Android内存优化——内存泄露检测分析方法

上一篇文章总结了一些常见的内存泄露场景及优化方案，这篇文章继续总结内存泄露的一些常用的检测和分析方法。

Lint代码检查

AndroidStudio自动Lint代码检查工具，一些常见的代码警告Lint工具都会给我们提示。使用也比较简单：

Analyze —> Inspect Code 然后选择检查范围：

Lint使用-1

Lint使用-2

Lint使用-3

比如如果存在非静态内部类的Handler，可能会导致内存泄露，检查结果就会显示在AndroidStudio的控制台。

其实，只要我们在设置里面勾选了Lint代码检查（AnroidStudio默认是勾选了的），在写代码的时候就会自动提示可能发生内存泄露。

Lint检查代码内存泄露

Lint提示内存泄露

通常在写Handler、静态字段、标记对象等可能存在的内存泄露时，Lint检查工具都会有一个警告提示信息，我们可以根据Lint检查的提示信息来避免这些有可能发生的内存泄露。

Android Monitor

在AndroidStudio中，可以通过Monitors来监控Memory、CPU、Network、GPU等。在Monitors监控中，我们可以获取内存的各种信息来分析内存泄露。

首先运行工程后，打开控制台的Android Monitor：

Android Monitor

在运行设备中使用app（各个页面的跳转，使用相应的各种功能），就可以看到内存使用的不断变化：

内存使用变化

淡蓝色和浅灰色区域就是内存分配的变化过程，浅灰色表示空闲内存，淡蓝色表示使用内存。

通常，我们在打开一个新的页面后，使用的内存就会增加，相应的，关闭一个页面后，系统执行了GC，使用的内存应该下降。如果我们在退出界面并执行GC后，内存使用并未下降明显，或者使用内存没有下降初始的使用大小，那么有可能就发生了内存泄露。

运行工程，在设备上操作app，观察Monitor中内存的变化，点击 initiate GC 触发GC，然后点击Dump Java Heap转出堆信息，稍等片刻，生成hprof文件，生成后会在Studio中自动打开。

hprof文件

点击右侧的Analyzer Tasks，再点击Perform Analyzer，展开下面分析结果
中的 Leaked Activities 就可以看到发生内存泄露的Activity了。

Monitor内存泄露分析

可以根据左侧的引用树，来查找持有Activity引用的位置，从而判断出哪个地方导致了内存泄露。

Mat

使用第三方的Mat工具来分析内存泄露，需要在官网下载独立版的Mat。

将Android Monitor生成的hprof文件导出为标准的hprof文件（必须这样导出，直接copy出来会报错的）：

导出hprof文件

使用Mat打开导出的hprof文件：

Mat打开hprof文件

点击Histogram（直方图），可以看到类对应的实例数量的统计。

直方图

在Class Name下面输入需要匹配的类名，根据类来查看它的实例的引用，进而分析是否存在内存泄露。

类的实例

可以看到TestActivity和MyHandler都只有一个实例被引用。

TestActivity点击右键—>Merge Shortest Paths to GC Roots —>exclude all phantom/weak/soft etc.references。

Merge Shortest Paths to GC Roots 可以查看一个对象到RC Roots是否存在引用链相连接，在JAVA中是通过可达性（Reachability Analysis)来判断对象是否存活，这个算法的基本思想是通过一系列的称谓"GC Roots"的对象作为起始点，从这些节点开始向下搜索，搜索所走得路径称为引用链，当一个对象到GC Roots没有任何引用链相连则该对象被判定为可以被回收的对象，反之不能被回收，我们可以选择 exclude all phantom/weak/soft etc.references(排查虚引用/弱引用/软引用等）因为被虚引用/弱引用/软引用的对象可以直接被GC给回收。

参考自Android 性能优化之使用MAT分析内存泄露问题。

TestActivity实例 RC Roots引用链

可以看到TestActivity实例存在GC Roots链，TextActivity实例被mMessageQueue.mMessae.target.this$0持有，那么发生了内存泄露，我们可以根据引用链来在代码中找到内存泄露的位置。

LeakCanary

LeakCanary是square开源的检测内存泄露的第三方库。它最大的有点就是开发者只需要添加简单代码，app在运行时如果发生了内存泄露，就会很直观的将内存泄露的详细信息展示在通知栏上，这样避免了Android Monitor或者Mat等工具的繁琐的分析过程。

项目地址：github.com/square/leak…

在Gradle文件中添加依赖：

 dependencies {debugCompile 'com.squareup.leakcanary:leakcanary-android:1.5'releaseCompile 'com.squareup.leakcanary:leakcanary-android-no-op:1.5'testCompile 'com.squareup.leakcanary:leakcanary-android-no-op:1.5'}复制代码

在入口的Application中进行初始化：

public class App extends Application {// 模拟内存泄露场景public static ArrayList<Activity> sActivities = new ArrayList<>();@Overridepublic void onCreate() {super.onCreate();if (LeakCanary.isInAnalyzerProcess(this)) {// This process is dedicated to LeakCanary for heap analysis.// You should not init your app in this process.return;}LeakCanary.install(this);// Normal app init code...}
}复制代码

在Application中新建一个静态List，里面存储Activity，来模拟内存泄露案例：

public class TestActivity extends AppCompatActivity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_test);App.sActivities.add(this);}public void back(View view) {finish();}
}复制代码

运行app后，在控制台可以看到LeakCanary的日志：

04-25 10:20:46.793 D/LeakCanary: In com.xiao.memoryleakexample:1.0:1.
04-25 10:20:46.793 D/LeakCanary: * com.xiao.memoryleakexample.TestActivity has leaked:
04-25 10:20:46.793 D/LeakCanary: * GC ROOT static com.xiao.memoryleakexample.app.App.sActivities
04-25 10:20:46.793 D/LeakCanary: * references java.util.ArrayList.array
04-25 10:20:46.793 D/LeakCanary: * references array java.lang.Object[].[0]
04-25 10:20:46.793 D/LeakCanary: * leaks com.xiao.memoryleakexample.TestActivity instance
04-25 10:20:46.793 D/LeakCanary: * Retaining: 88 KB.
04-25 10:20:46.793 D/LeakCanary: * Reference Key: 915bf11a-db9f-468e-8064-d6fb103710e9
04-25 10:20:46.793 D/LeakCanary: * Device: OPPO OPPO OPPO R9 Plusm A R9PlusmA
04-25 10:20:46.793 D/LeakCanary: * Android Version: 5.1.1 API: 22 LeakCanary: 1.5 00f37f5
04-25 10:20:46.793 D/LeakCanary: * Durations: watch=5049ms, gc=207ms, heap dump=979ms, analysis=122889ms
04-25 10:20:46.793 D/LeakCanary: * Details:
04-25 10:20:46.793 D/LeakCanary: * Class com.xiao.memoryleakexample.app.App
04-25 10:20:46.793 D/LeakCanary: |   static $staticOverhead = byte[24]@314667009 (0x12c17001)
04-25 10:20:46.793 D/LeakCanary: |   static sActivities = java.util.ArrayList@315492800 (0x12ce09c0)
04-25 10:20:46.793 D/LeakCanary: |   static serialVersionUID = -920324649544707127
04-25 10:20:46.793 D/LeakCanary: |   static $change = null
04-25 10:20:46.793 D/LeakCanary: * Instance of java.util.ArrayList
04-25 10:20:46.793 D/LeakCanary: |   static $staticOverhead = byte[16]@1893824473 (0x70e177d9)
04-25 10:20:46.793 D/LeakCanary: |   static MIN_CAPACITY_INCREMENT = 12
04-25 10:20:46.793 D/LeakCanary: |   static serialVersionUID = 8683452581122892189
04-25 10:20:46.793 D/LeakCanary: |   array = java.lang.Object[12]@318048768 (0x12f50a00)
04-25 10:20:46.793 D/LeakCanary: |   size = 1
04-25 10:20:46.793 D/LeakCanary: |   modCount = 1
04-25 10:20:46.793 D/LeakCanary: * Array of java.lang.Object[]
04-25 10:20:46.793 D/LeakCanary: |   [0] = com.xiao.memoryleakexample.TestActivity@316091520 (0x12d72c80)
04-25 10:20:46.793 D/LeakCanary: |   [1] = null
04-25 10:20:46.793 D/LeakCanary: |   [2] = null
04-25 10:20:46.793 D/LeakCanary: |   [3] = null
04-25 10:20:46.793 D/LeakCanary: |   [4] = null
04-25 10:20:46.793 D/LeakCanary: |   [5] = null
04-25 10:20:46.793 D/LeakCanary: |   [6] = null
04-25 10:20:46.793 D/LeakCanary: |   [7] = null
04-25 10:20:46.793 D/LeakCanary: |   [8] = null
04-25 10:20:46.793 D/LeakCanary: |   [9] = null
04-25 10:20:46.793 D/LeakCanary: |   [10] = null
04-25 10:20:46.793 D/LeakCanary: |   [11] = null
04-25 10:20:46.793 D/LeakCanary: * Instance of com.xiao.memoryleakexample.TestActivity
04-25 10:20:46.793 D/LeakCanary: |   static $staticOverhead = byte[16]@316125185 (0x12d7b001)
04-25 10:20:46.793 D/LeakCanary: |   static serialVersionUID = 836998863274086997
04-25 10:20:46.793 D/LeakCanary: |   static $change = null
04-25 10:20:46.793 D/LeakCanary: |   mHandler = com.xiao.memoryleakexample.TestActivity$MyHandler@318005952 (0x12f462c0)
04-25 10:20:46.793 D/LeakCanary: |   mDelegate = android.support.v7.app.AppCompatDelegateImplV14@314816320 (0x12c3b740)
04-25 10:20:46.793 D/LeakCanary: |   mEatKeyUpEvent = false
04-25 10:20:46.793 D/LeakCanary: |   mResources = null
04-25 10:20:46.793 D/LeakCanary: |   mThemeId = 2131230884
04-25 10:20:46.793 D/LeakCanary: |   mCreated = true
04-25 10:20:46.793 D/LeakCanary: |   mFragments = android.support.v4.app.FragmentController@317876896 (0x12f26aa0)
04-25 10:20:46.793 D/LeakCanary: |   mHandler = android.support.v4.app.FragmentActivity$1@318005920 (0x12f462a0)
04-25 10:20:46.793 D/LeakCanary: |   mNextCandidateRequestIndex = 0
04-25 10:20:46.793 D/LeakCanary: |   mOptionsMenuInvalidated = false
04-25 10:20:46.793 D/LeakCanary: |   mPendingFragmentActivityResults = android.support.v4.util.SparseArrayCompat@318008352 (0x12f46c20)
04-25 10:20:46.793 D/LeakCanary: |   mReallyStopped = true
04-25 10:20:46.793 D/LeakCanary: |   mRequestedPermissionsFromFragment = false
04-25 10:20:46.793 D/LeakCanary: |   mResumed = false
04-25 10:20:46.793 D/LeakCanary: |   mRetaining = false
04-25 10:20:46.793 D/LeakCanary: |   mStopped = true
04-25 10:20:46.793 D/LeakCanary: |   mStartedActivityFromFragment = false
04-25 10:20:46.793 D/LeakCanary: |   mStartedIntentSenderFromFragment = false
04-25 10:20:46.793 D/LeakCanary: |   mExtraDataMap = android.support.v4.util.SimpleArrayMap@318005888 (0x12f46280)
04-25 10:20:46.793 D/LeakCanary: |   mActionBar = null
04-25 10:20:46.793 D/LeakCanary: |   mActivityInfo = android.content.pm.ActivityInfo@318009472 (0x12f47080)
04-25 10:20:46.793 D/LeakCanary: |   mActivityTransitionState = android.app.ActivityTransitionState@317937344 (0x12f356c0)
04-25 10:20:46.793 D/LeakCanary: |   mAllLoaderManagers = android.util.ArrayMap@318081312 (0x12f58920)
04-25 10:20:46.793 D/LeakCanary: |   mApplication = com.xiao.memoryleakexample.app.App@315492832 (0x12ce09e0)
04-25 10:20:46.793 D/LeakCanary: |   mCalled = true
04-25 10:20:46.793 D/LeakCanary: |   mChangeCanvasToTranslucent = false
04-25 10:20:46.793 D/LeakCanary: |   mChangingConfigurations = false
04-25 10:20:46.793 D/LeakCanary: |   mCheckedForLoaderManager = true
04-25 10:20:46.793 D/LeakCanary: |   mComponent = android.content.ComponentName@314990768 (0x12c660b0)
04-25 10:20:46.793 D/LeakCanary: |   mConfigChangeFlags = 0
04-25 10:20:46.793 D/LeakCanary: |   mContainer = android.app.Activity$1@317876848 (0x12f26a70)
04-25 10:20:46.793 D/LeakCanary: |   mCurrentConfig = android.content.res.Configuration@317856672 (0x12f21ba0)
04-25 10:20:46.793 D/LeakCanary: |   mDecor = null
04-25 10:20:46.793 D/LeakCanary: |   mDefaultKeyMode = 0
04-25 10:20:46.793 D/LeakCanary: |   mDefaultKeySsb = null
04-25 10:20:46.793 D/LeakCanary: |   mDestroyed = true
04-25 10:20:46.793 D/LeakCanary: |   mDoReportFullyDrawn = false
04-25 10:20:46.793 D/LeakCanary: |   mEmbeddedID = null
04-25 10:20:46.793 D/LeakCanary: |   mEnableDefaultActionBarUp = false
04-25 10:20:46.793 D/LeakCanary: |   mEnterTransitionListener = android.app.SharedElementCallback$1@1893595344 (0x70ddf8d0)
04-25 10:20:46.793 D/LeakCanary: |   mExitTransitionListener = android.app.SharedElementCallback$1@1893595344 (0x70ddf8d0)
04-25 10:20:46.793 D/LeakCanary: |   mFinished = true
04-25 10:20:46.793 D/LeakCanary: |   mFragments = android.app.FragmentManagerImpl@317856448 (0x12f21ac0)
04-25 10:20:46.793 D/LeakCanary: |   mHandler = android.os.Handler@318005856 (0x12f46260)
04-25 10:20:46.793 D/LeakCanary: |   mIdent = 578025123
04-25 10:20:46.793 D/LeakCanary: |   mInstanceTracker = android.os.StrictMode$InstanceTracker@317876864 (0x12f26a80)
04-25 10:20:46.793 D/LeakCanary: |   mInstrumentation = android.app.Instrumentation@315352176 (0x12cbe470)
04-25 10:20:46.793 D/LeakCanary: |   mIntent = android.content.Intent@317362304 (0x12ea9080)
04-25 10:20:46.793 D/LeakCanary: |   mLastNonConfigurationInstances = null
04-25 10:20:46.793 D/LeakCanary: |   mLoaderManager = null
04-25 10:20:46.793 D/LeakCanary: |   mLoadersStarted = false
04-25 10:20:46.793 D/LeakCanary: |   mMainThread = android.app.ActivityThread@314856000 (0x12c45240)
04-25 10:20:46.803 D/LeakCanary: |   mManagedCursors = java.util.ArrayList@318005792 (0x12f46220)
04-25 10:20:46.803 D/LeakCanary: |   mManagedDialogs = null
04-25 10:20:46.803 D/LeakCanary: |   mMenuInflater = null
04-25 10:20:46.803 D/LeakCanary: |   mParent = null
04-25 10:20:46.803 D/LeakCanary: |   mReferrer = java.lang.String@314984512 (0x12c64840)
04-25 10:20:46.803 D/LeakCanary: |   mResultCode = 0
04-25 10:20:46.803 D/LeakCanary: |   mResultData = null
04-25 10:20:46.803 D/LeakCanary: |   mResumed = false
04-25 10:20:46.803 D/LeakCanary: |   mSearchManager = null
04-25 10:20:46.803 D/LeakCanary: |   mStartedActivity = false
04-25 10:20:46.803 D/LeakCanary: |   mStopped = true
04-25 10:20:46.803 D/LeakCanary: |   mTemporaryPause = false
04-25 10:20:46.803 D/LeakCanary: |   mTitle = java.lang.String@316164352 (0x12d84900)
04-25 10:20:46.803 D/LeakCanary: |   mTitleColor = 0
04-25 10:20:46.803 D/LeakCanary: |   mTitleReady = true
04-25 10:20:46.803 D/LeakCanary: |   mToken = android.os.BinderProxy@314983040 (0x12c64280)
04-25 10:20:46.803 D/LeakCanary: |   mTranslucentCallback = null
04-25 10:20:46.803 D/LeakCanary: |   mUiThread = java.lang.Thread@1967775656 (0x7549dfa8)
04-25 10:20:46.803 D/LeakCanary: |   mVisibleBehind = false
04-25 10:20:46.803 D/LeakCanary: |   mVisibleFromClient = true
04-25 10:20:46.803 D/LeakCanary: |   mVisibleFromServer = true
04-25 10:20:46.803 D/LeakCanary: |   mVoiceInteractor = null
04-25 10:20:46.803 D/LeakCanary: |   mWindow = com.android.internal.policy.impl.PhoneWindow@315631936 (0x12d02940)
04-25 10:20:46.803 D/LeakCanary: |   mWindowAdded = true
04-25 10:20:46.803 D/LeakCanary: |   mWindowManager = android.view.WindowManagerImpl@318006848 (0x12f46640)
04-25 10:20:46.803 D/LeakCanary: |   mInflater = com.android.internal.policy.impl.PhoneLayoutInflater@317929312 (0x12f33760)
04-25 10:20:46.803 D/LeakCanary: |   mOverrideConfiguration = null
04-25 10:20:46.803 D/LeakCanary: |   mResources = android.content.res.Resources@314591360 (0x12c04880)
04-25 10:20:46.803 D/LeakCanary: |   mTheme = android.content.res.Resources$Theme@318006400 (0x12f46480)
04-25 10:20:46.803 D/LeakCanary: |   mThemeResource = 2131230884
04-25 10:20:46.803 D/LeakCanary: |   mBase = android.app.ContextImpl@317145792 (0x12e742c0)
04-25 10:20:46.803 D/LeakCanary: * Excluded Refs:
04-25 10:20:46.803 D/LeakCanary: | Field: android.view.inputmethod.InputMethodManager.mNextServedView
04-25 10:20:46.803 D/LeakCanary: | Field: android.view.inputmethod.InputMethodManager.mServedView
04-25 10:20:46.803 D/LeakCanary: | Field: android.view.inputmethod.InputMethodManager.mServedInputConnection
04-25 10:20:46.803 D/LeakCanary: | Field: android.view.inputmethod.InputMethodManager.mCurRootView
04-25 10:20:46.803 D/LeakCanary: | Field: android.animation.LayoutTransition$1.val$parent
04-25 10:20:46.803 D/LeakCanary: | Field: android.view.textservice.SpellCheckerSession$1.this$0
04-25 10:20:46.803 D/LeakCanary: | Field: android.support.v7.internal.widget.ActivityChooserModel.mActivityChoserModelPolicy
04-25 10:20:46.803 D/LeakCanary: | Field: android.widget.ActivityChooserModel.mActivityChoserModelPolicy
04-25 10:20:46.803 D/LeakCanary: | Field: android.accounts.AccountManager$AmsTask$Response.this$1
04-25 10:20:46.803 D/LeakCanary: | Field: android.media.MediaScannerConnection.mContext
04-25 10:20:46.803 D/LeakCanary: | Field: android.os.UserManager.mContext
04-25 10:20:46.803 D/LeakCanary: | Field: android.media.AudioManager$1.this$0
04-25 10:20:46.803 D/LeakCanary: | Field: android.widget.Editor$Blink.this$0
04-25 10:20:46.803 D/LeakCanary: | Field: android.net.ConnectivityManager.sInstance
04-25 10:20:46.803 D/LeakCanary: | Field: android.view.Choreographer$FrameDisplayEventReceiver.mMessageQueue (always)
04-25 10:20:46.803 D/LeakCanary: | Static field: android.text.TextLine.sCached
04-25 10:20:46.803 D/LeakCanary: | Thread:FinalizerWatchdogDaemon (always)
04-25 10:20:46.803 D/LeakCanary: | Thread:main (always)
04-25 10:20:46.803 D/LeakCanary: | Thread:LeakCanary-Heap-Dump (always)
04-25 10:20:46.803 D/LeakCanary: | Class:java.lang.ref.WeakReference (always)
04-25 10:20:46.803 D/LeakCanary: | Class:java.lang.ref.SoftReference (always)
04-25 10:20:46.803 D/LeakCanary: | Class:java.lang.ref.PhantomReference (always)
04-25 10:20:46.803 D/LeakCanary: | Class:java.lang.ref.Finalizer (always)
04-25 10:20:46.803 D/LeakCanary: | Class:java.lang.ref.FinalizerReference (always)复制代码