android - 如何检查 viewStub 是否已经膨胀？

Question

我没有发现任何 bool 方法可以完成这项任务。我可以通过检查 viewStub 的 id 是否更改为指定为 inflatedid 的那个来做到这一点吗？

Java代码:

    protected void plantViewTree() {
    // TODO Auto-generated method stub

        ViewStub mViewstub = (ViewStub) findViewById(R.id.viewStub00);

            if (mViewStub is inflated) {
              //do somthing
              }else
               mViewstub.inflate();

}

更新对 eOutput 的评论

根据这段代码，toast 总是显示它的消息，这意味着由于 mViewStub 被分配给 findViewById 它永远不会为空，除了底层 alyout 中的 viewstub View 不可用。有什么建议吗？

protected void plantViewTree() {
    // TODO Auto-generated method stub
    ViewStub mViewstub = (ViewStub) findViewById(R.id.viewStub00);
    if (mViewstub != null)
        Toast.makeText(getApplicationContext(), "view is inflated", 
Toast.LENGTH_LONG).show();
    else
        mViewstub.inflate();
}

Answer 1

我们可以查看ViewStub源码，最重要的方法是inflate()，

 public View inflate() {
    final ViewParent viewParent = getParent();

    if (viewParent != null && viewParent instanceof ViewGroup) {
        if (mLayoutResource != 0) {
            final ViewGroup parent = (ViewGroup) viewParent;
            final LayoutInflater factory;
            if (mInflater != null) {
                factory = mInflater;
            } else {
                factory = LayoutInflater.from(mContext);
            }
            final View view = factory.inflate(mLayoutResource, parent,
                    false);

            if (mInflatedId != NO_ID) {
                view.setId(mInflatedId);
            }

            final int index = parent.indexOfChild(this);
            parent.removeViewInLayout(this);

            final ViewGroup.LayoutParams layoutParams = getLayoutParams();
            if (layoutParams != null) {
                parent.addView(view, index, layoutParams);
            } else {
                parent.addView(view, index);
            }

            mInflatedViewRef = new WeakReference<View>(view);

            if (mInflateListener != null) {
                mInflateListener.onInflate(this, view);
            }

            return view;
        } else {
            throw new IllegalArgumentException("ViewStub must have a valid layoutResource");
        }
    } else {
        throw new IllegalStateException("ViewStub must have a non-null ViewGroup viewParent");
    }
}

注意这一行 parent.removeViewInLayout(this) ，它在 inflate 之后在布局中被删除了。所以我们可以通过这种方式检查 viewStub 是否已经膨胀。

if (mViewStub.getParent() != null) {
    mViewStub.inflate();
} else {
    mViewStub.setVisibility(View.VISIBLE);
}