android - Preventing/catching "IllegalArgumentException: parameter must be a descendant of this view" error

Question

I have a ListView with some focusable components inside (mostly EditTexts). Yeah, I know this isn't exactly recommended, but in general, almost everything is working fine and the focus goes where it has to go (with a few tweaks I had to code). Anyway, my problem is that there's a weird race condition when scrolling the list with your finger and then suddenly using the trackball when the IME keyboard is being displayed. Something must go out of bounds and get recycled at which point the offsetRectBetweenParentAndChild() method must kick in and throw the IllegalArgumentException.

The problem is that this exception is thrown outside of any block in which I can insert a try/catch (as far as I know). So there are two valid solutions to this question, either:

1. Someone knows why this exception being thrown and how to stop it from happening
2. Someone knows how to put a try/catch block somewhere that will at least let my application survive. As far as I know the problem is that of focus, so it definitely shouldn't kill my application (which is what it's doing). I tried overriding the ViewGroup's methods but those two offset* methods are marked as final.

Stack trace:

08-17 18:23:09.825: ERROR/AndroidRuntime(1608): FATAL EXCEPTION: main
08-17 18:23:09.825: ERROR/AndroidRuntime(1608): java.lang.IllegalArgumentException: parameter must be a descendant of this view
08-17 18:23:09.825: ERROR/AndroidRuntime(1608):     at android.view.ViewGroup.offsetRectBetweenParentAndChild(ViewGroup.java:2633)
08-17 18:23:09.825: ERROR/AndroidRuntime(1608):     at android.view.ViewGroup.offsetDescendantRectToMyCoords(ViewGroup.java:2570)
08-17 18:23:09.825: ERROR/AndroidRuntime(1608):     at android.view.ViewRoot.scrollToRectOrFocus(ViewRoot.java:1624)
08-17 18:23:09.825: ERROR/AndroidRuntime(1608):     at android.view.ViewRoot.draw(ViewRoot.java:1357)
08-17 18:23:09.825: ERROR/AndroidRuntime(1608):     at android.view.ViewRoot.performTraversals(ViewRoot.java:1258)
08-17 18:23:09.825: ERROR/AndroidRuntime(1608):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1859)
08-17 18:23:09.825: ERROR/AndroidRuntime(1608):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-17 18:23:09.825: ERROR/AndroidRuntime(1608):     at android.os.Looper.loop(Looper.java:130)
08-17 18:23:09.825: ERROR/AndroidRuntime(1608):     at android.app.ActivityThread.main(ActivityThread.java:3683)
08-17 18:23:09.825: ERROR/AndroidRuntime(1608):     at java.lang.reflect.Method.invokeNative(Native Method)
08-17 18:23:09.825: ERROR/AndroidRuntime(1608):     at java.lang.reflect.Method.invoke(Method.java:507)
08-17 18:23:09.825: ERROR/AndroidRuntime(1608):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
08-17 18:23:09.825: ERROR/AndroidRuntime(1608):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
08-17 18:23:09.825: ERROR/AndroidRuntime(1608):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

While Bruce's answer does solve the problem, it does it in a very brutal way which harms the UX, as it will clear the focus of every view once we did a scroll.

It deals with the symptom of the problem but it does not solve the actual cause.

how to reproduce the problem:

Your EditText has focus and the keyboard is opened, you then scroll till the point the EditText is off the screen, and it wasn't recycled to a new EditText that is now shown.

Let's first understand why this problem happens:

ListView recycles its views and uses them again as you all know, but sometimes it does not need to use a view that has gone off the screen immediately so it keeps it for future use, and because it doesn't need to be shown anymore it will detach it causing that view.mParent to be null. however the keyboard needs to know how to pass the input to, and it does it by choosing the focused view, or EditText to be precise.

So the problem is that we have an EditText who has the focus, but suddenly does not have a parent, so we get a "parameter must be a descendant of this view” error. makes sense.

By using the scroll listener we are causing more problems.

The Solution:

We need to listen to an event which will tell us when a view has gone to the side heap and is no longer attached, luckily ListView exposes this event.

listView.setRecyclerListener(new AbsListView.RecyclerListener() {
        @Override
        public void onMovedToScrapHeap(View view) {
            if ( view.hasFocus()){
                view.clearFocus(); //we can put it inside the second if as well, but it makes sense to do it to all scraped views
                //Optional: also hide keyboard in that case
                if ( view instanceof EditText) {
                    InputMethodManager imm = (InputMethodManager) view.getContext().getSystemService(Context.INPUT_METHOD_SERVICE);
                    imm.hideSoftInputFromWindow(view.getWindowToken(), 0);
                }
            }
        }
    });