我想在数据绑定结构中设置动态布局高度.

我试了一下,但我得到了这个例外：

java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.Integer.intValue()' on a null object reference
                  at databinding.ItemGroupCommentsBinding.executeBindings(ItemGroupCommentsBinding.java:147)
                  at android.databinding.ViewDataBinding.executePendingBindings(ViewDataBinding.java:355)
                  at view.base.adapter.DataBindingAdapter.onBindViewHolder(DataBindingAdapter.java:32)
                  at view.base.adapter.DataBindingAdapter.onBindViewHolder(DataBindingAdapter.java:15)
                  at android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:6279)
                  at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:6312)
                  at android.support.v7.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:5258)
                  at android.support.v7.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:5521)
                  at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5363)
                  at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5359)
                  at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2141)
                  at android.support.v7.widget.GridLayoutManager.layoutChunk(GridLayoutManager.java:556)
                  at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1488)
                  at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:585)
                  at android.support.v7.widget.GridLayoutManager.onLayoutChildren(GridLayoutManager.java:170)
                  at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3506)
                  at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3254)
                  at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3767)
                  at android.view.View.layout(View.java:15604)
                  at android.view.ViewGroup.layout(ViewGroup.java:4966)
                  at android.support.v4.widget.SwipeRefreshLayout.onLayout(SwipeRefreshLayout.java:636)
                  at android.view.View.layout(View.java:15604)
                  at android.view.ViewGroup.layout(ViewGroup.java:4966)
                  at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1076)
                  at android.view.View.layout(View.java:15604)
                  at android.view.ViewGroup.layout(ViewGroup.java:4966)
                  at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
                  at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
                  at android.view.View.layout(View.java:15604)
                  at android.view.ViewGroup.layout(ViewGroup.java:4966)
                  at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
                  at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
                  at android.view.View.layout(View.java:15604)
                  at android.view.ViewGroup.layout(ViewGroup.java:4966)
                  at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
                  at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
                  at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
                  at android.view.View.layout(View.java:15604)
                  at android.view.ViewGroup.layout(ViewGroup.java:4966)
                  at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
                  at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
                  at android.view.View.layout(View.java:15604)
                  at android.view.ViewGroup.layout(ViewGroup.java:4966)
                  at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
                  at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
                  at android.view.View.layout(View.java:15604)
                  at android.view.ViewGroup.layout(ViewGroup.java:4966)
                  at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
                  at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
                  at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
                  at android.view.View.layout(View.java:15604)
                  at android.view.ViewGroup.layout(ViewGroup.java:4966)
                  at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
                  at android.widget.FrameLayout.onLayout(FrameLayout.java:508)

代码是：

Fragment.java：

@Override
public View onCreateView(LayoutInflater inflater,ViewGroup container,Bundle savedInstanceState) {
    db = DataBindingUtil.inflate(inflater,R.layout.fragment_group_comments,container,false);

    getSubComponent().inject(this);

    db.setVariable(BR.height,0);

    // Inflate the layout for this fragment
    return db.getRoot();
}

@BindingAdapter("android:layout_height")
public static void setLayoutHeight(View view,float commentNumber) {
    Timber.e("setLayoutHeight " + commentNumber);

    try {
        GridLayoutManager.LayoutParams layoutParams =
                (GridLayoutManager.LayoutParams) view.getLayoutParams();

        if (10 <= commentNumber && commentNumber < 10) {
            layoutParams.height = 400;
        } else if (11 <= commentNumber && commentNumber < 20) {
            layoutParams.height = 500;
        }

        view.setLayoutParams(layoutParams);
    } catch (Exception ignore) {}
}

item_.xml