Leakcanary source code (2)

Then the source code of the previous article , Analyze the meaning of the core code in this figure ：
moveToRetained Method
And then there was onObjectRetained Method

It is actually added here in the code below

This method points to scheduleRetainedObjectCheck, As you can see, it calls heapDumpTrigger.scheduleRetainedObjectCheck()
, Let's see. heapDumpTrigger.scheduleRetainedObjectCheck(), Look at the breakpoint method checkRetainedObjects()
a key 3 individual , The first place is to call gc, The second place , Check for residual object, If there is any residue in the third place , To inform users , Is a memory leak alert
Let's look at the details in the third place. The key point is This PendingIntent, Use FLAG_IMMUTABLE The tag builds a that cannot be modified PendingIntent.

call NotificationManagerCompat.notify() Then the work is finished . When the system displays a notification , And when the user clicks the notification , It will be in our PendingIntent On the call PendingIntent.send(), To start the broadcast of our application , Only then will I go heap dump , This is a bit lazy to load into the meaning of it , ha-ha . It's all details .

（sample in Click on recreate Button on the There is one checkRetainedObjects scheduleRetainedObjectCheck checkRetainedObjects loop , I don't know what the intention is ）

In the picture below , We can see that after we click on the notification , See what the code does

 fun onDumpHeapReceived(forceDump: Boolean) {
    
    backgroundHandler.post {
    
      dismissNoRetainedOnTapNotification()
      gcTrigger.runGc()
      val retainedReferenceCount = objectWatcher.retainedObjectCount
      if (!forceDump && retainedReferenceCount == 0) {
    
        SharkLog.d {
     "Ignoring user request to dump heap: no retained objects remaining after GC" }
        @Suppress("DEPRECATION")
        val builder = Notification.Builder(application)
          .setContentTitle(
            application.getString(R.string.leak_canary_notification_no_retained_object_title)
          )
          .setContentText(
            application.getString(
              R.string.leak_canary_notification_no_retained_object_content
            )
          )
          .setAutoCancel(true)
          .setContentIntent(NotificationReceiver.pendingIntent(application, CANCEL_NOTIFICATION))
        val notification =
          Notifications.buildNotification(application, builder, LEAKCANARY_LOW)
        notificationManager.notify(
          R.id.leak_canary_notification_no_retained_object_on_tap, notification
        )
        backgroundHandler.postDelayed(
          scheduleDismissNoRetainedOnTapNotification,
          DISMISS_NO_RETAINED_OBJECT_NOTIFICATION_MILLIS
        )
        lastDisplayedRetainedObjectCount = 0
        return@post
      }

      SharkLog.d {
     "Dumping the heap because user requested it" }
      dumpHeap(retainedReferenceCount, retry = false, "user request")
    }

Focus on the last line dumpheap Really start collecting hprof The file .

Heap Dump Also called heap dump file , It's a Java Memory snapshot of the process at a certain point in time .Heap Dump There are many types of . But on the whole heap dump It is saved when the snapshot is triggered java Information about objects and classes . Usually writing heap dump It will trigger once before the file FullGC, therefore heap dump What's in the file is FullGC The object information left after .
In the end, we found that what we really did was Debug To pick up hprof file .

unfinished , To be continued ...