fix deallocated clipboard/emoji views

[codokie]

When keyboard instance is destroyed (such as by switching to another keyboard), postDeallocateMemory() is issued by the handler of LatinIME, and the clipboard and emoji views memory is deallocated after 10 seconds (the delay of the message) even if the keyboard instance is recreated in the meantime.
cancelDeallocateMemory() does not seem to remove the pending message for some reason.
That causes all emojis/clipboard entries to suddenly vanish.

Here is a video taken from #616 showing how to reproduce the bug (credit to @Uranusek)

318530574-e4556051-3029-40b4-a479-ff27fc7df453.mp4

With the small check I altered, the memory of those views will not be deallocated any longer when they are visible

[codokie]

public void deallocateMemory() {
    if (mKeyboardView != null) {
        mKeyboardView.cancelAllOngoingEvents();
        mKeyboardView.deallocateMemory();
    }
...

I wonder if the keyboard view should be deallocated even when it is visible?
I have a feeling it shouldn't but I'm not sure if there would be any implications

[Helium314]

If we go this way, shouldn't mKeyboardView receive a similar check?
[edit: sorry, didn't see your post. So we have the same question]

But I would prefer understanding why the message is not canceled. Maybe this is also happening for other messages, potentially causing other bugs.

[Helium314]

Looks like this is a weird interaction of multiple instances of the service:

1. (LatinIme & handler) instance a is used initially, and destroyed when switching the keyboard. postDeallocateMemory is executed after LatinIME.onDestroy is finished. (apparently the system first destroys the service, and then calls onFinishInputView)
2. When switching back, instance b is created and initially calls cancelDeallocateMemory, but instance b doesn't have any pending messages.
3. A few seconds later, instance a receives the message and calls , which somehow finds the way to the current views.

[Helium314]

An alternative solution would be to add mHandler.removeAllMessages() at the end of LatinIME's onDestroy

This would be the way to go, the garbage collection should handle the rest anyway.

[Helium314]

Still deallocating memory definitely is a good idea, thanks!