• 主要是获取dialog 的BottomSheetBehavior 然后设置 setPeekHeight 和 BottomSheetCallback.

code

public class BottomSheetFragment extends BottomSheetDialogFragment {

    private Button button;
    private View contentView;
    //
    private BottomSheetBehavior<View> mBottomSheetBehavior;
    private BottomSheetBehavior.BottomSheetCallback mBottomSheetBehaviorCallback
            = new BottomSheetBehavior.BottomSheetCallback() {

        @Override
        public void onStateChanged(@NonNull View bottomSheet, int newState) {
            //禁止拖拽，
            if (newState == BottomSheetBehavior.STATE_DRAGGING) {
                //设置为收缩状态
                mBottomSheetBehavior.setState(BottomSheetBehavior.STATE_COLLAPSED);
            }
        }
        @Override
        public void onSlide(@NonNull View bottomSheet, float slideOffset) {
        }
    };


    @Override
    public void onStart() {
        super.onStart();
        Dialog dialog = getDialog();

        if (dialog != null) {
            View bottomSheet = dialog.findViewById(R.id.design_bottom_sheet);
            bottomSheet.getLayoutParams().height = ViewGroup.LayoutParams.MATCH_PARENT;
        }
        final View view = getView();
        view.post(new Runnable() {
            @Override
            public void run() {
                View parent = (View) view.getParent();
                CoordinatorLayout.LayoutParams params = (CoordinatorLayout.LayoutParams) (parent).getLayoutParams();
                CoordinatorLayout.Behavior behavior = params.getBehavior();
                mBottomSheetBehavior = (BottomSheetBehavior) behavior;
                mBottomSheetBehavior.setBottomSheetCallback(mBottomSheetBehaviorCallback);
                Display display = getActivity().getWindowManager().getDefaultDisplay();
                //设置高度
                int height = display.getHeight() / 2;
                mBottomSheetBehavior.setPeekHeight(height);

                parent.setBackgroundColor(Color.TRANSPARENT);
            }
        });
    }


    private void findView() {
        button = contentView.findViewById(R.id.button);
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
                             @Nullable Bundle savedInstanceState) {
        contentView = inflater.inflate(R.layout.bottom_sheet_dialog_content_view, container,
                false);
        findView();

        return contentView;
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        button.setText(TAG);
    }
}