Android內存優化——內存泄露檢測分析方法

上一篇文章總結了一些常見的內存泄露場景及優化方案，這篇文章繼續總結內存泄露的一些常用的檢測和分析方法。

Lint代碼檢查

AndroidStudio自動Lint代碼檢查工具，一些常見的代碼警告Lint工具都會給我們提示。使用也比較簡單：

Analyze —> Inspect Code 然后選擇檢查范圍：

Lint使用-1

Lint使用-2

Lint使用-3

比如如果存在非靜態內部類的Handler，可能會導致內存泄露，檢查結果就會顯示在AndroidStudio的控制臺。

其實，只要我們在設置里面勾選了Lint代碼檢查（AnroidStudio默認是勾選了的），在寫代碼的時候就會自動提示可能發生內存泄露。

Lint檢查代碼內存泄露

Lint提示內存泄露

通常在寫Handler、靜態字段、標記對象等可能存在的內存泄露時，Lint檢查工具都會有一個警告提示信息，我們可以根據Lint檢查的提示信息來避免這些有可能發生的內存泄露。

Android Monitor

在AndroidStudio中，可以通過Monitors來監控Memory、CPU、Network、GPU等。在Monitors監控中，我們可以獲取內存的各種信息來分析內存泄露。

首先運行工程后，打開控制臺的Android Monitor：

Android Monitor

在運行設備中使用app（各個頁面的跳轉，使用相應的各種功能），就可以看到內存使用的不斷變化：

內存使用變化

淡藍色和淺灰色區域就是內存分配的變化過程，淺灰色表示空閑內存，淡藍色表示使用內存。

通常，我們在打開一個新的頁面后，使用的內存就會增加，相應的，關閉一個頁面后，系統執行了GC，使用的內存應該下降。如果我們在退出界面并執行GC后，內存使用并未下降明顯，或者使用內存沒有下降初始的使用大小，那么有可能就發生了內存泄露。

運行工程，在設備上操作app，觀察Monitor中內存的變化，點擊 initiate GC 觸發GC，然后點擊Dump Java Heap轉出堆信息，稍等片刻，生成hprof文件，生成后會在Studio中自動打開。

hprof文件

點擊右側的Analyzer Tasks，再點擊Perform Analyzer，展開下面分析結果
中的 Leaked Activities 就可以看到發生內存泄露的Activity了。

Monitor內存泄露分析

可以根據左側的引用樹，來查找持有Activity引用的位置，從而判斷出哪個地方導致了內存泄露。

Mat

使用第三方的Mat工具來分析內存泄露，需要在官網下載獨立版的Mat。

將Android Monitor生成的hprof文件導出為標準的hprof文件（必須這樣導出，直接copy出來會報錯的）：

導出hprof文件

使用Mat打開導出的hprof文件：

Mat打開hprof文件

點擊Histogram（直方圖），可以看到類對應的實例數量的統計。

直方圖

在Class Name下面輸入需要匹配的類名，根據類來查看它的實例的引用，進而分析是否存在內存泄露。

類的實例

可以看到TestActivity和MyHandler都只有一個實例被引用。

TestActivity點擊右鍵—>Merge Shortest Paths to GC Roots —>exclude all phantom/weak/soft etc.references。

Merge Shortest Paths to GC Roots 可以查看一個對象到RC Roots是否存在引用鏈相連接，在JAVA中是通過可達性（Reachability Analysis)來判斷對象是否存活，這個算法的基本思想是通過一系列的稱謂"GC Roots"的對象作為起始點，從這些節點開始向下搜索，搜索所走得路徑稱為引用鏈，當一個對象到GC Roots沒有任何引用鏈相連則該對象被判定為可以被回收的對象，反之不能被回收，我們可以選擇 exclude all phantom/weak/soft etc.references(排查虛引用/弱引用/軟引用等）因為被虛引用/弱引用/軟引用的對象可以直接被GC給回收。

參考自Android 性能優化之使用MAT分析內存泄露問題。

TestActivity實例 RC Roots引用鏈

可以看到TestActivity實例存在GC Roots鏈，TextActivity實例被mMessageQueue.mMessae.target.this$0持有，那么發生了內存泄露，我們可以根據引用鏈來在代碼中找到內存泄露的位置。

LeakCanary

LeakCanary是square開源的檢測內存泄露的第三方庫。它最大的有點就是開發者只需要添加簡單代碼，app在運行時如果發生了內存泄露，就會很直觀的將內存泄露的詳細信息展示在通知欄上，這樣避免了Android Monitor或者Mat等工具的繁瑣的分析過程。

項目地址：github.com/square/leak…

在Gradle文件中添加依賴：

 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'}復制代碼

在入口的Application中進行初始化：

public class App extends Application {// 模擬內存泄露場景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...}
}復制代碼

在Application中新建一個靜態List，里面存儲Activity，來模擬內存泄露案例：

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();}
}復制代碼

運行app后，在控制臺可以看到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)復制代碼