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Android内存泄漏检测工具LeakCanary

开发者 https://www.devze.com 2023-04-14 10:22 出处:网络 作者: 不入流Android开发
目录背景LeaksCanary 介绍使用方法1.LeakCanary 如何自动初始化2.LeakCanary如何检测内存泄漏2.1LeakCanary初始化时做了什么2.2LeakCanary如何触发检测2.3LeakCanary如何检测泄漏的对象2.4弱引用 WeakReference背景
目录
  • 背景
  • LeaksCanary 介绍
  • 使用方法
    • 1.LeakCanary 如何自动初始化
    • 2.LeakCanary如何检测内存泄漏
      • 2.1LeakCanary初始化时做了什么
      • 2.2LeakCanary如何触发检测
      • 2.3LeakCanary如何检测泄漏的对象
      • 2.4弱引用 WeakReference

背景

在android应用中,一个好的产品,除了功能强大,好的性能也是必不可少的。有调查显示,近90%的受访者会因为App卡顿,内存大等问题而卸载该应用,因此手机的性能问题会影响用户的体验,如果用户觉得该应用的体验度不好,会直接卸载或切换其他平台。

对于性能优化,很多大公司会专门招聘性能优化的人员。也有些初级工程师会接触到这部分的工作,但是无从下手,对专业工具和专业代码使用以及分析比较吃力,排查起来也比较费劲。如果有专业的工具能够只管的把这些记录并标记好。这样初级工程师也可以通过详情的问题去排查,那么LeaksCanary就是这款工具了。

LeaksCanary 介绍

LeakCanary是Square公司为Android开发者提供的一个自动检测内存泄漏的工具。

LeakCanary本质上是一个基于MAT进行Android应用程序内存泄漏自动化检测的的开源工具,我们可以通过集成LeakCanary提供的jar包到自己的工程中,一旦检测到内存泄漏,LeakCanary就会dump Memory信息,并通过另一个进程分析内存泄漏的信息并展示出来,随时发现和定位内存泄漏问题,而不用每次在开发流程中都抽出专人来进行内存泄漏问题检测,极大地方便了Android应用程序的开发。

使用方法

1.LeakCanary 如何自动初始化

LeakCanary只需添加依赖就可以实现自动初始化。LeakCanary是通过ContentProvider实现初始化的,在ContentProvider 的 onCreate方法中初始化LeakCanary。并且MainProcessAppWatcherInstaller是在主线程中初始化的。注意:ContentProvider的初始化是在Application的onCreate之前完成的,所以LeakCanary的初始化方法AppWatcher.manualInstall(application)也是在Application的onCreate之前完成的。

internal class MainProcessAppWatcherInstaller : ContentProvider() {
   override fun onCreate(): Boolean {
      val application = context!!.applicationContext as Application
      AppWatcher.manualInstall(application)
      return true
    }
     ... ...
}

2.LeakCanary如何检测内存泄漏

2.1LeakCanary初始化时做了什么

AppWatcher.kt

@JvmOverloads
fun manualInstall(
  application: Application,
  retainedDelayMillis: Long = TimeUnit.SECONDS.toMillis(5),
  watchersToInstall: List<InstallableWatcher> = appDefaultWatchers(application)
) {
  checkMainThread()
  if (isInstalled) {
    throw IllegalStateException(
      "AppWatcher already installed, see exception cause for prior install call", installCause
    )
  }
  check(retainedDelayMillis >= 0) {
    "retainedDelayMillis $retainedDelayMillis must be at least 0 ms"
  }
  installCause = RuntimeException("manualInstall() first called here")
  this.retainedDelayMillis = retainedDelayMillis
  if (application.isDebuggableBuild) {
    LogcatSharkLog.install()
  }
  // Requires AppWatcher.objectWatcher to be set
  LeakCanaryDelegate.loadLeakCanary(application)
  watchersToInstall.forEach {
    it.install()
  }
}
fun appDefaultWatchers(
  application: Application,
  reachabilityWatcher: ReachabilityWatcher = objectWatcher
): List<InstallableWatcher> {
  return listOf(
    ActivityWatcher(application, reachabilityWatcher),
    FragmentAndViewModelWatcher(application, reachabilityWatcher),
    RootViewWatcher(reachabilityWatcher),
    ServiceWatcher(reachabilityWatcher)
  )
}

在appDefaultWatchers方法中,会默认初始化一些Watcher,在默认情况下,我们只会监控Activity,Fragment,RootView,Service这些对象是否泄漏。

2.2LeakCanary如何触发检测

以ActivityWatcher为例:

/**
 * Expects activities to become weakly reachable soon after they receive the [Activity.onDestroy]
 * callback.
 */
class ActivityWatcher(
  private val application: Application,
  private val reachabilityWatcher: ReachabilityWatcher
) : InstallableWatcher {
  private val lifecycleCallbacks =
    object : Application.ActivityLifecycleCallbacks by noOpDelegate() {
      override fun onActivityDestroyed(activity: Activity) {
        reachabilityWatcher.expectWeaklyReachable(
          activity, "${activity::class.Java.name} received Activity#onDestroy() callback"
        )
      }
    }
  override fun install() {
    application.registerActivityLifecycleCallbacks(lifecycleCallbacks)
  }
  override fun uninstall() {
    application.unregisterActivityLifecycleCallbacks(lifecycleCallbacks)
  }
}

在Activity.onDestory时,就会触发检测内存泄漏。通过ActivityLifecycleCallbacks监听生命周期变化,在onActivityDestroyed方法中调用ReachabilityWatcher的expectWeaklyReachable方法。

2.3LeakCanary如何检测泄漏的对象

以Activity为例,通过ReachabilityWatcher的expectWeaklyReachable方法检测。

fun interface ReachabilityWatwww.devze.comcher {
  /**
   * Expects the provided [watchedObject] to become weakly reachable soon. If not,
   * [watchedObject] will be considered retained.
   */
  fun expectWeaklyReachable(
    watchedObject: Any,
    description: String
  )
}
ObjectWatcher.kt
ObjectWatcher实现ReachabilityWatcher接口。
private val watchedObjects = mutableMapOf()
private val queue = ReferenceQueue()
@Synchronized override fun expectWeaklyReachable(
  watchedObject: Any,
  description: String
) {
  if (!isEnabled()) {
    return
  }
  removeWeaklyReachableObjects()
  val key = UUID.randomUUID()
    .toString()
  val watchUptimeMillis = clock.uptimeMillis()
  val reference =
    KeyedweakReference(watchedObject, keyjs, description, watchUptimeMillis, queue)
  SharkLog.d {
    "Watching " +
      (if (watchedObject is Class<*>) watchedObject.toString() else "instance of ${watchedObject.javaClass.name}") +
      (if (description.isNotE编程客栈mpty()) " ($description)" else "") +
      " with key $key"
  }
  watchedObjects[key] = reference
  checkRetainedExecutor.execute {
    moveToRetained(key)
  }
}

1.通过观察的实例watchedObject构建弱引用KeyedWeakwww.devze.comReference实例,watchedObject与ReferenceQueue关联,当对象被回收时,该弱引用对象将被存入ReferenceQueue当中。

2.弱引用KeyedWeakReference实例会被被存储在watchedObjects中(Map)。

3.检测过程中,会调用removeWeaklyReachableObjects,将已回收对象从watchedObjects中移除。

4.如果watchedObjects中没有移除对象,证明它没有被回收,那么就会调用moveToRetained。

private fun removeWeaklyReachableObjects() {
  // WeakReferences are enqueued as soon as the object to which they point to becomes weakly
  // reachable. This is before finalization or garbage collection has actually happened.
  var ref: KeyedWeakReference?
  do {
    ref = queue.poll() as KeyedWeakReference?
    if (ref != null) {
      watchedObjects.remove(ref.key)
    }
  } while (ref != null)
}
@Synchronized private fun moveToRetained(key: String) {
  remove开发者_Python教程WeaklyReachableObjects()
  val retainedRef = watchedObjects[key]
  if (retainedRef != null) {
    retainedRef.retainedUptimeMillis = clock.uphpptimeMillis()
    onObjectRetainedListeners.forEach { it.onObjectRetained() }
  }
}

2.4弱引用 WeakReference

只要 GC 发现一个对象只有弱引用,则就会回收此弱引用对象。

public class WeakReference<T> extends Reference<T> {
    public WeakReference(T referent) {
        super(referent);
    }
    public WeakReference(T referent, ReferenceQueue<? super T> q) {
        super(referent, q);
    }
}
var str: Any? = Any()
val quque = ReferenceQueue<Any>()
val weakReference = WeakReference<Any>(str, quque)
val weakReference_before_gc = weakReference.get()
Log.v("reference_tag", weakReference_before_gc.toString())
str = null
System.gc()
Handler().postDelayed( {
    val weakReference_after_gc = weakReference.get()
    Log.v("reference_tag", weakReference_after_gc.toString())
}, 2000)

到此这篇关于Android内存泄漏检测工具LeakCanary的文章就介绍到这了,更多相关Android LeakCanary内容请搜索我们以前的文章或继续浏览下面的相关文章希望大家以后多多支持我们!

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