Android BottomSheetBehavior setState() NullPointerException

user_5567192 0
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I'm trying to implement BottomSheetBehavior from Android Support Design Library. I initialize BottomSheetBehavior like this:

private void initBottomSheet() {
        new AsyncTask<Void, Void, Void>() {

            View bottomSheetFrame = rootView.findViewById(R.id.bottom_sheet);

            }

            @Override
            protected Void doInBackground(Void... params) {
                bottomSheetBehavior = BottomSheetBehavior.from(bottomSheetFrame);

                bottomSheetBehavior.setBottomSheetCallback(new BottomSheetBehavior.BottomSheetCallback() {
                    private boolean isOnTop = false;

                    @Override
                    public void onStateChanged(@NonNull View bottomSheet, int newState) {
                        switch (newState) {

                            case BottomSheetBehavior.STATE_DRAGGING: {
                                ...
                            }

                            case BottomSheetBehavior.STATE_SETTLING: {
                                ...
                            }

                            case BottomSheetBehavior.STATE_EXPANDED: {
                               ...
                            }

                            case BottomSheetBehavior.STATE_COLLAPSED: {
                                ...
                            }

                            case BottomSheetBehavior.STATE_HIDDEN: {
                                ...
                            }

                            default: {
                                break;
                            }
                        }
                    }

                    @Override
                    public void onSlide(@NonNull View bottomSheet, float slideOffset) {
                        ...
                });

                bottomSheetBehavior.setPeekHeight((int) Utils.convertDpToPixel(100f, activityContext));
                    bottomSheetBehavior.setState(BottomSheetBehavior.STATE_HIDDEN); // NPE here

                return null;
            }

            @Override
            protected void onPostExecute(Void aVoid) {
                super.onPostExecute(aVoid);
            }
        }.execute();
    }

It's very strange, because I can change state with Button click or some other action. Please, help me.

android-design-library android-support-library nullpointerexception android java
2 Answers

If you are using it in a Fragment, just be sure to call it on the onCreateView() method. And if you are using it on an Activity, then call it at the onCreate() method.

At those points, your Views have to be already created, unless you are creating them programmatically.

Since you are calling methods that are related with the UI from an AsyncTask, then you'll need to surround it with the runOnUiThread as explained here https://stackoverflow.com/a/27992603/973919

Basically, you need to call to anything that is related with views, from the main thread of the app, which is the UI thread.

user_9739190
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