監測記憶體洩漏神兵利器：LeakCanary原始碼分析
摘要：
1 在全域性Application類中註冊：
LeakCanary.install(this);
點進去看原始碼：
public static RefWatcher install(Application application) {...
1 在全域性Application類中註冊：
LeakCanary.install(this);
點進去看原始碼：
public static RefWatcher install(Application application) {
return refWatcher(application)// 1-1
.listenerServiceClass(DisplayLeakService.class)// 1-2
.excludedRefs(AndroidExcludedRefs.createAppDefaults().build())//1-3
.buildAndInstall();// 1-4 和 2-1
}
原始碼分為四部分：
- 1-1refWatcher(application) 建立一個 AndroidRefWatcherBuilder 物件
- 1-2.listenerServiceClass(DisplayLeakService.class) 傳入DisplayLeakService，該Service的主要作用是分析記憶體堆資訊，分析出記憶體洩漏的位置；
-
1-3.excludedRefs(AndroidExcludedRefs.createAppDefaults().build())
- 1-3-1AndroidExcludedRefs.createAppDefaults().build() 幫助分析跟蹤洩漏的軌跡的物件
- 1-4.buildAndInstall() 建立RefWatcher物件
2 RefWatcher 監聽記憶體洩漏（1-4中開始）:
2-1RefWatcher將全域性的context傳入
public RefWatcher buildAndInstall() {
RefWatcher refWatcher = build();
if (refWatcher != DISABLED) {
LeakCanary.enableDisplayLeakActivity(context);
ActivityRefWatcher.install((Application) context, refWatcher);//重點 2-2
}
return refWatcher;
}
2-2建立一個ActivityRefWatcher() 物件
public static void install(Application application, RefWatcher refWatcher) {
new ActivityRefWatcher(application, refWatcher).watchActivities();
}
2-3 ActivityRefWather物件中的重點方法監聽Activity的生命週期，在Activity銷燬時，呼叫RefWatcher的方法：
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);//重點呼叫 2-4
}
};
2-4 ActivityRefWatcher.this.onActivityDestroyed(activity)將Activity新增到監測佇列中：
void onActivityDestroyed(Activity activity) {
refWatcher.watch(activity);
}
public void watch(Object watchedReference) {
watch(watchedReference, "");
}
3watch()方法：將Activity封裝為弱引用物件，檢視是否被回收
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);//重點3-1
ensureGoneAsync(watchStartNanoTime, reference);// 重點 3-2
}
- 3-1 通過例項一個帶有鍵值的弱引用 KeyedWeakReference，將Activity唯一標識；
- 3-2 開啟一個執行緒，開始監測該Activity是否被回收，在gc後會呼叫：
private void ensureGoneAsync(final long watchStartNanoTime, final KeyedWeakReference reference) {
watchExecutor.execute(new Retryable() {
@Override public Retryable.Result run() {
return ensureGone(reference, watchStartNanoTime);//4-1
}
});
}
4 監測分析的最重點方法 ensureGone()
Retryable.Result ensureGone(final KeyedWeakReference reference, final long watchStartNanoTime) {
long gcStartNanoTime = System.nanoTime();
long watchDurationMs = NANOSECONDS.toMillis(gcStartNanoTime - watchStartNanoTime); //gc結束的時間
removeWeaklyReachableReferences();// 4-1
if (debuggerControl.isDebuggerAttached()) {
// The debugger can create false leaks.
return RETRY;
}
if (gone(reference)) {// 4-2
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;
}
- 4-1removeWeaklyReachableReferences()：將存入到ReferenceQueue<Object>queue這個佇列中的、現在不為空的，將其對應的鍵值消除，剩下的就是為空的引用；
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);
}
}
-
4-2gone(reference) ：當前 retainedKeys（是Set<String>型別） 中，已經沒有改Activity對應的引用了，證明在4-1中，已經被移除；也證明了在引用佇列queue中，該Activity不為空；
該ReferenceQueue<Object>queue的作用是：每次WeakReference所指向的物件被GC後，這個弱引用都會被放入這個與之相關聯的ReferenceQueue佇列中。所以在佇列中不為空的Activity就是被回收掉的Activity。
private boolean gone(KeyedWeakReference reference) {
return !retainedKeys.contains(reference.key);
}
-
4-3引用佇列ReferenceQueue原始碼分析 ：
ofollow,noindex">https://blog.csdn.net/Jesministrator/article/details/78786162