LeakCanary介绍
LeakCanary提供了一种很方便的方式，让我们在开发阶段测试内存泄露，我们不需要自己根据内存块来分析内存泄露的原因，我们只需要在项目中集成他，然后他就会帮我们检测内存泄露，并给出内存泄露的引用链
集成
- 在gradle中添加依赖，这种不区分debug和release
implementation 'com.squareup.leakcanary:leakcanary-android:1.5.1'
- 重写Application
public class App extends Application {
private RefWatcher mRefWatcher;
@Override
public 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;
}
mRefWatcher = LeakCanary.install(this);
}
public static RefWatcher getRefWatcher(Context context) {
App application = (App) context.getApplicationContext();
return application.mRefWatcher;
}
}
- 比如我们在Activity中制造Handler发延迟消息的内存泄露
public class ActivityOne extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_one);
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
}
}, 100000);
}
@Override
protected void onDestroy() {
super.onDestroy();
}
}
- 然后我们打开这个activity然后再关闭，桌面就会出现一个leaks的图标，然后我们打开它
这就是基本使用,其实这种形式只能监视Activity的内存泄露，至于为什么只能监视Activity的内存泄露我们下面再分析，如果想要监视其他的内存泄露怎么办，比如要监视Fragment的内存泄露，可以这样写，主动监视想要监视的对象
public abstract class BaseFragment extends Fragment { @Override public void onDestroy() { super.onDestroy(); RefWatcher refWatcher = App.getRefWatcher(getActivity()); refWatcher.watch(this); }}原理概述
通过监听Activity的onDestory，手动调用GC，然后通过ReferenceQueue+WeakReference，来判断Activity对象是否被回收，然后结合dump Heap的hpof文件，通过Haha开源库分析泄露的位置
主要的知识点
注册Activity的生命周期的监听器
通过Application.registerActivityLifecycleCallbacks()方法注册Activity的生命周期的监听器，每一个Actvity的生命周期都会回调到这个ActivityLifecycleCallbacks上，如果一个Activity走到了onDestory，那么就意味着他就不再存在，然后检测这个Activity是否是真的被销毁
通过ReferenceQueue+WeakReference，来判断对象是否被回收
WeakReference创建时，可以传入一个ReferenceQueue对象，假如WeakReference中引用对象被回收，那么就会把WeakReference对象添加到ReferenceQueue中，可以通过ReferenceQueue中是否为空来判断，被引用对象是否被回收
详细介绍推荐博客：www.jianshu.com/p/964fbc301…
MessageQueue中加入一个IdleHandler来得到主线程空闲回调
详细介绍请看Android Handler 源码解析
手动调用GC后还调用了System.runFinalization();，这个是强制调用已失去引用对象的finalize方法
在可达性算法中，不可达对象，也不是非死不可，这时他们处于“缓刑”阶段，要宣告一个对象真正死亡需要至少俩个标记阶段， 如果发现对象没有引用链，则会进行第一次标记，并进行一次筛选，筛选的条件是此对象是否有必要进行finalize（）方法，当对象没有覆盖finalize(),或者finalize（）已经调用过，这俩种都视为“没有必要执行”
Apolication中可通过processName判断是否是任务执行进程
通过processName，来判断进程
public static boolean isInServiceProcess(Context context, Class<? extends Service> serviceClass) {
PackageManager packageManager = context.getPackageManager();
PackageInfo packageInfo;
try {
packageInfo = packageManager.getPackageInfo(context.getPackageName(), GET_SERVICES);
} catch (Exception e) {
CanaryLog.d(e, "Could not get package info for %s", context.getPackageName());
return false;
}
String mainProcess = packageInfo.applicationInfo.processName;
ComponentName component = new ComponentName(context, serviceClass);
ServiceInfo serviceInfo;
try {
serviceInfo = packageManager.getServiceInfo(component, 0);
} catch (PackageManager.NameNotFoundException ignored) {
// Service is disabled.
return false;
}
if (serviceInfo.processName.equals(mainProcess)) {
CanaryLog.d("Did not expect service %s to run in main process %s", serviceClass, mainProcess);
// Technically we are in the service process, but we're not in the service dedicated process.
return false;
}
int myPid = android.os.Process.myPid();
ActivityManager activityManager =
(ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
ActivityManager.RunningAppProcessInfo myProcess = null;
List<ActivityManager.RunningAppProcessInfo> runningProcesses =
activityManager.getRunningAppProcesses();
if (runningProcesses != null) {
for (ActivityManager.RunningAppProcessInfo process : runningProcesses) {
if (process.pid == myPid) {
myProcess = process;
break;
}
}
}
if (myProcess == null) {
CanaryLog.d("Could not find running process for %d", myPid);
return false;
}
return myProcess.processName.equals(serviceInfo.processName);
}
源码分析
SDK初始化
mRefWatcher = LeakCanary.install(this);
这个是SDK向外暴露的方法，我们以此为入口进行源码的分析
public static RefWatcher install(Application application) {
return refWatcher(application).listenerServiceClass(DisplayLeakService.class)
.excludedRefs(AndroidExcludedRefs.createAppDefaults().build())
.buildAndInstall();
}
public static AndroidRefWatcherBuilder refWatcher(Context context) {
return new AndroidRefWatcherBuilder(context);
}
install方法首先初始化了一个AndroidRefWatcherBuilder类,然后通过listenerServiceClass方法设置了DisplayLeakService,这个类主要用于分析内存泄露的结果信息，然后发送通知给用户
public final class AndroidRefWatcherBuilder extends RefWatcherBuilder<AndroidRefWatcherBuilder> {
/** * Sets a custom {@link AbstractAnalysisResultService} to listen to analysis results. This * overrides any call to {@link #heapDumpListener(HeapDump.Listener)}. */
public AndroidRefWatcherBuilder listenerServiceClass(
Class<? extends AbstractAnalysisResultService> listenerServiceClass) {
return heapDumpListener(new ServiceHeapDumpListener(context, listenerServiceClass));
}
...
}
public class RefWatcherBuilder<T extends RefWatcherBuilder<T>> {
...
/** @see HeapDump.Listener */
public final T heapDumpListener(HeapDump.Listener heapDumpListener) {
this.heapDumpListener = heapDumpListener;
return self();
}
...
}
然后调用excludedRefs方法添加白名单，在AndroidExcludedRefs枚举类中定义了忽略列表信息，如果这些列表中的类发生了内存泄露，并不会显示出来，同时HeapAnalyzer计算GCRoot强引用路径，也会忽略这些类，如果你希望自己项目中某个类泄露的，但是不希望他显示，就可以把类添加到这个上面
public enum AndroidExcludedRefs {
// ######## Android SDK Excluded refs ########
ACTIVITY_CLIENT_RECORD__NEXT_IDLE(SDK_INT >= KITKAT && SDK_INT <= LOLLIPOP) {
@Override void add(ExcludedRefs.Builder excluded) {
excluded.instanceField("android.app.ActivityThread$ActivityClientRecord", "nextIdle")
.reason("Android AOSP sometimes keeps a reference to a destroyed activity as a"
+ " nextIdle client record in the android.app.ActivityThread.mActivities map."
+ " Not sure what's going on there, input welcome.");
}
}
...
}
最后调用了buildAndInstall方法，创建了一个RefWatcher对象并返回,这个对象是用于检测是否有对象未被回收导致的内存泄露
/** * Creates a {@link RefWatcher} instance and starts watching activity references (on ICS+). */
public RefWatcher buildAndInstall() {
RefWatcher refWatcher = build();
if (refWatcher != DISABLED) {
LeakCanary.enableDisplayLeakActivity(context);
ActivityRefWatcher.install((Application) context, refWatcher);
}
return refWatcher;
}
因为分析泄露是在另一个进程进行的，所以判断当前启动的Application是否在分析内存泄露的进程中，如果是就直接返回DISABLED,不在进行后续初始化，如果发现是在程序主进程中，就进行初始化
LeakCanary.enableDisplayLeakActivity(context);主要作用是调用PackageManager将DisplayLeakActivity设置为可用。
public static void enableDisplayLeakActivity(Context context) {
setEnabled(context, DisplayLeakActivity.class, true);
}
public static void setEnabled(Context context, final Class<?> componentClass, final boolean enabled) {
final Context appContext = context.getApplicationContext();
executeOnFileIoThread(new Runnable() {
@Override public void run() {
setEnabledBlocking(appContext, componentClass, enabled);
}
});
}
public static void setEnabledBlocking(Context appContext, Class<?> componentClass, boolean enabled) {
ComponentName component = new ComponentName(appContext, componentClass);
PackageManager packageManager = appContext.getPackageManager();
int newState = enabled ? COMPONENT_ENABLED_STATE_ENABLED : COMPONENT_ENABLED_STATE_DISABLED;
// Blocks on IPC.
packageManager.setComponentEnabledSetting(component, newState, DONT_KILL_APP);
}
从配置文件看LeakCanary这几个文件都是运行在新进程的，DisplayLeakActivity默认enable=false,这样就可以一开始隐藏启动图标
<application>
<service
android:name=".internal.HeapAnalyzerService"
android:process=":leakcanary"
android:enabled="false"/>
<service
android:name=".DisplayLeakService"
android:process=":leakcanary"
android:enabled="false"/>
<activity
android:theme="@style/leak_canary_LeakCanary.Base"
android:name=".internal.DisplayLeakActivity"
android:process=":leakcanary"
android:enabled="false"
android:label="@string/leak_canary_display_activity_label"
android:icon="@drawable/leak_canary_icon"
android:taskAffinity="com.squareup.leakcanary.${applicationId}">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
<activity
android:theme="@style/leak_canary_Theme.Transparent"
android:name=".internal.RequestStoragePermissionActivity"
android:process=":leakcanary"
android:taskAffinity="com.squareup.leakcanary.${applicationId}"
android:enabled="false"
android:excludeFromRecents="true"
android:icon="@drawable/leak_canary_icon"
android:label="@string/leak_canary_storage_permission_activity_label"/>
</application>
接着 ActivityRefWatcher.install((Application) context, refWatcher);这里把refWatcher当做参数传入，同时对Activity的生命周期进行了监听
public static void install(Application application, RefWatcher refWatcher) {
new ActivityRefWatcher(application, refWatcher).watchActivities();
}
public void watchActivities() {
// Make sure you don't get installed twice.
stopWatchingActivities();
application.registerActivityLifecycleCallbacks(lifecycleCallbacks);
}
public void stopWatchingActivities() {
application.unregisterActivityLifecycleCallbacks(lifecycleCallbacks);
}
private final Application.ActivityLifecycleCallbacks lifecycleCallbacks =
new Application.ActivityLifecycleCallbacks() {
@Override public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
}
@Override public void onActivityStarted(Activity activity) {
}
@Override public void onActivityResumed(Activity activity) {
}
@Override public void onActivityPaused(Activity activity) {
}
@Override public void onActivityStopped(Activity activity) {
}
@Override public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
}
@Override public void onActivityDestroyed(Activity activity) {
ActivityRefWatcher.this.onActivityDestroyed(activity);
}
};
void onActivityDestroyed(Activity activity) {
refWatcher.watch(activity);
}
首先就是注册Activity的生命周期的监听器lifecycleCallbacks，这个监听器可以监听项目中所有Activity的的生命周期，然后在Activity销毁调用onActivityDestroyed的时候，LeakCanary就会获取这个Activity，然后对其进行分析，看是否有内存泄露
分析内存泄露
这里分析对象是否内存泄露的是RefWatcher类，下面简单介绍一下这个类的成员变量
- WatchExecutor watchExecutor：确保任务在主线程进行，同时默认延迟5s执行任务，留时间给系统GC
- DebuggerControl debuggerControl：控制中心
- GcTrigger gcTrigger：内部调用
Runtime.getRuntime().gc(),手动触发GC - HeapDumper heapDumper：用于创建.hprof文件，用于储存head堆快照，可以知道哪些程序在大部分使用内存
- HeapDump.Listener heapdumpListener：分析结果完成后会告诉这个监听器
- ExcludedRefs excludedRefs：分析内存泄露的白名单
从上面可以看出，每当Activity销毁，就会调用RefWatcher的watch方法，去分析是否是内存泄露
public void watch(Object watchedReference) {
watch(watchedReference, "");
}
public void watch(Object watchedReference, String referenceName) {
if (this == DISABLED) {
return;
}
checkNotNull(watchedReference, "watchedReference");
checkNotNull(referenceName, "referenceName");
final long watchStartNanoTime = System.nanoTime();
String key = UUID.randomUUID().toString();
retainedKeys.add(key);
final KeyedWeakReference reference =
new KeyedWeakReference(watchedReference, key, referenceName, queue);
ensureGoneAsync(watchStartNanoTime, reference);
}
上面代码主要作用是，先生成一个随机数key放在retainedKeys容器里，用来区分对象是否被回收，创建了一个弱引用，然后把要分析的Activity对象存入，然后调用了ensureGoneAsync方法
private void ensureGoneAsync(final long watchStartNanoTime, final KeyedWeakReference reference) {
watchExecutor.execute(new Retryable() {
@Override public Retryable.Result run() {
return ensureGone(reference, watchStartNanoTime);
}
});
}
然后用watchExecutor去调度分析任务，这个主要是保证，在主线程进行，延迟5s，让系统有时间GC
@SuppressWarnings("ReferenceEquality") // Explicitly checking for named null.
Retryable.Result ensureGone(final KeyedWeakReference reference, final long watchStartNanoTime) {
long gcStartNanoTime = System.nanoTime();
long watchDurationMs = NANOSECONDS.toMillis(gcStartNanoTime - watchStartNanoTime);
removeWeaklyReachableReferences();
if (debuggerControl.isDebuggerAttached()) {
// The debugger can create false leaks.
return RETRY;
}
if (gone(reference)) {
return DONE;
}
gcTrigger.runGc();
removeWeaklyReachableReferences();
if (!gone(reference)) {
long startDumpHeap = System.nanoTime();
long gcDurationMs = NANOSECONDS.toMillis(startDumpHeap - gcStartNanoTime);
File heapDumpFile = heapDumper.dumpHeap();
if (heapDumpFile == RETRY_LATER) {
// Could not dump the heap.
return RETRY;
}
long heapDumpDurationMs = NANOSECONDS.toMillis(System.nanoTime() - startDumpHeap);
heapdumpListener.analyze(
new HeapDump(heapDumpFile, reference.key, reference.name, excludedRefs, watchDurationMs,
gcDurationMs, heapDumpDurationMs));
}
return DONE;
}
private void removeWeaklyReachableReferences() {
// 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.
KeyedWeakReference ref;
while ((ref = (KeyedWeakReference) queue.poll()) != null) {
retainedKeys.remove(ref.key);
}
}
private boolean gone(KeyedWeakReference reference) {
return !retainedKeys.contains(reference.key);
}
首先通过removeWeaklyReachableReferences()方法，尝试从弱引用队列获取待分析对象，如果不为空说明被系统回收了，就把retainedKeys中的key值移除，如果被系统回收直接返回DONE，如果没有被系统回收，就手动调用 gcTrigger.runGc();手动触发系统gc,然后再次调用removeWeaklyReachableReferences()方法，如过还是为空，则判断为内存泄露
GcTrigger DEFAULT = new GcTrigger() {
@Override public void runGc() {
// Code taken from AOSP FinalizationTest:
// https://android.googlesource.com/platform/libcore/+/master/support/src/test/java/libcore/
// java/lang/ref/FinalizationTester.java
// System.gc() does not garbage collect every time. Runtime.gc() is
// more likely to perfom a gc.
Runtime.getRuntime().gc();
enqueueReferences();
System.runFinalization();
}
private void enqueueReferences() {
// Hack. We don't have a programmatic way to wait for the reference queue daemon to move
// references to the appropriate queues.
try {
Thread.sleep(100);
} catch (InterruptedException e) {
throw new AssertionError();
}
}
};
手动触发GC后，调用enqueueReferences方法沉睡100ms，给系统GC时间， System.runFinalization();，这个是强制调用已失去引用对象的finalize方法
确定有内存泄漏后，调用heapDumper.dumpHeap();生成.hprof文件，然后回调到heapdumpListener监听，这个监听实现是ServiceHeapDumpListener类，会调analyze()方法
public final class ServiceHeapDumpListener implements HeapDump.Listener {
...
@Override public void analyze(HeapDump heapDump) {
checkNotNull(heapDump, "heapDump");
HeapAnalyzerService.runAnalysis(context, heapDump, listenerServiceClass);
}
}
HeapDump是一个modle类，里面用于储存一些分析类强引用的需要信息 HeapAnalyzerService.runAnalysis方法是发送了一个intent，启动了HeapAnalyzerService服务，这是一个intentService
public static void runAnalysis(Context context, HeapDump heapDump,
Class<? extends AbstractAnalysisResultService> listenerServiceClass) {
Intent intent = new Intent(context, HeapAnalyzerService.class);
intent.putExtra(LISTENER_CLASS_EXTRA, listenerServiceClass.getName());
intent.putExtra(HEAPDUMP_EXTRA, heapDump);
context.startService(intent);
}
启动服务后，会在onHandleIntent方法启动分析，找到内存泄露的引用关系
@Override
protected void onHandleIntent(Intent intent) {
if (intent == null) {
CanaryLog.d("HeapAnalyzerService received a null intent, ignoring.");
return;
}
String listenerClassName = intent.getStringExtra(LISTENER_CLASS_EXTRA);
HeapDump heapDump = (HeapDump) intent.getSerializableExtra(HEAPDUMP_EXTRA);
HeapAnalyzer heapAnalyzer = new HeapAnalyzer(heapDump.excludedRefs);
AnalysisResult result = heapAnalyzer.checkForLeak(heapDump.heapDumpFile, heapDump.referenceKey);
AbstractAnalysisResultService.sendResultToListener(this, listenerClassName, heapDump, result);
}
找到引用关系
- 启动分析内存泄露的服务后，会实例化一个
HeapAnalyzer对象,然后调用checkForLeak方法来分析最终得到的结果， checkForLeak这里用到了Square的另一个库haha，哈哈哈哈哈，名字真的就是叫这个，开源地址：github.com/square/haha…- 得到结果后调用
AbstractAnalysisResultService.sendResultToListener()方法,这个方法启动了另一个服务
public static void sendResultToListener(Context context, String listenerServiceClassName,
HeapDump heapDump, AnalysisResult result) {
Class<?> listenerServiceClass;
try {
listenerServiceClass = Class.forName(listenerServiceClassName);
} catch (ClassNotFoundException e) {
throw new RuntimeException(e);
}
Intent intent = new Intent(context, listenerServiceClass);
intent.putExtra(HEAP_DUMP_EXTRA, heapDump);
intent.putExtra(RESULT_EXTRA, result);
context.startService(intent);
}
listenerServiceClassName就是开始LeakCanary.install方法传入的DisplayLeakService，它本身也是一个intentService
@Override
protected final void onHandleIntent(Intent intent) {
HeapDump heapDump = (HeapDump) intent.getSerializableExtra(HEAP_DUMP_EXTRA);
AnalysisResult result = (AnalysisResult) intent.getSerializableExtra(RESULT_EXTRA);
try {
onHeapAnalyzed(heapDump, result);
} finally {
//noinspection ResultOfMethodCallIgnored
heapDump.heapDumpFile.delete();
}
}
然后调用自身的onHeapAnalyzed方法
protected final void onHeapAnalyzed(HeapDump heapDump, AnalysisResult result) {
String leakInfo = LeakCanary.leakInfo(this, heapDump, result, true);
CanaryLog.d("%s", new Object[]{leakInfo});
boolean resultSaved = false;
boolean shouldSaveResult = result.leakFound || result.failure != null;
if(shouldSaveResult) {
heapDump = this.renameHeapdump(heapDump);
resultSaved = this.saveResult(heapDump, result);
}
PendingIntent pendingIntent;
String contentTitle;
String contentText;
// 设置消息通知的 pendingIntent/contentTitle/contentText
...
int notificationId1 = (int)(SystemClock.uptimeMillis() / 1000L);
LeakCanaryInternals.showNotification(this, contentTitle, contentText, pendingIntent, notificationId1);
this.afterDefaultHandling(heapDump, result, leakInfo);
}
这个方法首先判断是否需要把信息存到本地，如果需要就存到本地，然后设置消息通知的基本信息，最后通过LeakCanaryInternals.showNotification方法调用系统的系统通知栏，告诉用户有内存泄露
至此LeakCanary的检测内存泄露源码，已经分析完了
今天的文章Android LeakCanary的使用和原理分享到此就结束了，感谢您的阅读。
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