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from this picture, the root lies in your brother's obj citation of Message, and the other citation is all WeakReference. Do you use any Handler to send messages?

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solution: rewrite onActivityCreated, to set all three Listener to empty

override fun onActivityCreated(savedInstanceState: Bundle?) {
    super.onActivityCreated(savedInstanceState)
    dialog.setOnShowListener(null)
    dialog.setOnCancelListener(null)
    dialog.setOnDismissListener(null)
}

I hope to adopt it, thank you!

problem analysis: there is an onActivityCreated method in
DialogFragment. Android implements this method by default:

public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        if (this.mShowsDialog) {
            View view = this.getView();
            if (view != null) {
                if (view.getParent() != null) {
                    throw new IllegalStateException("DialogFragment can not be attached to a container view");
                }

                this.mDialog.setContentView(view);
            }

            Activity activity = this.getActivity();
            if (activity != null) {
                this.mDialog.setOwnerActivity(activity);
            }

            this.mDialog.setCancelable(this.mCancelable);
            this.mDialog.setOnCancelListener(this);
            this.mDialog.setOnDismissListener(this);
            if (savedInstanceState != null) {
                Bundle dialogState = savedInstanceState.getBundle("android:savedDialogState");
                if (dialogState != null) {
                    this.mDialog.onRestoreInstanceState(dialogState);
                }
            }

        }
    }

SetOnCancelListener and setOnDismissListener are set by default in

code

this.mDialog.setOnCancelListener(this);
this.mDialog.setOnDismissListener(this);

use setOnDismissListener to analyze, setOnCancelListener is the same:

// Dialog 
private Message mDismissMessage;

// DialogmDismissMessage;
public void setOnDismissListener(@Nullable OnDismissListener listener) {
        if (mCancelAndDismissTaken != null) {
            throw new IllegalStateException(
                    "OnDismissListener is already taken by "
                    + mCancelAndDismissTaken + " and can not be replaced.");
        }
        if (listener != null) { // listenerMessage
            mDismissMessage = mListenersHandler.obtainMessage(DISMISS, listener);
        } else {
            mDismissMessage = null;
        }
    }

definition of mListenersHandler:

private static final class ListenersHandler extends Handler {
        private final WeakReference<DialogInterface> mDialog;

        public ListenersHandler(Dialog dialog) {
            mDialog = new WeakReference<>(dialog);
        }

        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case DISMISS:
                    ((OnDismissListener) msg.obj).onDismiss(mDialog.get());
                    break;
                case CANCEL:
                    ((OnCancelListener) msg.obj).onCancel(mDialog.get());
                    break;
                case SHOW:
                    ((OnShowListener) msg.obj).onShow(mDialog.get());
                    break;
            }
        }
    }

ListenersHandler mainly calls the implementation of Listener through Handler when dealing with Listener.

call location:
when the pop-up window is closed

@Override
    public void dismiss() {
        if (Looper.myLooper() == mHandler.getLooper()) {
            dismissDialog(); // 
        } else {
            mHandler.post(mDismissAction);
        }
    }
    
void dismissDialog() {
        if (mDecor == null || !mShowing) {
            return;
        }

        if (mWindow.isDestroyed()) {
            Log.e(TAG, "Tried to dismissDialog() but the Dialog's window was already destroyed!");
            return;
        }

        try {
            mWindowManager.removeViewImmediate(mDecor);
        } finally {
            if (mActionMode != null) {
                mActionMode.finish();
            }
            mDecor = null;
            mWindow.closeAllPanels();
            onStop();
            mShowing = false;

            sendDismissMessage(); // 
        }
    }
    
    private void sendDismissMessage() {
        if (mDismissMessage != null) {
            // Obtain a new message so this dialog can be re-used
            Message.obtain(mDismissMessage).sendToTarget(); // HandlerHandlermListenersHandler(ListenersHandler)
        }
    }

because mDismissMessage is a global variable, obj references Listener (DialogFragment), Dialog references mDismissMessage, holds references to each other, there is a number of references, resulting in a memory leak.

if there are any problems in the analysis, please correct them, thank you.

reference: https://www.cnblogs.com/endur.

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@ Coolspan Brother's use is wrong. If set to empty, the displayed Dialog will be redisplayed after Activity returns to the background and then re-enters!

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https://www.imooc.com/article.