Java – why doesn’t Android clean up memory after completing the activity?

In my case, I have two activities called a (main activities) and B (children's activities)

If I use Android memory monitor to get memory allocation, I can clearly see the memory allocation increase This is completely normal, because we did some image related things in the activity

So my problem is that if I press the button in activity B, it will enter activity a and the allocated memory will not be cleared Memory allocation will remain the same

Is this normal Android behavior?

If not, how can I manually clean up the memory?

I manually run GC as follows, but the same result has no luck: (

In activity B

@Override
    protected void onDestroy() {
       super.onDestroy();
       System.gc();
    }

Solution

1) Ondestroy is called when finish(); When called, simply press the back button and this method will not be called unless you program it

2)System. gc(); It will not work in ondestroy because your activity B is still active in ondestroy Once the activity B is completely terminated, you should call this method from other activities.

3) If the activity context is leaked to long-standing objects / threads / etc., the activity will remain in memory even if ondestroy is called (memory leak)

Note: call system gc(); Not only does it release your memory, it may not perform GC according to the situation See why is it bad practice to call system gc()?