android - Why does repeated Replace Fragment leak memory?

Question

As shown in the figure, when the two buttons below are clicked, REPALCEThere are two Fragmnets above, and a memory leak occurs when switching repeatedly

This is the code of Fragment:

public class Fragment2 extends Fragment {

    private List<Bitmap> lb = new ArrayList<>();

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        allocBitMap();
        allocBitMap();
        return inflater.inflate(R.layout.f2, container, false);
    }

    private void allocBitMap() {
        Bitmap b = BitmapFactory.decodeResource(getResources(), R.drawable.men);
        lb.add(b);
    }

    @Override
    public void onDestroy() {
        Log.e("onDestroy", "yes, onDestroy");
        super.onDestroy();
    }
}

This is part of the activity code

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.bt_left:
                transFragleft();
                break;
            case R.id.bt_right:
                transFragright();
                break;
        }
    }

    Fragment f1 = new Fragment1();
    Fragment f2 = new Fragment2();

    private void transFragleft(){
        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        ft.replace(R.id.rl_f, f1);
        ft.commit();
    }

    private void transFragright(){
        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        ft.replace(R.id.rl_f, f2);
        ft.commit();
    }

This is the memory status when switching repeatedly:

This is LOGCAT. You can see that onDestroy is executed and the entire Fragment life cycle ends immediately

04-27 09:46:04.682 29320-29320/com.sg.fragmentpitfall E/onDestroy: yes, onDestroy
04-27 09:46:06.344 29320-29320/com.sg.fragmentpitfall E/onDestroy: yes, onDestroy
04-27 09:46:07.895 29320-29320/com.sg.fragmentpitfall E/onDestroy: yes, onDestroy

So why is the memory he occupied still there?

Question 2:
How to allocate a certain amount of memory in JAVA for experiments? My bitmap method is too low, and there is CONTEXT in it;

Question 3:
Should we avoid using FRAGMENT (I know that using HIDE/SHOW is better than REPLACE

Thanks!

Answer 1

Integrate LeakCanary into the code to see what causes the memory leak.
And if the memory graph rises, it does not necessarily mean a memory leak. Every time you apply for a Bitmap, it may not meet the GC standards, so it’s no problem if the memory keeps increasing.

Answer 2

It’s not the fragment’s problem, it’s the bitmap you use