //创建堆存储触发器
    heapDumpTrigger = HeapDumpTrigger(
        application, backgroundHandler, AppWatcher.objectWatcher, gcTrigger, heapDumper,
        configProvider
    )
    //调用Application的registerVisibilityListener为Application注册ActivityLifecycleCallbacks
    application.registerVisibilityListener { applicationVisible ->
      this.applicationVisible = applicationVisible
      heapDumpTrigger.onApplicationVisibilityChanged(applicationVisible)
    }
    registerResumedActivityListener(application)
    addDynamicShortcut(application)

    disableDumpHeapInTests()
  }

HeapDumpTrigger的onApplicationVisibilityChanged方法

  fun onApplicationVisibilityChanged(applicationVisible: Boolean) {
    if (applicationVisible) {
      applicationInvisibleAt = -1L
    } else {
      //不可见
      applicationInvisibleAt = SystemClock.uptimeMillis()
      // Scheduling for after watchDuration so that any destroyed activity has time to become
      // watch and be part of this analysis.
      scheduleRetainedObjectCheck(
          reason = "app became invisible",
          rescheduling = false,
          //默认5s
          delayMillis = AppWatcher.config.watchDurationMillis
      )
    }
  }

  private fun scheduleRetainedObjectCheck(
    reason: String,
    rescheduling: Boolean,
    delayMillis: Long = 0L
  ) {
    val checkCurrentlyScheduledAt = checkScheduledAt
    if (checkCurrentlyScheduledAt > 0) {
      val scheduledIn = checkCurrentlyScheduledAt - SystemClock.uptimeMillis()
      SharkLog.d { "Ignoring request to check for retained objects ($reason), already scheduled in ${scheduledIn}ms" }
      return
    } else {
      val verb = if (rescheduling) "Rescheduling" else "Scheduling"
      val delay = if (delayMillis > 0) " in ${delayMillis}ms" else ""
      SharkLog.d { "$verb check for retained objects${delay} because $reason" }
    }
    checkScheduledAt = SystemClock.uptimeMillis() + delayMillis
    backgroundHandler.postDelayed({
      checkScheduledAt = 0
      //检测持有对象
      checkRetainedObjects(reason)
    }, delayMillis)
  }

  private fun checkRetainedObjects(reason: String) {
    val config = configProvider()
    // A tick will be rescheduled when this is turned back on.
    if (!config.dumpHeap) {
      SharkLog.d { "Ignoring check for retained objects scheduled because $reason: LeakCanary.Config.dumpHeap is false" }
      return
    }
    //获取持有对象个数
    var retainedReferenceCount = objectWatcher.retainedObjectCount

    if (retainedReferenceCount > 0) {
      //垃圾回收
      gcTrigger.runGc()
      retainedReferenceCount = objectWatcher.retainedObjectCount
    }

    if (checkRetainedCount(retainedReferenceCount, config.retainedVisibleThreshold)) return

    if (!config.dumpHeapWhenDebugging && DebuggerControl.isDebuggerAttached) {
      onRetainInstanceListener.onEvent(DebuggerIsAttached)
      showRetainedCountNotification(
          objectCount = retainedReferenceCount,
          contentText = application.getString(
              R.string.leak_canary_notification_retained_debugger_attached
          )
      )
      scheduleRetainedObjectCheck(
          reason = "debugger is attached",
          rescheduling = true,
          delayMillis = WAIT_FOR_DEBUG_MILLIS
      )
      return
    }
    val now = SystemClock.uptimeMillis()
    val elapsedSinceLastDumpMillis = now - lastHeapDumpUptimeMillis
    if (elapsedSinceLastDumpMillis < WAIT_BETWEEN_HEAP_DUMPS_MILLIS) {
      onRetainInstanceListener.onEvent(DumpHappenedRecently)
      showRetainedCountNotification(
          objectCount = retainedReferenceCount,
          contentText = application.getString(R.string.leak_canary_notification_retained_dump_wait)
      )
      scheduleRetainedObjectCheck(
          reason = "previous heap dump was ${elapsedSinceLastDumpMillis}ms ago (< ${WAIT_BETWEEN_HEAP_DUMPS_MILLIS}ms)",
          rescheduling = true,
          delayMillis = WAIT_BETWEEN_HEAP_DUMPS_MILLIS - elapsedSinceLastDumpMillis
      )
      return
    }

    SharkLog.d { "Check for retained objects found $retainedReferenceCount objects, dumping the heap" }
    dismissRetainedCountNotification()
    //存储堆信息
    dumpHeap(retainedReferenceCount, retry = true)
  }

ObjectWatcher的watch方法

  @Synchronized fun watch(
    watchedObject: Any,
    description: String
  ) {
    if (!isEnabled()) {
      return
    }
    //移除已经回收的对象
    removeWeaklyReachableObjects()
    //生成随机key
    val key = UUID.randomUUID()
        .toString()
    val watchUptimeMillis = clock.uptimeMillis()
    //构造KeyedWeakReference 用来监听目标对象
    val reference =
      KeyedWeakReference(watchedObject, key, description, watchUptimeMillis, queue)
    SharkLog.d {
      "Watching " +
          (if (watchedObject is Class<*>) watchedObject.toString() else "instance of ${watchedObject.javaClass.name}") +
          (if (description.isNotEmpty()) " ($description)" else "") +
          " with key $key"
    }
    //KeyedWeakReference
    watchedObjects[key] = reference
    checkRetainedExecutor.execute {
      moveToRetained(key)
    }
  }

  @Synchronized private fun moveToRetained(key: String) {
    removeWeaklyReachableObjects()
    val retainedRef = watchedObjects[key]
    if (retainedRef != null) {
      retainedRef.retainedUptimeMillis = clock.uptimeMillis()
      //执行InternalLeakCanary的onObjectRetained方法
      onObjectRetainedListeners.forEach { it.onObjectRetained() }
    }
  }

  override fun onObjectRetained() {
    if (this::heapDumpTrigger.isInitialized) {
      heapDumpTrigger.onObjectRetained()
    }
  }

 fun onObjectRetained() {
    scheduleRetainedObjectCheck(
        reason = "found new object retained",
        rescheduling = false
    )
  }

存储堆信息

HeapDumpTrigger的dumpHeap方法

  private fun dumpHeap(
    retainedReferenceCount: Int,
    retry: Boolean
  ) {
    saveResourceIdNamesToMemory()
    val heapDumpUptimeMillis = SystemClock.uptimeMillis()
    KeyedWeakReference.heapDumpUptimeMillis = heapDumpUptimeMillis
    //调用HeapDumper的dumpHeap存储堆信息
    val heapDumpFile = heapDumper.dumpHeap()
    if (heapDumpFile == null) {
      if (retry) {
        SharkLog.d { "Failed to dump heap, will retry in $WAIT_AFTER_DUMP_FAILED_MILLIS ms" }
        scheduleRetainedObjectCheck(
            reason = "failed to dump heap",
            rescheduling = true,
            delayMillis = WAIT_AFTER_DUMP_FAILED_MILLIS
        )
      } else {
        SharkLog.d { "Failed to dump heap, will not automatically retry" }
      }
      showRetainedCountNotification(
          objectCount = retainedReferenceCount,
          contentText = application.getString(
              R.string.leak_canary_notification_retained_dump_failed
          )
      )
      return
    }
    lastDisplayedRetainedObjectCount = 0
    lastHeapDumpUptimeMillis = SystemClock.uptimeMillis()
    objectWatcher.clearObjectsWatchedBefore(heapDumpUptimeMillis)
    //分析堆信息
    HeapAnalyzerService.runAnalysis(application, heapDumpFile)
  }

AndroidHeapDumper的dumpHeap方法

  override fun dumpHeap(): File? {
    //调用LeakDirectoryProvider的newHeapDumpFile方法获取存储文件路径
    val heapDumpFile = leakDirectoryProvider.newHeapDumpFile() ?: return null

    val waitingForToast = FutureResult<Toast?>()
    showToast(waitingForToast)

    if (!waitingForToast.wait(5, SECONDS)) {
      SharkLog.d { "Did not dump heap, too much time waiting for Toast." }
      return null
    }

    val notificationManager =
      context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
    if (Notifications.canShowNotification) {
      val dumpingHeap = context.getString(R.string.leak_canary_notification_dumping)
      val builder = Notification.Builder(context)
          .setContentTitle(dumpingHeap)
      val notification = Notifications.buildNotification(context, builder, LEAKCANARY_LOW)
      notificationManager.notify(R.id.leak_canary_notification_dumping_heap, notification)
    }

    val toast = waitingForToast.get()

    return try {
      //存储文件
      Debug.dumpHprofData(heapDumpFile.absolutePath)
      if (heapDumpFile.length() == 0L) {
        SharkLog.d { "Dumped heap file is 0 byte length" }
        null
      } else {
        heapDumpFile
      }
    } catch (e: Exception) {
      SharkLog.d(e) { "Could not dump heap" }
      // Abort heap dump
      null
    } finally {
      cancelToast(toast)
      notificationManager.cancel(R.id.leak_canary_notification_dumping_heap)
    }
  }

分析堆信息

HeapAnalyzerService的静态方法runAnalysis

    fun runAnalysis(
      context: Context,
      heapDumpFile: File
    ) {
      val intent = Intent(context, HeapAnalyzerService::class.java)
      intent.putExtra(HEAPDUMP_FILE_EXTRA, heapDumpFile)
      startForegroundService(context, intent)
    }

  override fun onHandleIntentInForeground(intent: Intent?) {
    if (intent == null || !intent.hasExtra(HEAPDUMP_FILE_EXTRA)) {
      SharkLog.d { "HeapAnalyzerService received a null or empty intent, ignoring." }
      return
    }

    // Since we're running in the main process we should be careful not to impact it.
    Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND)
    val heapDumpFile = intent.getSerializableExtra(HEAPDUMP_FILE_EXTRA) as File

    val config = LeakCanary.config
    //分析堆信息
    val heapAnalysis = if (heapDumpFile.exists()) {
      analyzeHeap(heapDumpFile, config)
    } else {
      missingFileFailure(heapDumpFile)
    }
 
    onAnalysisProgress(REPORTING_HEAP_ANALYSIS)
    //回调
    config.onHeapAnalyzedListener.onHeapAnalyzed(heapAnalysis)
  }

  private fun analyzeHeap(
    heapDumpFile: File,
    config: Config
  ): HeapAnalysis {
    //创建HeapAnalyzer
    val heapAnalyzer = HeapAnalyzer(this)

    val proguardMappingReader = try {
      ProguardMappingReader(assets.open(PROGUARD_MAPPING_FILE_NAME))
    } catch (e: IOException) {
      null
    }
    return heapAnalyzer.analyze(
        heapDumpFile = heapDumpFile,
        leakingObjectFinder = config.leakingObjectFinder,
        referenceMatchers = config.referenceMatchers,
        computeRetainedHeapSize = config.computeRetainedHeapSize,
        objectInspectors = config.objectInspectors,
        metadataExtractor = config.metadataExtractor,
        proguardMapping = proguardMappingReader?.readProguardMapping()
    )
  }

HeapAnalyzer的analyze方法

  fun analyze(
    heapDumpFile: File,
    leakingObjectFinder: LeakingObjectFinder,
    referenceMatchers: List<ReferenceMatcher> = emptyList(),
    computeRetainedHeapSize: Boolean = false,
    objectInspectors: List<ObjectInspector> = emptyList(),
    metadataExtractor: MetadataExtractor = MetadataExtractor.NO_OP,
    proguardMapping: ProguardMapping? = null
  ): HeapAnalysis {
    val analysisStartNanoTime = System.nanoTime()

    if (!heapDumpFile.exists()) {
      val exception = IllegalArgumentException("File does not exist: $heapDumpFile")
      return HeapAnalysisFailure(
          heapDumpFile, System.currentTimeMillis(), since(analysisStartNanoTime),
          HeapAnalysisException(exception)
      )
    }

    return try {
      listener.onAnalysisProgress(PARSING_HEAP_DUMP)
      Hprof.open(heapDumpFile)
          .use { hprof ->
            val graph = HprofHeapGraph.indexHprof(hprof, proguardMapping)
            val helpers =
              FindLeakInput(graph, referenceMatchers, computeRetainedHeapSize, objectInspectors)
            helpers.analyzeGraph(
                metadataExtractor, leakingObjectFinder, heapDumpFile, analysisStartNanoTime
            )
          }
    } catch (exception: Throwable) {
      HeapAnalysisFailure(
          heapDumpFile, System.currentTimeMillis(), since(analysisStartNanoTime),
          HeapAnalysisException(exception)
      )
    }
  }

  private fun FindLeakInput.analyzeGraph(
    metadataExtractor: MetadataExtractor,
    leakingObjectFinder: LeakingObjectFinder,
    heapDumpFile: File,
    analysisStartNanoTime: Long
  ): HeapAnalysisSuccess {
    listener.onAnalysisProgress(EXTRACTING_METADATA)
    val metadata = metadataExtractor.extractMetadata(graph)

    listener.onAnalysisProgress(FINDING_RETAINED_OBJECTS)
    val leakingObjectIds = leakingObjectFinder.findLeakingObjectIds(graph)

    val (applicationLeaks, libraryLeaks) = findLeaks(leakingObjectIds)

    return HeapAnalysisSuccess(
        heapDumpFile = heapDumpFile,
        createdAtTimeMillis = System.currentTimeMillis(),
        analysisDurationMillis = since(analysisStartNanoTime),
        metadata = metadata,
        applicationLeaks = applicationLeaks,
        libraryLeaks = libraryLeaks
    )
  }

  private fun FindLeakInput.findLeaks(leakingObjectIds: Set<Long>): Pair<List<ApplicationLeak>, List<LibraryLeak>> {
    val pathFinder = PathFinder(graph, listener, referenceMatchers)
    val pathFindingResults =
      pathFinder.findPathsFromGcRoots(leakingObjectIds, computeRetainedHeapSize)

    SharkLog.d { "Found ${leakingObjectIds.size} retained objects" }

    return buildLeakTraces(pathFindingResults)
  }

分析结果呈现

 override fun onHeapAnalyzed(heapAnalysis: HeapAnalysis) {
    SharkLog.d { "$heapAnalysis" }

    val id = LeaksDbHelper(application).writableDatabase.use { db ->
      HeapAnalysisTable.insert(db, heapAnalysis)
    }

    val (contentTitle, screenToShow) = when (heapAnalysis) {
      is HeapAnalysisFailure -> application.getString(
          R.string.leak_canary_analysis_failed
      ) to HeapAnalysisFailureScreen(id)
      is HeapAnalysisSuccess -> {
        val retainedObjectCount = heapAnalysis.allLeaks.sumBy { it.leakTraces.size }
        val leakTypeCount = heapAnalysis.applicationLeaks.size + heapAnalysis.libraryLeaks.size
        application.getString(
            R.string.leak_canary_analysis_success_notification, retainedObjectCount, leakTypeCount
        ) to HeapDumpScreen(id)
      }
    }

    if (InternalLeakCanary.formFactor == TV) {
      showToast(heapAnalysis)
      printIntentInfo()
    } else {
      showNotification(screenToShow, contentTitle)
    }
  }