How does LeakCanary detect memory leaks?

LeakCanary works in several stages:

1. Detecting leaks: It monitors the lifecycle of observed objects such as Fragment, Activity, View. When such an object is destroyed, LeakCanary places it in a WeakReference and triggers garbage collection.
2. Checking for references: After garbage collection, LeakCanary checks if a reference to the object still exists. If it does, it means the object was not collected and a leak likely occurred.
3. Heap dump: If a potential leak is detected, LeakCanary performs a heap dump of the application. This is a snapshot of all memory occupied by application objects at a specific moment.
4. Analyzing the object graph: LeakCanary analyzes the object graph in the heap dump to find a path from GC roots to the suspected leaking object. This path shows why the object was not collected.
5. Reporting: Based on the analysis, LeakCanary generates a report with detailed leak information, including the retention path (which object holds a reference to the leaked object), object type, and the location in the code where the leak probably occurred. The report is displayed as a notification or within the app.

// Example of simple object A tracking after its destruction
@Override
protected void onDestroy() {
    super.onDestroy();
    // Wrap the object in a WeakReference and pass it to LeakCanary
    refWatcher.watch(this);
}

LeakCanary uses its own parsers and algorithms to analyze hprof files (heap dump format) to efficiently find object retention paths.