这里是 protected void View.onScrollChanged(int l, int t, int oldl, int oldt)
的来源:
/**
* This is called in response to an internal scroll in this view (i.e., the
* view scrolled its own contents). This is typically as a result of
* {@link #scrollBy(int, int)} or {@link #scrollTo(int, int)} having been
* called.
*
* @param l Current horizontal scroll origin.
* @param t Current vertical scroll origin.
* @param oldl Previous horizontal scroll origin.
* @param oldt Previous vertical scroll origin.
*/
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
if (AccessibilityManager.getInstance(mContext).isEnabled()) {
postSendViewScrolledAccessibilityEventCallback();
}
mBackgroundSizeChanged = true;
final AttachInfo ai = mAttachInfo;
if (ai != null) {
ai.mViewScrollChanged = true;
}
}
问题是关于这一行:final AttachInfo ai = mAttachInfo;
。引入 ai
的目的是什么?为什么将其设为 final
?
最佳答案
很可能,mAttachInfo
是volatile
;那么ai
的目的就是为了避免两个线程访问这个对象时出现NullPOinterException
,mAttachInfo
是检查mAttachInfo!=null<后写的
但在执行 mAttachInfo.mViewScrollChanged = true;
关于java - 关于 View.onScrollChanged() 的来源,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/15406025/